Byte Magazine Volume 03 Number 07 - How To Get Your Tarbell Going

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MULTI-USER SYSTEM

■^ ^

OPERATES - Up to 4 terminals running INDEPENDENT programs HARDWARE TIME SHARE-Requires no modifications to computer IDEAL FOR — All multi-terminal applications

The SwTPC multi-user system converts our standard 6800 single user computer into a multi-user time share system that may be operated with up to four terminals. The four terminals operate independently and may be running four different programs.

No modifications to the computer are necessary, you simply plug in the multi-user board and add an interface for each additional terminal.

The multi-user system is ideal for program training, multistation business applications and for computer aided instruction (CAI). Speed reduction from a single user system is negligible because all switching is done in hardware.

Multi-user BASIC, suitable for program instruction and simple business applications, is included with the multi-user

board. An 8K disc BASIC is also available for systems in which disc drives are used. This software has a complete nine digit floating point math package, full string features and data files.

For computer aided instruction applications, a full feature version of PILOT is available. It includes math operators, misspelling match features and all other proposed for the ANSI! standard version. The 6800 multi-user system is just as economical, but far more flexible and powerful than multiple small machines for CAI applications.

MUB-68 Multi-User Board and BASIC Software

Assembled and tested $150.00

Kit $129.95

SOUTHWEST TECHNICAL PRODUCTS CORPORATION

219 W. RHAPSODY

SAN ANTONIO, TEXAS 78216

Circle 350 on inquiry card.

.4

Model Z-2

Up to 51ZK of RAM/ROM

Fill your

Model Z-2D

One or two disks

Up to 512K of RAM/ROM

Up to 184K of disk

kill

System Two

Dual disk

Up to 512K of RAM/ROM

Up to 184K of disk

needs

with the indiistryls

mostprofessloiial

:¥A

ii ■

#1 IN RELIABILITY

When you choose Cromemco you get not only the industry's finest microcomputers but also the industry's widest microcomputer selection.

What's more, you get a computer from the manufacturer that computer dealers rate #1 in product reliability.*

Your range of choice includes our advanced System Three with up to four 8" disk drives. Or choose from the System Two and Z-2D with 5" drives. Then for ROM-based work there's the Z2. Each of these computers further offers up to V2 megabyte of RAM (or ROM).

We say these are the industry's most professional microcomputers because they have outstanding features like these:

• Z-80A microprocessor — operates at 250 nanosecond cycle time — nearly twice the speed of most others.

'Rated in The 1977 Computer Store Survey by Image Resources, Westlake Village, CA.

Up to 512 kilobytes of RAM and 1 megabyte of disk storage

System Three

Two to four disks

Up to 512K of RAM/ROM

Up to 1 megabyte of disk

21 card slots to allow for unparalleled system expansion using industry-standard S-100 cards.

S-100 bus — don't overlook how important this is. It has the industry's widest support and Cromemco has professionally implemented it in a fully-shielded design.

Q

• Cromemco card support of more than a dozen circuit cards for process control, business systems, and data acquisition including cards for A-D and D-A conversion, for interfacing daisywheel or dot-matrix printers, even a card for programming PROIVIs.

• The industry's most professional software support, including FORTRAN IV, 16K Disk-Extended BASIC, Z-80 Macro Assembler, Cromemco Multi-User Operating System — and more coming.

• Rugged, professional all-metal construction for rack (or bench or floor cabinet) mounting. Cabinets available.

FOR TODAY AND TOMORROW

Cromemco computers, will meet your needs now and in the future because of their unquestioned technical leadership, professionalism and enormous expandability.

See them today at your dealer.

There's no substitute for getting the best.

see next

Circle 80 on inquiry card.

Crontenteo

Incorporated Specialists in computers and peripherals 260 BERNARDO AVE., MOUNTAIN VIEW, CA 94040 • (415) 964-7400

0

BYTE )ulv 1978

SEE YOUR LOCAL DEALER

Anchodie. AK 99501 ALASKA DIVERSIFIED DIGITAL ITOOWniHiiKDAvtrnw (907) 2T7-63I2

Hunlwllle. AL31WS COMPUTERLAND OF HUNTSVILLE 3020 Unlvcrlily Drtvi. N.W. (20S) 539-1200

*Llltle Rock, AR 72206 COMPUTER PRODUCTS UNLIMITED 2412Si>uihBr(Mdwiv {501) }T14)449

Ph«ni>..AZ 85021 COMPUTER RESEARCH CORP ZZ25 W Mm. View Ro^ - No, G (601)943-ST19

PhMnU,AZB5029 COMPUTER WORLD 2230 Wnl LirkxHir [6021 943-S925

laaan.Kiii'oraiSnt 8VTE SHOP OF TUCSON 26T2 E»t B'Bxfwiv (602) 327-4579

• CuKin, CA 90746 SUNSHINE COMPUTER COMPANY 20710 Soulh Ltapwood AMOue (213)327.2118

BYTE SHOP SACRAMENTO 6041 Gi«enbick Low (91G|961.BYTE

El Cerrllo, CA 94530 COMPUTERLAND EL CERRITO 11074 Sm Piblo Avenue (415)233-5010

• FMinUin Valley, CA 92708 ADVENTURES IN COMPUTING 8TS6 WiriKi Avtniw (714) 848-83SS

FrtMio, CA 93703 BYTE SHOP OF FRESNO 3139 t. McKinley Axniw (209)485-2417

Hiy*iid, CA 94S42 COMPUTERLAND OF HAYWARO 22634 Foothill Boulevird (415) 138-8080

ALGORITHM PERSONAL COMPUTERS

7561 RhiTw Drive

(714)751-8080

lotfcwood, CA 90302 COMPUTERLAND OF W. LOS ANGELES 6840 Li CIciHii Boulcvird (213) 776-8080

Lawndile. CA 93060 BYTE SHOP OF LAWNDALE 6S08 Hiwlhomc Boulrvud (2131371 2421

•Lownti. CA 95650 KINGMONT ENTERPRISES. INC. 9900 KIni Roid (916)988-8189

Los AnidM, CA 90025

AMERICAN RECORDER COMPANY

1655 Siwlclle Boulevard

(213)477-2063

McnIoPirk.CA 94025

COMPUTADATA PROCESSING SERVICE

2225 Shiion Roid - No. 224

MlulonVlefo.CA 92630 COMPUTERLAND SADDLEBACK VLV 24001 Vij FjbrkBiM ~ No 904 (714)7700131

• Mounutn Virw. CA 94040 BYTE OF Mt VIEW 1063 W El Cjmino Reil (415)969-5464

Oiutft. CA 92667 COMPUTER MART 633-a W«l KiltUt Bojlnard {714)633.1222

Palo Alto, CA 94306 BYTE SHOP PALO ALTO 2227 El Camino Rnl (415) 327-8080

Palo Alio. CA 94301 MICROTECH EXPORTS 912Cowp« SliHi (415)328-1712

Paud>ni,CA9ll01 BYTE SHOP PASADENA 496 South Lake Avenue (213)684-3311

Placcrville, CA 95667 GRANITE BUSINESS SYSTEMS 670 Plcaunl Valley Rud (916)626-1161

Sacramento, CA 95816 MICROCOMPUTER APPLICATIONS SYS 2322 Capital AMniM (916) 433-4944

San Diego. CA 92211 COMPUTERLAND OF SAN DIEGO 4233 Canroy Street (714) 560-9912

THE CW4PUTER CENTER 8205 Ronton Road (714) 192-5302

San Fran(lico,CA 94105 COMPUTERLAND OF SAN F RANCISCO 117 Fremont Street (415) 546-1592

• San FranclKO, CA 94103 THE COMPUTER STORE OF S.F. 1093 Motion Street (415)431-0640

SanFraiH:iico.CA9411S

THE NETWORK:

495 Third Avenue-No. 8

(415)221-1112

•DENOTES SYSTEM THREE' DEALER

San Joie.CA9SI14

BYTE SHOP Mi ol SAN (OSt

2626 Union Avenue

(408) 377-4685

San|ote.CA95123 THE COMPUTER ROOM

I24-HBIaiiamHi1l Road (408) 226-8383

San(o»e,CA'9S132 PLANE DATA WORKS 3 584 Minio Court (408) 2624566

(415)895-9363

• San Mateo, CA 94401 COMPUTER TERMINAL 309 S. San Maleo Drive (415) 347-9894

* Sania Ana, CA 92705

ADVANCED MICROCOMPUTER PROD

1310 £aii Edinger

(714)558-881)

Santa Oar a. CA 95051

THE BYTE SHOP OF SANTA CLARA

3400 El Cam.no Real

(408) 249-4221

THE COMPUTER STORE

BZO Broadway (213)451-0713

Sunnwak. CA 94086 BYTE INDUSTRIES 910 W Miudf (415)719-8000

RECREATIONAL COMPUTER CENTER 1324 South Mary Avenue (408) 712-)1IH

Tinlin. CA 92680 COMPUTERLAND OF TUSTIN 104 Weil Flrtl Street (714) 544-0542

•Van Nuyi.CA 91411 COMPUTER COMPONENTS 5848 Sepulveda Boulevard

Walnut Creek. CA 94596

BYTE SHOP COMPUTERS OF DIABLO VLY

2989 N Main Street

(415)933-6152

EnflewDod, CO 80110 BYTE SHOPOF ARAF _ _

3463 South Acoma Street (101) 76I4IZ1

Fairfield, CT*06430 COMPUTERLAND OF FAIRFIELD 2475 Black Rock Turnpike (203) 374-2227

WindMTLockt.CT 06096 THE COMPUTER STORE 61 South Main Street (203) 6174188

Newark. DE 19711

COMPUTERLAND OF NEWCASTLE CITY

^ttro Shopping Cenler

Kirkwood Highway

(302) 738-9656

Ft. Laudt.dak, FL J33J4 BYTE OF FT LAUDERDALE 1044 E Oakland Park Blvd. (105) 561 2983

Ft. Lauderdale, FL 13312 COMPUTERS FOR YOU, INC, 3608 W Broward Blvd. (305) 581-8945

• Ft Meyert.FL 33901 MICROCOMPUTER SYSTEMS, INC 12800 US 41 South (813)481-3376

Planlallon.FL 33317 COMPUTERAGE 1400 SW. 70th Avenue (305) 791-8080

(813) 879-4225

• Atlanta, GA 30340 ATLANTA COMPUTER MART S09t-B Buford Highway

Marietta, GA 30060 EDUCATIONAL DATA SERVICES 79 On ford Road

•Halku.Maui, HI 96708 CAPACITY, INC P,0. Box A (808) 5752930

•Honolulu. HI 96815 COMPACT COMPUTERS 305 Royal Hawaiian, Ste. 407 18081 373 2751

Kiilua, Oahu, HI 96734 MICROCOMPUTER ENTERPRISES 1450 Mokulua Drive (808) 261-3281

Arlington Heighti, IL 60004 COMPUTERLAND ARLINGTON HTS. 50 Eati Rand Road (112)255-6488

Champaign, IL 61820 BYTE SHOP CHAMPAIGN 1602 S Neil Street [217)352-2313

Chicago. IL 60632 BRONSON 1 BRATTON. INC. 5161 S. Millard Avenue (312)735«20D

Lide.lL 60532

COMPUTER A CONTROL AFFILIATE

4315 A>aiea.No.40l

1312)9684548

Lombard. IL 60148

MIDWEST MICROCOMPUTERS, INC,

708 South Main Street

(312) 495-9889

Napcrvillt, IL 60540 ILLINI MICROCOMPUTERS 612 Eati Olden Avenue (312)420UI3

NHet. IL 60648 COMPUTERLAND NILES 9511 N. Milwaukee Avanut (311)967.1714

BYTE luly 1978

□

Oak Lawn. IL 60453 COMPUTERLAND OF OAK LAWN 10935 Soulh Citno Avenue (312)422-8080

Ro<krDrd,IL 61101

IMPERIAL COMPUTER SVSTEMS

2105-23rd Avenue

(815) 22fr4200

•Bloommgion, IN47401 DATA DOMAIN 406 South College Avenue (812)334-1607

•Fort Wayne, IN 46805 DATA DOMAIN OF FORT WAVNE 2805 Eall Slate Boulevard

(219)484-7611

Indianapotli, IN 46268

DATA DOMAIN OF INDIANAPOLIS

7027 Michigan Road

(317)251-3139

West Lafayette. IN 47906

DATA DOMAIN OF WEST LAFAYETTE

219 Weu Columbia

(317) 743-3951

Mitiion, KS 66202 COMPUTER CENTER 5815 lohnsnn Drive (913)432-2983

Overlaitd Park. KS 66106

PERSONAL COMPUTER CENTER. INC.

3819W 95lhSl>eet

(911)649.5942

Lexington, KV 40501

DATA DOMAIN OF LEXINGTON

506-1/2 Euclid Avenue

(606) 233-3346

Louifville, KY 40222 COMPUTERLAND OF LOUISVILLE 813-8 Lyndon Lane (502) 425-8308

Louisville. KY 40220

DATA DOMAIN OF LOUISVILLE

3028 Hunlinger Lane

(502) 456-5242

Louisville, KV 40206 PRAGMATECH 2310 Hellwnod Avenue (S02) 89!-1230

•Surtington, MA 01803 THE COMPUTER STORE

(617)272-8m

College Park. MD 20740 INTELLIGENT BUSINESS MACHINES 7318 Baltimore. Avenue. Suite 100 (301) 779-7998

• P>kesville.MD21108 MODULAR SYSTEMS, INC 4005 Seven Mile Lane (301)4844322

• Rockville, MD 20852 COMPUTER WORKSHOP 1776 east ttfferMn (301)468-0463

Rockville, MD 20855

COMPUTERLAND Of GAITHERSBURG 16065 Frederick Road. Route 355 (301) 948-7616

Silver SpCing. MD 20901 CAM ENGINEERING. INC 9318 Worth Avenue (301) 589-1779

•Tow«>n.MO*2I204 COMPUTERS ETC.

13-A Allegheny Avenue (301) 296-0520

Ann ArtKH, Ml 48104

NEWMAN COMPUTER EXCHANGE

1250 North Main Sirect

(113) 994-4445

Ann Arboi, Ml 48104 THE COMPUTER STORE

Ann Arbor. Ml 48104

UNITED MICROSYSTEMS CORP

2601 South SUie Sireel

(313) 6684806

•Berrien Sprinp. Ml 49103 THE ABACUS

Route No 1, Box 191.(Nilet Avenue) (616) 429-3034

Grand Rapidt. Ml 49508 )EPSAN.GROUP K 4706 Morningtlde Drive. S.E. (616)698-9057

Royal Oak, Ml 48073

COMPUTER MART OF ROYAL OAK

1800 Weil 14 Mile Road

(313)576-0900

Edina, MN 55435 COMPUTER DEPOT, INC 3511 Wnf 70th Street (612) 927-5601

Chettertield. MO 63017

COMPUTER SYSTEMS CTR ST. LOUIS

13461 Olive Boulevard

(314) 576-5020

COMPUTERLAND OF NASHUA 419 Amhertt (603) 889-5238

Hoboken. N) 07030 HOBOKEN COMPUTER WORKS No, 20 Hudson Place (201)420-1644

•itelln.NI 08830 COMPUTER MART OF NEW JERSEY 501 Rout* No 27 (201) 2834)600

Morriiio<vn,N) 07960 COMPUTERLAND OF MORRISroWN

(301) 53*4077

Reno, NV 89502 BYTE SHOP OF RENO 4104 Kieuke Lai» (101) 826-8080

• Buffalo, NY 14226 CORSON COMPUTER CORP.. INC. 3834 Main Street (716) 832-0662

OeWilt,NY13214 COMPUTER ENTERPRISES 3470 Erie Boulevard Eati (315)446-1284

LOUIS SCHAEfFER

119 Hamlllon Avenue (516)374-1286

•Hollit,NY 11423 SYNCHRaSOUND ENTERPRISES 193-25 limaica Avenue

[112)468-7067

Ithaca, NY 14850 COMPUTERLAND OF ITHACA 235 Elmira Road (607) 277.4888

New York City. NY 10016 BYTE SHOP EAST 130 E. 40th Street [312) 889-4204

Rocheiler.NV 14609 COMPUTER HOUSE, INC 731 Atlantic Avenue (716)654-9218

• Cincinnatt. OH 45409 DIGITAL DESIGN

7694 Camargo Rd. [Madiera) (513)5614733

Cincinnati. OH 45202 21STCENTURY SHOP 16 Convention Way Skywalk, Vine A Race (513)651-2111

Columbui, OH 43201

MIDWESTERN DIGITAL ELECTRONICS

80 Weil Line Avenue, Suite 1J

(614) 294-2991

•Oaylon, OH 45409 DATA DOMAIN Of DAYTON 1932 Brown Street (513) 223-2348

Keni. OH 44240 OHIO MICRO SYSTEMS 233 South Water Street (216) 678-5202

Mayfietd Heights, OH 44124 COMPUTERLAND OF CLEVELAND EAST 1288 Sam Center Road (216) 461.1200

Oklahoma City, OK 73106 HIGH TECHNOLOGY 1611 Norlhwett 23rd Street (405) 528-8008

Beaverion OR 97005 BYTE SHOP OF BEAVERTON 3482 S W Cedar HUh Boulevard (503) 644-1687

Eugene, OR 97401 REAL OREGON COMPUTER CO205 Wett Tenth Street, P O. Boi 12 (503) 4841040

• Tualatin, OR 91062 CREATIVE SYSTEMS 8101 S W. Nyberg Road (503) 638-8406

Alliun Park, PA 15101 R. OONKRIGGER 93BO SpringTIel (412) 3f

Huntington Valley. PA 19006 MARKETLINE SVSTEMS, INC 2337Phllmoni Avenue (315)9474670

King of Pruttia, PA 19406 COMPUTER MART OF PENNSYLVANIA 550 Oe Kalb Pike (Route 302) (215) 26S-2580

Piinburgh, PA 15237 ELECTRONICS PLACE 7250 McNlght Road

Warwick, Rl 02886 COMPUTER POWER, INC 1800 Pott Road (401) 738-4477

• Columbia. SC 29205 BYTE SHOP OF COLUMBIA 1018 Green Street

(803) 771-7814

Mcmphit.TN 38101 COMPUTER STORE 1162 Couitland Place (901)274-1938

Nashville, TN 37206 COMPUTER WORLD 625 Main Street (611)2444094

• Nashville. TN 37211 SURYA CORPORATION 5755 Nolentville Road (615)834-1638

Amarlilo, TX 79109 COMPUTER CORNER, INC. 1800 Soulh Georgia St., No. 3 (806)313-4194

• Austin, TX 78731 COMPUTERS N THINGS 2835 Hancock Drive (512)451-5970

MICRO SVSTEMS SERVICES. INC 5301 Everhari, Space H-PO. Boi6131 (512)8554516

• DallB.TX 71243 COMPUSHOP

211 Keyston Park. 13933 North Central (214) 234-3412

•Houiton.TX 77057 COMPUTERLAND OF S.W HOUSTON 6439 Westheimer (713)977-0909

•Houston, TX 77006 COMPUTERTEX 2100 Richmond Avenue (711) 5264934

Hounon.TX 77036 INTERACTIVE COMPUTERS 7646-1/2 Dathwood. P.O. Box 36584 (713)977-7037

Crametneo

incorporated Specialists in computers and peripherals 280 BERNARDO AVE., MOUNTAIN VIEW, CA • (415) 964-7400

•Houtton.TX 77098 THE MOS

1853 Richmond Avenue (713) 527-8008

Lubbock, TX 79412 COMPUTER MART OF W TEXAS 3506 0 Avenue, O (806)765-7134

Richardson. TX 75080

THE MICRO STORE

634 South Central EiprcHway

Provo, UT 84601

THE COMPUTER WORKS

735 South State Street, P.O Box N

(801) 373-7522

AInandria, VA 22304 COMPUTERS PLUS, INC 678 S Pkkeli Sireel {703)751-4656

McLean, VA 22101 COMPUTER SVSTEMS STORE 1984 Chain Bridge Road (703)831-8333

Seattle, WA 98115

THE RETAIL COMPUTER STORE

410 N,E 71nd Street

(206) 524-4101

•AppleltMi,WI 54911 SOUND WORLD, INC. 3015 W Wiscomin Avenue (414) 7)4-7698

Maditon, Wl 53711

THE MADISON COMPUTER STORE

1861 Monroe Street

(608) 255-1153

Milwaukee. Wl 51208 MILWAUKEE COMPUTER STORE 4710 Wett North Avenue (414) 445-4280

•Racine. Wl S1405 COLORTRON TV 2111 UthrnpAvenu (414)617-2003

• INTERNATIONAL •

SONTROM INSTRUMENTS

Croydon. Vkt-.Ausirilia, 3136 COMPUTER ART A EDUCATION 1 Stephen Cretcent

Prahran. Vic I aria, Australia. 3181 GEMINI MICROCOMPUTERS P.O. Box 99

Wett Penh, 6001. W Autt Ta AUSTRALIAN COMPUTER PRODUCTS 1300 Hay Street (091.3224497

• A-3401 Fishamend, Austria KREBSGES. MBH, Hainburgcr Stiabe 34 013326818223

Calgary, Alberta, Canada ROBO-TRONICS 509-16 Avenue N,W. (403) 282-9496

Montreal, Quebec. Can H3B 3C9 FUTUR BYTE, INC1191 Phillips Square (114)861-3120

Toronto, Ont. Can. M4G 3B5 COMPUTER MART, LTD

1143 Bayvlew Avenue (416)484-9708

Toronto, Ont , Can. M4R 1A1

FIRST CANADIAN COMPUTER STORE

44 Eglinton Avenue We«

(416)482-8080

TRINTRONICS, LTD. 186 Queen Street West (416) 598-0260

ingdon. IWNJ

Cambi., England PE1 COMART LIMITED 24 A Market Square 0480-215-005

Parii 15011, France COMPUTER BOUTIQUE 149 Avenue dcWapam

Chtyoda-Ky, Tokyo 101, )a BYTE SHOP S(XK)H 144 Sotokanda 03 251-1984

Tokyo 106, Japan

lEE CORPORATION

4-33, 3-Chome, Ropongi. Minitoka

(03)585-2331

•MexicolS, DF. MexKO INTELEX.SA PA. De Lot Santos 70 (905)516-9970

Makati, Riial, The Phiillplnei DECISION SYSTEMS CORP. 150 Amanolo St, A Pisay Rd. Lcgatpi Village

• 10052 Stockholm 29, Sweden DATORISERING KONSULT AB

F*ck3

4051 batel. SwiiierUnd EUREX.INC Beinwiier Sir. 11 061-157069

• SOOlZurich.'swiiierluHl COMICRO AC Badeneniratte 281

•Hiltrup4400,Muniler,W Germany BASIS MICROCOMPUTER VERTRIEB Von-Flotow-Sfabe I 02501-4800

•2000Wedel.H«leln.W Germany DIGITRONIC tOMPUTERSVSTEME Elei Der Doapdkche 3-1 04103 7393

-i i

u

•s

Circle 80 on Inquiry card.

^

*■

12 28 60 72 98 152 162

32

42 48 64 84 124

4

6

11

16

96

112

115

117 118 118 119 123 172 177 206 208 208

In the Queue

Foreground

KIMER: A KIM-1 TIMER

Software—Baker THE AXIOM EX800 PRINTER: A User's Report

Product Description—Bosen THE Z-80 IN PARALLEL

Hardware—Loewer CONTROLLING DC MOTORS

/hardware—Walton BUILD A KEYBOARD FUNCTION DECODER

Hardware—Ciarcia A HIGH LEVEL LANGUAGE FOR 8 BIT MACHINES

Software—Williams-Conley HOW TO GET YOUR TARBELL GOING

Hardware—Weinstein

Background

TOP-DOWN MODULAR PROGRAMMING

Software—Hearn WHO'S AFRAID OF DYNAMIC MEMORIES?

Memory Design Tutorial—Haucl< ANTIQUE MECHANICAL COMPUTERS, Part 1: Early Automata

His tory—Williams THE FIRST TEN YEARS OF AMATEUR COMPUTING

History—Libes A SHORT HISTORY OF COMPUTING

History—Reid-Green HOW TO CHOOSE A MICROPROCESSOR

Architecture-Frenzel

Nucleus

In This BYTE

Some Thoughts About Modems

Letters

The Second West Coast Computer Faire

Clubs, Newsletters

Languages Forum: BASIC to Assembly Language Linkage

Technical Forum: Fooling with the Stack Pointer

More on Varistors Book Reviews BYTE's Bits BYTE's Bugs

Programming Quickies: Beating North Star-MITS Incompatibility College Sports Report Event Queue What's New? Unclassified Ads BOMB Reader Service

EiiTE

July 1978

BYTE is published monthly bv BYTE Publications Inc. 70 Main St, Peterborough NH 03458. Address all mail except subscriptions to aboue address: phone 1603) 924-7217. Address all editorial correspondence to the editor at the above address. Unacceptable manuscripts will be returned if accompanied by sufficient first class postage. Not responsible for lost manuscripts or photos Opinions expressed by the authors are not necessarily those of BYTE. Address all subscriptions, change of address Form 3B79 and fulfillment complaints to BYTE Subscriptions, PO Box 590, Martinsville NJ 08836. Second class postage paid at Peterborough NH 03458 and at additional mailing offices-USPS Publication No. 102410. Canadian second class registration No. 9321. Subscriptions are $15 for one year, $27 for two years, and $39 for three years in the USA and its possessions. In Canada and Mexico, $17.50 for one year, $32 for two years, and $46.50 for three years. $25 for a one year subscription by surface mail worldwide. Air delivery to selected areas at additional rates available upon request. $25 for a one year subscription by air delivery to Europe. Single copy price is $2.00 in the USA and its possessions, $2.40 in Canada and Mexico $3 50 in Europe, and $4.00 elsew/here. Foreign subscriptions and sales should be remitted in United States funds. Printed' in United States of America. Each separate contribution to this issue and the issue as a collective work copyright la 1978 by BYTE Publication Inc. All rights reserved

Subscription WATS Line: (800) 258-5485

Volume 3 Number 7

PUBLISHER

Virginia Londner

EDITOR IN CHIEF

Car! T Helmers |r

VICE-PRESIDENT, PRODUCTION

Judith Hjvey

PRODUCTION MANAt.ER

Karen Gregory

ADVERTISING DIRECTOR

EAST, MIDWEST

John Hayes

ADVERTISING DIRECTOR

WEST, SOUTHWEST

Debra Boudrreau

CIRCULATION MANAGER

Gregorv Spiufaden

SENIOR EDITOR

Christopher P Morgan

BOOK EDITOR

Blaise W Lifflck

COMPTROLLER

Michael Galan

EDITOR

Raymond A G Cole

PRODUCTION EDITORS

David William Hayward

Nancy Salmon

BOOK PUBLISHER

Thomas ) Herman

BOOK PRODUCTION

Edmond C Kelly |r

NEW PRODUCTS EDITOR

CLUBS, NEWSLETTERS

Laura A Hanson

ASSISTANT TO COMPTROLLER

Rulh M Walsh

EDITORIAL ASSISTANT

Becky LifTick

ADVERTISING

Noreen Bardstey

JillCallihan

Patricia Clark

PRODUCTION ASSISTANT

Cheryl A Nurd

CIRCULATION ASSISTANTS

Sarah Bauhan

Christine Dixon

Ann Graves

Pamela R Heaslip

DEALER SALES

Ginnie F Boudrieau

TRAFFIC MANAGER

Thomas Harvey

ART

Stephen Kruse

Wai Chiu Li

Dorothy Shamonsky

Ellen Shamonsky

RECEPTIONIST

Jacqueline Earnshaw

DRAFTING

Techart Associates

TYPOGRAPHY

Goodway Graphics

PHOTOGRAPHY

Ed Crabtrce

PRINTING

The George Banta Company

ASSOCIATE EDITOR

Daniel Fylstra

ASSOCIATES

Walter Banks

Steve Ciarcia

David Fytsira

Portia Isaacson

ADVERTISING SALES REPRESENTATIVES

EAST, MIDWEST

Hajar Associates Inc

17 DuranI S(

WeslRoxbury MA 02132

(617)325 5380

100 W Chicago Av

Chicago IL 60610

(312)3378008

WEST, SOUTHWEST Buckley/Boris Associates Inc 912 South Barrington. Suite 202 Los Angeles CA 90049 (213)826-4621

DISTRIBUTORS EASTERN CANADA RS-232 Distribution Company 186 Queen St W. Suite 232 Toronto ONTARIO WESTERN CANADA Kitronic Ltd 26236 26th AvRR 5 Aldergrove BC VOX 1A0

July 1978©BYTE Publications Inc

This month's cover shows Babbage's 1822 difference engine, a device designed to calculate values in mathematical tables. Charles Babbage was one of the earlier pioneers in the field of computational machinery, whose work paved the way for later breakthroughs in computing.

In This El^YE

One way to demonstrate your KIM-1 computer is to use it as a clock. Robert Baker's article KIMER: A KIM-I Timer shows you how to display hours, minutes and seconds on the computer's LED display. The program can also be used as a timer.

page 12

Heat sensitive aluminized paper is the key ingredient in Axiom's unusual EX800 printer. Find out about one user's reactions to this peripheral in The Axiom EX800 Printer: A User's Report by R J Bosen. page 28

Transforming the goal "I want thus and so function" into a program which performs that function is an act of design. Albert D Hearn provides the novice programmer with some background philosophy about design of personalized programs in his article entitled Modular Programming.

page 32

Are you afraid of dynamic memories? Let author Lane T Hauck remove some of the mysteries about these devices in Who's Afraid Of Dynamic Memories? The greatest potential of the dynamic memory for the experimenter is its low price; reading the article should prove to be a "refreshing" experience. page 42

Dr James M Williams takes readers on a fascinating tour of early experiments in automata in his article Antique Mechanical Computers, Part 1: Early Automata. Read about Vaucanson's mechanical duck and the

4 July 1978 ® BYTE PuWicatioiB Inc

Other miraculous pre-19th century devices that foreshadowed today's computers. page 48

Today more and more design engineers are introducing parallel processing into computer systems to improve throughput rates. With the advent of inexpensive microprocessors, experimenters can now investigate this fascinating area. Find out more by reading Robert Loewer's The Z-80 in Parallel. page 60

When did personal computing really begin? Was it 1974 or 1971? The surprising answer is 1966. Sol Libes' The First Ten Years of Amateur Computing traces the growth of this rapidly growing field over the past decade, and gives credit to the true pioneers.

page 64

The ability to control DC motors allows you to imagine applications from games to robotics. Robert L Walton describes a simple method of shaft position control in his article, Controlling DC Motors. page 72

Have you ever wondered how this business of computing ever got started? And just what were the major developments and discoveries that made the computer industry what it is today? Well, take A Short History of Computing course by reading the article by Keith S Reid-Green. It provides a perspective on the antecedents of today's developments in the field of computing. page 84

If you would like to turn your printer or other peripheral on and off from your computer keyboard, Steve Ciarcia describes a simple way to do it with an EROM in Ciarcia's Circuit Cellar: Build a Keyboard Function Decoder. page 98

How do I choose a microprocessor for personal computing? In some respects the problem is analogous to attempting to choose between a V-8 and a V-6 automobile engine of the same horsepower: both make the car go and most users couldn't care less about the type of engine so long as the car gets them to their desired destinations. Similar considerations apply in the choice of a personal computer product based on the microprocessor it contains. Who cares what microprocessor the product contains, so long as it accomplishes a certain minimum level of function with respect to systems and applications software? Lou Frenzel of the Heath Company gives some thoughts on How to Choose a Microprocessor in an article in this issue. page 124

Thinking of writing your own high level language interpreter for your home computer? If so, Ted Williams' and Steve Conley's article, A High Level Language for 8 Bit Machines, will supply you with an overview of one such implementation. The language that they develop is suitable for use as both an interpreter or a compiler. page 152

If you own a Tarbell cassette interface, read How to Get Your Tarbell Going. Author Larry Weinstein explains how the unit works and gives some suggestions for improving performance. page 162

A

I

: i

' A

The Ultimate Turn-on

On/off control everyviiereby computer over the AC wiring

Now it's simple and economical to control AC devices remotely from an S-100 or Apple II computer. Mountain Hardware's new Introl™ system delivers on/off commands over the existing AC lines — so you don't have to string a foot of ware!

Control at any AC outlet. The

Introl system impresses a codemodulated 50 KHz control signal on the house wiring. Then decodes the signal at any outlet to switch AC devices on and off. You can control lights, refrigerators, TVs, solenoid valves, sprinklers, burglar alarms—and many other things we leave to your fertile imagination. With the addition of input sensors to your computer system, you can automatically control variables such as temperature and soil moisture.

Here's how it works. You plug m a single AC Controller board at the computer bus and connect the AC Interface Adapter to any convenient 115 VAC outlet. The AC Controller is now connected to address as many as 64 channels remotely. But it's completely isolated

from the 115v power, so there's no chance of short or shock.

At any outlet where you seek control, plug in a Dual Channel AC Remote. Then plug one or two devices to be controlled into the box. Every AC remote has two independent 500 watt channels. When commanded by the computer, the Dual Channel AC Remote turns the devices on and off independently. When polled by the computer, the Dual Channel AC Remote sends a signal back, telling the computer the status of each device. Bidirectional communication provides error free operation.

Simple programming. You write your control program in BASIC or Assembler language. Software subroutines for the control programs come with the eguipment — along with complete documentation. With your computer, you can program on/off commands at any day and time using our optional Clock boards for S-100 or Apple II computers. A self contained power source assures fail safe operation.

Modest prices. The Introl Remote Control System consists of one AC Controller, either S-100 or Apple II, and one Dual Channel AC Remote. It costs $329 completely assembled and tested. Additional Dual Channel AC Remotes are $99.

The 100,000 Day Clock for S-lOO's costs $219 assembled and tested. The Apple Clock costs $179 assembled and tested.

All prices are f.o.b. Scotts Valley, CA. Prices are USA Domestic. California residents add 6% sales tax.

Where to find it. The Introl System can now be found at computer shops throughout the U.S. and Canada. Drop by and ask for a demonstration. Mountain Hardware, Inc., 5523 Scotts Valley Dr., Scotts Valley, CA 95066. (408)438-4734.

AC Controller (Apple)

Dual Channel AC Remote

OS

Circle 260 on inquiry card.

^ Mountain Hardware

AC Controller (S-100)

BYTE July 1978 5

a

EdilopisI

Some Thoughts About Modems

By Carl Helmers

Articles Policy

By Jt Publkatiom Im is coniinuully seeking quality manuscripts written by individuals who are applying personal computer systems, designing such sys terns, or who have knowledge which will prove useful to our readers, hor a more informal description ot procedures and requirements, potential authors should send a self-addressed, stamped envelope to BY ft Authors Guide, 70 Main St, Peterborough NH 034 iS.

Articles which are accepted are purchased with a rate of $4 5 per published page, based on technical quality and suitability lor the intended reader ship. As to articles appearing in BY It magazine, each month, the authors of the two leading articles in the reader poll (BYTt's Ongoing Monitor Box or "BOMB") are presented with bonus checks of fWO and 150. Unsolicited materials should be accompanied by lull name and address, as well as return postage.^

In the June 1978 issue of BYTE, on pages 103 and 104, we printed a short report on activities of Ward Christensen and Randy Suess of the Chicago Area Computer Hobbyist Exchange (or CACHE). These two gentlemen have implemented a sort of public bulletin board in the form of a computer system which answers the phone through an auto answer modem, determines the data rate of the caller's modem, generates an interactive self-documenting conversation, and is able to store messages on a floppy disk. (For those who missed the original notice, the phone number to call is (312) 528-7141. You will need a Bell 103 style modem running in originate mode at 110 or 300 bps. I

Another very active input is the continuing activity of the PCNET committee on the West Coast, which will sooner or later get around to defining a protocol appropriate to a number of users talking to each other. I also received considerable inspiration from a memo on Telemail put out by Ken Bowles of the University of California at San Diego. All these inputs add up to this present exploration of the state of modem technology as applied to the personal computer.

If you look into the technology of telecommunications, it is easy to get turned off by timesharing. After all, what reason is there to have your own computer if it is not to avoid all that accounting and bill paying on an hourly basis which is use of a timesharing account? Isn't it better to pay a lump sum and have a self-contained computer which runs without any outside ties? This view of identity between timesharing to a big computer and telecommunications in general has been a somewhat erroneous conclusion in my world view for several years.

The conclusion is easy to arrive at, since virtually all use of moderately large computers is done by timesharing telecommunications facilities. But viewpoints change

when an open mind is maintained. The demonstration provided by the gentlemen of CACHE is a key input which sent me on an intellectual excursion into simple, easily implementable uses of the small computer with the phone network. The ideas which come from these thoughts are oriented towards a small integer number of people communicating with one another. These ideas are the kind which can be implemented whenever two or a few people share a common goal and live far enough away from one another to make telecommunications via their personal computers a useful practice in lieu of physical travel. The technology is present and fairly inexpensive, so there is no reason why it should not be used. And, as readers will find in the form of future articles in the magazine, the technology is being used. Now let's turn to two characteristic models of modems and what they can do for their owners.

Simple Communications:

Two Computers + Two People + One Phone Line + Acoustic Couplers

One of the simplest of models to implement in this sphere of computer to computer data communications is duplex transmission through the phone with similar modems at each end. For example, let us suppose that two readers are each the owner of a personal system with a spare serial port talking RS-232 levels to an acoustic modem. Further, let's suppose that they want to talk to one another using digital techniques to send words by way of the phone line. An ordinary telephone of the household variety is their link to each other via the phone network. A simple program model for conversations carried out through a typewriter style terminal keyboard with a display of mes

Continued on page 104

:»

!

luly 1978®BYTE Pgblicilions Inc

7

THE COMPLETE (DO

1

LookToThe North Star HORia)N Computer.

HORIZON™— a complete, high-performance microprocessor system with integrated floppy disk memory. HORIZON is attractive, professionally engineered, and ideal for business, educational and personal applications.

To begin programming in extended BASIC, merely add a CRT or hard-copy terminal HORIZON-1 includes a Z80A processor, IbK RAM, minifloppy™ disk and 12-slot S-100 motherboard with serial terminal interface — all standard equipment.

WHAT ABOUT PERFORMANCE?

I he ZbOA proc essor operates at 4MHZ — double the power of the 8080 And our 16K RAM board lets the Z80A execute at full speed. HORIZON can load or save a 10K byte disk program in less than 2 seconds. Each diskette can store 90K bytes.

AND SOFTWARE, TOO

HORIZON includes the North Star Disk Operating System and full extended BASIC on diskette ready at power-on. Our BASIC, now in widespread use, has everything desired in a BASIC, including sequential and random disk files, formatted output, a powerful line editor strings, machine language CALL and more.

EXPAND YOUR HORIZON

Also available - Hardware floating point board (FPB); additional 16K memory boards with parity option. Add a second disk drive and you have HORIZON-2 Economical serial and parallel I/O ports may be installed on the motherboard. Many widely available S-100 bus peripheral boards can be added to HORIZON

QUALITY AT THE RIGHT PRICE

HORIZON processor board, RAM, FPB and MICRO DISK SYSTEM can be bought separately for either Z80 or 8080 S-100 bus systems.

HORIZON-1 $1599 kit; $1899 assembled.

HORlZON-2 $1999 kit; $2349 assembled.

16K RAM-$399 kit; $459 assembled; Parity option $39 kit; $59 assembled. FPB $259 kit; $359 assembled. Z80 board $199 kit; $259 assembled Prices subject to change. HORIZON offered in choice of wood or blue metal cover at no extra charge

Write for free color catalogue or visit your local computer store.

North Star * Comruters

2547 Ninth Street • Berkeley, California 94710 • (415) 549-0858

Circle 285 on inquiry card.

BYTt July 1978

Sol Terminal Computer

The answer is d

It^ the serious solution to the small computer question.

Sol Systems are the key to effective, economical small computer power. Sol Systems give you the force of a powerful general purpose computer, the problem solving capability of high level languages and the operational simplicity of everyday office equipment.

From the ground up, Sol Systems were designed to do a complete job without adding a load of costly extras. In fact, when you compare the "everything included" price of a quality, field proven Sol System with anything else on the market, you'll be happily surprised to find out how little the extra performance and convenience costs.

For example, complete Sol Systems with 16,384 bytes of RAM memory start at less than $2500? Expanded systems • with 49,152 bytes of RAM memory, 1.5 million bytes of on-line disk memory, disk operating system and Extended Disk BASIC cost less than $8000? Both systems are fully n

assembled, burned-in, tested and ready to go.

Sol Compatibility

Sol Systems feature the S-100 bus for pin-to-pin ■•

compatibility with a wide variety of add-on devices such as voice input and computer graphics. Standard Sol parallel and serial interfaces will drive most standard printers, modems and other peripherals.

A word about languages

No system is complete without software, and at Processor Technology we have tailored a group of high level languages, an assembler and other packages to suit the wide capabilities of our hardware. *

Take a look at our exclusive Extended BASIC as an example. In cassette form, this BASIC features string and advanced

*U.S. prices only.

Sol System.

file handling, special screen commands, timed input, complete matrix, logarithmic and trigonometric functions, exponential numbers, 8 digit precision and square root. The language handles serial access files, provides tape rewind and offers cursor control for graphics capability.

The disk version has all the number crunching talents of the cassette BASIC plus instant access to data and programs on floppy disks. It includes random as well as sequential files and a unique ability to update sequential data in place.

Processor Technology FORTRAN is similar to FORTRAN IV and has a full set of extensions designed for the "stand alone" computer environment. Thousands of special application programs available through books and periodicals have already been written in this well established language.

Processor Technology PILOT is an excellent language for teachers. It is a string-oriented language designed expressly for interactive applications such as programmed instruction, drill and testing.

No wonder we call it the serious solution to the small computer question.

It's the small computer system to do the general ledger and

the payroll. Solve engineering and scientific problems. Use it for word processing. Program it for computer aided instruction. Use it anywhere you want versatile computer power!

Sold and serviced only by the best dealers.

Sol Systems are sold and serviced by an outstanding group of conveniently located computer stores throughout the United States and Canada. They are also available in Australia, Europe, the United Kingdom, Central America, South America, Japan and Singapore.

For more information contact your nearest dealer listed on the following page. Or write Department B, Processor Technology Corporation, 7100 .Johnson Industrial Drive, Pleasanton, CA 94566. Phone (415) 829-2600.

Circle 305 on inquiry card.

Processorlechnology

See Sol at all these fine computer centers.

ALABAMA

Birmingham ICP—Computerland

(205) 979-0707

CALIFORNIA

Costa Mesa Orange County

Computer Center (714)646-0221

Hayward The Byte Shop

(415) 537-2983

Hayward Computerland of

Hayward (415)538-8080

Lawndale The Byte Shop

(213)371-2421

Modesto Computer Magic

(209) 527-5156

Mountain View Digital Deli

(415) 961-2670

San Rafael The Byte Shop

(415)457-9311

Tarzana Byte Shop of Tarzana

(213) 343-3919

Walnut Creek The Byte Shop

(415)933-6252

COLORADO

Boulder The Byte Shop

(303) 444-6550

Denver The Byte Shop

(303)399-8995

FLORIDA

Ft Lauderdale . Byte Shop of

Ft, Lauderdale (305) 561-2983

Miami Byte Shop of Miami

(305) 264-2983

Tampa

Microcomputer

Systems Inc. (813) 879-4301

Atlanta Computer Mart (404) 455-0647

The Data Domain (312)397-8700

IOWA

Davenport , The Computer Store

of Davenport (319) 386-3330

GEORGIA

Atlanta

ILLINOIS

Schaumburg

MARYLAND

Towson Computers, Etc.

(301)296-0520

MICHIGAN

Ann Arbor The Computer Store of

Ann Arbor (313) 995-7616

MINNESOTA

Minneapolis Computer Depot

(612)927-5601

NEVADA

Reno Byte Shop of Reno

(702) 826-8080

NEW JERSEY

Cherry Hill Computer Emporium

(609) 667-7555

Iselin The Computer Mart of

New Jersey (201)283-0600

NEW YORK

Endwell

New York White Plains

The Computer Tree

(607)748-1223

... The Computer Mart of New York (212)686-7923

The Computer Corner (914)949-3282

NORTH CAROLINA

Raleigh ROMs N RAMs

(919) 781-0003

OHIO

Akron Basic Computer Shop

(216) 867-0808

Columbus The Byte Shop

(614) 486-7761

Dayton

OREGON

Beaverton

Eugene Portland

Computer Mart of

Dayton (513)296-1248

Byte Shop Computer

Store (503)644-2486

The Real Oregon

Computer Co (503) 484-1040

. . Byte Shop Computer Store (503)223-3496

RHODE ISLAND

Warwick

SOUTH CAROLINA

Columbia

Computer Power. Inc. (401) /38-4477

The Byte Shop (803) 771-7824

TENNESSEE

Kingsport Microproducts &

Systems (615) 245-8081

TEXAS

Arlington Computer Port

(817)469-1502

Houston Interactive Computers

(713) 772-5257

Lubbock Neighborhood Computer

Store (806)797-1468

VIRGINIA

McLean The Computer Systems

Store (703)821-8333

WASHINGTON

Bellevue Byte Shop Computer

Store (206) 746-0651

WISCONSIN

Madison The Madison Computer

Store (608)255-5552

Milwaukee The Milwaukee

Computer Store (414) 259-9140

WASHINGTON, D.C.

Washington, DC Georgetown

Computer Store (202)362-2127

CANADA

London, Ontario The Computer

Circuit Ltd (519) 672-9370

Toronto, Ontario Computer

Mart Ltd. (416) 484-9708

Vancouver B.C Basic Computer

Group Ltd (604)736-7474

Vancouver, B C Pacific Computer

Store (604)438-3282

AUSTRALIA

Victoria Sontron Instruments

(03) 569 7867

PHILIPPINES

San Juan, Metro Manila Integrated

Computer Systems, Inc.

JAPAN

Tokyo Moon base Shinjuku

(03) 375-5078 5079

H

m.

■*?

*IE

ProcessorTechn<

10 BY Tt |ul> 1978

§ §!•

ly

Circle 305 on inquiry card.

Letters

DESIGNERS BEWARE: SOME 2716 CONFUSION

I just came across a very untidy situation involving read only memory numbers which may be of interest to a great number of readers. We are all familiar by now with the advantages of the 2716 erasable read only memory; however, everyone should be aware that while the Intel version (and possibly others) requires only a single +5 V supply, Texas Instruments makes a similar device with identical memory organization, number TMS2716 that requires ±5 V and +12 V supplies. This part is designed to be pin compatible with the older 2708s. Texas Instruments has another part labeled TMS2516 which is pin compatible with an Intel type 2716, requiring only a +5 V supply. While this is assuredly somewhat bizarre, there seems to be argument amongst the two companies as to who claimed the name 2716 first. It is definitely something that many will be in need to be aware of.

David Marke

Solar Dynamics Ltd

3904 Warehouse Row, Suite C

Austin TX 78704

HOW TO STAY IN CIRCULATION

I was somewhat astonished (an understatement) to find, wrapped in the splendor of the March 1978 (I think) plain brown BYTE wrapper, an April 1978 Playboy. Now don't get me wrong, I enjoy looking at lovely ladies; in fact it is one of my most time consuming hobbies. However, 1 can pick up Hef's rag anywhere in Ottawa, and right now my computer needs more tips on operating than I do. So, if you would, I'd appreciate an issue of BYTE that matches the enclosed mailing sticker. Thank you.

Kevin Szabo

Box 86, Hillcrest Dr

RR #1, Manotick

Ontario CANADA KOA 2N0

WHERE TO GETTECO

Carl Helmers' editorial in the March 1978 BYTE, page 6, was interesting to me, since the LSI-11 can run the RT11 operating system, for which there is a version of real TECO (a superset of the old PDP6/PDP10 TECO) with most or all of the features he wants, plus ability to use floppies, etc. Sources for said TECO are available from DECUS for a minimal charge. I've worked on the

Continued on page 120

YOURS FOR ONLY

^149.95

Now, the first complete software oriented video system (theVB-IB.) is even morG versatile. The newly improved VB-1B Video Interface Board gives you 128 possible characters to play with. Graphics galore. Horizontal and vertical oscillators that operate within 1.6% of actual TV standards to get rid of wiggle, rolling and jitters. The VB-1B cuts snow by up to 50% and provides 8% left and right margins. And we'll give you a "Doodle" program so you can play around with graphic shapes on your own screen. Easy connection and adjustments . . , with the new VB-1B. Available—along with all our other S-100 bus compatible products—either from your local computer store or from us diroctiy.

r^r CI

iu

i.^.^L

2116 Walsh Avenue

B95050

Circle 335 on inquiry card

A Division of Solid State Music

Telephone (408) 246-2707

|uly 1978eiBYTt Publications Inc 11

,■4

KIMER: A KIM-1 Timer

Listing J: Combination digital cloc/i and timer program written for tine MOS Teclinology KIM-1 computer. The LED readout is used to display hours, minutes and seconds.

Address

Hexadecimal

Label

Op Code

Comments

Code

00 00

00

SETHR:

#00

01

00

SETMIN:

#00

02

00

CNTR;

#00

02 00

A5 00

START:

LDA

SETHR

Set starting time.

02 02

85 FB

STA

POINTH

02 04

A5 01

LDA

SETMIN

02 06

85 FA

STA

POINTL

02 08

A9 00

LDA

#00

02 OA

85 F9

STA

INH

02 OC

8D 03 17

STA

1703

Set PB7 as input.

02 OF

A9 04

LDA

#04

Set timer loop count.

02 11

85 02

STA

CNTR

02 13

A2 20

TIMER:

LDX

#20

Timer calibration.

02 15

CA

DELAY:

DEX

02 16

DO FD

BNE

DELAY

02 18

A9 F1

LDA

#F1

Start timer.

02 1A

8D OF 17

STA

170F

02 ID

20 IF IF

WAIT:

JSR

SCANDS

Display current time.

02 20

2C 07 17

BIT

1707

Wait for timer interrupt.

02 23

10 F8

BPL

WAIT

02 25

C6 02

DEC

CNTR

Decrement counter.

02 27

DO EA

BNE

TIMER

Finish second timeout.

02 29

F8

SEP

Set decimal mode.

02 2A

18

CLC

Clear carry.

02 2B

AO 00

LDY

#00

02 2D

A5 F9

LDA

INH

Get seconds.

02 2F

69 01

ADC

#01

Add 1.

02 31

85 F9

STA

INH

02 33

C9 60

CMP

#60

Check if next minute.

02 35

FO 04

BEQ

MIN

Branch if yes.

02 37

A2 19

LDX

#19

Set delay count.

02 39

DO 23

BNE

SET

Wait for next timer start

02 3B

84 F9

MIN:

STY

INH

Clear seconds.

02 3D

18

CLC

02 3E

A5 FA

LDA

POINTL

Get minutes.

02 40

69 01

ADC

#01

Add 1.

02 42

85 FA

STA

POINTL

02 44

C9 60

CMP

#60

Check if next hour.

02 46

FO 04

BEQ

HRS

Branch if yes.

02 48

A2 14

LDX

#14

Set delay count.

02 4A

DO 12

BNE

SET

Wait for next timer start

02 4C

84 FA

HRS:

STY

POINTL

Clear minutes.

02 4E

A2 10

LDX

#10

Set delay count.

02 50

18

CLC

02 51

A5 FB

LDA

POINTH

Get hours digits.

02 53

69 01

ADC

#01

Add 1.

02 55

85 FB

STA

POINTH

02 57

C9 24

CMP

#24

Check if next day.

02 59

DO 03

BNE

SET

Branch if not.

02 5B

84 FB

STY

POINTH

Clear hours.

02 5D

CA

DEX

Adjust delay count.

02 5E

D8

SET:

CLD

Clear decimal mode.

02 5F

A9 04

LDA

#04

Reset loop count.

02 61

85 02

STA

CNTR

02 63

4C 15 02

JMP

DELAY

Start next cycle.

Robert Baker 15 Windsor Dr Atco NJ 08004

This short program converts your KIM-l into a 24 hour digital clocl< and illustrates the use of the built-in timer for long time delays, and the use of instruction loops for shorter delays. The 7 segment displays are used for output, and are used in conjunction with one of the routines in the read only memory which drives them.

To use the internal timer, 10 pin PB7 of 6530-003 must be set as an input pin to allow testing of the timer interrupt. This is accomplished by setting bit 7 of the direction register (location 1703) to 0 before using the timer. The timer is started by loading it with the desired delay count, and the address used determines the timer frequency and whether or not to enable the timer interrupt. Bits 0 and 1 of the address select the timer frequency as 1, 8, 64, or 1024 us per timer count while bit 3 enables the timer interrupt if set to 1.

This clock program uses the internal timer for a time delay of approximately 250 ms. After four time delays (1 second), the current time is incremented by 1 and the timing cycle continues. Whenever the time count is being incremented, instruction timing delays are added where needed to keep all time delays constant for whatever program route is taken. An additional instruction delay is added within the 1 second timer to calibrate the timer to exactly 1 second. If your system clock is slightly slower or faster, you may have to adjust the timer count (location 0219) for about 1 ms increments and the calibration count (location 0214) for 4 jis increments.

To set the clock, enter the desired starting time hours in location 0000 and minutes in location 0001. To start the clock, set the program starting address (0200) and depress "GO" at the desired starting time (as set in locations 0000 and 0001). If the starting time is set as 0000 (hours and minutes), the program can be used to measure elapsed times for special applications by using the "ST" button to stop the program. For even fancier applications, you can add testing of an external switch to start and stop the clock. If you would rather have a 12 hour clock, simply change the contents of location 0258 from 24 to 1 2.»

«: >

* I

12

July 1978 O BYTE Publication! Inc

Hie Computer for the Professional

The 8813 was built with you, the professional, in mind.

It quickly and easily processes cost estimates, payrolls,

accounts, inventory, patient/client records and much

more. You can write reports, briefs, and proposals on

the 8813's typewriter keyboard, see them on the video

screen, and instantly correct, revise, or print them.

Using the 8813, one person can process what would

normally require many secretaries, several bookkeepers,

and a great deal of time. And data storage takes a small

fraction of the space used by previous methods.

You don't need to learn complicated computer languages. The 8813 understands commands in EngUsh. If you want to write your own programs, the 8813 includes a simple computer language, BASIC, that you can master in a few days. The 8813 slashes the professional's overhead. It's a powerful time and money-saving ally. Prices for complete systems including printer start at less than $8,000.

See the 8813 at your local dealer or contact PolyMorphic Systems, 460 Ward Drive, Santa Barbara, California, 93111, (805) 967-0468, for the name of the dealer nearest you.

PolyMorphic Systems

BYTE July 1978

13

WliyApplel] St selling pei

h the VTorlcTs l>iial comimter.

rhich personal computer will be most enjoyable and rewarding for you? Since we delivered our first Apple® II in April, 1977, more people have chosen our computer than all other personal computers combined. Here are the reasons Apple has become such an overwhelming favorite.

Apple is a fully tested and assembled mainframe computer. You won't need to spend weeks and months in assembly. Just take an Apple home, plug it in, hook up your color TV* and any cassette tape deck—-and the fun begins.

To ensure that the fun never stops, and to keep Apple working hard, we've spent the last year expanding the Apple system. There are new peripherals, new software, and the Apple II Basic Programming Manual. And wait till you see the Apple magazine to keep

owners on top of what's new. Apple is so powerful and easy to use that you'll find dozens of applications. There are Apples in major universities, helping teach computer skills. There are Apples in the office, where they're being programmed to control inventories, chart stocks and balance the books. And there are Apples at home, where they can help manage the family budget, control your home's environment, teach arithmetic and foreign languages and, of course, enable you to create hundreds of sound and action video games.

When you buy an Apple II you're investing in the leading edge of technology. Apple was the first computer to come with BASIC in ROM, for example. And the first computer with up to 48K bytes RAM on one board, using advanced, high density 16K devices. We're working to keep Apple the most up-to-date personal computer money can buy. Apple II delivers the features you need to enjoy the real

satisfaction a personal computer can bring, today and in the future. *

& hi-resolutjon « graiihics.too.

Don't settle for a black and white display! Connect your^ Apple to a color TV and BASIC gives you instant , command of three display modes: Text, 40h x 48v * Color-graphics in 15 colors,, and a 280h x 192v High

Resolution " array that lets you plot graphs and compose ' 3-D images. ^ Apple gives you the addedcapability of combining text and graphics, too.

Back to basics, and assembly lan^ua^ too.

Apple speaks three languages: fast ^ integer BASIC, floating point BASIC ^ for scientific and financial applications, and 6502 assembly language. That's ■" maximum programming flexibility. And, a to preserve user's space, both integer BASIC and monitor are permanently stored in 8K bytes of ROM, so you < have an easy-to-use, universal language instantly available. BASIC gives you graphic commands: COLOR=, VLIN, ^ HLIN, PLOT and SCRN. And direct memory access, with PEEK, POKE and CALL commands. -•

Software: Oufs and yotns.

There's a growing selection of preprogrammed software from the Apple , Software Bank—Basic Finance, Checkbook, High Resolution Graphics and more. Now there's a User Section in our bank, to make it easy for you to obtain programs developed

A

/

^ by other Apple owners. Our Software Bank is your link to Apple owners all over the world.

Alive with the sound of music.

Apple's exclusive built-in speaker delivers the added dimension of sound to your programs. Sound to compose electronic music. Sound to liven up games and educational programs. Sound, so that any program can "talk" back to you. That's an example of Apple's "people compatible" design. Another is its light, durable injection-molded case, so you can take Apple with you. And the professional quality, typewriter-style keyboard has n-key rollover, for fast, error-free operator interaction.

Apple is tiie proven computer.

Apple is a state-of-the-art single board computer, with advanced LSI design to keep component count to a minimum. That makes it more reliable. If glitches do occur, the fully socketed board and built-in diagnostics simplify troubleshooting. In fact, on our assembly line, we use Apples to test new Apples.

*Apple II plugs into any standard TV using /

an inexpensive modulator (not included).

*ln California, call 408/996-1010.

4

Apple peripherals are smart peripherals.

Watch the far right column of this ad each month for the latest in our growing family of peripherals. We call them "intelligent interfaces." They're smart peripherals, so you can plug them in and run them from BASIC without having to develop custom software. No other personal computer comes close to Apple's expandability. In addition to the built-in video interface, cassette I/O, and four A/D inputs with two continuously variable game paddles, Apple has eight peripheral slots, three TTL inputs and four TTL outputs. Plus a powerful, state-of-the-art switching power supply that can drive all your Apple peripherals.

Available now.

Apple is in stock and ready for delivery at a store near you. Call us for the dealer nearest you. Or, for more details and a copy of our "Consumer's Guide to Personal Computers," call

800/538-9696** or write Apple Computer, Inc., 10260 Bandley Drive, Cupertino, CA 95014.

ulry card.

g|npplG computer

Programming is a snap! I'm halfway through Apple's BASIC manual and already I've programmed my own space wars game.

Those math programs I wrote last week-1 just rewrote them using Apple's mini-assembler and got them

to run a hundred times faster

New from Apple.

Introducing Disk IP: instant access to your files.

Our newest peripheral is Disk II, a high-deiisity 5V4" floppy disk drive for fast, lowcost data retrieval. It's perfect for storing large bodies of data such as household finances, address files and inventories; you can find any record in just half a second. No more searching through stacks of cassettes; with a few keystrokes, your system will load, store and run any file by name.

Disk II consists of

interface cards and fourteen drives, for control of nearly 1.6 megabytes of data, with no expansion chassis. The combination of ROM-based bootstrap loader and an operating system in RAM provides complete disk handling capability, including these special features:

• Soft sectored • Random or sequential file access • Program chaining capability

• Universal DOS command processor works with existing languages and monitor

• Full disk capability in systems with as little as 16K RAM • Storage capacity: 113 kilobytes/diskette.

See Disk II now at your Apple dealer. Sold complete with controller and DOS at $495.t

Peripherals in stock

Hobby Board (A2B0001X), Parallel Print( Interface (A2B0002X), Communication Ii terface (A2B0003X), Disk II (A2M0004X

Coming soon

High speed Serial Interface, Printer II, Printer IIA, Monitor II, Modem IIA.

' Price subject to change without notice.

Circle 15 on inquiry c

Apple's smart peripherals make

expansion easy. Just plug 'em in ai

they're ready to run. I've already

added two disks, a printer and f^

communications card.

The Second West Coast Computer Faire

Photo 1: Some of the

14,000+ crowd amble by a young hacker programming music on a Video Brain computer.

By Chris Morgan, Editor

San Jose was the place to be last March 3, 4 and 5 for the Second West Coast Computer Faire. The Convention Center was easily able to handle the crowd of 14,169 who came to see the latest developments in personal computing.

A quick examination of some of the hundreds of manufacturers' booths revealed some trends: floppy disks are on the increase, with new models being shown or promised by Heathkit, Apple, Radio Shack and many others; more and more personal computers are now being offered with builtin floppy disks; peripherals and add-ons are

2: Robot trials at

mabyte booth, a

attraction at the

West Coast Com

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13: IBM's booth, an [us addition to the

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Photo 4: Ira Baxter's chess playing system display, which competed in the Microcomputer Chess Tournament at the Faire.

\

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ri

Photo 5: Apple Computer's new minifloppy drive.

's Larry Weinstein displays Star Wars graphics.

now available for a wide variety of computer buses.

I enjoyed the many special features of the show, particularly the excellent computer generated art on display in the lobby. The microcomputer chess tournament proved to be one of the hits of the show. Larry Wagner from Atari presided over the 3 day battle of the processors, taking time out to give me a guided tour of the tournament. The level of play was impressive, and the winning program, called SARGON, was a 16 K byte Z-80 assembler program written by a husband and wife team, Kathe and Dan Spracklen. It beat some highly touted com

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Hardware. Software. Peripherals. We've got the best in the business!

P.O. Box 6528 Denver, CO 80206 (303) 777-7133

Photo 7: Heath's new H27 dual floppy drive, scheduled to be available later this year.

.1 4

Photo 8: Students from Mills College Center for Contemporary Music in Oakland demonstrate- a digital and analog hybrid music synthesizer system, one of many special exhibits at the Faire.

petition. (A copy of the SARGON program is available for $15 postpaid from the Spracl<lens, 10832 Macouba PI, San Diego CA92124.)

I was impressed with the professional appearance of the show, which held its own with many of the established engineering and computing shows. The Third West Coast Computer Faire will be held this coming November 3, 4 and 5 in Los Angeles. Plan to see it if you can."

Photo 9: Cromemco color video unit displays chess program at the Computer Room of San Jose booth.

20 July 1978 (S BYTE Publicalions Inc

NORTH STAR 16K RAM A star from our Horizon

^ ■ri*'''''r"'

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aeisffiii

-W- ■ I

illiiiiiiiiiiiriiiimiiimiiiihliiiiiiimliilir

• ..t..fiMti)iliM*>IMMI«IIIMIIMIMMIIIIII)M

The North Star 16K RAM board is a star performer in our HORIZON computer. Just as important, it is the ideal memory for most other S-100 bus systems. No other RAM board can surpass the speed, reliability, and quality features of the North Star 16K RAM at any price.

SPEED —The North Star 16K RAM is the fastest S-100 bus memory board available. No wait states are required, even with a Z80 at 4MHz. And, of course, this outstanding 16K RAM will operate with both 8080 and Z80 processors at 2MHz. Industry standard 200ns dynamic RAM chips are used. Invisible on-board refresh circuitry allows the processor to run at full speed.

RELIABILITY — The North Star 16K RAM is designed to match the same high standards as our MICRO DISK SYSTEM and HORIZON computer. For example, all address and data signals are fully buffered. A parity check option is available with the 16K RAM for applications requiring immediate hardware error detection. If a memory

error occurs, a status flip/flop is set and an interrupt can inform the processor. Or, if preferred, an error status light will go on.

FEATURES —The North Star 16K RAM offers many desirable features. Addressability is switch-selectable to start at any 8K boundary. The board can perform bank switching for special software applications, such as timesharing. Also, bank switching can be used to expand the amount of RAM beyond 64K bytes. Power consumption is minimal — the maximum power requirements are: .6A @ 8V; .4A @ -h16V, and .1A @ -16V.

PRICES — $399 kit. $459 assembled, tested and burnedin. Parity option: $39 Kit. $59 assembled, tested and burned-in.

Write for free color catalog or visit your local computer store.

North Star * Computers

2547 Ninth Street • Berkeley, California 94710 • (415) 549-0858

Circle 285 on inquiry card.

BYTE luly 1978

21

fe,*f;.'> .■:'-•■

Apfrficatlons Programs for your p®fs<mal comfHit^

INTRODUCING THE G2 PROGRAM

LIBRARY.

Now you doiTt hove 1o be a programmer 1o use

WAIII' COIHIlllltPf I ^* ^^ there's a reliable, professional source of useful and entertaining F '^"' %%r ■ ■ ■!# W ■%#■ • programs for your personal computet The G2 Program Library from GRT unlocks the full power of your personal computet Without any programming knowledge on your part ^ The G2 Program Library consists of applications programs pre-recorded on cassette tapes. A detailed manual

with each cassette provides complete instructions. And G2 programs contain prompting instructions. So they're easy to use every step of the way. Just load the tape and 02 puts your computer to work.

The first three G2 program tapes are available now: For exciting family games, get Beat the House. You'll find ^i Blackjack, Craps, Roulette and Slot Machine programs, with truly random chances and realistic, casino-hlffi payoffs. Interested in your health? You'll want Ginic Biorhythms, Dieting and Longevity programs give you new perspectives in health and happiness, along with some pleasant guidelines to foUow.

Need a better handle on your money? Buy Personal Finance. Qieckbook is a comprehensive program to balance your account and keep within your budget, while Best Choice is a novel way to make decisions based on the facts you know and the relative importance of each. Use it for everything from choosing a new car to If selecting your next stereo.

Soon, every dealer that handles personal computers will stock the G2 Program Library. For the G2 dealer 1^ nearest you, call us toll-free at 800/538-1770. (In California, 800/662-9810.) And if your favorite computer outlet doesn't yet offer G2, have him call the same numben

G2 is the newest product Une from GRT, the world's largest independent producer of pre-recorded tapes. We've assembled a team of software specialists to produce the G2 Program Library. The fbest library of personal computer ■> programs available.

j^ Soon you'll see G2 program tapes in many other fields of interest Including advanced programs to challenge

[ the interest of even the most serious computer usen The G2 IVogram i Library is available for most popular brands of personal computers. Just select the package marked for the computer you own.

Start building your G2 Program Library now. And put the full power of your computer to . work for you. THE REASON

^ YOU BOUGHT

^ YOUR COMPUTER. I

CRT

A product of GRT Corporation Custom Products Division

1286 North Lawrence Station Road r^^ „i„ i/io „ • _i nn

Sunnyvale, California94086 Circle 148 on inquiry card. BYTE |uiy W8 23

There's an Ohio Scientific dealer near you.

ALABAMA M.C.S. Corp. Pelham Mall Pelham, AL 35124 (205)663-1287

ALASKA

Scientific Business Instr's 500 W. 27th

Anchorage, AK 99503 (907) 277-2650

CALIFORNIA

Expansion Techniques 2534 Ganesha Altadena, CA 91001 (213) 794-0476

Shuey Aircraft 1009 E. Vermont Anaheim, CA 92805 (714)991-3940

Olson Electronics 11332 East South Cerritos, CA 90701 (213)860-0060

Computer Power 1276 Via Rancho Escondido, CA 92025 (714)746-0064

Adventures in Computing

8756 Warner

Fountain Valley, CA 92706

(714)848-8388

Olson Electronics 4642 West Century Inglewood, CA 90304 (213)674-5740

Olson Electronics Kearny Mesa, 4840 Convoy San Diego, CA 92111 (714)292-1100

Systems Engineering

900 3rd Street

San Francisco, CA 94107

(415)777-3150

Olson Electronics 2125 El Camino Real Santa Clara, CA 95051 (408) 248-4886

COLORADO

Total Data Systems 125 Fairway Lane Fort Collins, CO 80521 (303)491-5692

Tricomp/Computer Country 7115 N. Federal Westminster, CO 80030 (303) 426-7743

Delaware Microsystems 92 East Main #1 Newark, DE 19711 (302) 738-3700 (after 7 PM)

FLORIDA Olson Electronics 5833 Ponce de Leon Coral Gables, FL 33146 (305) 666-3327

Olson Electronics 1644 N. E. Second Miami, FL 33132 (305)374-4121

Calculator Place 12 South Orange Sarasota, FL 33577 (813)366-7449

Olson Electronics

6901 22nd Avenue, N,

Tyrone Square Mall

St. Petersburg, FL 33710

(813)345-9119

Olson Electronics 1215 South Dale Mabry Tampa, FL 33609 (813)253-3129

GEORGIA

Electronic Information 120 Heatherwood Athens, GA 30601 (404) 353-2858

Secom Systems 5241-F New Peach Tree Chamblee, GA 30341 (404) 455-0672

Olson Electronics 2571 N. Decatur Decatur, GA 30033 (404) 378-4201

HAWAII

Small Computer Systems 3140 Wailalae Honolulu, HI 96816 (808) 732-5246

ILLINOIS

American Microprocessors

1100 E. Broadway

Alton, IL 62002

(618)465-4489

Tech-Tronics 714 S. University Carbondale, IL 62901 (618)549-8495

Adonis Computing 2855 W. Nelson Chicago, IL 60618 (312)463-0847

Electronic Systems 611 N.Wells Chicago, IL 60610 (312)944-6565

Olson Electronics 4101 N. Milwaukee Chicago. IL 60641 (312)545-7336

Olson Electronics

1734 0gden

Downers Grove, IL 60515

(312)852-9650

A & H Associates, Ltd. 2530 Crawford Evanston, IL 60602 (312)328-2800

No-Name 2701 Grand Galesburg, IL 61401 (309)343-6135

CompuTermlnal Systems,Inc. 1132 Waukegan Glenview, IL 60025 (312) 724-3690

Tek-Aids Industries 1711 Chestnut Glenview, IL 60025 (312)724-2620

American Microprocessors 6934 N. University Peoria. IL 61614 (309) 692-5852

American Microprocessors 20 N. Milwaukee Pralrieview, IL 60069 (312)634-0076

Wysocki Electric 3080 South Blvd. Rockford, IL 61109 (815)874-4846

Data Domain 1612 E. Algonquin Schaumburg, IL 60195 (312)397-8700

INDIANA

American Microprocessors 146 N. Broad Griffith, IN 46319 (219)924-7901

American Microprocessors 3602 East Washington Indianapolis, IN 46201 (317)359-7445

American Microprocessors 2655 Irving Portage, IN 46368 (219) 760-2278

Computer Management 610 Monroe LaPorle, IN 46350 (219)362-5812

Data Domain 406 S. College Bloomington.lN 46401 (812)334-3607

Data Domain 7027 N. Michigan Indianapolis, IN 46268 (317)251-3139 Data Domain 10 N. Third

LaFayette, IN 47902 (317)423-2548

Olson Electronics 5353 N. Keystone Indianapolis, IN 46220 (317)253-1584

IOWA

American Microprocessors 102 E. 4th

Waterloo, lA 50703 (319) 296-2255 John E. Chllds 1201 E. Second Ohumwa, lA 52501 (515)682-2165

Microbus

1910Mt. Vernon, S. E. Cedar Rapids, lA 52403 (319) 364-5075

KANSAS

Barney & Associates

425 N. Broadway

Pittsburg, KS 66762

(316)231-1970

Technigraphics 5911 Claredon Wichita, KA 67220 (316) 744-2443

KENTUCKY

Data Domain 3028 Hunslnger Louisville, KY 40220 (502) 456-5242

Olson Electronics 117 Southland Lexington, KY 40503 (606)278-9413

Olson Electronics 4137Shelbyville Louisville, KY 40207 (502) 893-2562

MARYLAND

Systems Engineering 1749 Rockvllle Pike #307 Rockville, MD 20842 (301)468-1822

The Mathbox

4431 Lehigh

College Park, MD 20740

(301)277-6828

MASSACHUSETTS Bradshaw Enterprises 18 Harborvlew Hingham, MA 02043 (617)749-6844

Computer Shop-Aircom 288 Norfolk

Cambridge, MA 02139 (617)661-2670

MICHIGAN

The Abacus

Route 1, Box 193

Niles Road

Berrien Springs, Ml 49103

(616)429-3034

Concept Engineering 3706 Mallbu Lansing, Ml 48910 (517)394-0585

Great Lakes Photo 5001 Eastman Midland, Ml 48640 (517)631-5461

Microcomputer World 313 Michigan N. E. Grand Rapids, Ml 49503 (616)451-8972

Olson Electronics

29121 DeQuindre

Madison Heights, Ml 48071

(313)546-0190

MINNESOTA

Custom Computer Systems

1823 Lowry

Minneapolis, MN 55411

(612)588-3944

Micro Business Sales 4345 Lyndale N. Minneapolis, MN 55412 (612)871-9230

MISSISSIPPI

Jack Fisher Sales

100 Main

Michigan City, MS 38647

(601)224-6470

MISSOURI

The Computer Bit

1320 S. Glenstone

Springfield, MO 65804

(417)883-2709

Computer Place Rt. #4, Box 91-D Joplin, MO 64801 (417)781-1986

Futureworld 1909 Seven Pines St. Louis, MO 63141 (314)434-1121

Impact Systems

Decker Building

613 W. 3rd

P.O. Box 478

Lee's Summit, MO 66463

(816)524-5919

Norman Electronics

402 Wall

Joplin, MO 74801

(417)724-0368

MONTANA

Linco

P.O Box 2418

Cut Bank, MT 59427

(406)336-3117

NEBRASKA

Omaha Computer Store 4540 South 84th Omaha, NB 68127 (402) 592-3590

NEW JERSEY

Computer Corner 224 Passaic Fairfield, NJ 07006 (201)835-7080

Computer Power 235 Nutley Nutley, NJ 07110 (201) 667-5502

NEW YORK

Associated Consultants

33 Ogden

East Williston, NY 11596

(516)746-1079

Brag Microcomputers 19 (Cambridge Rochester, NY 14607 (716)442-5861

Computer Mart of N. Y.

118 Madison

New York, NY 10016

(212)686-7923

Microcomputer Workshop 234 Tennyson Terrace Williamsvllle, NY 14221 (716) 632-8270

Ylngco

Two World Trade Center

Penthouse 107th Floor

New York, NY 10048

(212)775-9000

OHIO

Byte Shop 2432 Chester Columbus, OH 43221 (614)486-7761

Johnson Computer 123 W.Washington Medina, OH 44256 (216)725-4560

Lucas Office Equipment

& Service 869 E. Franklin Centerville. OH 45469 (513)433-8484

Olson Electronics 69 West State Akron, OH 44308 (216) 7620301

Olson Electronics 1994 Brittaln Akron, OH 44310 (216)633-4338

Olson Electronics 3265 W. Market Akron, OH 44313 (216)864-3407

Olson Electronics 2020 Euclid Cleveland, OH 44115 (216)621-6387

Olson Electronics 6813 Pearl

Cleveland, OH 44130 (216)845-2424

Olson Electronics 6153Mayfleld Cleveland, OH 44124 (216)449-2690

Olson Electronics 21850 Center Ridge Cleveland, OH 44116 (216)331-4600

Olson Electronics 1975 Henderson Columbus, OH 43220 (614)451-3245

Otson Electronics 7401 Market Southern Park Mall Youngstown, OH 44512 (216)758-3828

OKLAHOMA

Accounting Systems 2709 Orlando

Oklahoma City, OK 73120 (405)751-1537

Gauger Engineering 910 Orient Clinton, OK 73601

Gauger Engineering 3824 S. 79th East Tulsa, OK 74145 (918)627-1064

OREGON

Flal Computer 11013 S. E. 52nd Milwaukle, OR 97222 (503) 654-9574

PENNSYLVANIA

Abacus Data Systems

Route 8

Reno, PA 16343

(814)677-6502

Olson Electronics 5918 Penn

Pittsburgh, PA 15206 (412)362-1333

Olson Electronics 3405 Saw Mill Run Pittsburgh, PA 15227 (412)881-0702

Olson Electronics 4778McKnlght Pittsburgh, PA 15237 (412)366-7298

TENNESSEE

Computer Power of Memphis 3065 James Memphis, TN 38128 (901)386-9905

Computer Powerof Oak Ridge 800 Oak Ridge Turnpike Oak Ridge, TN 38730 (615)4829031

Smart Machine Mart Sd

5151 Hlllson {

Nashville, TN 37211 i

(615)833-9773 A

SOUTH DAKOTA Exe Engineering 804 E. Lewis Vermillion, SD 57069 (605)624-6411

TEXAS

Mr. Computer

744 FM 1960 W, Suite E

Houston, TX 77090

(713)444-7419

UTAH

Small Computer Systems

4450 Trinity

Salt Lake City, UT 84120

(801)967-7635

VIRGINIA

H/B Computers

217 E. Main

Charlottesville, VA 22101

(804)295-1975

Microsystems, Inc. 5320 Williamson Roanoke, VA 24012 (703) 563-0693

WASHINGTON

Ye Olde Computer Shoppe 1301 George Washington Richland, V\iA 99352 (509) 946-3330

WISCONSIN

Madison Computer Store

1863 Monroe

Madison, Wl 53711

(608) 255-5552

MicroComp

785 S. Main

Fond du Lac, Wl 54935

(414)922-2515

Olson Electronics 3125 South 108th West Allls, Wl 53227 (414)541-1406

WYOMING

Control Technology 204 Crazy Horse Lane Gillette, WY 82716 (307) 682-0300

CANADA

Omega Computing Ltd.

Box 220

Station P

Toronto, Ontario

Canada M5S 2F7

(416) 425-9200

Robo-Tronics 509 16th N. W. Calgary, Alberta Canada T2M 0J6 (403) 282-9468

f IIROPF

Pan Atlantic Computer

System GmbH 61 Armstadt Frankfurterstrasse 78 West Germany

^

24

BYTE July 1978

Circle 290 on inquiry card.

The

C2-8P

* An exceptional value in personal computing

ennuBuan n

If you are interested in an ultra high per[formance personal computer which can be fully expanded to a mainframe class microsomputer system, consider the C2-8P.

Features:

Minimally equipped with 8K BASIC-in-ROM, 4K RAM, lachine code monitor, video display interface, cassette iterface and keyboard with upper and lower case |haracters. (Video monitor and cassette recorder optional <tras.)

The fastest full feature BASIC in the microcomputer gdustry.

Boasts the most sophisticated video display In perpnal computing with 32 rows by 64 columns of upper jse, lower case, graphics and gaming elements for an ef:tive screen resolution of 256 by 512 elements. 'The CPU's direct screen access, coupled with its ultra yt BASIC and high resolution, makes the C2-8P capable |spectacular video animation directly in BASIC, -ully assembled and tested; 8 slot mainframe class procomputer, six open slots for expansion. Supports Jo Sclentific's ultra low cost dynamic RAM boards or I high reliability static RAMs.

The C2-8P can support more in-case expansion than its four nearest competitors combined.

The C2-8P is the only BASIC-in-ROM computer that can be directly expanded today to a complete business system with line printer and 8" floppy disk drives.

It is the only personal class computer that can be expanded to support a Hard Disk! (CD-74)

The C2-8P is the fastest in BASIC, has the most sophisticated video display and is the most internally expandable personal computer. Therefore, it should be the highest priced?

Wrong: The C2-8P is priced considerably below several models advertised in this magazine. The C2-8P is just one of several models of personal computers by Ohio Scientific, the company that first offered full feature BASIC-in-ROM personal computers.

For more Information, contact your local Ohio Scientific dealer or the factory at (216) 562-3101.

1333 S. Chillicothe Road • Aurora, Ohio 44202

-BYTE July 1978 25

The C3-B

by Ohio Scientific

The worid's most powerful

microcomputer system

is far more affordable

than you may thinic:

STANDARD FEATURES:

■ 74 million byte Winchester technology disk drive yields mainframe class file access speeds and capacity.

18 High level data file software makes high performance file structures like multikey ISAM easy to use.

S Triple processor CPU with 6502A, 6800 and Z-80 gives the programmer the best of all worlds in performance and versatility.

■ Switchable and programmable CPU clocks at 1, 2 and 4 MHz yield maximum performance from each microprocessor.

J

1 1

-V

\

■ The included 6502A based extended disk BASIC by Microsoft out-benchmarks every micro available, including 4 MHzZ-80 and LSI-11 with extended arithmetic.

■ 48K of high reliability static RAM is standard.

■ High density 8" floppys provide program and data mobility from machine to machine.

■ Completely integrated mechanical system with UL-recognized power supplies; continuous duty cycle cooling; modular construction and rack slide mounted subassemblies.

■ Based on a 16 slot Bus-oriented architecture with only 7 slots used in the base machine.

■ Directly expandable to 300 megabytes of disk, 768K of RAM in 16 partitions, 16 communication ports, plus console and three printers.

i» C3-B's have been in production since February, 1978, and are available now on very reasonable delivery schedules.

The C3-B was designed by Ohio Scientific as the state of art in small business computing. The system places its power where it's

needed in the small business environment; in the data files. The C3-B's advanced Winchester technology disk, coupled with its smart controller and dedicated high speed memory channel, gives the C3-B data file performance comparable with today's most powerful maxi-computers.

The system can easily expand upward from single user to multiuser operation. Optional hardware and software include a real time clock and a 16 terminal (plus console) real time operating system. Multiple terminal programs such as multi-station order entry can be programmed directly in BASIC. The system is super fast because multiterminal I/O can be handled simultaneously with disk I/O due to the smart disk controller!

By simply adding memory in the alternate partitions, the system can be expanded to full multi-tasking, multi-programming operation. The multi-terminal hardware supports both asynchronous and synchronous protocols in conjunction with terminals and smaller computers such as Ohio Scientific's BASICin —ROM and floppy disk based systems at transfer rates up to 500K bits per second.

■ The C3-B costs only slightly more than many floppy only computers but offers at least a thousand times performance improvement over such machines (50 times storage capacity multiplied by 20 times access speed improvement).

But what if your business client cannot justify starting with a C3-B? Then start with Ohio Scientific's inexpensive C3-S1 floppy disk based system running OS-65U. When he is ready, add the CD-74 big disk and directly transfer programs and files from floppy to big disk with NO modifications.

That's upward expandability!

*Rack as shown on right complete with 74 megabyte disk, dual floppys, 48K of static RAM, OS-65U operating system and one CRT terminal under $13,000.

Multiple terminal systems with printers and applications software are priced in the mid-20's.

1333 S. Ghillicothe Road • Aurora, Ohio 44202

BYTE luly 1978 27

Photo 1: The Axiom EX800 printer. It uses special aluminizedpaper; when a tiny electrical spark jumps from the print head to the paper, the layer of aluminum is burned off revealing the next layer which is darkly colored. Printing speed is a maximum of J 60 characters per second including upper and lower case letters. The printer allows 80 column page width and quadruple width characters.

The Axiom EX800 Printer:

A User's Report

--« i i I

nr, :_. L- !^ - i_! ri

-=1. ts i~ sj a^ T

'! M ki n o n

!■ i U V i!> K Y ci a I! i_ d t T y h t -3 k I !i! T! -_! s--- 1 ! - i i ^ 5—= f- 5^-? r^- -== I

_3 ri L m Ti O F' '^ r" :S "t

Figure I: A sample printout of the Axiom EX800 printer. This sample was made by photographically reproducing the original silver colored paper image ata J:l scale.

28 July 1978 © BYTE Publicjtions Inc

R J Bosen

POB93

Magna UT 84044

Some time ago I decided I needed a hard copy printer to make my computer system really useful, but as I looked over the possibilities on the market I concluded that every alternative was either too expensive, too slow, or too limited in capability for my needs (which included good legibility and lower case printing).

Just as I was about to abandon my plans, I saw a press release concerning a company called "Axiom" and a printer that appeared to solve all of my problems. It was advertised at $660, could print up to 160 characters per second (including upper and lower case letters) with an 80 column page width, and offered double and quadruple width characters as a bonus. 1 immediately wrote to Axiom and was surprised to receive a thick information packet within a week.

My first (and only) disappointment came as I discovered that the 80 column page width was squeezed onto a 5 inch roll of special paper which was a little hard to read, but other features of the printer looked promising enough to justify further investigation, so I experimented with the printout sample they sent me to see if ! could find ways around these annoyances. I went to a photocopy center and found it was quite easy to get very sharp copies which were much more readable than the original. I decided that if the narrow page width became a serious problem I could write software to split a wide page into two 5 inch columns and print a page in two passes. Experimenting with the photocopier confirmed the feasibility of this idea as I successfullly laid two 5 inch pieces of the sample printout side by side and obtained the illusion of a 9 inch page width.

I phoned the desk at Axiom to place my order; ten days later the printer was in my hands. I opened it up to reveal an Intel 4004 processor controlling an electrosensitive printing mechanism that works with special paper, consisting of a layer of paper, a layer of ink, and an aluminum upper layer. The print head strokes across the paper and burns the aluminum off in tiny dots, exposing the ink underneath in patterns stored in the processor read only memory. The processor controls character size and line length, allowing very flexible mixing of character sizes anywhere on any line and giving automatic line feeds when the end of the line has been reached. Other benefits of the

I

3

i

*■ f

t

microprocessor control include a self-test feature activated by pushing a button on the back panel which prints a test pattern on the paper, and a convenient parallel interface with simple handshai<ing. A serial interface is optional.

I found the documentation very complete and readable and had no trouble interfacing with my parallel data port and writing driver software in a couple of dozen bytes. Trying it out on line proved to be a rewarding experience; my interface and driver software worked the first time. I was finally able to try out the many ideas I had been considering while waiting for shipment. I noticed the effect of the 128 character buffer that Axiom provided: short printouts require almost no processor time, as the parallel interface transfers data from the processor memory to the printer buffer very fast and the processor is immediately freed to do other jobs. I was pleased with the quietness. It is not as loud as a Teletype even though it is about 14 times faster. It didn't take me long to discover the buzzer that can be activated by a special character, and I have learned to use it for special effects in game programs even when the printer is not needed.

The only problems I have ever had with this printer have been concerned in one way or another with the paper. This is not to imply that I have had a lot of problems. I haven't. But finding a supplier for paper was a problem for me in Salt Lake City. I called every paper supplier in the phone book and I couldn't get anyone to even recognize the existence of "electrosensitive" paper. Fortunately, within a few weeks I found myself in DePere Wl repairing a computer system for my employer, and while there I took a tour of the Nicollet Paper Company, where the electrosensitive paper is made. They sold me a case of 24 rolls of the special paper at about $3 a roll and let me look at some of the experimental paper they are developing for use by electrosensitive printers. This new paper is much whiter than the silver grey originally shipped to me and I am anxious to see it introduced in production quantities.

I am very pleased with the Axiom EX800 printer, and I recommend it to anyone who needs a printer of this nature. Incidentally, Axiom also has a similar printer with a graphics capability that may be of interest to experimenters. You can obtain more information by writing to Axiom Corporation, 425 E Green St, Pasadena CA 91101 .■

The LFD-400 is ready to plug in and run

the moment you receive it.

Nothing else to buy! Not even extra memory!

YOU GET:

O The popular ShugartSA 400 minifloppy™ drive. Drive alignment

is double checked by PerCom before shipment. O The drive power supply—fully assembled and tested. Q LFD-400 Controller/Interface—plugs into the SS-50 bus •

accommodates tfiree 2708 EPROMs • fully assembled and tested. O MINIDOS™ —the remarkable LFD-400 disk operating system on

a 2708 EPROM • plugs into the LFD-400 Controller card • no

extra memory required • no "booting" needed. O Attractive metal enclosure.

O Interconnecting cable—fully assembled and tested. O Two diskettes—one blank, the other containing numerous

software routines including patches for SWTP 8K BASIC and the

TSC Editor/Assembler O 70-page instruction manual—includes operating instructions,

schematics, service procedures, and the complete listing of

MINIDOS™. ® Technical Memo updates—helpful hints which supplement the

manual Instructions. ® 90-day limited warranty.

Minifloppy is a trademark of Sfiugart Associates. tvllNIOOS is a tfademarl( of PERCOM Data Company, Inc.

The LFD-400 Is readily expanded to either two or ttiree drives. Write for details. Send for our free broctiure for more information about the LFD-400 Floppy Disk System and LFD-400 software.

To save you money, the LFD-400 Floppy Disk System is available only from PerCom. Because of the special pricing, group and dealer discounts are not available.

MC and VISA welcome. COD orders require 30% deposit plus 5% liandling charge. Allow three extra weeks if payment is by personal check. The LFD-400 Floppy Disk System is available immediately. Allow three weeks for testing and transportation. Texas residents add 5% sales tax.

PEFQOM

PERCOM DATA COMPANY, INC.

Dept B 318 BARNES'GARLAND, TX. 75042 (214) 272-3421

PERCOM™ 'peripherals for personal computing'

Circle 301 on inquiry card.

)uly 1978©BYTE Publicitions Inc

29

COOK BOOK • ASSEMBLER • __ MONITOR • POCKET GUIDE • TAPES UNDERSTANDING MICROCOMPUTERS COOK BOOK • ASSEMBLER • EDITOR ^OR • POCKET GUIDE • TAPES . ^II^NDING MICROCOMPUTERS ASSEMBLER • EDITOR OCKET GUIDE • TAPES NG MICROCOMPUTERS ASSEMBLER • EDITOR JCET GUIDE • TAPES MICROCOMPUTE

Order your SCELBI Personal Computer Books and Tapes today! They are "must" Items for your collection. And, they make ideal special occasion gifts for that computer buddy too!

f cEUi coNPunn

CONIUUINO INC.

Prices shown for North American customers. Master Charge, VISA, Postal and Bank Money Orders preferred. Personal checks delay shipping up to 4 weeks. Pricing, specifications, availability subject to change without notice. IMPORTANT! Include 750 postage/ handling for each item delivered by U.S. Mail Book Post Office Box 133 PP STN, Department B, MilfOrd, CT 06460 Rate; or $2 for each item shipped First Class or UPS.

i

1

BYTE July 1978

■^

f^y

SCELBTS 8080

STANDARD

scan HBnin

\ CltlKTIH MC.

°""n and Skill to your ^« '

I ■... . ...^■..^.:^.-.........H ^°"'^computer.

Scelbi's '8080' Standard Assembler assembles programs written in symbolic language for '8080'. Describes operation of assembler. Detailed discussions of all major routines. Contains 2 completely assembled listings — hexadecimal and octal. Operating instructions. Even includes routine for loading programs produced by the assembler. All memory references are labeled; can reassemble to reside in ROM. (Some RAM required) $19.95. Optional object code on punched paper tape, specify 8080SA-OPT: $10.00. Optional commented source listing on punched paper tape, specify 8080SA-SPT:

$39.00.

Understanding MicroComputers and Small Computer Systems, A profusely illustrated, easy-reading "must" book explaining fundamental concepts behind operation of microcomputers in simple English. Gives extra knowledge for reading and understanding computer magazines and manufacturers' literature. Makes you feel "at home" around computers. Accepted as the standard for the neophyte, you must own this 300-page no-nonsense, easy-reading text. Includes simple-to-use glossary of key microcomputeroriented words. Order now. Hard cover: $14.95. Soft cover: $9.95.

SCELBI'S 8080

STANDARD EDITOR

Kail ciartTH I CHsatTiu lie.

Scelbi's '8080' Standard Editor is an efficient way to edit text when preparing program source listings or other text material. Operates in 2 modes? Text Entry and Command. Memory references labeled for easy reassembly into any general area of memory; e.g. reassemble to reside in just IK of ROM. (Some RAM required) $12.95. Optional object code on punched paper tape, specify 8080ED-OPT: $6.00. Optional commented source listing on paper tape too. Specify 8080ED-SPT, $20.00.

SCELBTS 8080

STANDARD MONnOR

Kllll tIBPIIH t CmMTIH lie.

Scelbi's BUtJU Stantiara ivionitor. Describes "Monitor Control" package to control operation from external "keyboard". Routines to examine and modify memory locations, CPU registers, continuous 2-point "bug" status report, control bulk storage, I/O devices. And more. $9.95. Optional object code on punched paper tape, specify 8080SM-OPT: $5.00. Optional commented source listing on punched paper tape, specify 8080SMSPT: $15.00.

The '8080' Proerammer's Pocket '•■A compact 3x41/2", everready, instant reference for octal or hexadecimal codes, that explains instruction set in detail. Order your copy today. Keep one in your pocket. One near your computer, A "must"! Only $2.95 each.

Circle 310

°" '"Quiry card.

ADVANCE NOTICE!!!

Watch for the all new

Scelbi's First Book of

BASIC Programs!

Coming soon!

Want to be on Scelbi's exclusive

mailing list? Want to know about

upcoming Sceibi Books? Don't

use the "BINGO" Card — but

write us DIRECTLY. It identifies

you as a "truly interested"

customer who is worthy of

special handling!

\

J

V

Top-Down

Modular

Programming

Albert D Hearn 98 SW 13th Av Boca Raton FL 33432

If you have done some programming, you know that it's one of the most enjoyable and satisfying parts of personal computer use. The very thought that the vast power in the small system's processor is limited only by the program that you write for it is tremendously exciting.

If you are new to the computer game, the programs you have written up to now have probably been relatively small and uncomplicated, but you have developed a lot of experience and confidence from them. Most likely you haven't used any particular technique in designing and writing your programs: you have probably approached program design in an informal way and relied upon your good senses to guide you in this unfamiliar task. You have probably also gained an understanding of the full capabilities of the instruction set and some of the little tricks (yes, ADDing a binary number to itself really does result in a left shift of one bit) which can be so useful. You are also capable of writing 10 routines to do about any kind of data transfer you want.

So now you are ready to do a program which does something really useful. The program you have in mind is going to be larger and more complicated than those you have done previously. While you might not expect this, your previous informal methods of designing and coding might possibly be inadequate and could cause you much grief if you attempt to use them on a larger program.

Hopefully, I can help you prevent these kinds of difficulties by showing you in'this article an easy to use method of designing and structuring larger programs which can greatly simplify your personal efforts, regardless of complexity.

The Concept

Someone once said, "To solve a complex problem, simply break it down into a number of less complex pieces, then proceed to solve it one piece at a time." This approach has been used for many years in the design and building of electronic equipment. It results in a "building block," or "modular" construction, where each block or module does some distinct part of the total function of the equipment. For instance, think of the last time you saw a diagram of a radio receiver. It was probably in the form of a set of separate blocks representing the RF amplifier, mixer, IF amplifier, and so on. The blocks were all connected with flow lines showing the sequence in which each equipment module processed a signal coming from the antenna. The diagram enabled the reader to understand the function of the radio one module at a time, in relation to the whole radio.

So how does the idea of using building blocks and solving problems piecemeal relate to the programming of personal computers? The answer is that these same ideas are very applicable to programming and have been in use in commercial programming for a number of years. There is no reason that good use of them can't be made in the amateur computer hobby also.

Top-down Design

Top-down design of microprocessor programs requires that you first have a clear notion about what it is that you want the program to do. You should ask yourself questions like, "What function do I want performed?", "What input information is available?", and "What output information or action do I expect?" When you can answer these questions, you've actually completed the highest level of design.

32 July 1978 IS BYTE Publicilions Inc

Photo courtesy of ComputerLond of San Francisco

Computerland* 4he DP Department HaseHine & Diablo on Display.

Time was, buying tiardware meant deaiing factory direct. Ttien came tl^e distributor, or factory indirect. The plione/mail order ad reads, "15% off." 15% off what? Delivery schedule maybe. After sales service perhaps. The only real savings just might be the Toll Free number in the ad.

Now there's an alternative. Introducing ComputerLand, a national networl< of DP equipment stores, with outlets across the nation. This means you, and the DP director, programmer, general manager or purchasing agent can take a quicl< ride across town, try out working equipment in a user environment, make product comparisons, then drive off with the hardware of your choice. And, still be back in time for the afternoon coffee break.

Below is a sampling of the quality business information products, from more than 60 manufacturers of micro and minicomputer systems and peripherals, available for you to tr/ out, buy or lease and take home today from ComputerLand.

ComputefLoAcI

14400 Catal.na Street, San Leandro. CA 94577 14151 895 9363

Franchise opportunities avaiiable.

HAZELTINE 1500

D 24 X 80 Display (upper/lower case) n High legibility 7X10 dot matrix D Teletypewriter format for alphanumerics plus numeric pad D Switch-selectable upper/ lower case D R S -232/C 20 ma.current loop interface

D Switch-reversible video.

DIABLO 1620-3

D HyType daisy wheel character printer n Full keyboard with numeric pad D Microprocessor controlled D R S -232/C interface D 45 CPS D Tractor feed D Internal power supply.

(c; Copyright ComputerLand 1978

ALABAMA

289 Eail Highland Avenue

104 W F.rst Street

GEORGIA

MICHIGAN

NEW YORK

3020 Un,ve.5.(V 0' , N W

San Bernardino 714 886-6838

Tuitin 714 544-0542

2423 Cobb Parkway

2927 38ThSfreet,S E

1612 Niagara Falls Blvd.

Hur>t5v.ll* 205 639 1?00

4333 Convoy Suwt San Diego 714.5609912

1816 Vgnacio Valiev Road

SrT<vrna404g63<>406

Kentwood 616-942 2931

Buffalo 716fl36-6511

Wilfiul Creek 416-935-6502

ILLINOIS

29673 Nonhwtttern Highway

225 Elmiia Road

CALIFORNIA 6743 Dublin Blxd

117 F.emoniStieel SanF.anosco415 546 1592

6840 LaCicno«iBlvd Ioglewood213 776«)80

50 Eaii Rand Road

Arlington Meighis 31 2 255-6488

Soijint.aid313356-8111 MINNESOTA

Ithaca 607-277-4888 OHIO

Dubl>n41583a8090

1077 Saratoga Sunnyvale Ho»d

COLORADO

9611 No. M.lwsukM Avenue

9070 Morgan CirclaDr'M

1288 SOM Canter Ho.0

11074 San Pablo Avenue El Ce"iio<16.333 5010

San JoM 408 253-8080

2422 So CoiO'ado Blvd

Nilei3129671714

BlooTiington 612-884-1474

Mayliald Haighii 216-461

42 42nd Avenue

Denver 303 759-4685

10936 S Cicero Avenue

N6W HAMPSHIRE

OREGON

22634 Fooifiill Blvd Mavward 415 536 8080

San Maieo416672fl080

CONNECTICUT

Oak Lawn 312-422 8080

419 Amneni

12020S W MainStraai

4S46 El Cam.no H^al Loi Alioi 4)5941 8I5J

6S40 La Ctegega Blvd

KENTUCKY

Nashua 603-889 5238

T.jard 503-620-61 70

Santa Rosa 707 52B 1775 16720 So Hawihorne BivO

24 75 Slack Rock Turnpike Fairtieid203 374 2227

813 6 Lyndon Lane Louiiville 502426 8308

NEW JERSEY 1442 E Route 70

TEXAS 3300Andarton Lane

lnglewood?13 7 76 8080

Lawndale 213 371 7144

DELAWARE

MARYLAND

Cherry Hill 609 795-5900

Austin 612-452 5701

24001 Vis Fabnonte =904

ElCidPUza Suite 104

Ajtro Shopping Centet

16065 frede-ick Road, IRi. 3551

2 De Haft Siratt

6439 Wetthaimar

MiHion Vieio 714 770-0131

Thousand Oaks 805-495-3554

Newark 302 738 9566

Rockville 301 948-7676

Morritlown 201 539-4077

HousTon 713-977-0909

WASHINGTON

1500 South 336th Slrsel Parkway Center. Suite 12 Federal Way 206-838-9363

WISCONSIN

690 5. Whitney Way Madison IDiiactory Aisisiani

INTERNATIONAL

52 58 Clarence Strati Svdfiey NSW 2000 AultraLaTLX AA 24757

"SEE US AT PERSONAL COMPUTING '78 IN PHILADELPHIA, AUGUST 24-27"

Circle 75 on inquiry card.

BYTE July 1978 33

The New WHl7 ''Mini'' Floppya Giant Leap Forward in H8 Systems Sopliistication!

pNow you can give your H8 the power and versatility only a floppy disk system can provide! The WH17 lets you load programs in seconds instead of minutes, store hundreds of programs on a single disk with immediate access, update files virtually instantly. It's far more versatile and reliable than paper tape or cassette storage and really makes your H8 a "total capa^ bility" computer system!

Storage media for the WH17

consists of the standard, hardsectored, 40-track diskette. Measuring just 5.25" in diameter, each disk offers the user access to 400 sectors (10 per track) oi better than 102K* bytes of available program and data storage area.

Supplied fully assembled, the WH17's model 82 WANGCO drive posts a conservative 30' ms track seek specification, and random sector typical access times of less than 350* ms. (A figure considerably better than that of many equivalent comletitive drives.)

A diskette containing all required H8 operating systems is sold separately. This software includes the Heath Disk Operat ing System (HDOS), with its unique diagnostic, BUG-8, console debugger, TED-8, a powerful text editor, HASL-8, and extended Benton Harbor BASIC.

The fully assembled WH17, with dual-drive, controller and systems software, wrill be available in June, 1978, for S975.

f HEATHKIT COMPUTERS

Systems Engineered for Personal Computing

petit;

Uniis of Schlumbergef Pioducts Coiporatton Rsidij pr-ces ort somo producls may be slightly

ABBONA-PhooniK, 2727 w Indian School Hd. (602) 279-6247

CAUFOBNIA-Anahelm, 330 E Ba« Rd |714) 776-9420. El CKrIto, 6000 Poltoro Avs 1415) 236-6870, Los Ana«lM. Z30S 8 Flowm SI. (213) 749-0261: Pommn. 1555 Orango GrovB AV8. N. (714) 623-3543; RMwxxl Cll». 2001 MiddMwId Rd. (415) 363-8156: SacranMnlD, 1960 Fullon Avs i»16) 486-1575: S«n DIagD (U M(u),S363 Center Or (714)461-0110;S«llJo»e<C«mptl««),2350S Bascom A»e (40a)'377.8920; Wooillend HIII«,Si504 Ventura Blvd. (213) 883-0531 COLORADO-Denver. 5940 W 3am Ave 1303)422-3408

CONWCTICUT-H«rHor<((*»on),396WMamSt (Rte 44). (203) 678-0323.

FLOHIDA-Mleml (Htaleeh). 4705W leih Ave (305) 823-2260; Tiiltltia,4013 West HillSDOiouah Am, (813)386-2541.

QEORSIA-Altanla, 5285 Boswell Hd 1404) 252-4341

ILLINOIS-CMcago. 3462-66 W. Devon Ave (3l2j 583-3920; Chicago (Downew Srave), 2a409d«n Ave. (312) 852-1304

INOIANA-lndlena)>oll«,2112E 62ndSI (317)257-4321

KANS,« - Kansas CHy (Mission), 5960 Lamar Ave 1913) 362-4486

KENTUCKY-Loulsvlllo. 12401 Shelbyville Rd

(502)245-7811

LOUISIANA-Naw Orleans (Kenner), 1900 Veterans

Memorial Hwy. (604) 722-6321.

l«ARYLAND-Bsitlmors,1713E JoppaRd 1301)

661-4446: RockVllle, 5542 Nicholson Larra (301) 861-5420. ^

BASSACHUSETTS-Boston (Psaboijy), 242 Anaover SI (617) 531 -9330; Boston (Wslluley). 165 Worcester Ave. (Rt. 9 lUSt vrest ol Rt. 128) (617) 237-1510. MICMIOAN-0«ro8.l8B45W.Ei9htMileRd i3l3i 535-6460; E.D«1rott, 181496 EiaWMIIeHd (313)772-0416 HINNESOTA-Mlnneaiiolls (Hopkins), 101 Shady Oak Rd. r612| 938-6371

MISSOURI- St. Louis (BridgeJon). 3794 McKelvey Rd (314)291-1850

NEBRASKA-Omaha, 9207 Maple St (4021391-2071. NEW JERSEY-Fslr Lawn, 35-07 Sroadviay (Rte. 4) (201) 791-6936; Ocean. 1013 Slate Hwy. 35(201) 775-1231

NEW YORK-Buflaki(Amhersl). 3476 Sheridan Dr (716) 835-3090: Jerlclio. Long island, IS Jericho Turnpike (5l6)334-8l8l;Roohsatsr,937Je(lersonHd (7161244-5470 White Plains (North White Plains). 7 Reservoir Bd

(914) 761-7690

OHIO-anclnna« (Woodlawn). 10133 Spnnqtiekl Pike (513) 771-8850; Clevelana. 5444 Peail Bd (2161 686-2590. Columbus, 250O Morse Rd. (814)475-7200: Tolatlo, 48 S Byrne Rd. (419) 537-1887

PENNSYLVANIA-PtlllsiMphIa, 6316 Roosevelt Blvd (215) 288-0180. Frsior (Chester Co.). 630 Uncasler Pike HI 30) (215) 847-5555; Plttslwrgh, 3482 Wm PennHlvy. (412)824-3664

RHODE ISLAND- Providence (Warwick), 556 Greenwich Ave (4011 738-5150

TEXAS - Dallas, 2715 Ross Ave. (214) 826-4063; Houslon,370S Westheimer (713) 623-2090. San Antonio, 7111 Blanco HO. (512) 341-8676

VIROINIA-Ale«»n<lrl«,6201 HiCtimonoHwy (703) 765-5515, Norfolk jVlrainla Beach), 1056 independence Bivd (8041480-0997

WASHINGTON-Seattle.SOSeihAve No (2061682-2172 WISCONSIN- Milwaukee, 5215 W Fond du Lac (414) 873-8250

Schlumberger

Heath Company, Dept. 334-430 Benton Haitx>r, Ml 49022

Please send me my FREE Catalog. I am not on your mailing list.

City .

.State _

_Zip^

"Prices and specitications subject to change wittiout notice.

I

I

I

.J

34 BYTE July 1978

HEATHKIT CATALOG

Read about nearly 400 money-saving, fun-to-build electronic kits. Use coupon to send for your mail order catalog or bring coupon to a Heathkit Electronic Center for your catalog.

Get Your Copy Today!

Circle 160 on inquiry card.

Figure 7: A basic topdown design diagram is a structure like tiiis. The number ofieveis may vary, and the number of boxes may vary, but the basic idea is given by this prototype.

level I (highest)

level 2

level 3 (lowest)

Figure 2: The first level of design is the act of saying "I want a program to do thus and so." Here "thus and so " Is defined to mean checkbook balancing.

checkbook bank stmt deposit slips checks

implied inputs

balance checkbook

implied outputs

comparison ot checkbook and bank balances errors corrections

The basic principle of top-down design procedure says that you start at a very high level of function definition and then progressively expand that function into more and more detail until you're at a low enough level to begin coding your program. Actually, this is a very natural way to design solutions to any problem, but, for some reason, this method was very slowly applied to programming. The top-down method is different from bottom-up, where the concern is for coding and details before a real program design has been done. Bottom-up methods work on the "how" aspects of the program before the "what" aspects. An analogy of this method would be the building of a house, using no structural plans, by first laying down a convenient foundation and then gradually adding wood and stone until some desirable structure has evolved.

Let's take an example of a function that could be performed on a microprocessor system for the purpose of illustrating the technique of modular, top-down program design. The function, monthly checkbook balancing, was selected because it is a process that is familiar to most of us and it contains all of the elements which make it a good example.

In order to design what you want the program to do, begin by drawing a multilevel design diagram like the one shown in figure 1. The diagram will describe what the program does at a number of different levels of detail, starting with the highest

level which is a single block describing the overall function. The next lower level of blocks breaks the higher level function into a number of more detailed subfunctions. The next level takes those blocks and breaks them into even greater detail, and so on. An important point to remember is that the total function of the program is represented at each level.

Figure 2 illustrates the first steps in the top-down design of your checkbook balancing program. The first block simply states that the program will balance your checkbook. There are no details in that block and it certainly doesn't invite coding at this point in the design. For input, you know that you will have your checkbook entries, monthly statement from the bank, deposit slips and cancelled checks. The output you want is a comparison of your checkbook balance (adjusted for recent deposits, service charges and outstanding checks) and the balance shown on the bank statement. You also want to know where any errors were made and what corrections are required.

The second level of design, shown in figure 3, breaks the first level block into three major subfunctions. Although this subdivision could have been done differently in terms of the content of the second level blocks, the sum total of those functions always adds up to the entire function of the program. The idea is that you start the process slowly and don't attempt to develop too much detail too soon. Keep the number of subfunctions small, five or fewer, under

July 1978 O BYTE Publications Inc 35

Figure 3: Once the first level of design has been determined, the next level is specified by breaking up the task into parts which are fundamentally independent of one another. Here, checkbook balancing is viewed as three separate modules of function.

balance checkbook

balance deposits

bolance checks and charges

compare bonk and checkbook bolonces

( stort j

match deposits in checkbook against bank statement

adjust bonk balance for any late deposits

match concelled checks to checkbook entries and bonk statement

adjust checkbook balance for any bonk charges

adjust bank balance for any outstanding checks

compare bonk balance to checkbook balance

determine any differences and correct mistakes

C end J

Figure 5: After the modular structure of the application is determined in a hierarchy such as those exemplified In figures I to 4, then attention can be given to sequencing of functions. This flowchart shows general level sequencing of the checkbook balancing application.

balance checkbook

balance checks and charges

match cancelled checks to checkbook entries and bank statement

adjust checkbook balance for any bank charges

adjust bank balance for any outstanding checks

Figure 4: Carrying the process one step further, the next level is shown here for one of the branches of the structure of the programs.

each function block. Don't worry about the order in which these subfunctions will be performed in your program. Remember, you're only concerned at this point about what is to be done, not how it is to be done.

Next, take the design to the next lower level by further subdividing each of the second level blocks. Figure 4 illustrates a portion of this step. Just make sure that each subblock represents a complete subfunction and that the subfunctions at any level are equivalent to the program function.

You might ask at this point, "How many levels must I go through?", or "How do I know when to stop?" There is no precise answer to these questions, although the following guidelines should help. In general, you will find that you should stop when the lowest level of functions is so simple that you can easily write a program module to do each one. A module should be considered to have about 50 program instructions, or less. Experience will help you to know when you have reached this point. Also, you will find that the more complex the program, the more design levels you will need; generally, about three or four levels will be sufficient.

Another method of determining if you've

carried the design to a low enough level comes about almost automatically. If you are attempting to complete one of the lower levels and you find that the order of subfunction execution is becoming difficult to ignore, then you've probably gone far enough. Also, if you find that it is becoming necessary to show that program branching or decision making is required (top-down design diagrams should show no decision logic), then you know that you have about the right level of design. You are now ready to start thinking about the how of your program.

Modular Construction.

If you try to make each block at the lowest level of your design diagram into a module, you might determine that some blocks are simple and can be combined into fewer modules. On the other hand, there will probably be blocks which would result in modules larger than the minimum size of 50 instructions we have established. In this case, take the blocks through one or more additional levels of design.

Now decide what sequence the functions should be performed in. Begin drawing a

36 luly 1978 © BYTE Publicitions Inc

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SL80-12 8080 Mnemonic Assembler $25.00 SL80-12P Assembler with paper tape $34.00

BYTE lulv 1578

37

executive

f start J

return

yes

call

return

yes

call

return

call

yes

call

return

r end j

processing details

call

input and format all required data

match concelled checKs to checkbooK and bank statement

subtract charges from checkbook

subtract checks from bank balance

compare bank

balance to checkbook

indicate amt. of mismatch and locate error

processmg subroutine modules

Figure 6: While the sequencing of the diagram shown in figure 5 is adequate, it is often usefui to explicitly partition all sequencing of execution in a separate module called the "executive" for the application. This flowchart shows a simple example of such an executive program which sequences the major operations of the application.

flowchart showing the required sequence. Will each function be performed for each pass through the program? If not, add decision blocks showing the conditions under which each such function is executed. Also add any function blocks which may be necessary to initialize data, clear tables, lO data, etc.

Figure 5 shows a sequence of functions which results from the design of your example checkbook balancing program. Actually, the functions shown are probably too high level for this step, but for the sake of illustration, the diagram should make the point.

At this time, I would recommend that you consider making use of a special program structure called an executive routine, which offers some significant advantages. The executive is the main routine in the program and primarily contains calls to the function modules which do all the processing duties. It makes all decisions about the sequence of execution, it also contains the starting and ending points of the program. The objective of the executive is to concentrate most of the decision logic and common function of the program into a separate routine which becomes another program module.

In this way, the function modules need not, and should not, make sequencing decisions. They should never directly pass control to another function module. This should be done only through the executive. A function module's only responsibility is to be given control by the executive, do its assigned job, and then return control back to the executive. Function modules are written in the form of subroutines using the call and return facilities of the programming language being used. They should also contain a generous sprinkling of comment statements to insure a high degree of understandability, as well as a well-defined lO interface to the outside world and the rest of the program.

Figure 6 illustrates the final step in the modular, top-down design of your checkbook balancing program. You have added an executive routine and some necessary housekeeping routines. You could begin coding the program from this flowchart by first writing the executive and the associated subroutine calls for each of the processing modules. By writing dummy subroutines which simply return control when they are called, you can test your executive for correct operation without the need for the real processing modules.

The next step, of course, is writing the processing routines. This is simplified by the design approach described in this article because it allows you to work on each routine as a separate unit which can be written and tested independently of all other routines in the program. When all routines are completed, they simply plug into the executive to form a total program. Later, if you want to change the sequence of execution, add or delete functions, it can be simply a matter of manipulating modular routines. ■

38 |uly 1978 ® BYTE Publications Inc

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BYTE July 1978 41

Who's Afraid of Dynamic Memories?

It is not necessary to refresh euery cell of the dynamic programmable memory individually, but only the rows of the memory matrix.

(Conversation overheard in local computer store):

Customer: What's the difference between static and dynamic memory? Salesman: Static memory worlds and ■ dynamic memory doesn 't.

It is unfortunate that the dynamic memory has had a rocky start in the small systems world, but it is not really surprising. The dynamic programmable memory is a part generally avoided by most designers because it is not nearly as simple to use as static memory. But taking the extra trouble and design care can pay handsome cost and performance dividends, since the dynamic memory is inherently a lower cost part than its static counterpart (by present standards of technology).

The purpose of this article is to remove some of the mystery about dynamic memory parts. In order to best cover all the trade-offs involved in a dynamic memory design, the discussion centers around the design of an actual dynamic programmable memory with the following specifications:

1. 32 K bytes on one card.

2. Altair (S-100) bus compatible (an elusive specification, as we'll see later).

3. Refresh mechanism invisible to the processor.

4. Lowest power dissipation possible with current integrated circuits.

5. Full speed operation in a 2 mHz system (no wait states).

6. Foolproof operation: refresh maintained despite halted processor and direct memory access operations, interrupts and prolonged wait states.

Note: A commonly seen misnomer is the abbreviation "RAM" used to refer to a typical volatile programmable memory part such as those discussed in this article. RAM stands for "random access memory, "which is descriptive of any memory part which addresses a unique memory cell given a set of binary inputs. A "read only memory " for example is also a random access memory, yet it is quite different In function from the volatile programmable memories. Thus in reading advertisements and manufacturers' literature, be aware that the term RAM as used really means "volatile programmable memory," a resource for the programmer who uses the system.. .CH

Lane T Hauck

Director of Research and Development

Noval Inc

8401 Aero Dr

San Diego CA 92123

Figure 1 is the usual starting point in any discussion of programmable memory. It is shown here only to point out that the static programmable memory cell uses six MOS transistors, while the dynamic cell uses only one (end of cost advantage argument).

The dynamic programmable memory ceil uses a charge storage technique to store digital information. The capacitor C^- in figure lb is charged for one logic state and discharged for the opposite state. Capacitors, being what they are, don't hold charge forever (due to leakage), so the cell shown works fine, but only for a few milliseconds. After that, the charge decays below a usable value. This is the reason for the mechanism called refresh. A refresh operation reads the value of the charge on the capacitor, amplifies it to its initial value, and dumps it back into the capacitor.

Life would really be difficult if the designer had to implement the entire refresh operation (read, amplify, write) in a dynamic memory system. Dynamic memory designers have made things simple by establishing the following refresh "rules":

1. It is not necessary to refresh every cell in the dynamic memory individually, but only the rows of the memory matrix.

2. A refresh operation is accomplished by simply accessing the required number of rows with any type of memory operation (read, write, or do nothing but set up the correct addresses accompanied by a "strobe" or timing pulse).

Programmable memories are organized in an XY matrix of rows and columns. The matrix is generally square, so it is possible to deduce the number of rows in the memory that must be accessed during

42 July 1978©BYTE Publicitions Inc

TARBELL SETS STANDARDS

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20620 South Leapwood Avenue, Suite P Carson, California 90746

(213) 538-4251

Circle 360 on inquiry card.

BYTE luly 1978 43

VDD

(a)

ROW SEL

(b)

CC

Figure 1: Comparison of static and dynamic memory cells. The static memory cell (figure la) Is actually a flip flop (or bistable multivibrator) made up of six MOS transistors and capable of storing one bit of information. The dynamic memory cell (figure lb) uses one MOS transistor and a capacitor to store one bit of information. The major differences between the two memory storage techniques are cost (dynamic memories are significantly cheaper than static memories) and the fact that dynamic memories must be "refreshed" regularly to maintain the charges on the capacitors.

CESSOR ADDRESS LINES

REFRESH COUNTER

r MULTIP

LEXER ,

A

6

MULTIPLEXER

REFRESH

ARBITRATION

LOGIC

CONTROL

ADDRESS LINES nYNAMir MTMnRY D.u

ARf

(AY

Figure 2: Refresh implementation block diagram. Dynamic memory cells must be refreshed periodically, or the capacitors used to store the bits of information will discharge. Refreshing is done by simply accessing the cells in question with any type of memory operation (read, write, or do nothing but set up and strobe the correct addresses). Because dynamic memory cells share common lines, it Is necessary to access only the rows of the memory matrix. All dynamic memories are set up so that the row decoders are fed by the least significant address lines (AO thru A 5 for a 4 K part, for instance). The memory address lines are fed by a multiplexer that selects either the A lines (processor address lines) or the B lines (refresh counter lines) as directed by the refresh arbitration logic. The selected lines are then fed into the dynamic memory array. The refresh arbitration logic insures that the refresh operations and the processor operations do not interfere with each other.

a refresh interval. For example, a 4 K by 1 bit memory is 64 by 64, so 64 memory cycles must be performed for refresh; a 16 K by 1 bit memory is 128 by 128 and requires 128 refresh cycles. The specification for refresh interval is generally 2 ms. This means that all rows of the memory matrix must be "exercised" at least once every 2 ms.

Hovk' do you knovk" v^'here the "rows" are? All dynamic memories are set up so that the row decoders are fed by the least significant address lines; for a 4 K part, this means the six low order address lines, or AO, A1, A2, A3, A4 and A5. During the refresh operation, the remaining address lines A6 thru All are in "don't care" states. For a 16 K part, the seven low order address lines AO thru A6 constitute the row address lines.

Figure 2 shows how refresh is accomplished. The memory address lines are fed by a multiplexer that selects address inputs from multiple sources. When the A inputs are selected, the processor accesses the memory; when the B inputs are selected, the refresh address counter accesses the memory. The role of the refresh arbitration logic is to insure that the refresh operations and processor access operations do not interfere with each other. The block diagram in figure 2 shows a 2 input multiplexer. A later section of this article shows how the number of inputs may be expanded to accommodate a multiplexed address programmable memory.

Some system designs allow the use of dynamic memories without having to implement any refresh circuitry whatsoever. The most common system of this type is a video system that uses raster scanning. In order to present a stable image on the video display, all information is stored in a refresh memory. As the electron beam scans the screen, a digital address that identifies the beam position is developed by the video display's timing circuitry and fed to the memory address lines. The memory thus sequences continuously through its addresses. This satisfies the refresh requirement automatically, since the refresh counter of figure 2 is in effect replaced by the video display's counters.

The 4 K dynamic memory is currently available in three different packages: 22 pin, 18 pin and 16 pin. The survivor of the incompatibility battle is clearly the 16 pin package, due largely to its superior design, low power and true compatibility between multiple sources. Ironically, the smallest package, the 16 pinner, was the easiest one to convert to a 16 K memory part. [Several manufacturers of personal computers take advantage of this to offer memory in different combinations of 4 K and 16 K byte blocks . . .CM/ We'll see how this was done

44

July 1978©BYTE Publicalions Inc

The AJ 841 l/Q A completely refurbished IBM Selectrk ASCII terminal with RS232 or parallel interface.

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PHONE I

Circle 10 on Inquiry card.

BYTE )ulv 1978

45

The current wonder of the semiconductor world is the 16 K dynamic programmable memory.

when address multiplexing is discussed later in this article.

The current wonder of the semiconductor world is the 16 K dynamic programmable memory. The 16 K dynamic memory part that provides the prototype for the industry is the MOSTEK 1V1K4116. This is the part that virtually all semiconductor memory makers are laboring to emulate, due to its high performance and low power. Intel is another large supplier of 16 K dynamic memories in the form of the 2116, but the 2116 dissipates much more power than the 4116 and is not truly compatible with the 4116 type part which the rest of the industry is lining up behind. Intel will shortly have a newly designed part that performs like the 4116. Texas Instruments is also in the process of redesigning their 16 pin part to perform like a 4116.

The 16 K dynamic memory is in high demand these days, and the suppliers have not begun to meet the demand. This spells bad news for the experimenter, because prices will remain high (^20 to $30 each even in high volume) until the suppliers catch up to the demand. The day the 16 K chip becomes a "jellybean" part, such as the 2102, is probably about two years off.

There is, however, a sneaky way that the 16 K part can be used economically today. Like all integrated circuits, the 16 K part undergoes thorough testing before it is packaged and sold as a part. The die size of the 16 K part is so large that the probability of something being wrong with one or a few array cells is fairly high. Clever manufacturers (presently MOSTEK and Intel) are taking the parts which have problems as a 16 K part, and retesting them to see if either of the two 8 K halves of the array function perfectly. And they do indeed find many parts which are perfectly acceptable 8 K parts. These parts are not factory "rejects": they meet all specifications for the 16 K device, but you can only use half of the part. Two part numbers specify the devices and tell the designer that a particular address line (AO) must be always high or always low. This permanently selects only the "good half."

If you look closely at some of the current dense Altair (S-100) bus compatible memory boards, you'll see these devices (Intel calls theirs the 2108; MOSTEK's is the 4115). This type of part makes everybody happy.

Continued on page 140

^

>

RAS

CAS

"IHCV|L

ADDRESSES

WRITE

'OUT

K

'RAS

'^RCD •

n:

••RAH

ROW ADDRESS

COLUMN ADDRESS

Irsh 'gas

A

'.rj'

m

TTMMUm

■ rcs

\

'RCH

"OH VOL

OPEN

-c

VALID DATA

'off

>

Figure 3: Dynamic memory timing for tfie l\10STEK /VIK4176 16 K dynamic memory (Courtesy MOSTEK). Tlie foilowing steps are necessary for a memory cycie: set up tiie low order 7 bit address on tfie address line (for tiie case of the 16 K memory) by setting tiie address multiplexer to state 2; wait for tiie address lines to settle; drop the row address strobe (RAS) line to the low state to latch the low address into the port; wait the "row address hold time"; set up the high order 7 bit address on the address lines; finally, drop the column address line to the low state, which latches the high address into the port.

<•:

46 July 1978 © BYTE Publicilions Inc

GET THE

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BYTE luly 1978 47

^

Antique Mechanical Computers

Part 1: Early Automata

Dr James M Williams

58 Trumbull St

New Haven CT 06510

There is a high technology

in every age, not just our

own.

My purpose in writing these articles Is to remind computer enthusiasts that there is a high technology in every age, not just our own. Described herein are some of the stellar accomplishments of earlier times. The technology of electronics is merely the latest link in a continuous chain of technological developments spanning 20,000 years. Before that, there was a mechanical technology.

Part 1 of this three part series describes some highlights in the development of automata up to the 18th century. Part 2 continues with 18th and 19th century developments, and part 3 concludes with a description of Torres' 1911 chess automaton.

I am not going to speak here of those incandescent moments long ago when the truly great and critical achievements of mechanics were discovered: that day when an ancient man hooked a stick under one large stone and over another to invent the lever. Nor will I consider the wheel, which, however it came about, multiplied mechanical possibilities so manyfold (pulley, cam, gear, crank, escapement) that as the knowledge spread humanity was irrevocably changed. We simply do not know the story of mechanical knowledge and its spread, so we must spin scenarios instead of histories. We will also have to concentrate on highlights, since an exhaustive treatment of mechanical computers would fill many books.

We do know most of the latest chapter, however. It has taken place in the past 350 years, beginning in Renaissance times, flourishing in the Industrial Revolution, and finally levelling off in the early years of this century. The mechanisms that are

now commonplace were being born back then, and what exciting times they must have been. Glance through a compilation of mechanisms and note the dates of first appearances in machinery. You will be surprised to see how many basic movements date from two centuries ago. And with study and application, a man could learn them, make them his own, and employ them in mechanisms of his own. Consider the thrill of the obscure local blacksmith in, say, Saxony 400 years ago who copied in wood the mechanism of the town clock's strikingjack — the clock, a wonder that was the envy of other towns, imported at great expense from Italy — and discovered for himself the means of transforming rotary motion into intermittent linear motion, via a cam. (Medieval cathedral clocks generally had a life-size figure, man, angel, or devil, which carried a mace to strike hours on a bell: the "striking-Jacques" or "strikingjack.") Imagine the challenge and excitement in realizing that one could construct a clock that would strike noon fairly consistently when the shadow of the church steeple touches a particular joint of flagstone in the village square. Could one compress this wonderous mechanism into a container small enough to carry, and be able to see the time whenever he wished? Could one construct a clock for the pocket?

The first ones showed up around 1650, bulky as an ostrich egg and not much better at keeping reliable time. A little over two centuries ago a carpenter from Yorkshire, England, James Harrison, who had taught himself mechanics over a period of 30 years, constructed his fourth highly

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*

Photo 1: The bird organ, a popular novelty of the 18th and 19th centuries. The device is a sophisticated automaton capable of imitating the sound and movements of a real bird: the wings flap, the head turns, and the beak moves to the accompaniment of assorted bird whistles.

PIVOT POINTS

PITCH PISTON

VOLUME VALVE

Figure 7; Schematic diagram of a typical bird organ mechanism. Two metal cams control the bird's voice: the far cam controls the pitch piston (located in the body of the bird whistle), and the near cam controls the volume valve (located inside the wind chest).

accurate watch (chronometer) and won a prize of X20,000 from the British government in 1760. Determined to make the British Navy the master of the seas, the Admiralty offered a prize for a watch that would permit a ship to calculate its longitude with an accuracy of 60 nautical miles after being at sea for six weeks. (Latitude is relatively easy to calculate by accurately measuring the elevation above the horizon of any celestial body. Longitude is more difficult, and requires knowing the elevation at a time known relative to a fixed reference, the zero meridian at Greenwich, England.)

Mechanicians (an excellent name for the practitioners of this craft) chose to work in the field for much the same reasons we all choose a field today: because it was an absorbing and genteel means of earning a living, because it offered accomplishments one could show with pride, and because it was the area for future expansion, the growing edge of the technology. Look at the legacy of machines they have left us: the Linotype, the typewriter and its relatives, the reproducing piano (and its less intelligent cousin, the player piano), clocks and watches of every description. They are all fine mechanisms, but most of them were perfected and essentially attained their present configuration 80 years ago and more. Electronic devices have displaced most of them.

The flowering of mechanical technology had other branches that have now died out, though, leaving only accounts in books and a few decaying museum specimens of machinery which once stirred general admiration and brought fame to their creators: the Orrery, a clockwork model of the solar system, complete with moons, that once stood proudly in the exhibition room of every significant university; the dazzling variety of music boxes which once were found in every parlor; and so on. And who nowadays recalls the bird organ (see photo 1 and figure 1)?

The bird organ was a mechanical device that produced a very close simulation of a bird's song; 200 years ago it was a very expensive and much cherished ornament in the parlor of every gentle home. I have seen electronic versions of circuits for such a device and have built one, but together with its transformer and loudspeaker it occupies most of the space in a small birdhouse. A commercial version I purchased is slightly smaller, housed in a 3 inch plastic sphere. Around the year 1800 there was a bird organ made for sale to replace the

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In computer terms, the bird organ can be described as a spring driven power train controlled by a mechanical read only memory.

head of a gentleman's walking stick. A hinged lid sprang open by a concealed catch, and out popped a minute feather covered bird model that opened its beak, spread its wings and sang. The entire device, except for its winding key, was housed in a gold ornamented cylinder 114 by 2 inches (3.8 by 5 cm) long. How's that for miniaturization? And I'll wager it made a better song than my blocking oscillator version.

There were bird organs, or accounts of them, in antiquity. The Greeks used steam or air to drive whistles mounted in bird figures; the Arabs and Persians supposedly did the same. The mechanism was sometimes a cluster of tuned whistles like a bank of miniature organ pipes, and this arrangement is found in a clock from 1750, but the modern bird organ dates from about 1770 and was likely devised as a means of teaching domesticated songbirds to sing. Soon miniaturized, it was incorporated into decorative objets d'art of all sorts: snuff boxes, perfume flasks, table centerpieces (these often had small fountains of water and other distractions built in), clocks, even watches (but these were very rare), and free standing forms. One delightful version of the latter, perhaps 9 inches (23 cm) high, depicts a lady seated at her desk and a bird on a perch pole nearby. Her hand is on a (mock) bird organ, which she cranks while her pet listens attentively. The bird then tries to copy the song, but makes errors, which she corrects by playing the lesson again so that the bird "learns" and repeats it accurately, with much enthusiastic flapping of wings, pivoting on the perch, etc.

Large or small, the mechanism of bird organs was always the same (see figure 1): a main spring drove a gear train which operated a bellows to compress air in a wind box, and another gear train drove an intricately cut cam which, via a piston, varied the pitch of a whistle connected to the air supply. A similar cam operated a valve to control the volume of the whistle tone. More gears drove cams that controlled the beak, wings, and pivoting actions via push wires ascending the perch pole and the bird's hollow legs. Songs of eight or nine species are to be found among bird organ mechanisms (some elaborate devices had double or triple songs), and the nightingale was most popular. Remember the fairy tale about the mechanical nightingale by brothers Grimm, about 1855? It lived in a jewelled tree, and some devices were made in this form, but the objet d'art was perhaps most popular, being finished in enamel and gold and frequently decorated with precious stones. While bird organs were essentially one of a

kind machines, there was a sort of production line for them maintained by the most famous makers, and many thousands of them exist in museums. A great many were exported from France and Switzerland to the Orient. They are still made, and, while expensive, they are no longer the luxury of rich men. [A German bird organ about the size of a pocket calculator Is currently available for under $400 ... CM]

In computer terms, the complete mechanism might be described as a spring driven power train controlled by a mechanical read only memory whose values are stored as a distance of the edge of the cam from the cam's center of rotation. In 45 seconds of singing, there might be a fair number of places where the notes sound, perhaps, six to eight per second (during a trill).

Referring to figure 1, if we have two cams which rotate in 45 seconds, and we allow a time division of ten samples per second, and if we allow eight bits of precision per sample, we would require 900 bytes of read only memory to simulate the control functions of these cams.

A longer song, as in the tutorial automaton described above, might require three times as many bytes together with a smaller number to control bird and figure motion. This gives a total of 3 K bytes of mechanical read only memory divided unequally among several cams (something approaching the storage capacity of contemporary read only memory parts).

A better way to look at this sort of mechanism might be as a computer with analog storage (varying cam curves) and analog output (varying positions of the volume valve and pitch piston). Information is stored in the intricate curves of the cams. The information is fixed there for all time, or until wear or rust alter it, and may be recovered whenever it is needed by rotating the cam while the cam-follower rides on its periphery. It is in every way an "analog" of the desired sound, but it is not a recording, because it has been distorted in storage to suit the particular readout mechanism being employed (the cam-follower). (I have described the stored information as digital in order to facilitate the comparison; this has validity because of the relatively small number of analog positions and their resolvability into bytes of restricted number.) Even in the 1770 to 1850 era the cam was not a new invention, but this application was novel. It was a benchmark in the field of mechanics. Storage of information had now become a tool of the mechanician, where formerly mere repetitive movement, the regular back and forth movement of a

52 luly 1978 @ BYTE Publicitiom Inc

clock's mechanism, was known to be available.

With the possibility of storing information comes the possibility of crafting complex and seemingly nonrepetitive movement. If it is the desire of the builder of the mechanism, these movements may be arranged to mimic the movements of living organisms. This is the basis of more complex mechanical toys like the rabbit that walks about beating on a drum. (Incidentally, in 1880 a minute gold rabbit, perhaps an inch high, who also played his drum, was sold as a brooch. Not to mention a 3 inch gold caterpillar that sedately crawled its path, circa 1850.)

However engaging, these were fundamentally simple and regular movements that did not tax the designer. Mechanicians have constructed far more complex machines designed to duplicate the most intricate and coordinated movements performed by living creatures and to produce an effect of illusory life for the few minutes the mechanism operates. Why would clever, dedicated people do such a thing? Why build an automaton?

Machines That Imitate Life: a Rationale

Until modern times there was a pervasive and unchallengeable view that the bodies of human beings were not fit subjects for investigation. Death was the penalty for human dissection during the middle ages, except for rare occasions when the Church sponsored demonstrations of the corpses of criminals. Clearly, anything so sternly forbidden must have been well worth investigating; could it have been that the secret of life lay concealed in the structure of the body? There were some who took the risk, and they always found that animal and human structure were very similar. Since, in the influential and respected view of Rene Descartes (1596-1650), animals were machines that differed from humans chiefly in their lack of divine inspiration, it is easy to see the framework for a "mechanistic" view of living organisms. The notion held much appeal. It explained in terms that were comprehensible to the average educated man how living creatures were constructed by substituting mechanism for mystery.

Popular expositions of science from the 1890s right up to the 1940s typically depicted drawings of a person cut away to reveal bellows and pump rooms in the chest, the chemical factory in the abdomen, the telephone switchboard in the skull, the pistons and gears in the limbs, and so on.

I suggest that this conception of organisms as chains of mechanisms, and the corollary, of a god as the divine watchmaker who constructed and set them in motion, was perhaps the most influential factor leading to the construction of machines designed to imitate life. Note the variety of literature in which the attempt to create life is central to the theme: from ballads and fairy tales dating back to the beginning of language to Mary Shelley's Frankenstein (1818); from Offenbach's opera with the clockwork ballerina. Tales of Hoffman (1881), through countless science fiction works, to tales such as Shaw's Pygmalion. And of course there is recombinant DNA research, the leading edge of biochemical investigation at this moment where the purpose is, manifestly, to explore the mechanisms of life in living cells. The impulse is still there in us although the metaphor is different in different ages, and the mechanisms employed are dependent on available technology.

Astonishing Automata

About 1709, in Grenoble, the Edison of automata, Jacques de Vaucanson, was born. Little is known of his early life, except that he was something of a rake and a seminary dropout who disrupted affairs at the monastery by making wood and paper wings that flew about. But much is remembered of his automata, which, though they no longer exist, were the marvel of their age, the object of admiration by all gentlemen who saw them, and the envy of mechanicians ever since.

Vaucanson was not a showman, but a philosopher and inventor. He often spoke of "moving anatomy," his expression for the concept that life, especially life in lower animals, was in fact a series of undirected movements (what we would today call "reflex movements"), and that by duplicating the movements and actions of a live creature, one might succeed in duplicating the life of the creature. While such a notion seems absurd to us (it is, according to current understandings of the formation of ideas, magical, and therefore primitive) there is precedent for it from a character no less important than St Thomas Aquinas. Vaucanson had a splendid opportunity to come across St Thomas's writings, since he lived in a monastery for perhaps 15 years. Books were expensive treasures in 1709, and monasteries were the main places where collections existed. St Thomas's works would probably have been among them. In the Summa Theologica (Q13; Art 2; Reply obj 3; Part II) there is a passage: "Animals

About 1709, In Grenoble, the Edison of automata, Jacques de Vaucanson, was born.

July 197aOBYTE Publications Inc 53

show orderly behavior and are machines, as distinct from man who has been endowed with a rational soul and therefore acts by reason."

If animals are orderly machines, it might be possible to make a machine that looks and behaves like an animal. If one took

special pains to reproduce vital details like respiration, digestion and excretion, etc (so runs the argument), one would then have created the next best thing to a real living animal.

Vaucanson arrived in Paris in 1735 at the age of 26 to pursue his moving anatomy con

AVEC PERMISSION |

DU MAGISTRAT DE LA VILLE, |

On expofera a la vue dn Pttblique les^. chefs etOeuvres Mechaniques du Celibre Mon- H fieitr VAUCANSON,. Membre de PAcademie Royale des Sciences de Paris, m qui confiftent en trois Figures Automates. S

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'A premiere, Un hoinme de Grandeur naturellc habiliti en SAUVAGEqui joui Onzc airs fur la Flute travcrficrc par 'cs^« menies mouvemenis des Levres dcs doiu & le fouBle de fa bouche comme I'homme vivanc. e^

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QR l^Es 3. Pieces qui ont fait meriter une Recompenfc a I'Authcur d*une Penfion de 8- m'"e & ?■ cent Litres par Ic Roy, Ji qui ont en-Sw Hi gag^ un grand nombre des Pcrfonnes de diftinflion a des longs & penibles Voyages pour les voir. marque micux Icur mcrite qu'un plus ^J ^£ long detail. On Efpere que dans cette Ville un chacun fera charm^ de propter de Toccafion de les voir & qu'its en feront la dilTerence ^5 ^S du nombre des bagatels, que I'on fait voir tous les jours au publique- Coin.'nelePi-oprictairedoit fctrouver le 12. a Francfurt il donnera ak maA pendanr 8- jours a commenccr ce jourd'huy 2. Reprcfenrations pjr jour a 3. & 5. hcures apres midy au Poii du Miroir > Ton payera 94. {^ jWj Sols au premi^, 16. au fecond & 6. au croiilcTTie place, & comme 1107 a aucune rrichexic dam ccs beaux ouvrages Ton enfeta voir S^ ^$ fintericur a de.couvert en payant 24. Sols par perToniie , l^n vend aulH dans la n>^mc Sate le m^naire prefentc par TAuteur a Meffieurs^P

gde I'Academie Royale qui concJcnt un ample detail des pieces contcn6es dans ces ouvrages & aufli TApprobation des RkfTteursdc ''Aca-^^ _demie. g

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Figure 2a: Three automata invented by Jacques de Vaucanson in the mid-18th century. Shown are a flute player, mechanical duck, and a flageolet (whistle) and drum player. The novelty of these figures caused a sensation in their time (from an 18th century engraving, courtesy Bettmann Archive).

54 luly l978SBYTt Publicjtionslnc

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cepts. He promptly ran out of money. There is documentation to show he had the idea ". . . of getting assistance by producing some machines that could excite public curiosity . . ." as a means of raising funds. He excited plenty of public curiosity, for in 1738 he simultaneously displayed three automata (see figure 2a). An automaton duck ". . . made of gilded copper who dtiiiks, eats, quacks, splashes about on the water, and digests his food like a living duck" was one, and a pair of automata musicians who played flute and drums were the others.

The machines were life-size and were mounted on cubical pedestals about three feet on a side, which contained the bulky mechanism. They were unique and original, and they created a public sensation for 50 years. To me, the flute player seems the most remarkable mechanism of the three. De Juvigny, a friend of Vaucanson's, wrote in 1777, "At first many people would not believe that the sounds were produced by the flute the automaton was holding. These people believed that the sounds must come from a bird organ or German organ enclosed in the body of the figure. The most incredulous, however, were soon convinced that the automaton was in fact blowing the flute,

that the breath coming from his lips made it play and that the movement of his fingers determined the different notes. . . The pectators were permitted to see even the innermost springs and to follow their movements." Figure 2b shows the mechanism in outline form. All that needs mention is the weight motor (not shown), and the fact that different weights were added to each bellows in the set of three to provide different pressures of air. High, medium and low pressures provided the designer with the possibility of playing notes loudly or softly in the lowest register, or of shifting the flute to a higher register by employing greater pressures. The distributor valve selected the correct pressure for a given note.

Ihe illustration merely hints at the head mechanism, which must have been extremely complex. This description of flute playing is from the Encyclopedia Brittanica: "The flute is held sideways to the right of the player, who forms his lips to make an aperture and directs his breath stream across the mouth hole and onto its further edge, where it breaks up into eddies that alternate regularly above and below this edge and so excite the air column of the flute into vibration. Stability of the notes in the various registers and at different loudnesses is achieved by

Figure 2b: Details of Vaucanson 's remarkably sophisticated flute player automaton. A music boxlike drum with programmed pins controlled the motion of the fingers, volume of air and shape of the mouth (made of rubber) so that the device actually played a standard flute.

luly 1978 ; BYTL Publiialioni Inc

55

"(Vaucanson's mechanical duck) is the most admirable thing imaginable, a piece of human workmanship almost passing understanding."

control of lip aperture, angle of breath impact, and breath force. The compass is three octaves. . . ." Vaucanson's complications came from his decision to use the true flute, blown from the side, and not a recorder, which is an air pipe instrument blown from one end like a pennywhistle or organ pipe. In both instruments, air column length is varied by closing the appropriate holes in the body. To some degree Vaucanson simplified his task by employing seven active fingers (instead of eight, the modern standard: or maybe his particular flute had only seven fingerholes), but he took on and overcame the challenge of providing means to produce the proper size of lip aperture and the proper angle of breath stream to mouth hole. It seems quite likely that Vaucanson used actual rubber, first seen in France in 1736, in the lip mechanism, for there is evidence (in another automaton) that he knew how to fabricate rubber.

Now, I can imagine a mechanism that would dilate and contract the aperture in a set of rubber lips, and vary somewhat the angle of a stream of air blown through the hole, but I have the considerable advantage of being able to draw on two centuries' accu

Figure 2c: Details of Vaucanson's mechanical duck, showing the intestinelike tubing within. The duck could drink, quack and splash about, and was able to eat, digest and eliminate food (from an 18th century engraving, courtesy Bettmann Archive).

mulation of mechanical knowledge. Vaucanson was starting from scratch, building a mechanism never before seen, to produce a motion never before defined, to perform a task never before attempted. That he succeeded so well is astonishing; that he did it within 36 months is staggering. And remember, he employed mainly hand tools. There was no local machine shop he could call on to mill a part. We have no record of where Vaucanson learned his mechanics, but his skills were prodigious.

The combination tabor (drum) and flageolet (pennywhistle) player shown at the right in figure 2a was undoubtedly constructed along similar lines; I have not seen an explanation of its mechanism. It would have been simpler, since the flageolet is easier to play than a flute (only four or five finger holes, blown from one end), and machinery to make the right arm beat the drum would be relatively simple to figure out. It seems unlikely the two automata could have been so well synchronized that they played together.

Vaucanson's Mechanical Duck

It always startles me to read things like this anonymous appreciation of Vaucanson's duck: "It is the most admirable thing imaginable, a piece of human worksmanship almost passing understanding." I try to account for the powerful attraction that constructing simulacra of lower animals held for men 200 years ago. Still, it catches me off guard to see the adulation the duck evoked. Dr G C Beireis, the fourth owner of the machine in 1785, rhapsodizes, "It was in this duck that Vaucanson's genius reached its highest point. I have still not got over my astonishment at this work. (He had seen it thirty years earlier.) One single wing contains more than 400 articulated pieces." I doubt we would feel that way today about an automated Scottie, say, but maybe ducks make better pets.

It was, from all accounts, a singular likeness to a duck, and here is what it did:

After a light touch on a point on the base, the duck in the most natural way in the world begins to look around him, eyeing the audience with an intelligent air. His lord and master, however, apparently interprets this differently, for soon he goes off to look for something for the bird to eat. No sooner has he filled a dish with oatmeal porridge than our famished friend plunges his beak deep into it, showing his satisfaction by some characteristic movements of his tail. The

56 July 1978 @ BYTE Publicilions Inc

way in which he takes the porridge and swallows it greedily is extraordinarily true to life. In next to no time the basin has been half emptied, although on several occasions the bird, as if alarmed by some unfamiliar noises, has raised his head and glanced curiously around him.

After this, satisfied with his frugal meal, he stands up and begins to flap his wings and to stretch himself while expressing his gratitude by several contented quacks. But most astonishing of all are the contractions of the bird's body clearly showing that his stomach is a little upset by this rapid meal and the effects of a painful digestion become obvious. However, the brave bird holds out, and after a few moments we are convinced in the most concrete manner that he has overcome his internal difficulties. The truth is that the smell which now spreads through the room becomes almost unbearable. We wish to express to the artist inventor the pleasure which his demonstration gave to us. (From Chapuis' book, Automata: Historical and Teclinical Study, see detailed bibliography in part 3 of this article.)

Something here for everyone, isn't there? Passion, satisfaction, and a dash of slapstick. The mechanicians in the audience were dazzled by Vaucanson's skill in building a duck that could swivel its neck in every direction while sitting or standing; this does suggest some remarkable techniques for managing the pushwires ascending the legs, maybe even some internal mechanisms within the body.

Probably written by Vaucanson and certainly based on data only he could have provided, the following passage from an article in a 1777 dictionary of science shows how proud he was of the internal mechanisms that caused grain to be ". . . digested as in real animals by dissolution and not by (grinding) . . . the inventor does not set this up as a perfect digestive system capable of manufacturing blood and nourishing juices to support the animal, and it would be unfair to reproach him with this shortcoming." But it is clear how well he knew the 18th century idea that blood comes from food, and he implies he was trying to follow it. Indeed, in some accounts the body was covered by latticework so the interior mechanisms could be viewed as they did their job. Vaucanson had good reason to be proud, for the body contained his new invention, the rubber tube. Any machine

capable of making that kind of smell had to be alive!

One wonders what the "...chemical laboratory where the principal part of the food could be decomposed..." mentioned in the article might refer to. It may have been that his rubber tube intestine actually contained some chemicals or enzymes that attacked the starch in oat porridge, causing it "...to leave the body in markedly changed form." But there was hardly time enough in a performance of a few minutes to convert anything. More likely the operator between performances drained the stomach of its contents and loaded the nether-part of the intestine with the imitation duck dung that so impressed audiences.

The duck and the two musicians probably made a good deal of money for Vaucanson, but because it was necessary to transport them to other capitals of Europe for further exhibition he sold them all in 1743 to showmen who took them to England, Russia, and finally to Germany. In St Petersburg in 1782 the third owners tinkered with the mechanisms, interchanging parts so they would break if anyone else tried to show them. Dr Beireis had this partly repaired, but when Goethe viewed the duck in 1805, he found, "Vaucanson's automata were paralyzed. The duck had lost its feathers and, reduced to a skeleton, would still bravely eat its oats, but could no longer digest them." The duck was 108 years old when Rechsteiner, a skilled mechanician, was hired to repair it. It was exhibited in Italy in 1844 and in London two years later. After that it dropped out of sight. Some photographs turned up in the early 1950s, evidently left by the former curator of the Paris Museum of Arts and Crafts. They are glass plate negatives that probably date from before 1900. The skeleton they reveal, together with the appearance of the mechanism, strongly suggests the wreckage of Vaucanson's duck, as they were labelled. The plates were said to be from Dresden, and if the duck survived World War II, one hopes it is in a dry attic. The musicians were lost from sight sometime around 1800. None of the imitations of Vaucanson's automata, including mekaniker Rechsteiner's duplicate duck, now survives. These wondrous mechanisms are altogether lost.

Vaucanson himself seems to have prospered (he was a member of the Academy of Science in 1777) and continued inventing. In 1741 he devised the system of punched cards that controlled looms in the jacquard tapestry factory. This is generally considered to be the first digital number storage and readout system. In 1760 he invented the

Satisfied with his frugal meal, the mechanical duck stands up and begins to flap his wings and to stretch himself while expressing his gratitude with several contented quacks.

luly 1978 ra BYTE Publications Inc 57

Note:

A complete bibliography for this part of "Antique Mechanical Computers" will appear with "Part 3: Human and Machine Action and the Torres Chess Automaton" in September 1978 BYTE.

modern metal-cutting lathe, with a shaped guideway to prevent chatter and twisting of the tool.

Mechanism of the Automata

While relatively simple to explain and easy to grasp when explained, Vaucanson's machines really are very sophisticated in performance and embody concepts easily 100 years ahead of their time. The weightmotor is a heavy weight suspended from a rope wrapped around a drum windlass, which, while slowly falling, drives a geartrain (speed controlled by a governor). These gears slowly turn a cam-drum, the master controller "memory" mechanism, one rotation of which equals one performance of the automaton. This drum, perhaps the diameter of a small keg and three feet long, has on its surface an array of rows of studs of some sort, nails or wooden knobs. Cam-followers, some sort of spring loaded levers, ride on the drum surface, one for each row (circle) of studs in the array, and each cam-follower is for a moment pushed out of place if a stud rotates by to push on it.

There are as many circles of studs on the drum as there are functions of the automaton to be controlled, and the cam-follower unique to that circle of studs does the controlling. Thus, one row, say, controls the dilation and contraction mechanism of the lips, and another row might manage the movements of the first finger, left hand, and so on. There would be about 12 functions to be controlled, so about 12 rows or circles of studs are on the drum. It is rather like a giant music box movement, except that instead of steel needles being plucked, cam-followers are displaced, and with displacement each follower pulls on a flexible cable which is linked by its own pulley system to the finger, lip, or valve that is unique to it. In some cases, like the lip control mechanism, the requirement to produce music is for smooth variation from one size to another, so the row of studs for that function is replaced by a smoothly varying curve, a cam. In other cases, the fingering mechanism, a finger either does or does not cover a flute hole. This is digital control (the word comes from counting on the fingers); the former is analog, meaning that a little movement here causes a proportional movement there.

When it is all put together and regulated carefully, the machine will play the flute using wind pressures as selected by the distributor valve. For the sake of impressive appearance, the machine is covered with a wooden framework in human shape and is

clothed, but it would do its job bare. However, it would look like a machine and not a person.

The tabor and flageolet player is similar, but probably only two levels of wind were employed, and the fingering is simpler, probably four fingers.

The duck was essentially a giant version of the mechanism that operated the bird figures described earlier but with many more, and more complex, movements. While it is possible that some weight sensitive area was built into the pedestal so that the duck started to gobble the food only when a plate was placed before it, it seems much more likely that the operator carefully memorized the duck's movements (which, of course, are identical every time) and returned with the plate at just the right moment. Otherwise the bird would have been gulping down thin air.

If they still existed, these machines would provide an intriguing catalog of early 18th century movements, probably including some that Vaucanson devised for special purposes that would not be rediscovered for 75 years or more. But, as computers, the machines were incredible. Here, 240 years ago, was a digital and analog computer preprogrammed with perhaps 300 to 500 bytes of read only memory, each byte 10 or 12 bits wide. Vaucanson appears to be the first person to have seen the need for synchronous control of multiple functions (how else could you play a flute except by regulating breath angle and pressure while simultaneously fingering the proper notes?) as well as the first who saw \hQ possibility of designing mechanisms to effect such control. That he used the music box spindle approach to his problem is not to his discredit, for that mechanism was known to function reliably over long periods while undergoing little wear. His incorporation of music box memory devices into an array on a single drum (the master controller) enabled him to produce some remarkable results. He could control a variety of simultaneous, interdependent functions because they were all driven by the same "clock." This was parallel data processing, in relatively small chunks, to be sure, but parallel beyond doubt. The likes of it were not seen again in mechanics until the player piano with its paper tape. It is not so very different from the way the central nervous system deals with data in many parallel channels simultaneously.

But why is this surprising? Jacques de Vaucanson was attempting to create life. It was his genius to approach the task in the manner of living things."

,1

58 July 1978'0 BYTE Publicilions Inc

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BYTE July 1978 59

The Z-80 in Parallel

Bob Loewer Micro Diversions Inc 7900 Westpark Dr Suite 308 McLean VA 22101

PROCESSOR.

I

1

PROCESSOR,

Many design engineers have introduced various types of parallel processing into systems in order to achieve higher throughput rates. Almost without exception though, these applications have been limited to medium and large scale computers due to price and complexity.

In the past two years, microprocessors have reached a level of sophistication which makes them candidates for parallel processing systems. Such systems could conceivably offer minicomputer performance at micro

P ME MORV I 32K

a SHARED MEMORY (52KI

MEMORY (32K)

J

DATA BUS I ADDRESS BUS

I CONTROL BUS

Figure 1: The author's parallel Z-80 system. Both processors work independently, each supported by 32 K bytes of programmable memory. The processors are linked by 32 K bytes of shared programmable memory. The shared memory, addressable by either processor as the upper 32 K, has its own address and data buses. Shared memory conflicts are resolved by the arbiter circuit shown in figure 2a.

computer cost. This article is an investigation of that idea.

The Z-80

The Z-80 microprocessor, manufactured by Zilog, is a third generation LSI device which offers full software compatibility with the 8080 processor. Upgraded features provided by the Z-80 include: two sets of exchangeable registers, indexing, a full range instruction set (including register or memory bit operations), eleven addressing modes, a nonmaskable interrupt, dynamic memory refresh address generation, and an Interrupt register to provide a high speed vectored interrupt response to any location in memory.

The Z-80's minimum number of control bus signals makes it easy to interface in multiple processor configurations.

System Layout

My design consists largely of two Z-80 microprocessors (processor X and processor Y) operating independently, each supported by 32 K bytes of programmable memory (see figure 1). The processors are indirectly linked by 32 K bytes of common memory, making a system total of 96 K bytes. The shared memory, addressable by either processor as the upper 32 K, has its own address and data buses. Data or address signals are gated onto their respective bus when (1) either processor performs an operation involving a read or write against the shared memory, or (2) either processor attempts an op code fetch from the shared memory, or (3) machine instructions combine (1) and (2).

Shared memory bus conflicts are resolved by the arbiter (see figure 2a). Since the processors use opposite phases of the clock, requests for bus access can never be initiated at exactly the same time. However, depending upon the instruction sequences being executed, bus request conflicts can occur. This problem, summarized in table 3, has been carefully examined and is represented by figure 3b. It illustrates what is assumed to

60

July 19780BYTE Publications Inc

\ ^ X SELECT

{^^ Y SELECT

^l> ^

About the Author

Bob Loewer is an employee of the Telenet Communications Corporation and a graduate student at the University of Maryland at College Park. He is cofounder of Micro Diversions Inc, a company Involved with microcomputers and microcomputer education. This article describes Bob's early research on parallel microprocessor systems.

\ ^ Y WAIT

Figure 2a: The shared memory arbiter. This circuit resolves conflicts between the two processors if both attempt to gain simultaneous access to the shared memory bus. For example, a request from processor X (XMREQ low) will cause IC3a to drive the XSELECT line low and will also disable IC3b. Processor Y will be locked out during X's memory request. If Y makes a memory request while locked out, the output of IC4a will go low, activating the YWAIT line.

be the worst possible case of bus conflict; both processors simultaneously executing shared memory read or write instructions from the shared memory. Of course, one cannot predict when each processor will attempt to access the shared memory, so all possible interprocessor state relationships have been investigated.

The basic memory read or write instruction has seven "T" cycles (T is defined as the duration of one clock period). The T states and their functions are:

M1,T1 IVI1,T2 M1,T3 M1,T4 M2,T1 1V12,T2 M2,T3

Instruction decoding

Op code fetch

Memory read or write operation

The M cycles are machine cycles. Table 3 shows the seven interprocessor T state alignments: M1,T1 active for one processor when states Ml.TI thru M2,T3 for the other are active. Figure 3b illustrates an example of the processor request signals and signals from the conflict arbitration logic. Note that after a very short period (maximum of seven clock cycles) the arbiter synchronizes and thereby provides complete cooperation between the two processors' fetch and

execution cycles by putting one of the processors into one or two wait states. Further, in the seven possible interprocessor T state relationships, there are two in which opposing shared memory access request signals are synchronized, in which case the arbiter does nothing. This means that, regardless of the processors' instruction

Number

Type

+ 5 V

GND

IC1

74S04

14

7

IC2

74S10

14

7

IC3

74S126

14

7

IC4

74S32

14

7

IC5

74125

14

7

IC6

74125

14

7

IC7

74125

14

7

IC8

74125

14

7

IC9

74125

14

7

IC10

74125

14

7

IC11

74125

14

7

IC12

74125

14

7

IC13

7432

14

7

IC14

7408

14

7

IC15

74S157

16

8

IC16

74S157

16

8

IC17

74S157

16

8

IC18

74S157

16

8

Table I: Power wiring table for figures 2a and 2b.

July 1978 ® BYTE Publicalions Inc 61

SHARED MEMORY DATa BUS

Figure 2b: Control circuitry for tlie siiared memory parallel Z-80 system. The respective processor data buses and the shared memory data bus are shown at the top. The shared memory address bus is at the right. The shared memory arbiter is shown in the center (see figure 2a for a detailed schematic). This circuit works on a first come, first served basis to resolve all conflicts between the two processors.

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62 luly 1978 © BYTE Publications Inc

Ml

-OP CODE FETCH

-IVIEMORY READ (OR WRITE)

Figure 3a: The basic Z-80 memory read or write cycle. Clock periods are referred to as T cycles and the basic operations are referred to as M (for machine) cycles. The first machine cycle of any instruction is a fetch cycle (Ml). Subsequent M cycles move data to or from the memory.

sequences, 86 percent of the time the system is at most one wait state away from synchronization. Thereafter, both processors can execute read and write instructions from the shared memory at 100 percent processor utilization, assuming the instruction synchronization is not lost.

Certainly opposing software will not consist solely of instructions which offer no bus interference. But it is clear that the most efficient method of solving the shared memory bus conflict problem is the one that will achieve short term interprocessor synchronization whenever possible.

Arbitration Logic

Each processor provides signals to the arbiter which identify a valid shared memory access request. IC2a and IC2b receive RFSH, MREQ, and A15 (the high order address bit signal) from their respective processors. MREQ indicates that a memory read or write operation is underway: either A1 5 line

going high identifies the shared memory as the object of the request; and the RFSH lines insure that the dynamic memory refresh strobe from one processor will not interfere with the shared memory access request of the other.

IC3a and IC3b provide an opposing grant or deny shared memory bus access proviso that is strictly first come, first served. A request from, say, processor X will cause IC3a to drive XSELECT low, and coincidentally disable IC3b. Processor Y will be locked out for the length of processor X's memory request. Now suppose processor Y does make a request for bus access when processor X is using the bus. This condition will force IC4a to its low state, activating the YWAIT line. The wait signal will continue until processor X concludes its memory access. Under no circumstances, however, will processor Y be forced into more than one wait state for this processor X access. When XMREQ goes high, XSELECT follows

Continued on page 174

Beginning Event

Finishing Event

Stipulation

Delay Before Occurrence (ns)

XA15 high XRFSH high XMREQ low

XAIBhigh XRFSH high XMREQ low

YA15 high YRFSH high YMREQIow

YAlShigh YRFSH high YMREQIow

XA15 high XRFSH high XMREQ low

YA15 high YRFSH high YMREQIow

28

to XSELECT low

YSELECT high

to XSELECT low

YSELECT low

25 after YSELECT goes high 28

to YSELECTlow

XSELECT high

to YSELECT low

XSELECTlow

25 after XSELECT goes high 53

53

22 22

to XWAIT low

YSELECT low

To YWAIT low

XSELECTlow

XSELECT high

to YWAIT high

YSELECTlow

YSELECThigh

to YWAIT high

XSELECT low

Table 2: Timing considerations in the arbiter circuitry. The arbiter takes a finite amount of time for its logic circuits to effect the changes shown. The corresponding delays are shown at the right.

)uly I978©BYTE Publications Inc 63

Photo 7: HalChamberlin's home built HAL-4096 computer system, built in 1972. This system, which is still In service handling lO for an IIVIP-16 microcomputer system, features TTL logic, a 16 bit word length, 16 registers, 4 K bytes of magnetic core memory (a surplus IBIVI 1620), and priority interrupt.

The First Ten Years of Amateur Computing

If one could find a

specific date for the birth

of personal computing, it

would be May 5 1966.

Sol Libes

President, Amateur Computer Group of New Jersey

995 Chimney Ridge

Springfield NJ 07081

Most people I meet are under the mistaken notion that personal computing started only two or three years ago, with the introduction of the Altair 8800 by MITS. Nothing could be further from the truth. In fact, the amateur computing hobby was then almost ten years old.

I therefore decided to write this article to set the record straight, give credit to the early pioneers in this hobby and shed some light on the early history of microprocessors.

If one could find a specific date for the birth of personal computing, it would be May 5 1966. For it was on that date that Steven B Gray founded the Amateur Computer Society and began publishing a quarterly called \he ACS Newsletter.

The newsletter exchanged information on where to get surplus computer gear, how to build not too complicated circuits, where to get integrated circuits, tips, experiences and where to get help. By the end of 1966, the Society reported that it had over 70 members.

1966 also saw the publication of the first books on how to build a home computer.

Typical was We Built Our Own Computers by A B Bolt and published by Cambridge University Press.

In January 1968, a survey in the ACS Newsletter reported that two amateurs had their home built systems up and running and that many others were actively working on their systems. The survey indicated that programmable memory sizes ranged from 4 to 8 K with some as high as 20 K, all magnetic core of course. Teletypes and Flexowriters were popular for 10. Clock speeds ranged from 500 kHz to 1 MHz, with the average 500 kHz. Most used discrete transistors, and a few reported using those new and hard to come by RTL integrated circuits. Instruction sets were small, ranging from 11 to 34 instructions. Word sizes were from four to 32 bits, with 12 bits the typical number. Registers ranged from two to 11, with three most common. Most reported that they had been working on their machines for about two years.

The April 1968 issue of Popular Mechanics reported on ECHO IV (Electronic Computing Home Operator), a home built computer constructed by Jim Sutherland. It had four registers, used a 4 bit word, had 8 K bytes of core memory, 18 instructions and a clock speed of 160 kHz.

In December 1968 Don Tarbell (now

64 July 1978 © BYTE Publications Inc

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BYTE July 1978 65

The first computer kit was introduced in 1971. It featured 52 TTL integrated circuits, a 32 by 8 bit programmable memory, and 15 instructions for $503.

Photo 2: The author's TVT-1, designed by Don Lancaster and built in late 1973. Intended only as a TV typewriter, it was interfaced to a modem and used with an IBM timesharing system.

known for his high speed tape cassette interface) reported on his home built computer in the ACS Newsletter. It had a 4 bit word size, four registers, 10 kHz clock and was constructed using RTL integrated circuit logic. He used a Teletype for 10.

In 1967, Dave Digby ran an ad in CQ magazine offering a computer kit. It was advertised as featuring RTL logic, four registers, a 512 to 1024 byte delay line memory, and serial input and output. The price was $1000. As far as I know, he never delivered any units.

Most early builders constructed copies of the Digital Equipment Corporation's PDP-8 minicomputer with their own modifications. In the surplus area, 1000 Minutemen I missile guidance processors became available in 1971.

1971 also saw the introduction of the first computer kit. It was part of the National Radio Institute's course on computer electronics. It used 52 TTL integrated circuits, had a 32 by 8 bit integrated circuit memory, 15 instructions and an operator's panel, and it sold for $503. Louis E Frenzel, then of NRI and now at Heathkit, was the designer.

In late 1971, the Kenback Corporation

The Kenback-1 computer featured a 1 K byte MOS shift register memory made by a small, young manufacturer called Intel.

introduced the Kenback-1 computer for $750. It was intended primarily for educational use. It had a 1 K byte MOS shift register memory made by a small, young integrated circuit manufacturer called Intel. It also had three registers, an 8 bit word size, 65 instructions, operator's panel, and an audio cassette for program storage.

The December 1971 issue oi Computers and Automation described five home built computer systems. And by the end of the year 1971, there were reported to be 195 members in the Amateur Computer Society.

In 1972 things continued to pick up. In June Don Tarbell reported that he had written an editor program for his new home built system and was working on an assembler program. His system used an 8 bit word, 16 registers, and 4 K bytes of core memory.

Early 1972 saw the introduction of the 8008 microprocessor, by Intel, the opening of a number of used computer equipment stores, large price drops in TTL logic and the availability of the 1101 programmable memory at low cost. All of this proved to be a tremendous stimulus for amateur computer experimenters.

In the September 1972 issue of the ACS Newsletter Hal Chamberlin reported on his home built HAL-4096. This 16 bit machine utilized surplus IBM 1620 core memories. Hal furnished a complete set of construction plans for $2. The system had 16 registers, priority interrupt, Selectric and paper tape 10, and many other very advanced features.

The September 14 1972 issue of Electronic Design carried an article on how to build a circuit which would display 1024 ASCII characters on a TV set.

In 1973 amateur computing advanced in several areas. In May, the EPD company advertised the System One computer kit for $695. It had 1 K bytes of memory with expansion to 8 K and contained 82 integrated circuits. It had 57 instructions encoded in a diode matrix read only memory.

The September 1973 issue of Radio Electronics published Don Lancaster's plans for the construction of the TVT-1. Although intended as a TV typewriter, many enterprising experimenters interfaced it to modems and home built computers.

In late 1973, the Sceibi Computer Consulting Company introduced the first computer kit using a microprocessor. The kit was called the Scelbi-8H and it sold for $565. It used the Intel 8008 and had

66 luly 1978 © BYTE Publications Inc

see TURNOFF RELRV 6:DELflV 300: REM STOP ARM.. WRIT

sense inputs

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210

TURf-40N LITE 4 : REM

Expansion bus

Socl(ets for up to 16l( of on-board RAM

8 user definable indicator lites

ZIBLTM Lite port

in PROIM displays an

8-bltword

Programming slots

for 2 TMS 2716s; stores

user's programs

4 3/4-amp reed relays

4 general purpose relays, 5 amp at 115 VAC

Dynabyte*s new Basic Controller: Check out its capabilities and imagine your applications

The Basic Controller^'^ is a powerful, versatile and easy to use single board microcomputer system designed for control applications.

It is heavily into control I/O: relays, flags and sense inputs. What makes controlling these l/Os (and the external devices they control) so easy is our ZIBL^"^ (Z-80 Industrial Basic Language). It is a superset of NIBL, National Semiconductor's control BASIC, and was written by us specifically for control applications.

We've divided the control world into six categories: sense inputs, flag outputs, lites, relays, A/Ds and D/As. ZIBL implements 64 channels of each in such a way that you need not know anything more about them than their names.

In ZIBL it is valid to say:

100 IF TIME = 053010 AND SENSE (18) = OTURNON RELAYS Simple, isn't it!

Some but not all of the Basic Controller's mouth watering features

Circle 110 on inquiry card.

include:

• File structures that allow multiple programs written in ZIBL to reside concurrently in RAM. Each program may be individually LOADed, RENAMEd, or RUN. Any program may access another program as though it were a subroutine, while still retaining its own line numbers and variables.

• Complete communication versatility. LISTing, PRINTing and INPUTing may be done to or from any serial or parallel I/O channel or the self-contained CRT I/O.

• Single key SAVE or LOAD to and from cassette.

• Single key SAVE to EPROM. No worry about PROM addressing or programming routines, it is handled by ZIBL — automatically — even if there are other programs already in PROM.

• ZIBL in ROM: TURNON, TORNOFF DEUW, TIME, REM, IF THEN, DO GNTIL, GOTO, GOSGB, @(exp), TRACE MODE, UNK, READ, DATA, DIR, RND(x,y), strings

triple precision integer arithmetic, plus the usual statements.

• Onboard: Z-80 MPU, 32 flags, 32 sense, 8 relays, 8 lites, 2 serial, 1 parallel, cassette I/O, 64x16 video, keyboard port, two 2716 sockets with programming capability, up to 16k on-board RAM, up to 48k off-board RAM, real time clock, vectored interrupts, Lite Port on board, a kitchen sink, and an Expansion Bus.

$750 assembled, tested, warranted 1 year. You add power supply, keyboard and monitor. Available now — see your computer retailer.

1005 ElwellCt, Palo Alto, CA 94303 (415)965-1010

BYTE luly 1978 67

1 K bytes of integrated circuit programmable memory. It was expandable to 16 K bytes of programmable memory ($2760) and had options such as cassette 10, ASCII keyboard input, oscilloscope output and serial 10.

In 1973, Digital Equipment Corporation offered the PDP-8A with 1 K words of 12 bit programmable memory for $875. Also in 1973, a small publishing house catering to computer and digital electronics hobbyists began publishing with a book on wire wrap construction techniques. It was called M P Publishing Company and was a part time activity of Carl Helmers (who later began a monthly called Experimenters' Computer System which after five issues was transformed into BYTE in 1975).

1974 marked a year of substantial increase in amateur computing. In July, Radio-Electronics magazine carried a construction article by Jonathan Titus on building the Mark-S processor, which used the Intel 8008 microprocessor. It is estimated that over 500 of these units were built by avid experimenters.

In October, Southwest Technical Products Company (SwTPC) introduced the TVT-II kit for $180 and an ASCII keyboard kit for $40.

In September, Hal Singer started the IVIicro-8 Newsletter to exchange information

Photo 3: The author's Mark-8 processor, built in late 1974. Designed by Jonathan Titus, it uses the Intel 8008 microprocessor and has I K bytes of programmable memory.

among hundreds of experimenters who were building the Mark-8 unit.

In November 1974, Hal Chamberlin and some associates began another very popular but short-lived magazine called The Computer Hobbyist.

1975 was the year that personal computing exploded. It began, in January, when Popular Electronics carried an article on the Altair 8800 microcomputer by MITS. First deliveries were in April 1975. The kit sold for $375 and included 1 K bytes of programmable memory, but no 10. MITS claims that by the end of 1976 they had sold over 10,000 Altair 8800s (80% to hobbyists).

In April, the first computer club held its meeting. Started by Bob Reiling and Gordon French, and calling itself The Homebrew Computer Club, it met in Menio Park CA. One month later the Amateur Computer Group of New Jersey was formed.

In the fall of 1975, MITS released its 4 K and 8 K BASIC interpreters, SwTPC introduced their 6800 based microcomputer, and the first decade of amateur computing was complete. Since then, the field as we know it today has rapidly matured and expanded.

Some Microprocessor History

Intel Corporation must be credited with developing the microprocessor, the single chip integrated circuit which performs the basic functions of a central processing unit.

In 1969, a Japanese company, Busicom, contracted with Intel to develop a chip set for a printer-calculator. It used a 4 bit data bus and consisted of four integrated circuits in a set: a processor, read only memory with 10, programmable memory with lO, and a shift register type memory. Busicom permitted Intel to market the chip set for noncalculator applications, and the first generation of microprocessors was born.

The processor chip was designated the 4004, and it sold for $200. It came in an 18 pin dual in line package (DIP) and would interface only with the other chips in the family. Programs had to be stored in the erasable read only memory. Data and address information was multiplexed on the 4 bit bus. Since program could only be executed out of read only memory, and since progammable memory was used only to store data, debugging software proved to be difficult. Further, a great deal of support logic was required.

At nearly the same time, Datapoint, a manufacturer of intelligent terminals, contracted with Intel and Texas Instruments to produce a true processor on a

68 July 1978 @ BYTE Publlcitiom Inc

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The INFO 2000 Disk System eliminates the "I/O configuration blues" by incorporating all necessary interface ports. A CP/M Loader and all I/O drivers are contained in EPROM so there is no need for special software customization. Just plug the system into your S-100 microcomputer and begin immediate operation using the CP/M disk operating system. The INFO 2000 Disk System is supported by the most extensive library of software available, including 3 different BASICS, 2 ANSI FORTRAN IVs, several assemblers, text editors, debugging tools, utilities and numerous applications packages.

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weeks from receipt of order. INFO 2000 Disk Systems also available for Digital Group and Heath H8 microcomputers. /■213) 532-1702 Dealer inquiries welcomed. •Cp/M is a registered trademark of Digital Research.

Circle 178 on inquiry card.

BYTE |ulv 1978

69

.m^'

t mn ^;':. ,N.^ ^^.

• A' ■'-/

■i-«ff*\

.^ ^ /

/'//o^o 4; /?o^er Amidon's 4 bit processor, built in 1972 and fondly referred to as the "Spider." It was built with TTL logic and used to control an amateur radio (R TTY). The Spider was featured on the cover of April 1977 BYTE.

chip. Intel succeeded in doing this. Unfortunately, the device proved to be too slov/ for Datapoint's use. Intel decided, therefore, in 1971, to market the device for $200 and call it the 8008. It marked the first generation of "true" microprocessor integrated circuits.

The 8008 used an 8 bit data word with a more powerful instruction set than the 4004, but it still had many of the disadvantages of the 4004. It required considerable support logic. The 8008 however was a more general purpose device. For example, it contained a set of logical operations that the 4004 did not have. Its instruction set was similar to a minicomputer's, and it could directly address 16 K bytes of programmable memory. It even had interrupt capability.

At the same time, Intel introduced the 1101, a 256 by 1 bit programmable memory (which enabled the experimenter to build a 1 K by 8 bit memory with only 32 integrated circuits!), and the 1702 256 by 8 bit EROM. With the 8008, 1101 and 1702 integrated circuits, general purpose computers could now be built.

In 1972 several other manufacturers recognized this emerging market. Most notable was National Semiconductor who introduced the IMP-16, a chip set which may have been a little ahead of its time. It was a bit slice system of variable word

length and user definable instruction set. It later developed into the third generation Pace microprocessor.

In late 1973, Intel introduced the 8080 processor, and, soon after. Motorola introduced the 6800. The 8080 has become the de facto industry standard, used in more applications than any other processor. The 8080 is basically an enhancement of the 8008. It came in a 40 pin dual in line package and could directly address 64 K bytes of programmable memory and read only memory. It had a true bidirectional data bus and an expanded instruction set. However, it still required an external clock and multiple power supplies. The 6800 on the other hand required only one TTL compatible power supply, had simpler control circuitry, and an instruction set more compatible with larger computers.

1975 and 1976 saw the introduction of enhanced third generation microprocessors. The Zilog Z-80, an enhanced 8080, featured a larger instruction set, more registers, on chip clock, and more. The 6502, from MOS Technology, was an enhancement of the 6800. The Texas Instruments TMS9900 and TMS9980 became the first widely available single chip 16 bit microprocessors.

1977 marked the introduction of the fourth generation of microprocessors. In fact, these devices now could be called

70 luly 1978 © BYTE Publicitions Inc

microcomputers in a single integrated circuit. Tliese new devices include the complete microprocessor, read only memory, programmable memory, and 10 circuitry on one chip. A minimum of support logic is required.

The future promises an increase in word size, functions, speed and memory capacity. (It looks like the single chip processor that runs BASIC may soon be a reality.) The next ten years in microprocessors and personal computing should be even more amazing than the past decade."

Photo 5: The Scelbi-SH processor. This was the first kit to utiiize a microprocessor. It employed an Intel 8008 processor and was introduced in late 1973; design work began on the unit in August 1972. The prototype featured an oscilloscope display and audio tape unit. Sceibi has since discontinued their hardware line to concentrate on software and applications publications. The last Scelbi-8H was sold in December 1974.

TURTLES

Small home robots controllable by your computer.

Attachable to any computer via parallel interface (not included)

Terrapin^" Turtles can:

• 'walk' (on 2" radius wheels)

• 'talk' (via 2-tone speaker)

• 'blink' (with lights as eyes)

• 'draw'(with solenoid-controlled pen)

• 'feel' (using S'/?" radius dome as touch sensor)

Use your Turtle to map rooms, solve mazes, dance, explore Artificial Intelligence, teach geometry or programming.

A unique peripheral to keep you "in touch" with your computer.

Limited delivery from stock • Brochures available

Kit $300 Assembled $500

Terrapin, Inc.

S-100 Interface $40 Shipping $5 Mass. residents add 5% sales tax

33 Edinborough Street, 6th Floor Boston, MA 02111 (617) 482-1033

Circle 374 on inquiry card.

July 197g@BYTE Publications Inc 71

f5V

GO [I>

dirO

560ii

(TYPICAL FOR 6)

Figure 1: Schematic diagram for t/ie motor driver. The 7400, Id, has +5 V connected to pin 14 and pin 7 is connected to ground.

Controlling DC Motors

Robert L Walton 5616 Houston Rd Eaton Rapids Ml 48827

About the Author;

Robert Walton is a process computer engineer employed by Consumers Power Company. He has designed and homebrewed an 8008 based system with 9 K of memory, Kansas City audio tape interface, ASCII keyboard, 128 by 128 dot graphic video interface, and a front panel which allows examination and modification of contents in memory during program execution. More recently he has been experimenting with a KIM-1.

This article wilt explain one inexpensive way to control the position of asnnall 1.5 V to 3 V hobby DC motor to within a quarter turn out of a total range of 16,384 turns. Various types of mechanical apparatus may be attached to this shaft for accurate positioning. The feedback portion of this circuit may be used alone for position sensing of shafts which reverse direction during operation. Modifications to obtain resolution better than a quarter turn and to drive higher powered DC motors will be discussed.

The impetus for developing this circuit came while estimating the cost and complexity of implementing the circuit shown by Leon Sweer, Thomas Dwyer and Margot Critchfield in the article "Controlling Small DC Motors with Analog Signals" (August 1977 BYTE, page 18). My lack of a digital to analog converter, the apparently high power dissipation in the power op amp, and the mechanical complexity of the feedback potentiometer gear reduction were all negative factors. An "all digital" scheme was devised to overcome these problems.

The motor driver circuit is shown in figure 1. The circuit is simplified considerably by the presence of only three modes of operation: full forward, full reverse, and completely stopped. All transistors are in cutoff or saturation at all times. The signals labeled FOR and REV are at a high level, +5 V, while the motor is stopped. When FOR is brought low, Q1, Q4, and Q6 become saturated, or "turned on." This effectively connects motor pin 1 to+5 V and motor pin 2 to ground. When REV is brought low, Q2, Q3, and Q5 conduct, connecting motor pin 1 to ground and motor pin 2 to -i-5 V.

Note that FOR and REV must never be grounded simultaneously; if this situation occurs, heavy current will flow through Q1, Q2, Q3, and Q4, potentially damaging the devices. To eliminate the possibility of this happening due to a programming bug while the motor drive is connected to a computer, the FOR and REV signals have been modified to GO and DIR signals by the gate logic of ICl. The motor will be stopped as long as the GO signal is low. It will run forward

72 luly 1978 e-BYTE Publicilions Inc

p= ^^ \L^^^ M 'f^^ ^um(^iim ^

MODEL CC-8

$185.00 (4800 Baud)

$195.00 (9600 Baud and 220V/50 Hz)

9600 BAUD CASSETTE RECORDER

An ASYNCHRONOUS NRZ type Recorder with remote motor start/stop. Error rate 108 at 4800 BAUD. Can be used from 110 to 9600 BAUD into a UART - no clocking required. This is not an audio recorder. It takes RS232 or TTL signals from the terminal or computer and gives back the same signals. No audio interface is used. Motor start/stop is manual or through TTL or RS232 signals.

Tape speeds are 1.6" / 3.0" and 6.0" per second. 110 volt, 60 Hz, 5 v/atts. (220 Volts on special order). Can use high quality audio cassettes (Philips Type) or certified data cassettes. Can be used in remote locations from a 12 Volt battery.

Recommended for DATA LOGGING, WORD PROCESSING, COMPUTER PROGRAM RELOADING and DATA STORAGE. Manual control except for motor start/stop. 6800, 8080 or Z80 software for file or record searching available on request with order. Used by major computer manufacturers. Bell Telephone and U.S. Government for program reloading and field servicing.

AVAILABILITY - Off the shelf.

PROVIDES MONITOR AND TAPE SOFTWARE in ROM. TERMINAL and TAPE PORTS on SAME BOARD. CONTROLS ONE or TWO TAPE UNITS (CC-8 or 3M3B).

This is a complete 8080, 8085, or Z80 system controller. It provides the terminal I/O (RS232, 20 mA or TTL) and the data cartridge I/O, plus the motor controlling parallel I/O latches. Two kilobytes of on board ROM provide turn on and go control of your Altair or IMSAI. NO MORE BOOTSTRAPPING. Loads and Dumps memory in hex on the terminal, formats tape cartridge files, has word processing and paper tape routines. Best of all, it has the search routines to locate files and records by means of six, five, and four letter strings. Just type in the file name and the recorder and software do the rest. Can be used in the BiSync (IBM), BiPhase (Phase encoded) or NRZ modes with suitable recorders, interfaces and software.

This is Revision 8 of this controller. This version features 2708 type EPROM's so that you can write your own software or relocate it as desired. One 2708 preprogrammed is supplied with the board. A socket is available for the second ROM allowing up to a full 2K of monitor programs.

Fits all SI00 bus computers using 8080 or Z80 MPU's. Requires 2 MHz clock from bus. Cannot be used with audio cassettes without an interface. Cassette or cartridge inputs are TTL or RS232 level.

AVAILABILITY - Off the shelf.

2SIO (R) CONTROLLER $190.00, Tested & Assmb.

itiiiiii"*'"'"'*

6800 CONTROLLER for SWTP $190.00, Tested & Assmb.

PROVIDES MONITOR AND TAPE SOFTWARE in EPROM. EXPANDS MIKBUG with IK of ADDITIONAL ROM PROGRAM

This is a complete tape controller for the SWTP 6800 system. Has 3K of EPROM space for your own programs. A 1 K ROM (2708) is provided with all tape and monitor functions. The ROM program is identical to our extensive 8080 ROM program.

Has one ACIA for one or two tape drives, one UART for an additional Serial port and a 4 bit parallel port for motor control. Will control one or two CC-8 or 3M3B drives with the software provided. Can be used with other tape drives controllable with 4 TTL bits if appropriate software changes are made.

Extra serial port is provided for your use with a second terminal or printer (RS232, TTL or 20 ma).

The ROM program supplements the MIKbug program and is entered automatically on reset. SWTbug compatible ROM is also available.

AVAILABILITY - Off the shelf.

Z 80 BOARD for SWTP COMPUTER

Now you can use the 8080/Z80 software programs in your SWTP 6800 machine. Replaces your MPU board with a Z80 and ROM so that you are up and running with your present SWTP memory and MPS card. 1 K ROM on board replaces MIKBUG.

AVAILABILITY - Off the shelf.

_$190.00, Tested & Assmb.

For U.P.S. delivery, add $3.00. Overseas and air shipments charges collect, N.J. Residents add 5% Sales Tax. WRITE or CALL for further information. Phone Orders on Master Charge and BankAmericard accepted.

Naticnal Multiplex Cerpcraticn

j 3474 Rand Avenue, South Plainfield NJ 07080 Box 288 Phone (201) 561-3600 TWX 710-997-9530 c^^,^^.

Circle 275 on inquiry card.

BYTE July 1978 73

Figure 2: Opaque disk to be attaclied to motor stiaft. Two gaps are cut so ttie disl^ will be rotationaiiy balanced.

when GO and DIR are high, and reverse when GO is high and DIR is low. The DIR signal may be reversed with GO remaining high without damage. This reversal may occur as often as desired, even many times per second, without electronic damage. Diodes D1, D2, D3 and D4 are used to suppress switching transients from the motor.

Higher powered motors or higher voltage motors may be accommodated by using 7426 open collector gates in place of the 7400 gates or by using additional transistor driver stages, as appropriate.

Position Feedback

Determining how many times a shaft has

turned in one direction is simple. Attach an opaque disk with periodic gaps in it to the shaft as shown in figure 2. Shine a beam of light on one side of the disk and place a phototransistor on the other side. Apply the

TOP VIEW

MOTOR

SlOe VIEW

Figure 3: Placement of phototransistors A and B. Thie ptiototransistors should be within an eighth of an inch of the disk. The disk should be opaque and painted flat black. The 60° gap size and 30° placement of the phototransistors will provide a steady count once every 90 of rotation.

DARK fl LIGHT

DARK B

DARK A LIGHT

r

4a COUNTERCLOCKWISE ROTATION

r

4t: CLOCKWISE ROTATION 30» ROTATION

Figure 4: Phototransistor timing diagram. Note that the counter must count up when a dark to light transition occurs on A and B is dark, or when a light to dark transition occurs on B and A is dark. The counter must count down when a dark to light transition occurs on B and A is dark or when a light to dark transition occurs on A and B is dark. This assumes that a counterclockwise rotation causes an increase in count.

output of the phototransistor to a Schmitt trigger and count the high to low transitions. Note that it is not possible to determine the direction the shaft is rotating by observing the electrical signals generated.

By adding another phototransistor, it is possible to determine the direction the shaft is turning. The two phototransistors, identified as A and B, must be arranged as shown in figure 3. The direction of rotation can be determined by observing which phototransistor is the first one on when the gap is encountered as shown in figure 4. The direction can also be determined by observing which phototransistor is the last one off. It is really necessary to use both of these transitions in order to avoid miscounting when the oscillating situation explained in the caption of figure 5 is encountered.

The circuit to detect and register the shaft turns is shown in figure 6. This circuit functions by propagation delay. Signals A and B are high when their respective phototransistors are on. Signals AD and BD are signals A and B, respectively, delayed by passing through four inverters. Similar terminology applies to A-hB and (A+B)D. These signals are then "anded" and "ored" together to make up and down counting signals for the four cascaded counters.

The four counters provide 16 bits of position information, or one part in 65,536. In the unlikely event that additional precision is required, more counters may be added. Note that the circuit generates four counts per revolution. If more counts per revolution are required, additional narrower gaps may be cut in the opaque disk and the phototransistors may be placed closer together.

Construction

The opaque disk may be made from a sandwich of two index cards and aluminum foil glued together. The disk may then be drilled to fit the motor shaft and fastened with a drop of epoxy. If the motor shaft is mounted vertically with the disk up, the phototransistor may be mounted beneath the disk. An incandescent desk lamp may be used to illuminate the disk. The phototransistors may have to be adjusted a little to get the unit functioning. Be sure the collector of each phototransistor reads over 4 V when dark and under 0.5 V when illuminated. Be sure this is true all the way around the disk. Note: you will not be able to see the up and down counter inputs or the outputs of the four "and" gates on any but the very fastest oscilloscopes.

To test the circuit, wire the GO motor input high and wire pin 7 of IC7 (figure 6)

74 )ulv 1978©BYTE Publications Inc

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THIS new professional club is designed to meet your day-to-day on-the-job needs by providing practical books in your field on a regular basis at below publisher prices. If you're missing out on important technical literature—if today's high cost of reading curbs the growth of your library—here's the solution to your problem.

The Computer Professionals' Book Club was organized for you, to provide an economical reading program that cannot fail to be of value. Administered by the McGraw-Hill Book Cbmpany, all books are chosen by qualified editors and consultants. Their understanding of the standards and values of the literature in your field guarantees the appropriateness of the selections.

How the Club operates: Every month you receive free of charge The Computer Professionals' Book Club Bulletin. This announces and describes the Club's featured book of the month as well as alternate selections available at special members' prices. If you want to examine the Club's feature of the month, you do nothing. If you prefer one of the alternate selections—or if you want no book at all—you notify the club by returning the card enclosed with each Bulletin.

As a Club Member, you agree only to the purchase of four books (including your first selection) over a two-year period. Considering the many books published annually, there will surely be at least four you would want to own anyway. By joining the club, you save both money and the trouble of searching for the best books.

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Please enroll me as a member and send me the two books indicated, I am to receive the- bonus book at the introductory price ol $1.89 plus my first selection, plus tax, postage, and handling If not completely satisfied, I may return |he books within 10 days and request that my membership be cancelled. If I keep the books, I agree to take a minimum ol three additional books during the next two years at special Club prices (guaranteed 15% discount, often more). I will receive the Club Bulletin 13 times a year. If I want to examine the featured selection, I need take no action. It will be shipped automatically. If, however, I want an alternate selection—or no book at all—I simply notify the Club by returning the convenient card always enclosed, I will always have a minimum of 10 days in which to return the card and you will credit my account fully, including postage, it this is not the case. Membership in the club is continuous but cancellable by me at any time after the fourbook purchase requirement has been filled. This order subject to acceptance by McGraw-Hill. Orders from outside the continental U.S. must be prepaid. Company, business, or Institutional tax exemption status Is not appliable to pur

chases made through individual Club memberships. All prices subiect to change without notice. Offer good for new members only. A shipping and handling charge is added to all shipments. Members are billed when books arrive.

Write Code tt of $1 89 bonus book selection here

Write code # of first selection here

P39299

Circle 219 on inquiry card.

BYTE luly 1978 75

Photo J: A breadboard of the motor controller. The photocells may be seen In front of the motor. • .

to the motor DIR input. Tie tine LOAD input (figure 6) to +5 V. The motor should seel< one end of one of the gaps and "chatter" there. The rate of chatter may be anywhere from five to 100 times per second. The angle the disk turns during this chatter should be only a few degrees. Experiment with the lighting to obtain the fastest chatter rate. Passing your hand in front of the lamp will cause the motor to run away. When your hand is removed, the shaft will again seek a position.

Use

It is wise to have a mechanical arrangement using a slipclutch or a similar device to

prevent mechanical or electrical damage if the motor runs away. Such an accident could result from a program problem or a burnt out light source. Such an arrangement also provides the facility for automatically zeroing the position when power is first applied to the circuit. The motor is driven in one direction long enough to ensure that the slipclutch is slipping, and then the LOAD line is momentarily lowered to load the counters with the known position. The counters will then contain the correct absolute position until power is turned off or the slipclutch operates again.

To set the motor to a specific position, perform the program in listing 1 (flowchart

POSITION OF A -,,

POSITION OF A--_

POSITION OF B--'

nttBK A

LIGHT nABK- p

Figure 5: Reason for decoding trailing edge of signals. A 30° oscillation of the disk between the positions shown will create the above waveform. If the trailing edge was not decoded, the counter would be decremented once for each oscillation and lose track of the correct position.

76 )uly 1978©BYTE Publicaliom Inc

the electric pencil II

^^ e 1Q78 Mirhafil ?ihraver

TM

"Hie Electric Pencil II is a Character Oriented Word Processing System. This means that text is entered as a string of continuous characters and is manipulated as such. This allows the user enormous freedom and ease in the movement and handling of text. Since line endings are never delineated, any number of characters, words, lines or paragraphs may be inserted or deleted anywhere in the text. The entirety of the text shifts and opens up or closes as needed in full view of the user. The typing of carriage returns as well as word hyphenation is not required since lines of text are formatted automatically.

1978 Michael Shrayer

As text is typed in and the end of a screen line is reached, a partially completed word is shifted to the beginning of the following line. Whenever text is inserted or deleted, existing text is pushed down or pulled up in a wrap around fashion. Everything appears on the video display screen as it occurs which eliminates any guesswork. Text may be reviewed at will by variable speed scrolling both in the forward and reverse directions. By using the search or the search and replace function, any string of characters may be located and/or replaced with any other string of characters as desired.

When text is printed. The Electric Pencil II automatically inserts carriage returns where they are needed. Numerous combinations of line length, page length, line spacing and page spacing allow for any form to be handled. Character spacing, BOLD PACE, multicolumn as well as bidirectional printing are included in the Diablo versions. Right justification gives right-hand margins that are even. Pages may be numbered as well as titled. This entire page (excepting the large titles and logo) was printed by the Diablo version of The Electric Pencil II in one pass.

NowonCP/M

You've probably seen The Electric Pencil in

action by now. It's the most powerful 8080/Z80 character oriented word processor on the market today. Michael Shrayer is now proud to present the new Electric Pencil II.

NEW FEATURES: !!

Supports Four Disk Drives Disk Storage and Retrieva Printing !!! Print Value Bidirectional Multispeed Print Value Scoreboard Cassette Backup Capabili Control !!! Non-Print Indentation !!! Centering

! CP/M Compatible 1!! Disk Operating System !!! Simple File Management !!! Quick and Easy

1 !!! Dynamic Print Formatting !!! Multicolumn Chaining !!! Page-at-a-time Scrolling !!! New Scrolling Controls 1!! New Subsystem with

!!! Automatic Word and Record Number Tally !!!

ty !!! Full Margin Control !!! End-of-Page

ing Text Commenting !!! Line and Paragraph !!! Underlining !!! BOLD FACE !!!

WIDE SCREEN VIDEO!!!

Available to Imsai VIO video users for a huge 80x24 character screen !!

HAVE WE GOT A VERSION FOR YOU ?

The Electric Pencil II operates with any 8080/Z80 based microcomputer that supports a CP/M disk system and uses a Imsai VIO, Processor Technology VDM-1, Polymorphic VTI, Solid State Music VB-IB, Vector Graphic Flashwriter or any similar memory mapped video interface. Specify when using CP/M that has been modified for Micropolis or North Star disk systems as follows: For North Star add suffix A to version number, for Micropolis add suffix B to version number, e.g. SS-IIA, DV-IIB.

Vers.

Video

Printer TTY or similar

Price

SS-II

SOL

$225.

SP-II

VTI

TTY or

similar

$225.

SV-II

VDM

TTY or

similar

$225.

SI-II

VIO

TTY or

similar

$250.

DS-II

SOL

Diablo

1610/20

$275.

DP-II

VTI

Diablo

1610/20

$275.

DV-II

VDM

Diablo

1610/20

$275.

DI-II

VIO

Diablo

1610/20

$300.

ss

MICHAEL SHRAYER SOFTWARE

1253 Vista Superba Drive

GLendaLe, CA 91205

(213) 956-1593

The Electric Pencil I is still available for non CP/M users:

coming attractions

Sort & Merge Utility !!!

The NEC printer package !!!

The HELIOS Electric Pencil !!!

Pencil to CP/M file conversion !!!

CP/M to Pencil file conversion !!!

Vers.

Video

Printer

Cassette

Disk Drive

Price

SS

SOL

TTY or

similar

CUTS

$ioo.

SP

VTI

TTY or

similar

Tarbell

$ioo.

sv

VDM

TTY or

similar

Tarbell

$100.

SSN

SOL

TTY or

similar

CUTS

North Star

$125.

SPN

VTI

TTY or

similar

Tarbell

North Star

$125.

SVN

VDM

TTY or

similar

Tarbell

North Star

$125.

DS

SOL

Diablo

1610/20

CUTS

$150.

DP

VTI

Diablo

1610/20

Tarbell

$150.

DV

VDM

Diablo

1610/20

Tarbell

$150.

DSN

SOL

Diablo

1610/20

CUTS

North Star

$175.

DPN

VTI

Diablo

1610/20

Tarbell

North Star

$175.

DVN

VDM

Diablo

1610/20

Tarbell

North Star

$175.

Demand a demo Srom your dealer I

Circle 316 on inquiry card.

BYTE jury 1978 77

in figure 7) at least twenty times per second. On an 8 bit machine, reading a 16 bit real time quantity poses a problem. If one byte is read and then the other, there is a real possibility that the 16 bit input may have changed between the two operations. Therefore the position is read twice and checked for agreement before proceeding. With a 16 bit machine, only a single input operation need be performed.

The motor will race at top speed toward the desired setting. When it goes past the setting, it will turn around and race back, again overshooting. After a couple of quick oscillations, the desired position will have been reached and the motor will shut off. A better algorithm could be devised by estimating the speed of the motor and anticipating the overshoot, causing the motor to approach zero speed very close to

Figure 6: Schematic diagram for the encoder circuit. The data input lines should be wired to the state corresponding to the desired initial position of the motor. The dotted in capacitors may be required to obtain sufficiently wide clock pulses for the up and down counters.

TIME DELAY

t>M>4>M>

12 ap I

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104 7404

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np>I

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I

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7404

(A + B)D

IC6 7408

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IC7 4 74193

Vd

LD

A

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C

D

ON OA 08 OC CD CL

GND

CAR BOL

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14

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IDATA

OUTPUT

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A

B

C

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ON OA OB OC OD CL

GND

(TO 3 I COMPUTER)

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74193

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/77

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/77 Iqutput Kto I computer)

78 July 1978©BYTE Publications Inc

Personal Computers & Microprocessing

Here are two inexpensive programmed learning courses designed to keep you up-to-date in digital electronics.

Design of Digital Systems - six volumes

The products of digital electronics technology will play an important role in your future. Calculators, digital watches and TV games are already commonplace. Now, microprocessors are generating a whole new range of products. Personal computers will be in widespread use very soon. Your TV, telephone and computer will combine to change your children's education, your job— your entire way of life.

WRITTEN BY EXPERTS

These courses were written by experts in electronics and learning systems so that you could teach yourself the theory and application of digital logic. Learning by selfinstruction has the advantages of being faster and more thorough than classroom learning. You work at your own pace and respond by answering questions on each new piece of information before proceeding.

After completing these courses you will have broadened your career prospects as well as your understanding of the rapidly changing technological world around you.

The courses are designed as much for the professional engineer as for the amateur enthusiast. You'll learn about microprocessing as well as personal computing — not to mention all the other aspects of digital electronics design.

ADVANCED COURSE DESIGN OF DIGITAL SYSTEMS

Design of Digital Systems is written for the engineer and serious hobbyist who wants to learn more about digital electronics. Its six large-format volumes—each 11%" x 8%" are packed with information, diagrams and questions designed to lead you step by step through number systems and Boolean algebra to memories, counters and simple arithmetic circuits,and finally to a complete understanding of the design and operation of microprocessors and computers.

CONTENTS

The contents of Design of Digital Systems include:

Book 1: Octal, hexadecimal and binary number systems; representation of negative numbers; complementary systems; binary mulitplication and division.

Book 2: OR and AND functions; logic gates; NOT, exclusive-OR, NAND.NOR and exclusive - NOR functions; multiple input gates; truth tables; DeMorgan's Laws; canonical forms; logic conventions; Karnaugh mapping; three-state and wired logic.

Also aviilabU at laadtng computer itoras:

Campuler Mdrt ot New Yurk. 1 18 Mddisun Ave . New Vurk, NY Erie Computer Co., 1253 West 8th Si . Erie, PA. Interactive Compulets. 7646'/, Dastiwoud. Houston, TX Interactive Computers, 16440 Et Camino Real, Housloii, TX, Interactive Computers, 217 W, Salt Franuisco, Same Ee, NM, Readout Computer Slores, 6 Winspear Ave,, Buffalo, NY Imperial Computer Systems, liK ,2105 23rd Ave . Rixkford, IL Home Computer Center. 6101 Yoiiije SI,, Wiltowdale, Oni.rrio, Canada artd inanv othort. Ask your dealer.

Book 3: Half adders and full adders; subtractors; serial and parallel adders; processors and arithmetic logic units (ALUs); multiplication and division systems.

Book 4: Flip-flops; shift registers; asynchronous counters; ring, Johnson and exclusive -OR feedback counter; random access memories (RAMs); read-only memories (ROMs).

Book 5: Structure of calculators; keyboard encoding; decoding display data; register systems; control unit; program ROM; address decoding; instruction sets; instruction decoding; control program structure.

Book 6: Central processing unit (CPU); memory organization; character representation; program storage; address modes; input/output systems; program interrupts; interrupt priorities; programming; assemblers; executive programs, operating systems, and time-sharing.

BASIC COURSE

NO RISK GUARANTEE

There's absolutely no risk to you. if you're not completely satisfied with your courses, simply return them to GFN within 30 days. We'll send you a prompt, full refund. Plus return postage.

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HOWTO ORDER

To order by credit card, call GFN's tollfree number - (800)331-1000; or send your check or money order (payable to GFN Industries, Inc.) to the address below.

Prices include overseas surface mail postage. Air iVIaii: additional costs (10 volumes); Caribbean S10; Europe $15; Africa, South America S20; Australia, Asia $25; or write for exact quote

Write for educational discounts, quantity discounts and dealer costs.

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Both courses - 10 volumes $29.90

Digital Computer Logic & Electronics

CONTENTS

Digital Computer Logi: and Electronics is designed for the beginner. No mathmetical knowledge other than simple arithmetic is assumed, though you should have an aptitude for logical thought, it consists of 4 volumeseach 1 r/2" X 8%"—and serves as an introduction to the subject of digital electronics.

Contents include: Binary, octal and decimal number systems; conversion between number systems; AND, OR, NOR and NAND gates and inverters; Boolean algebra and truth tables; DeMorgan's Laws; design of logical circuits using NOR gates; R-S and J-K flipflops; binary counters, shift registers and half-adders.

^

GFN Industries, Inc. Suite 400-B 888 Seventh Ave. New York N.Y. 10019

Call TOLL-FREE (800)331-1000

(orders only)

BYTE luly 1978 79

Octal Address

Operation Codes

001 000 001 002

066 056

aaa bbb

001 004

101

001 005 001 006

310 107

001 007 001 010 001 Oil

320 101 271

001 012 001 015 001 016

110 107 272

004

001

001 017 001 022

110 277

004

001

001 023 001 026 001 031

140 110 301

047 054

001 001

001 032

061

Commentary

set memory address registers to location of high byte of desired position get low byte of current position save in B register get high byte of current position save in C register read low byte again compare to previous read

re-read if not same read high byte again compare to previous read

re-read if not same compare high byte with desired high byte jump if less jump if greater high byte equal-recall low byte to A decrement address registers to point to low byte of desired position

compare low byte to desired low byte jump if less jump if greater equal, set A for DIR and GO = 0 go output DIR & GO position low — set GO = 1, DIR = 0 go output GO & DIR position high — set GO= I.DIR = 1 output GO and DIR

Listing 1: Intel 8008 program for motor control. This segment of code should be executed at least 20 times per second. The desired position is in location bbb-aaa (high byte) and the next previous location (low byte). The two locations must be on the same page. Input port 0 is the low byte of the counter and port 3 is the high byte. Output port 0 has DIR in its least significant bit and GO in the next bit.

001 033 277

Mnemonic

LLI aaa LHI bbb

READ INP 0

LBA INP 3

LCA INP 0 CPB

JFZ READ INP 3 CPC

JFZ READ CPM

JTC LOW JFZ HIGH LAB

DCL

CPM

001 001 001

034 037 042

140 047 110 054 006 000

001 001

JTC LOW JFZ HIGH LAI 0

001 001

044 047

104 056 006 002

001

LOW

JMP OUT LAI 2

001 001

051 054

104 056 006 003

001

HIGH

JMP OUT LAI 3

001

056

127

OUT

OUT3

Figure 7: Program flowchart Variables DU and DL hold the upper and lower bytes of the desired position. This program must be executed at least 20 times per second. If the motor runs away, complement the DIR bit outputs. Do not attempt to reach positions closer than 50 turns to 0 or 65535 with this algorithm because of the counter overflow which occurs.

the desired position. Such a scheme would reduce the settling time of the system to a minimum.

Modifications

For those purists who insist on doing everything in software, the Schmitt trigger outputs may be tied directly to two computer input lines, or even interrupt lines, and the decoding and counting may be done in the computer. For those other purists who prefer not to tie their machine up with repetitive loops such as the one in figure 7, this positioning scheme may be implemented in hardware by installing four 4 bit comparators on the counter outputs. Cascade the comparators together and connect two output ports from a computer to the other comparator inputs. Invert the "equal" comparator output and connect it to GO. Connect the "greater than" comparator output to DIR. If the motor runs away connect the "less than" comparator output to DIR. Now the computer outputs 16 bit position values and the circuit positions the motor to follow the computer output."

( BEGIN J

.

NPUT LOWER BYTE OF COUNTER INTO LI

1

INPUT UPPER BYTE OF COUNTER INTO Ul

1

'

INPUT LOWER BYTE OF COUNTER INTO L2

1

INPUT UPPER BYTE OF COUNTER INTO U2

—

5!0</li.l2\

|YES

NS-/ui.U2^^

( "° )

80

July l97geiBYTE Publications Inc

THE 1st FULL DAY INDUSTRY TRADE SHOW AUG. 24th

I Personal C Computing

LARGEST SHOW EVER HELD!

300 BOOTHS

Open Only To:

EXHIBITORS

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PHILADELPHIA

Personal Computing and Small Business Computer Show

PHILADELPHIA CIVIC CENTER :::XA,m"»

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^ •A Full Day To See Your Suppliers, Dealers, Distributors ^0«^ • New Products and New Manufacturers

• Plus Three Additional Days

• Aug. 25th-27th, Personal Computing Show

\ Distinctive Badge for Admission to Aug. 24th Trade Show

) Special Seminars and Meetings

^Admission to Personal Computing Show Aug. 25th-27th

»Hotel and Philadelphia Information Package

I Newsletter

See our ad on page 151.

I I Send Dealer-Retailer

Registrations at $15.00 each

I I Send Exhibitor Information

COMPANY NAME

NAME.

Amount Enclosed $

STREET. CITY

.STATE

-ZIP

PHONE.

Please include your business card or Letterhead.

Send To:

PERSONAL COMPUTING Inc.

Rt. 1 Box 242 • Mays Landing, N. J. 08330

609—653 1188

BYTE

Circle 302 on inquiry card.

BYTE July 1978 81

r

Books to Make the Summer

Just Arrived I

_The Cheap Video Cookbook, the latest in Don Lancaster's series of hardware books,

Cheop Video , ,

coo«ei<3©i>c

Ij ±

I ifl

continues where the TV Typewriter Cookbook leaves off. New, inexpensive video display circuits (and the software to drive them) are described. The designs allow a variety of alphanumeric and graphics formats to be implemented, including high resolution graphics. The circuits are designed for use on 6500 or 6800 systems, but can be adapted to other processors. Chapters also cover methods for displaying memory contents and a description of transparency techniques. 256 pp. $5.95.

BASIC: A Hands-on Method by Herbert D Peckham is a light-hearted but thorough

self-study course in BASIC, designed for people new to the subject. The introduction defines what BASIC is, gives some background on its origins, and tells you how to get started. Chapters cover: computer arithmetic and program management; input, output and simple applications; decisions and branching; looping; working with collections of numbers; subroutines; and more. Although the book is oriented towards the implementation of BASIC on time sharing terminals, the ideas and techniques are applicable to the personal computer. 244 pp. $7.95.

Not Just a Good Buy But An Investment

Microprocessor Lexicon, Acronyms

and Definitions by SYBEX. 110 pp. This little book is a necessity to anyone who wants an explanation of those hard-tofathom acronyms and other micro terms. Included are sections on signals in the main standards, functions of essential chips, and more. At 414" x 5Vs" it can be pocketed easily. For only $2.95 every microcomputerphile should have a copy.

The 8080 Programmer's Pocket

Guide written by Sceibi Computer Consulting Inc is a handy 3" x 4" compendium of 8080 facts. Included are detailed descriptions of the 8080 instruction set, information about an 8080 paper tape loader program, and an instruction set summary and index. 8080 programmers will want a copy of this useful book. 130 pp. Only $2.95.

jT^iS^^

Computer Science: A First Course, Second Edition, by Forsythe, Keenan, Organick,

and Stenberg. Over 760 pp. $18.25 hardcover.

Computer Science: Projects and Study Problems by A I Forsythe, E I Organick, and

R C Plummer. This companion text to Computer Science: A First Course is a series of work problems designed to intrigue the reader. Problems include plotting graphs, simultaneous equations, the eight queens problem, designing a perceptron (a machine that learns), as well as a series of problems specifically designed to complement the chapters of Computer Science: A First Course. 292 pp. $9.75.

Computer Science: Programming in FORTRAN IV by A I Forsythe, R M Aiken,

C E Hughes, and E I Organick. This supplement to Computer Science: A First Course, Second Edition, shows how to turn flowcharts into equivalent FORTRAN programs. Features include chapters on FORTRAN 10 statements, assignment statements, rounding, formatting, subroutines, practical applications, etc. The advent of FORTRAN software packages for small systems makes this a timely addition to the literature. 210 pp. $5.25.

The TTL Data Book for Design Engineers, Second Edition, by Texas Instruments is a

> Supplement to

I The TTL

^

BITS

.( current source of information on the design specifications and characteristics of the Texas

Instruments 7400 series of devices. In it you'll find a complete section of 7400 series pinout diagrams at the front, plus the usual detailed descriptive information on the more complicated circuits. How do you find out what a 74412 does? Turn to its pinout diagram on page 5-74, then vector to the detail information on page 7-502 where you discover that it's Texas Instruments' version of the Intel 821 2 part. 828 pp. Only $4.95 hardcover.

Supplement to the TTL Data Book for Design Engineers, Second Edition, by Texas

Instruments. As the name implies, this supplement brings your Texas Instruments TTL Data Book up to date with the latest information about new TTL devices. The 56-page book includes information about synchronous counters, function generators, and many other devices. $1.25.

The Microcomputer Bookstore

82 BYTE |ulv 1978

■^

Last All Year Long

BASIC with Business Applications by Richard W Lott focuses on the BASIC language

and its application to specific business problems. The book is divided into two sections. Part one introduces the BASIC language and the concept of logical flowcharting. Part two presents problems and possible solutions. Topics include: interest rate calculation, break-even analysis, loan rates, and depreciation. Exercises at the end of each chapter give a greater understanding of BASIC by actual programming. This book is a great aid to the beginner wanting to learn BASIC without having a technical or scientific background. 284 pp. $10.50.

Financial Analysis and Business Decisions on the Pocket Calculator by Jon M Smith is

designed to aid the experimenter in performing applied analysis. It gives a variety of numerical techniques, approximations, tables, graphs, and flowcharts for calculations. All methods have been optimized for the pocket calculator, and the book stresses the use of the businesstype calculator having the usual complement of business functions. Topics include: calculating present and future values, consumer finances, real estate calculations, business statistics, and systems analysis. 317 pp. An invaluable source tool at $14.95 hardcover.

Charging for Computer Services by D Bernard, J C Emery, R L Nolan, and R H Scott

Business

is written for managers who must deal with service charges. This book provides the manager with principles and guidelines for a better understanding of the charge problem. The book provides general design principles along with specific suggestions to deal with specific problem areas. Charging for Computer Services is a necessary book for the manager who must make decisions in this vital area. 120 pp. $10.00 hardcover.

A.I.

Introduction to Artificial Intelligence by Philip C Jackson Jr surveys the field beginning with Turing's test, the mathematical description of phenomena, finite state machines and limits to computational ability, followed by chapters on problem solving, game playing, pattern perception, theorem proving, semantic information processing, parallel processing, evolutionary systems, robots, and a look at the future of the field. This thoughtful and unusual book will make a useful addition to your library. A 50-page bibliography is included. 453 pp. $18.50 hardcover.

r

Just Out!

Howi to Build a Computer-controlled Robot by Tod Loofbourrow. This book combines

the dream of robotics—to create an intelligence other than human—with the reality, by providing both hands-on experience with robotics and an application of a microprocessor. You can learn the fundamentals while utilizing the ultimate in current hobby computer technology. This book details the step-by-step directions for building a robot, named "Mike," controlled by a KIM-I microprocessor, with the complete control programs clearly written out. Photographs, diagrams, and tables help to direct you in the construction. $7.95.

BITS

DIAL YOUR BANK CARD ORDERS ON OUR TOLL-FREE HOT LINE: 1-800-258-5477.

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Prices subject to ctiange without notice.

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Circle 35 on inquiry card.

BYTE liriy 1978 83

A Short History of Computing

Keith S Reid-Green

Director, Software Systems Development

Educational Testing Service

Princeton NJ 08540

A few weeks ago a master's degree candidate in computer science confided, with an embarrassed laugh, that he had never seen a computer. His experience with the machines of his chosen vocation had consisted entirely of submitting punched cards through a hole in a wall and later getting printed results the same way. While his opportunities to see equipment are restricted due to his student status, there are also thousands of working programmers and analysts using large scale equipment who have no contact with existing hardware and will never have a chance to see any first or second generation computers in operation.

This is in sharp contrast with the way programmers worked in the late 1950s and early 1960s. Before 1964, when multiprogramming computers were introduced, the typical programmer had opportunities to come in contact with the computer if he or she wanted to do so. Prior to 1960, in fact, most programmers actually operated the machine when debugging their programs. These people learned of the computer as a physical device; the current programmer is more likely to think of it as a vague logical entity at the other end of a terminal. Thus, many large system programmers have the rare distinction of using a tool without knowing how it works or what it looks like. This is in spite of the fact that many important computer developments have

Photo 1: A Chinese abacus.

Photo Acknowledgements

Photos 1 and 3 courtesy of Bettmann Archive, New York.

Photos 2, 4, 5, 6, 7, and 8 courtesy of the IBM Corporation.

Photo 9 courtesy of Cray Research Inc. Photo 10 courtesy of the Sperry Rand Corporation.

84 July 1978 © BYTE Publications Inc

Photo 2: Pascal's adding machine. Note that the rightmost dial has 12 positions and its neighbor has 20. The machine was intended for calculations involving the French currency of the period.

occurred within the average programmer's lifetime.

However, in the past year or two, dramatic reductions in the cost of minicomputer components and the advent of the microcomputer have returned the hands-on computer to respectability in two ways. First, it is now possible to justify hands-on debugging on a small computer, since the hourly rate of the programmer is higher than that of the machine. Second, the decreasing cost of home computing has fostered the birth of a new class of "renaissance programmers": people who combine programming expertise with hardware knowledge and aren't afraid to admit it. Renaissance programmers can learn much from the lessons of computer history; simple and inelegant hardware isn't necessarily best, but it's frequently cheapest.

In short, the stored program computer became a necessary tool only recently, even though various mechanical aids to computation have been in existence for centuries.

One of the first such aids was the abacus, the invention of which is claimed by the Chinese. It was known in Egypt as early as 460 BC. The Chinese version of the abacus (as shown in photo 1) consists of a frame strung with wires containing seven beads each. Part of the frame separates the topmost two beads from the lower five. The right-hand wire represents units, the next tens, the next hundreds, and so on. The operator slides the beads to perform addition and subtraction and reads the resulting sum from the final position of the beads. The principle of the abacus became known to Roman and early European traders, who adopted it in a form in which stones (called by the Latin calculi, hence the word "calculate") are moved around in grooves on a flat board.

The use of precision instruments dates back to the Alexandrian astronomers. Like the mathematics of the period, however, the development of scientific instruments died away with the demise of the Alexandrian

July 1978 @ BYTE Publicitiom Inc 85

school. The Arabs renewed interest in astronomy in the period between 800 and 1500 AD, and it was during this time that the first specialists in instrument making appeared. The center of instrument making shifted to Nuremberg, beginning about 1400. By the middle of the 16th Century, precise engraving on brass was well advanced due in part to the interest in book printing.

Calendrical calculators used for determining the moon's phases and the positions of the planets crop up in all the major periods of scientific thought in the past two thousand years. Parts of a Greek machine about 1800 years old, apparently used to simulate the motions of the planets, were found in 1902 in the remains of a ship off the island of Antikythera. The gears of the machine indicate amazing technical ability and knowledge. Later calendrical calculators, which were usually of the type in which two or more flat disks were rotated about the same axis, came to include a means of telling time at night by visually aligning part of the Big Dipper with the pole star.

Trigonometric calculators, working on a graphical principle, were in use in the Arabic period. Such calculators were used mainly to determine triangular relationships in surveying. The popularity of this device was renewed in 14th Century Europe; in fact, calculating aids of all kinds grew rapidly in popularity as well as in scope from this time onward, largely due to the difficulty of the current arithmetic techniques. Napier was continually seeking ways to improve computational methods through his inventions. One such invention, "Napier's bones," consisted of a number of flat sticks similar to the kind now used in ice cream bars. Each stick was marked off into squares containing numbers. To perform calculations, the user manipulated the sticks up and down in a manner reminiscent of the abacus. Of particular interest is the fact that Napier's invention was used for general calculation at a time when many other devices were used for the specific determination of one measurement, such as the volume of liquid in a partly full barrel, or the range of an artillery shot.

Pascal invented and built what is often called the first real calculating machine in 1642 (shown in photo 2). The machine consisted of a set of geared wheels arranged so that a complete revolution of any wheel rotated the wheel to its left one tenth of a revolution. Digits were inscribed on the side of each wheel. Additions and subtractions could be performed by the rotation of the wheels; this was done with the aid of a stylus. Pascal's calculator design is still

widely seen in the form of inexpensive plastic versions found in variety stores.

In 1671 Leibniz invented a machine capable of multiplication and division, but it is said to have been prone to inaccuracies.

The work of Pascal, Leibniz, and other pioneers of mechanical calculation was greatly facilitated by the knowledge of gears and escapements gained through advances in the clock. In the 13th Century, a clock was devised for Alfonso X of Spain which used a falling weight to turn a dial. The weight was regulated by a cylindrical container divided into partitions and partly filled with mercury. The mercury flowed slowly through small holes in the partitions as the cylinder rotated; this tended to counterbalance the weight. By the 15th Century, the recoil of a spring regulated by an escapement had made its appearance as a source of motive power. Gear trains of increasing complexity and ingenuity were invented. Clocks could now strike on the hours, have minute and second hands (at first on separate dials), and record calendrical and astronomical events. Gears opened the door to wonderful automata and gadgets such as the Strasbourg clock of 1354. This device included a mechanical rooster which flapped its wings, stretched its metal feathers, opened its beak and crowed every day at noon. Later, important improvements in timekeeping included Galileo's invention of the pendulum; and the accurate driving of a clock without weights or pendulum which led to the portable watch.

Although mechanical and machine shop techniques still had a long way to go (consider the 19th Century machinist's inability to fit a piston tightly into a cylinder), the importance of mechanical inventions as aids to computation was overshadowed by electrical discoveries beginning with the invention of the battery by Volta in 1800.

During the 1700s, much experimental work had been done with static electricity. The so-called electrical machine underwent a number of improvements. Other electrical inventions like the Leyden jar appeared, but all were based on static electricity which releases very little energy in a very spectacular way. In 1820, following Volta's discovery. Oersted recognized the principle of electromagnetism that allowed Faraday to complete the work leading to the dynamo, and eventually to the electric motor. It was not until 1873, however, that Gramme demonstrated a commercially practicable direct current motor in Vienna. Alternating current (AC) was shown to be the most feasible type of electric power for distribution, and subsequently the AC motor was

86 July 1978 £> BYTE Publications Inc

GAMES COMPUTERS

Chess Skill in Man and Machine edited by Peter W Frey. This is a most challenging book, concerning itself with the when, how, and why of computer chess. 217 pp. $14.80 hardcover.

Game Playing with Computers by Donald D Spencer. Read this book for an Introduction to numerous recreational uses of the computer. Topics include mathematical problems, casino games, board games, unusual gambling games, and logic games. Many BASIC language programs and listings are included to show details. 312 pp. $16.95 hardcover.

What to do After You Hit

Return or PCC's First Book of Computer Games. This is PCC's first book of computer games, a compendium of computer games, including listings of 37 selected BASIC games. 170 pp. $8.00.

BASIC Computer Games:

Microcomputer Edition edited by David H Ahl. Here are 102 classic computer games, every one in standard microcomputer BASIC; every one complete with large legible listing, sample run and descriptive notes. All the classics are here: Super Star Trek, Football, Blackjack, Lunar Lander, Tic Tac Toe, Nim, Life and Horserace. This revision of 101 BASIC Computer Games is a must even if you own the original. 185 pp. $7.50.

The Best of Creative Computing Volume I.

The Best of Creative Computing Volume II

Culled from the pages of Creative Computing Magazine, these two volumes provide fiction, fun, foolishness, and plenty of nuts and bolts commentary and programming information for anyone curious or serious about the wonderful world of personal computing. $8.95 per volume.

PLAY

Just Arrived*.

Chess and Computers by

David Levy. If you enjoy playing chess, then you will thoroughly enjoy Chess and Computers. This 145-page book is loaded with chess games played by and with computers. When you settle down with this book, it would be a good idea to set up your chess board and play the games. Half the enjoyment is found in playing along, duplicating the moves, reading the comments by the author and adding your own comments. $8.95.

Game Playing With BASIC

by Donald D Spencer lets you enjoy the challenge of competing with your own computer. Games described include: 3D Tic Tac Toe, Nim, Roulette, Slot Machines, Magic Squares, Keno, Morra, Baccarat, Knight's Magic Tour, and many others. The style is nontechnical, and each section gives complete rules for the game, how it works, illustrative flowcharts, and example outputs for each program. The last chapter contains 26 games for reader solution, including Hexapawn and Poker Dice. 166 pp. $6.95.

57 Practical Programs and

Games in BASIC by Ken Tracton is just that: a collection of practical BASIC applications programs for experimenters, students and professionals. In addition to the more conventional programs, there are several unusual ones (Hydrocarbon Combustion, Interactive Growth Patterns, Vector Cross Product, and Pi-Network Impedance Matching, to name a few). The book includes many flowcharts and diagrams to augment the text and programs. 204 pp. $7.95.

BITS

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T.M.

For your convenience in ordering, please use this page plus the order form on page 83. You may photocopy this page if you wish to keep your BYTE intact.

CALL BANK CARD ORDERS TOLL FREE 1-800-258-5477.

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BYTE July 1978 87

Photo 3: The Jacquard loom, one of the first machines to use holes punched In cards to control Its actions.

88 luly 1978 e BYTE Publications Inc

invented in 1888 by Tesla. The value of electric power for transportation was quictcly recognized and employed in tramways and electric railways. This led to improvements in methods for controlling electricity. Electric lighting methods sprang up like weeds during the latter half of the 19th Century. The most successful were due to the efforts of Swan in England and Edison in the United States. Work on electric lighting, the telegraph and the telephone led to the wonder of the age: radio. In 1895, Marconi transmitted a radio message over a distance of one mile, and six years later from England to Newfoundland.

As a consequence of the rapid growth of interest in the radio, much work was done on the vacuum tube. Lee de Forest discovered the principle of the triode in 1907. Until the development of the transistor, the vacuum tube was the most important device in computer technology due to its ability to respond to changes in electrical voltage in extremely short periods of time. The cathode ray tube, invented by William Crookes, was used in computers for a few years prior to 1960. It faded temporarily from view but returned in 1964 due to advances in technology that improved its economic feasibility as well as its value as a display tool. In 1948 Bardeen, Brattain and Shockley developed the transistor, which began to replace the vacuum tube in computers in 1959. The transistor has many advantages over the vacuum tube as a computer component: it lasts much longer, generates much less heat, and takes up less space. It therefore replaced the vacuum tube, only to fall prey in turn to microminiaturization. Of course, the transistor principle didn't go away, but the little flying saucers with three wires coming out of their bases did.

Oddly enough, one of the most fundamental devices in the early history of computing predates the electronic computer by more than two hundred years. The punched card was first used to control patterns woven by the automatic loom. Although Jacquard is commonly thought to have originated the use of cards, it was actually done first by Falcon in 1728. Falcon's cards, which were connected together like a roll of postage stamps, were used by Jacquard to control the first fully automatic loom in France, and later appeared in Great Britain about 1810 (see photo 3). At about the same time, Charles Babbage began to devote his thinking to the development of computing machinery. Babbage's first machine, the Difference Engine, shown in photo 4, was completed in 1822 and was used in the

computation of tables. His attempts to build a larger Difference Engine were unsuccessful, even though he spent £23,000 on the project (£6,000 of his own, and £17,000 of the government's).

In 1833 Babbage began a project that was to be his life's work and his supreme frustration: the Analytical Engine. This machine was manifestly similar in theory to modern computers, but in fact was never completed. During the forty years devoted to the project, many excellent engineering drawings were made of parts of the Analytical Engine, and some parts of the machine were actually completed at the expense of Babbage's considerable personal fortune. The machine, which was to derive its motive power from a steam engine, was to use punched cards to direct its activities. The Engine was to include the capability of retaining and displaying upon demand any of its 1000 fiftydigit numbers (the first suggestion that a computing machine should have a memory) and was to be capable of changing its course of action depending on calculated results. Unfortunately for Babbage, his theories

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luly 1978 ® BYTE PuMicitions Inc 89

Photo 5: The first use of punched cards for data processing, Hollerith's card sorter dramatically reduced the time required to process data collected in the 1890 census.

were years ahead of existing engineering technology, but he contributed to posterity the idea that punched cards could be used as inputs to computers.

Herman Hollerith put punched cards to use in 1890 in his electric accounting machines, which were not computers, but machines designed to sort and collate cards according to the positions of holes punched in the cards (see photo 5). Hollerith's machines were put to effective use in the United States census of 1890.

In 1911, the Computing-Tabulating-Recording Company was formed, which changed its name to International Business Machines in 1924. In the period between 1932 and 1945 many advances were made in electric accounting machines, culminating in 1946 with IBM's announcement of the IBM 602 and 603 electronic calculators, which were capable of performing arithmetic on data punched onto a card and of punching the result onto the same card. It was Remington Rand, however, who announced the first commercially available electronic

data processing machine, the Univac I, the first of which was delivered to the US Census Bureau in 1950. In 1963, just thirteen years after the beginning of the computer business, computer rental costs in the United States exceeded a billion dollars.

Univac I was not the first computer, even though it was the first to be offered for sale. Several one of a kind computers were built in the period between 1944 and 1950 partly as a result of the war. In 1939 work was begun by IBM on the Automatic Sequence Controlled Calculator, Mark 1, which was completed in 1944 and used at Harvard University (see photo 6). Relays were used to retain numbers; since relays are electromechanical and have parts that actually move, they are very slow by modern standards.

In 1943, Eckert, Mauchly and Goldstine started to build the ENIAC (Electronic Numerical Integrator and Calculator), which became the first electronic computer using vacuum tubes instead of relays (see photo 7). The next year John von Neumann

90

luly 197g©BYTE Publicalions Inc

became interested in EN I AC and by 1946 had recognized a fundamental flaw in its design. In "Preliminary Discussion of the Logical Design of an Electronic Computing Instrument," von Neumann pointed out the advantages of using the computer's memory to store not only data but the program itself. Machines without stored program capabilities were limited in scope, since they had to be partly rewired in order to solve a new problem (as was the case with EN I AC). This process sometimes took days during which time the machine could not be used. If rewiring of such machines was to be avoided, instructions had to be entered and executed one at a time, which greatly limited the machine's decision making capabilities. Machines with stored program capabilities automatically store not only numeric data but also the program (which looks like numbers and can be treated like numbers) in memory. In short, stored program instructions can be used to modify other instructions, a concept that leads to programs

which can modify themselves. It is the von Neumann stored program concept which is universally used in modern computers from the smallest microcomputer to the largest number crunchers.

The growth of the missile industry in the 1950s greatly stimulated the progress of computers used for scientific work. The nature of missile data handling at that time was such that work loads were very high during the week or so after a firing and virtually nonexistent in between. Computers were too expensive to leave idle, which led managers to look for other work for the machines. Business data processing grew from these roots to its present status, accounting for the lion's share of machine usage today.

The latter part of 1959 saw the arrival of the transistorized computer. As a consequence of this innovation, air conditioning and power requirements for computers were reduced. Several new computers in that year were announced by IBM, Control

Photo 6: IBM's Automatic Sequence Controlled Calculator (ASCC), the Mark I, built at Harvard between 1939 and 1944.

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Photo 7: In 1943, Eckert, Mauchly, and Goldstine started to build the EN I A C, Electronic Numerical Integrator and Calculator, which became the first electronic computer to use vacuum tubes instead of electromechanical switches.

Data Corporation, General Electric, and other manufacturers. Among the IBM announcements were the 7070 general purpose computer; the 7090, a high speed computer designed for a predominance of scientific work; the 1401, a relatively inexpensive computer aimed at the medium sized business and the 1620, a low priced scientifically oriented computer. The fantastic growth of the computer field continued through 1961 and 1962 with the announcement of more than 20 new machines each year. In 1963, continuing the family line from the grandfather 704 (as shown in photo 8), the IBM 7040 was announced. This machine embodied many of the features of the 7090 at a reduced cost. In the same year at least 23 other computers were announced by several different manufacturers. In 1964, IBM announced the 7010, an enlarged and

Photo 8: The IBM 704 had a core memory capacity of 32 K words with 36 bits per word. Although a card reader, punch, printer, magnetic tape drives and drums and a video display were available as peripherals, the concept of simultaneous IO and processing was not yet developed.

92 luly 197gSBYTE Publicilions Inc

OSBORNE ^ ASSOCIATES, INC.

The World Leaders In Microprocessor Books

If you want information on microprocessors, begin with the Osborne books.

ir New prices apply to orders postmarked after June 30, 1978

PROGRAM BOOKS WRITTEN IN BASIC

Payroll With Cost Accounting Accounts Payable And Accounts

Receivable General Ledger

These books may be used independently, or implemented together as a complete accounting system. Each contains program listings, user's manual and thorough documentation. Written in an extended version of BASIC.

#22002 (400 pages), #23002* #24002* $15.00 ($12.50 prior to July 1, 1978)

Some Common BASIC Programs

76 short practical programs, most of which can be used on any microcomputer with any version cf BASIC. Complete with program descriptions, listings, remarks and examples,

#21002 (200 pages) $8.50 ($7.50 prior to July 1, 1978)

AN INTRODUCTION TO MICROCOMPUTERS

Volume 0 - The Beginner's Book

If you know nothing about computers, then this is the book for you. It introduces computer logic and terminology in language a beginner can understand. Computer software, hardware and component parts are described, and simple explanations are given for how they work. Text is supplemented with creative illustrations and numerous photographs. Volume 0 prepares the novice for Volume I. #6001 (300 pages) $7.95 ($7.50 prior to July 1, 1978)

Volume I — Basic Concepts

This best selling text describes hardware and programming concepts common to all microprocessors. These concepts are explained clearly and thoroughly, beginning at an elementary level. Worldwide, Volume I has a greater yearly sales volume than any other computer text. #2001 (350 pages) $8.50 ($7.50 prior to July 1, 1978) Volume II — Some Real Products (revised June 1977)

Every common microprocessor and all support devices are described. Only data sheets are copied from manufacturers. Major chip slice products are also discussed. #3001A (1250 pages) $15.00 (no change in price)

ASSEMBLY LANGUAGE PROGRAMMING

8080A/8085 Assembly Language Programming

6800 Assembly Language Programming

These books describe how to program a microcomputer using assembly language. They discuss classical programming techniques, and contain simplified programming examples relevant to today's microcomputer applications, #31003, 32003 (400 pages each) $8.50 each ($7.50 prior to July 1, 1978)

PROGRAMMING FOR LOGIC DESIGN

8080 Programming For Logic Design 6800 Programming For Logic Design Z80 Programming For Logic Design

These books describe the meeting ground of programmers and logic designers: written for both, they provide detailed examples to illustrate effective usage of microprocessors in traditional digital applications. #4001, #5001, #7001 (300 pages each) $8.50 each ($7.50 prior to July 1, 1978)

OSBORNE & ASSOCIATES. INC. • P.O. Box 2036 • DEPT. 110 -Berkeley, California 94702 •

See prices above

6001 Volume 0 — The Beginner's Book

2001 Volume I — Basic Concepts

3001A Volume I! —Some Real Products (1977 edition)

4001 8080 Programming For Logic Design

5001 6800 Programming For Logic Design

7001 Z80 Programming For Logic Design

31003 8080A/8085 Assembly Language Programming

32003 6800 Assembly Language Programming

21002 Some Common BASIC Programs

22002 Payroll With Cost Accounting

PRICE

QTY

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6%, California residents outside SF Bay Area

Payment by check or money order

must be enclosed for orders of

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TOTAL

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(4151 548 2805 TWX 910 366 7277

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CITY STATE ZIP PHONE

SHIPPING CHARGES

O 4th class $0.35 per book (allow 3-4 weeks within U.S., not applicable to discounted orders) a $0.75 per book. UPS (allow 10 days) in the U.S. □ $1.50 per book, special rush shipment by air in the U.S. D All foreign orders, $3.00 per book for air shipment Shipping for targe orders to be arranged.

"l^These books are scheduled to be published during 1978. Please notify me when they are available:

D 23002 Accounts Payable and Accounts Receivable D 24002 General Ledger

Please send information on;

D Becoming an O&A dealer

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F8

Circle 293 on inquiry card.

BYTE July 1978 93

Photo 9: Cray Research Inc has recently introduced their entry into the field of supercomputers, the Cray-1, which can perform between 20 million and 60 million floating point calculations per second.

faster version of the 1410, and the 360, which came in many different sizes and embodied many features not found in previous computers. Control Data Corporation announced the 6600, and General Electric their 400 series. The IBM 360/370 is typical of a trend in computer manufacturing which is currently followed by most manufacturers: upward compatibility. In the years prior to 1965, every manufacturer spent huge sums of money on research and programming support for several types of computers; several went out of business doing so. Likewise, computer users spent a lot of money to develop their systems for a particular computer only to find it had been superseded by a faster, less expensive machine. As a consequence, the deadly management decision of the period was, "Do we get the cheaper machine and spend the money on reprogramming, or do we risk staying with an obsolete computer and losing our programmers to the company across the street?"

Current developments point to a new trend away from the bigger machines. The combination of lower prices for components and programmable read only memories is attracting many manufacturers to the field of minicomputers and microcomputers. The current trend is clearly toward the personal computer, with TV game microprocessors leading the way."

Photo 10: The UNI VAC I computer system was the first commercial computer produced by Remington Rand (now the Sperry Univac division of Sperry Rand Corporation). The first UNIVAC I was supplied to the United States Bureau of the Census in March 1951. It was the first computer to be equipped with extensive peripheral equipment.

94 July 1978 IS BYTE Publiciliom Inc

Everything you've ever

^vanted toKnow aJbout microconqiuteis in

ONE conmlete book

foronfc^ $10.95

Over 400 pages. Full 8V2" x 11" size.

The ultimate book about microcomputers. Written by experts .. . SCELBI and BYTE. Over |

400 pages. A collector's item, \

featuring The Basics ~^ " "~' *~

from the first 16 issues of BYTE and SCELBI's classic library of books. Your microcomputer bookshelf is incomplete without this priceless edition

You can't buy information organized like this anywhere. This is the book that everyone who is into microcomputers needs for reference, for ideas, for clues to problem solving. It is a truly authoritative text, featuring easy-to-read, easy-to-understand articles by more than 50 recognized professional authors, who know and love microcomputers from the ground up. Logical and complete, it features many glossaries, and is illuminated with profuse illustrations and photographs.

The Scelbi/BYTE Primer is divided into four logical sections, that take you from point "0" through building and programming your own computer... step-by-step-by-step.

What can you do with a microcomputer? Checkbook balancing. Recipe converting and food inventory. Heating and air conditioning control. Home and business security and management. Playing the ponies. Analysis of the stock market. Maintaining massive data banks. Self-instruction. Toys and games. Small business accounting and inventory. And lots, lots more.

Circle 322 on inquiry card.

How does a microcomputer do

it? Lots of "how to" theory. Introducing you to microcomputer operation. 6800, 6502, Z80 CPU chip capabilities. RAM and ROM memories. Addressing methods.

Til

SSElH/ei'TE FIVITIErV

Over 400 pages. Selected articles from BYTE and SCELBI books. Profusely illustrated. Many photographs. $10.95, plus$1 shipping and handling.

How to control peripherals. Transmission of information to and from computers. Magnetic recording devices for bulk storage. Analog to digital conversion. How a computer can talk. Other I/O techniques. And more.

Order your copy today!

SCELBI COMPUTER

CONSULTING INC.

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Prices shown for North American customers. Master Charge. Postal and bank Money Orders preferred. Personal checks delay shipping up to 4 weeks. Pricing, specifications, availability subject to change without notice.

**«^

All about building a microcomputer system. Over 12 complete construction articles. Flipflops. LED devices. Recycling used ICs. Modular construction. Making your own p.c. boards. Prototype board construction. Make your own logic probes. Construction plans for 6800 and Z80 computers. Building plans for l/Os — TV and CRT displays, cassette interfaces, etc. Mathematics functions. ROM programmer. Plus much, much more.

How to program a microcomputer. Programming for the beginner. Assembling programs by hand. Monitoring programs. Number conversions. Game of Hexpawn. Design your own assembler. Lots more.

And that's only the beginning! Others have spent millions acquiring the type of microcomputer information found within the 400 pages of The Sceibi/ BYTE Primer. But, it costs you only $10.95, plus $1 for postage and handling, complete! You know the quality of Sceibi and BYTE. This is your assurance of excellence throughout this MUST text. Order your copy today! And, get one for a friend!

BYTE |ury 1978 95

Our MacroFloppy™ goes twice the distance.

For '695.

Introducing the Micropolis MacroFloppv™:1041 and .1042 disk dnve subsystems. For the S-100/8080/Z-80 bus. Pacl<ing 100% more capacity into a 5%-inch floppy disk than anyone else. 143K bytes, to be exact. For as little as $695.

The MacroFloppv;1041 comes with the Micropolis Mod I floppy packaged inside a protective enclosure (without power supply). And includes an S-100 controller Interconnect cable, Micropolis BASIC User's Manual, A diskette containing Micropolis BASIC, and a compatible DOS with assembler and editor The :1041 is eyen designed to be used either on your desk top, or to be integrated right into your S-100 chassis.

The MacroFloppy:1042 comes with even/thing the :1041 has, and more. Such as d.c. regulators, its own line voltage power supply and, to top it off a striking cover Making it look right at home just about anywhere.

Both MacroFloppy systems are fully assembled, tested, burned-in, and tested again. For zero start-up pain, and long term reliability. They're also backed up by our famous Micropolis facton/ warranty.

And both systems are pnced just right. $695 for the MacroFloppv:1041 and $795 for the MacroFloppy:1042.

You really couldn't ask for anything more.

At Micropolis, we have more bytes in store for you.

For a deschptive brochure, in the U.S. call or write Micropolis Corporation, 7959 Deehng Avenue, Canoga Park, California 91304. Phone (213)705-1121.

Or better yet, see your local dealer

Circle 235 on inquiry card

MICROPOLIS

More bytes in store for you.

jIuFisand Newsletters

Conducted by David Wozmak

The Computer Hobbyist Group of North Texas

The Printed Circuit is a monthly publication of The Computer Hobbyist Group of North Texas, a nonprofit organization dedicated to the interests of the personal and hobby computer enthusiast. The officers of the club are R Neil Ferguson, president; Bill Lewis, vice-president; Dave Aos, secretary, and Ted Palmer, treasurer. Subscription to Tlie Printed Circuit may be obtained by joining the group at a rate of $7 per year. Dues should be sent to Ted Palmer, 1704 Downey Dr, Fort Worth TX 76112. All correspondence regarding 777e Printed Circuit should be addressed to POB 1344, Grand Prarie TX 75051.

ACG-N)

The Amateur Computer Group of New Jersey cosponsored the Trenton Computer Festival on April 22 thru 23. The show had an attendance of just over 2000. There were a number of presentations on items of interest to the hobbyist. The talks included such topics as beginning in personal computing, software, robotics, amateur radio, interfacing, and many special microcomputer applications. The list of speakers included Carl Helmers from BYTE, Sol Libes

(ACG-NJ), David Ahl (Creative Computing), and many others.

Also featured at the festival was a flea market covering more than 5 acres, more than 40 exhibition booths, and the MSC IEEE Student Paper Finals.

ACG-NJ is a nonprofit educational corporation located in northern New Jersey. IVIembership is $5 per year (US and Canada) or $12 year (foreign). This fee covers a newsletter subscription. ACG-NJ can be reached by writing to the Amateur Computer Group of New Jersey, UCTI, 1776 Raritan Rd, Scotch Plains NJ 07076.

SEMCO

The Southeastern Michigan Computer Organization is a charter member of the Midwest Affiliation of Computer Clubs (MACC) and is a nonprofit, registered organization. The club has many special interest groups (SIGs) built around the various computers: SIG-6800, SIG-HUG (Heath Users Group for H8 and H11), SIG-RS (Radio Shack TRS-80), SIG-S-100 (IMSAI and Altair, S-100 bus), SIG-KIM, SIG-Digital, and also SIG-BIG, which is a group for those interested in big machines.

SEMCO puts out a newsletter, 777e Data Bus, which has an excellent format. It has

96 luly 1978 ® BYTE PuWicitiom Inc

TM

MetaFloppy

The Micropolls MetaFloppv™ gives you more than four times the capacity of anyone else's 5%-inch floppy Because it uses 77 tracks instead of the usual 35.

The field-proven MetaFloppy with thousands of units delivered, comes in a complete family of models. And, like our MacroFloppy™ family of disk drives, MetaFloppy is designed for the S-100/8080/Z-80 bus.

For maximum capacity choose our new MetaFloppy:1054 system Which actually provides you with more than a million bytes of reliable on-line storage. For less money than you'd believe possible

The MetaFloppy:1054 comes complete with four drives in dual configuration. A controller Power supply Chassis. Enclosure. All cabling A new BASIC software package And a DOS with assembler and editor There's even a builtin Autoload ROM to eliminate tiresome button pushing

If that's more storage than you need nght now, try our MetaFloppy:1053, with 630,000 bytes on-line. Or our MetaFloppv:1045, with 315,000 bytes on-line Either way you can expand to over a million bytes on-line in easy stages, when you need to Or want to

In other words, if your application keeps growing, we've got you covered. With MetaFloppy

The system that goes beyond the floppy

For a descriptive brochure, in the U.S call or write Micropolis Corporation, 7959 Deenng Avenue, Canoga Park, California 91304 Phone (213) 703-1121

Or better yet, see your local dealer

MICROPOLIS"

More bytes in store for you.

goes beyond.

Circle 236 on inquiry card.

club information, and articles which are both informative and entertaining.

Membership is $10 per year and includes the newsletter. For more information write to the Southeastern Michigan Computer Organization, POB 9578, Detroit Ml 48202.

Sacramento Microcomputer Users Group

SMUG meets on the fourth Tuesday of every month at 7:30 PM (July 25, August 22) on 99th St, off Hwy 50, in Sacramento. Write to SMUG for exact location or for other information at POB 161513, Sacramento CA 95816.

Alamo Computer Enthusiasts

Located in San Antonio, this group meets on the fourth Friday of each month at 7:30 PM in room 104, Chapman Graduate Center, Trinity University. Special interest groups include the Z-80, 8080, 6800, 6502, North Star BASIC, Microsoft BASIC, Teletypes, graphics, and process controllers. For more information write to the Alamo Computer Enthusiasts, 7517 Jonquill, San Antonio TX 78233.

The Apple Core

The San Francisco Apple Users Group, or

the Apple Core, has been formed, and has held three meetings to date. The group was organized by Scot Kamins from San Francisco in early April 1978.

Membership regulations are somewhat exclusive; members must own or use an Apple computer. For more information contact Scot Kamins, organizer, San Francisco Apple Users Group, POB 4816, Main PO, San Francisco CA 94101.

Microprocessing Club of Gloucester County College

Located in Sewell NJ, the Microprocessing Club of Gloucester County College is now up and running. Membership is open to students of GCC and honorary membership is open to all (however, honorary members cannot vote). To find out more about this club contact Mike Seller, Microprocessing Club, Gloucester County College, Tanyard Rd, Sewell NJ 08080.

NECS

The New England Computer Society meets monthly at the Mitre Corp cafeteria, Bedford MA. For information write to the New England Computer Society, POB 198, Bedford MA 01730.*

J uly 1978 © BYTE PuUicitiora Inc 97

jispcis's

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QgIIsp

Build a Keyboard Function Decoder

Steve Ciarcia

POB 582

Glastonbury CT 06033

Figure 1: Sample hardware circuit to decode a single control code (in this case, CONTROL R). The pulse output width is the same as that of the key pressed strobe.

KEY-PRESSED STROBE

ASCII CONTROL R BINARY CODE

' 0 B6 [3>

0 85 I >—

, B4|3>

0 BJ I ^>—

0 BZ I ^>—

I Bo[;[>

0 Bl [3>

"Dear, when you go downstairs would you turn the printer on for me?"

IVly wife Joyce was on her way to the basement with an armload of photographic supplies. "And could you see if I turned the video display off as well?"

I was reclining in an overstuffed chair with the keyboard in my lap. Joyce stopped at the doorway and said, "Who was your last servant?"

"Please do it for me, honey," I said, chastened. "I have papers all over my lap and you wouldn't want me to spill my martini, would you?"

"Hey, kid, I thought computers were supposed to make life easier for us poor folk."

"They do! It's the peripherals that don't."

The next logical question I asked myself was: why shouldn't turning the printer or recorder on and off be as easy to do as any other computer transaction? A couple of quick solutions came to mind. One is to install an intercom system and station a person next to the computer while the remote terminal is in operation.

A second and more practical alternative is to put long extensions on the power lines of your peripherals and apply power to them from a remote location, but this means rewiring your house if the computer is downstairs and the terminal is upstairs (as in my case).

The third and probably best approach is

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to use some of the unused functions on your keyboard to control peripherals remotely. There are a number of unprinted characters on a keyboard such as: end of transmission, end of text, or device control codes. By attaching an ASCII decoding circuit to monitor the line between the keyboard and the computer, these functions can be isolated and utilized as peripheral device control signals — more about this later.

The ASCII Code

Most keyboards use ASCII coding, a 7 bit binary code with an eighth bit sometimes added for parity checking. (Here we ignore the proposed extensions to the officially defined ASCII code which makes it a true 8 bit code or nine bits with parity.) A complete list of ASCII codes is outlined in "Complete ASCII" by Dave Ciemiewicz (February 1978 BYTE, page 19). When your computer program is executing and awaiting data from the keyboard, a special keyboard input routine is usually activated in the program. The subroutine first determines whether a key has been pressed by checking for a key-pressed strobe signal. On systems that do not check parity (and thus use only 7 bit ASCII), the eighth bit of an input port is often set as the strobe bit. The other seven bits are not considered unless thfs strobe bit is "true." When this is the case, the seven bits are compared to a valid entry table within the program to determine what to do with the input. If there is no valid comparison, the input key does nothing.

The software read and compare routine is analogous to a hardware address decoder. For a particular ASCII code like CONTROL R hexadecimal 12, a circuit such as that in figure 1 could be used to decode and identify only this particular code. For routine uses such as a hardware reset, this is the way many computer experimenters decode an ASCII code. This basic circuit can be duplicated many times to decode other codes. Figure 2 illustrates how this approach can enable a CONTROL R to turn on a device

98

luly 1978©BYTE Publicilions Inc

Wait No Longer!

The new educational programs are here.

■pviscover how to get more out of ■'-' your computer.

Magnemedia has produced the innovative line of software products you've been waiting for. Designed for use both at home or in the classroom, these programs make learning an exciting experience.

This software comes in handsome two-cassette albums. Each cassette provides voice instruction on one side and a machine readable code on the other. Separate instruction booklets are provided in non-technical language.

All software is for APPLE II. Programs available for other micro computers indicated by following key:

• RADIO SHACK TRS-80

(Level II)

T^ COMMODORE PET

^ HEATH H8 (Extended

Basic)

Programs Now Available

• Quiz Baseball (16K)—An exciting game for two teams or players, using your questions. Computer simulates action, totaling batting averages and scores.

• Save-A-SketchTM(8K) — Create a colored picture with your

Arizona Personal Computer Place, Mesa (602) 833-8949

Arkansas Datacope. Little Rock (501) 666-8588

California A-Vidd Electronics Co., Long Beacti (213) 598-0444 Byte Stiop, Marina Del Rey (213) 530-3860 Byte Stlop, Tustin (714) 731-1686

Byte Stiop Computer Store, Walnut Creek (415) 933-6253 Byte Sfiop No. 8, Hayward (415) 537-2983 Computerland, El Cerrito (415) 233-5010 Computerland, Lawndale (213) 371-4010 Computerland, Mission Viejo (714) 770-0131 Computerland of West L.A., Inglewood (213) 776-8080 Computers Are Fun, Los Angeles (213) 475-0566 Recreational Computer Ctrs, Sunnyvale (408) 735-7480 Ttie Computer Store, Santa Monica (213) 451-0713

Colorado Ttie Byte Shop. Inc., Englewood (303) 761-6232

Connecticut Computerland, Fairfield (203) 374-2227

Florida Byte Stiop, Miami (305) 264-2983 Georgia Byte Sflop, Atlanta (404) 255-8984 Datamart Inc., Atlanta (404) 266-0336

computer keyboard. Save it for your gallery or use it as an illustration in another computer program.

• Save-A-StoryTM (16K)—Write or copy a story for practice in typing, speed reading, or for storage in your computer library.

• Learning Basic (16K) —A package of two cassettes with multiple programs. Learn programming the easy way—let the computer teach you.

• Mystery WordTM(8K)—Develop your logic skills by guessing the secret word. Computer tells you how many letters are correct in each guess.

• Reverse (8K)—A challenging math game that's a real brain teaser. How many times will you have to switch the numbers to get them in proper order?

• SupermathTM (16K)-The computer teaches you to add, subtract, multiply and divide on your own level—in color!

• True/False Quiz (8K)* i^ ^ — Tells you how to enter your own quiz.

• Variable Message (8K)tV — You choose message and colors, the computer does the rest.

• Matching Quiz (8K) • —Three changeable categories in each program. Match item on left correctly with one on right and they both

FAuthorized Distributors!

Computerland of Atlanta, Smyrna (404) 953-0406

Illinois Byte Shop, Champagne (217) 352-2323 Computerland, Arlington Heights (312) 255-6488 Imperial Computer Systems, Rockford (815) 226-8200

Kansas Personal Computer Center, Overland Park (913) 649-5942

Louisiana Computer Shoppe, Metairie (504) 454-6600

Maryland Computerland, Rockville (301) 948-7676

Massachusetts The Computer Store, Burlington (617) 272-8770

Michigan Computerland of Grand Rapids, Kentwood (616) 942-2931

New Hampshire Computerland. Nashua (603) 889-5238

New Mexico Interactive Computers, Santa Fe (505) 892-9997

__ Write to: ..

Magnemedia

17845 Sky Park Circle, Suite H Irvine, CA 92714 (714) 549-9122

disappear.

• Don't FallTM (8K)^-The computer chooses a word—you try to guess the letters without falling off cliff. Then you give the computer a word.

• Memory Aide (8K)^—Help memorizing facts, verses, lists. Computer prompts you, asks you to provide missing words, etc.

• Study Aide (8K)—The computer gives questions in random order. If you miss, it saves the question for a later try.

• Keyboard Organ (4K)—Turn your computer into a musical instrument. Play the keys hke a piano!

• Grading Routine (16K) — Takes the drudgery out of finding class curves. Different categories, grading scales, etc.

• Drawing (4K)*i5r.^ — Computer picks word at random from list you supply.

Here's the best news of all—each package of two programs sells for only $12.00! Individual programs are available for $7.50.

Magnemedia software is in stock at computer stores everywhere. (Dealers listed below). If not available yet at your store, ask them to order for you.

New Jersey Computer Corner, Pompton Lanes (201) 835-7080 The Computer Emporium, Cherry HIM (609) 667-7555

New Vorii Computer Shop of Syracuse, De Witt (315) 446-1284 Computer Tree Inc., Endwell, (607) 748-1223 Computer Micro Systems, Manhasset (516) 627-3640

North Carolina Byte Shop, Raleigh (919) 833-0210

Ohio 21st Century Shop, Cincinnati (513) 651-2111

Oklahoma Microlithics Inc., Oklahoma City (405) 947-5646

Texas Byte Shop, Richardson (214) 234-5955 CompuShop, Dallas (214) 234-3412 Computer Terminal, El Paso (915) 532-1777 Computerland, Austin (512) 452-5701 Computers 'n Things, Austin (512) 453-5970 Interactive Computers, Houston (713) 486-0291 Interactive Computers. Houston (713) 772-5257 Micro Computer Shop, Corpus Christi (512) 865-4516

Washington Ye Olde Computer Shoppe. Richland (509) 946-3330

Ontario, Canada The Computer Mart. Toronto (416) 484-9708

Circle 216 on inquiry card.

BYTE July 1978 99

Figure 2: Printer on and off control designed with discrete logic elements. Pressing CONTROL R causes a logic signal to activate an external relay in series with the printer power line. Pressing CONTROL T resets this circuit and turns the printer off

KEY-PRESSED STROBE

ASCII INPUT FROM KEYBOARD

CONTROL R IS PRINTER ON HEXADECIMAL 12

CONTROL T IS PRINTER OFF HEXADECIMAL 14

1 ^ OUTPUT SIGNAL

1 ^ TO RELAY, ETC^

PRINTER ON

KEY-PRESSED STROBE

ASCII INPUT CONTROL R FROM KEYBOARD 022 OCTAL

such as a printer, and a CONTROL T to turn it off. TPie method reaches a point of diminishing returns when more than one device is to be controlled, though.

Another disadvantage of this handwired decoding is that it is difficult to change the decoded value. I recently received a letter from a reader who needed a remote reset button. He built a circuit similar to the one in figure 1, and it worked fine for the soft

I702A

ALL OTHER OUTPUT BITS REMAIN HIGH HEXADECIMAL 7F STORED AT HEXADECIMAL ADDRESS 92

A7 ADDRESS INPUT

DO-D7 DATA

OUTPUT

Figure 3: 7 702A erasable read only memory used as an 8 bit address decoder. When CONTROL R Is depressed on the keyboard, the output at D7goes low (or true) for a period equal to that of the key-pressed strobe. This circuit can replace up to eight of the circuits shown In figure /.

ware he was using at the time. But when he changed from MaxiBASIC to Zapple BASIC, he found that the control code he had chosen for reset was necessary for use in the BASIC, so out came the soldering iron and in went another integrated circuit. Then came the expansion of more software from other manufacturers, and the circuit had to be changed again. His complaint was concerned not with the method of decoding the signal but rather with the difficulty in changing its particular address.

I, of course, wanted to have a hardware reset and peripheral device controller. I could build a combination of the circuits in figures 1 and 2 and hope that the next piece of software I get doesn't use one of the control codes I used, but a concept this simple shouldn't require that much wiring or make it that hard to change addresses.

Since I like the idea of using the keyboard to control the peripheral devices and don't like to solder any more than necessary, the best alternative for me is a programmable read only memory board control code decoder.

Consider how a programmable read only memory works: a binary code is impressed on the address input lines and, in the case of the 1702A, an 8 bit binary word stored at that location appears at the output. By se

100

July 1978©BYTE PuUicallons Inc

Control

Keyboard

Hexadecimal

Octal

Parity

Character

Equivalent

Alternate Code Names

00

000

EVEN

NUL

@

NULL.CTRL SHIFT P.TAPE LEADER

01

001

ODD

SOH

A

START OF HEADER.SOM

02

002

ODD

STX

B

START OF TEXT.EOA

03

003

EVEN

ETX

C

END OF TEXT, EOM

04

004

ODD

EOT

D

END OF TRANSMISSION,END

05

005

EVEN

ENQ

E

ENOUIRY,WRU,WHO ARE YOU

06

006

EVEN

ACK

F

ACKNOWLEDGE,RU,ARE YOU

07

007

ODD

BEL

G

BELL

08

010

ODD

BS

H

BACKSPACE,FEO

09

Oil

EVEN

HT

1

HORIZONTAL TAB.TAB

OA

012

EVEN

LF

J

LINE FEED,NEW LINE,NL

OB

013

ODD

VT

K

VERTICAL TAB,VTAB

QC

014

EVEN

FF

L

FORM FEED.FORM PAGE

OD

015

ODD

CR

M

CARRIAGE RETURN,EOL

OE

016

ODD

SO

N

SHIFT OUT,RED SHIFT

OF

017

EVEN

SI

0

SHIFT IN,BLACK SHIFT

10

020

ODD

DLE

P

DATA LINK ESCAPE,DCO

11

021

EVEN

DC1

Q

XOIM,READER ON

12

022

EVEN

DC2

R

TAPE,PUNCH ON

13

023

ODD

DC3

S

XOFF,READER OFF

14

024

EVEN

DC4

T

TAPE,PUNCH OFF

15

025

ODD

NAK

U

NEGATIVE ACKNOWLEDGE,ERR

16

026

ODD

SYN

V

SYNCHRONOUS IDLE,SYNC

17

027

EVEN

ETB

w

END OF TEXT BUFFER,LEM

18

030

EVEN

CAN

X

CANCEUCANCL

19

031

ODD

EM

Y

END OF MEDIUM

1A

032

ODD

SUB

z

SUBSTITUTE

IB

033

EVEN

ESC

[

ESCAPE,PREFIX

1C

034

ODD

FS

/

FILE SEPARATOR

ID

035

EVEN

GS

]

GROUP SEPARATOR

IE

036

EVEN

RS

A

RECORD SEPARATOR

IF

037

ODD

US

UNIT SEPARATOR

Note: To transmit any

control code, depress

the CTRL key while pressing the character l<ey

on the same 1

ine under

Keyboard Equivalent.

Table 1: ASCII code control characters.

of

lectively storing specific values at designated locations in the programmable read only memory, a single 1702A can be structured to perform the functions of eight separate decoders like the one in figure 1. For example, if a CONTROL R code were impressed on the address lines of the 1702A, and hexadecimal 7F (binary 01111111) is stored in hexadecimal address 12, the most significant output bit will go low whenever this pattern appears. All other output lines will remain at a high level. The same method can be used for eight different ASCII codes. The function of the circuit shown in figure 1 can be performed by an erasable read only memory (EROM) as shown in figure 3.

To use an EROM for this purpose, first choose eight different ASCII codes which are available on your keyboard and which are not used as software control codes. By convention, CONTROL Q, CONTROL R, CONTROL S and CONTROL T have been set aside to represent Reader On, Punch On, Reader Off and Punch Off, respectively. The other four control codes could be CONTROL W, X, Y and Z, etc. Table 1 shows the ASCII control codes.

An unprogrammed (erased) EROM has all bits set to the 1 state. This is true for the 1702A, the 2708 and the 2716. Next,

choose eight control codes and make a list such as the one in table 2.

Store the binary word listed at the respective address location equivalent to the ASCII code with the eighth bit (the strobe bit) set high. For a CONTROL R, a hexadecimal 14 code, this would become an address of hexadecimal 94. When one of these particular keys is pressed, a particular output bit of the EROM goes low for the duration of the keypressed strobe. Obviously, if only a short pulse is necessary for your control application, no further logic is necessary. In my application it is necessary to "hold" the

Table 2: Hexadecimal values to be stored In EROM to decode eight control codes.

Hexadecimal

Hexadecimal

EROM

Hexadecimal Value to be

Keyboard

Code

Address*

Stored in EROM

CTLO

11

91

7F

CTLR

12

92

BF

CTLS

13

93

DF

CTLT

14

94

EF

CTLW

17

97

F7

CTLX

18

98

FB

CTL Y

19

99

FD

CTLZ

1A

9A

FE

Note: All other

address locations

should have hex

adecimal FF (fully erased data)

stored in them.

*The EROM address is the

7 bit ASCII code with the eighth bit set high.

luly 1978©BYTE Publicatians Inc

101

state of three devices and pulse two of them. This requires latches made from external gates to maintain the control output after the initiating pulse. One method is to trigger an RS flip flop on and off with two separate codes. In this way, CONTROL R and CONTROL T can be used to turn the printer on and off, respectively. Figure 4 illustrates the completed keyboard function decoder utilizing a 1702A EROM. It allows latched on and off control of three devices and pulsed control of two more. I chose a 1702A because of its cost advantages: at $3.50 it is more

appealing than a $12.50 2708; but the 2708 may be more easily programmed for most people (see "Program Your Next EROM in BASIC," March 1978 BYTE, page 84). It can be used instead of the 1702A with the appropriate pin assignment changed. Since the 2708 is a 1 K EROM and the 1702A is 256 bytes, the two extra address lines A9 and A10 should be grounded on the 2708. If you decide to use the method of figure 2 and not use an EROM to make the circuit of figure 4, it will take 14 TTL chips just to create the logical equivalent of the EROM.

KEY PRESSED STROBE

ASCII INPUT

FROM

KEYBOARD

Figure 4: EROM-based function decoder circuit with ttiree latched and two strobed outputs. These outputs can be used to controi soiid state reiays and, in turn, printers and other peripherais.

■12V I > ■

► 5v(3>

m

Notes:

RECORDER CONTROL

PRINTER CONTROL

AUXILIARY CONTROL

J V- —1 r- STROBE

1 ^ '-' CONTROL Y

J ^ —I r- STROBE

I -^ '-' CONTROL Z

1. The EROM is programmed as per the EROM address and binary value information listed in table 1. All other address locations should be left fully erased (hexadecimal FF).

2. The signal outputs from integrated circuits 7 and 8 can be connected to solid state relays, which in turn provide on and off control of the designated peripherals. For an explanation and a design of a solid state relay, see "Tune In and Turn On, Part 2," May 1978 BYTE, page 97.

3. All resistors are 1 /4 W 5% unless otherwise specified.

Key Pressed

CONTROLQ CONTROLR CONTROLS CONTROLT CONTROLW CONTROL X CONTROLY CONTROLZ

Function

Recorder power on Printer power on Recorder power off Printer power off Auxiliary power on Auxiliary power off Bit 1 low true pulse Bit 0 low true pulse

102 July 1978 e BYTE PuMicitJom Inc

Table 3: Power wiring tabie for figures 2 and 4.

Number

Type

+5V

Gnd

IC1

7404

14

IC2

7404

14

IC3

7430

14

IC4

7430

14

IC5

7400

14

IC6

1702A

see schematic

IC7

7400

14

7

IC8

7400

14

7

Some Final Thoughts

I guess I don't have to worry about finding someone to be my peripheral "slave" any more. The uses of this remote control system can be extended beyond the ones I've outlined; my horizons were limited at the time. Once I sit back in that chair with a keyboard in my lap, it takes an earthquake to move me.

Do you have any questions, comments or ideas for an article? Write to me; I try to answer every letter. Please enclose a stamped self-addressed envelope. Next month: a touch panel digitizer."

o

I

To further improve service to our customers we have installed a toll-free '\ WATS line in our Peterborough, New Hampshire office.^ If you would i ke to order a subscription to\ BYTE, or if

Toll-free \ ^°"'^'^^\

I vril 11^^ ^ question relat->

to a BYTE '

BYTE'S New

i

Subscriber W.A.T.S. Line

ed

(800)258-5485

We thank you and look forward to serving you.

3ULaAiLflJUUL8JUA

subscription,

you are invited^

to call'

(800)258-5485

between 8:30 AM and

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^♦Applies to calls made

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A RAM board for only $289? Central Data's got it!

Central Data's 16K RAM board comes completely assembled, tested and burned in for only $289. Our competitors find that hard to beat. But, the low price is not all we offer.

The Central Data 16K RAM board is complete when you buy it from us, but we offer the added feature of expandability to 32K. Someday you'll need more than 16K, and when that day comes, you'll be ready. The cost of adding 16K to your present Central Data 16K RAM board is $200. A 32K RAM board, assembled, tested and burned in, is $475.

The invisible refresh feature of our board means that the performance of your system can never be degraded by wait cycles.

Our RAM board is S-100 compatible, and it has an access time of 450ns.

Each Central Data board comes with a one-year warranty.

To order your 16K RAM board or to receive more information, write to us at Central Data today.

^%«i

'iili'silnSM

trmi

mlml Oafia Ooo^p

PO Box 2484, Station A Champaign, IL61820 (217)359-8010

Circle 45 on inquiry card.

July l97g@BYTE PuUicitions Inc 103

IDS

INTERNATIONAL DATA SYSTEMS, INC.

400 North Washington Street, Suite 200. Falls Church, Virginia 22046 U.S.A. Telephone (703) 536-7373

88-MODEM: A complete serial I/O port and an Originate/Answer MODEM on an SI 00 bus compatible board The 88-MODEM features automatic auto-dialer (not software timed), operates at any software selected baud rate between 66 and 600 baud, has separate 8-pole transmit and receive active filters, and all functions are software selected The 88-MODEM provides communication to -58 dbm and is intended for use with either a CBS (1001 D) or GBT Data Access Arrangement for connection to the telephone system The kit price is S245 00

88-UFC UNIVERSAL FREOUENCY COUNTER: The 88-UFC is an SI 00 compatible frequency and period measurement module. The 88-UFC has four software selected inputs Frequency measurement to above 600MHz and period measurement to 1 /10th microsecond are standard. The counter provides nine digits of readout and is pnced ai $179,00 in kit form

88-SPM CLOCK MODULE: The 88-SPM provides a time of day clock and an independent realtime clock on one SI 00 compatible module Provisions are included for battery backup so the 88-SPM can maintain the time during power-off conditions $96 00 kit

1001D (Type CBT) Data Access Arrangement $125,00

88-RCB 16 Channel Relay Control Board Kit $179,00

MCTK Morse Code Trainer/Keyer Kit 2900

TSM Temperature Sensing Module Kit 24,00

DAC-8 8-Bit Digital to Analog Converter Kit 19,00 88-TCXO Temperature Compensated Crystal

Oscillator for 88-UFC 145,00

88-XTAL Crystal Timebase option tor 8B-SPM 25,00

TERMS Payment with order shipped prepaid, added for COD, Master Charge accepted

Continued from page 6

sages sent and received would be the following little loop:

var

hangup : boolean; hangup := false; repeat

look at keyboard, send latest Input"] jnessages to line and display J

look at line, send any input] messages to display J

until hangup ;

(This program fragment is represented in PASCAL with the use of italics enclosed in square brackets [] to denote functions described verbally but not in detail. Note that "hangup" is a dummy variable within the context of this fragment as shown.)

This simple programming model is applied at both ends of the communications line through the phone network. It might in fact be implemented in two totally different computer and software systems, say in assembly language on one party's computer and in PASCAL on the other party's computer. It also has the unfortunate disadvantage of displaying the incoming message from the line mixed with the latest outgoing message from the keyboard.

Walking through the process of establishing and holding a conversation illustrates some fundamental points which apply to any computer to computer communications method. In this case, much of the work involved in setting up the conversation, the protocol, is accomplished manually. Let's look at what a conversation between two parties might be like, using X and Y as suitable arbitrary names in this script:

Phone rings. X picks up the phone.

X: "Hello, X here."

Y: "Hi, X. Shall we proceed with the communications experiment?"

Note the implicit protocol: Y assumes X Is looking for a computer to computer conversation.

X: "Sure. I'll load my program. Let me set my modem in the originate mode."

Y: "Fine. I'll set my modem in the answer mode and load my program."

Note the complementary settings of the modem modes. For a full duplex conversation, one end must be in answer mode, the other end in originate mode. A mode is simply the set of transmission and reception frequencies chosen for use by the modem from two alternatives.

X: "I'm starting my program. How's yours doing?"

104 luly 1978 e BYTE Pul>licaliom Inc

Circle 185 on inquiry card.

Y: "Mine is just fine. Do you hear the

tones from the modem?" X: "Yes. Okay, let's try the phones." Both parties conclude verbal communications by placing their phone handsets in the acoustic couplers. A computer to computer conversation ensues, using data from the keyboards and sending data to the displays at each end.

This is perhaps one of the simplest models of computer to computer communications over a phone line via a modem. But it illustrates a couple of important points which are required in any system which uses the dialup network.

First, there must be a protocol tying the two systems together logically. This protocol provides a method of establishing contact. Here, I used the conversation as an example due to the simplicity of the equipment and the model. It could be as complicated as a full network protocol like those of ARPA, PCNET or CIE Net. The protocol must also involve the agreement upon a functional model of the software driving the communications channel. Here the PASCAL program fragment, however it is implemented in detail, provides the common functional model for both ends of the line. The actual details of a conversation are independent of the protocol used.

Second, the equipment used at both ends must be compatible with respect to modem design. Here, I have tacitly assumed a modem is available which has one outgoing channel and one incoming channel. This could be a Bell 103 style modem which is one of the most commonly available forms on the market, or it could be some haywire kluge with nonstandard frequencies which are shared by the two parties to the conversation and nobody else. The choice of "answer" or "originate" in the context of this example is arbitrary; when using such a modem with a timesharing computer, the choice is not arbitrary.

Third, the protocol can easily be automated to some extent; with proper equipment and appropriate systems software running in your system and your network correspondent's system, the entire conversation can take place without human intervention from start to finish. But more on that subject a little later.

The conversation just described, and its protocol, are not intended as a serious suggestion for the use of a typical acoustically coupled modem. It represents if anything just a costly way to bypass the US Postal Service and all its problems and transmission delays; but then the same is true of the tele

16K RAM

Fully Assembled, Tested^ Burned-in

.»m\T\ii""'* Fully static

^'"^""'" Using the TMS 4044

250 nsec. chips—$425

Z-80A 4 Mhz. Fast—^Thls fully assembled and tested 16K board was designed to operate without wait states in a 4 Mhz. Z-80A system allowing over-generous time for CPU board buffers.

450 nsec. chips—$375

For 2 Mhz. Systems—Same circuit as above but priced lower because of less expensive memory chips. It is fully assembled, burned-ln, tested and guaranteed.

8K Versions Also Available

Both boards available fully assembled with sockets for all 32 MOS chips but supplied with only 8K of chips. 8K—250 nsec—$265. 4K chip set—$95. 8K-450 nsec.—$235. 4K chip set—$85.

Fully Static is Best—Both boards use the state-ofthe-art Texas Instruments TMS 4044 which requires no complicated and critical clocks or refresh. The fully static memory chip allows a straight-forward, "clean" design for the board ensuring DMA compatibility. They use a single 8 volt power supply at 1.7 amps nominal.

Fully S-100 Bus Compatible—Each 4K addressable to any 4K slot and separately protected by DIP switches.

Commercial Quality Components—First quality factory parts, fully socketed, buffered, board masked on both sides, silk-screened, gold contacts, bus bars for lower noise.

Guaranteed—Parts and labor guaranteed for one full year. You may return undamaged board within ten days for a full refund. (Factory orders only—dealer return policy may vary).

C/jec/f your local computer store first

Factory Orders — You may phone for MC, VISA. Cashier's check, MO. speed shipment for mail orders. Personal check OK. Shipped prepaid with cross country orders sent by air. Shipping — Stock to 72 hours normal. We will confirm order and give expected shipping date for delays beyond this. Washington residents add 5.4% tax. Spec, sheet, schematic, warranty statement sent upon request.

V Seattle Computer Products. Inc.

^•r^ 16611 111th S.E., Renton, Washington 98055 (206) 255-0750

Circle 313 on inquiry card.

July 1978 3 BYTE Publiuliominc 105

Computers For Everyone! Prices For Everyone!

PET 2001-8 by Commodore

• 8K user RAM (expandable to 32K)

• 8K BASIC in ROM

• Built-in video display

• Built-in keyboard with graphic characters

• Built-in cassette recorder

PET 8001-8 C8k BAM) $795.

10 Blank C-10 casseUe SO.

"BASIC BASIC" Book 9.

L reg. $824.

You pay only

$795.

Apple II16K by Apple Computers

16Kuser RAM (expandable to 48K)

6K Integer BASIC In ROM

2K Monitor m ROM

Pull ASCII kejfboard

16-oolor graphics (low resolution 40H x 40V)

4-color graphics (high resolution 280H x 192V)

Game Paddles Included

Includes BASIC software on cassette:

• leKStartreck program • Color demonstration programs

• 1 OK Floating poixit BASIC • Breakout video game tnterpi^ter

Yoiir color TV set reqiilred for display

APPLE n C16K BAM) $1195.

Merlton cassette recorder 80.

M&B BP ModTilator 30.

L ^6- $1305.

You pay only

$1195.

Add $10-00 per system for shipping and handling. To quali^ for these special package prices, ftill payment must accompany your order. We will refund full amount if you wish to cancel before we ship.

Write or Call

cemputcf cmcrpri/c/"

P.O. Box 71

Fayetteville, N.Y. 13066

Phone C318) 637-6208 Today!

Operating Hours: M-W10-8E.S.T. Th-riO-9E.S.T.

Closed Sot. & Sun.

phone used without a computer. The interesting uses are those which tal<e advantage of the computer at both ends of the conversation. Establishing communications between modems will involve a similar phone call scenario; but now instead of the toy program, suppose we substitute a more interesting process.

For starters, a useful utility already employed by many personal computer people is that of a file swapping program. Here, instead of keyboard input, after the communications is established and verified in a keyboard to display mode, one or the other of the two parties to the conversation accesses a local file on floppy disk and dumps it into the floppy disk of his correspondent over the phone lines. The file sent might be verified by the receiving person by one or more methods such as grouping the data into blocks with checksums or simply sending the message redundantly.

The content of the file sent by this method is arbitrary. The file could be as simple as the edited text of a letter, or as complicated as the source code of the latest version of a computer game which the receiving person is to try out, evaluate and comment upon. And of course, for the occasional business user or privacy fanatic, the program does not have to send the data directly: it could use a prime factors cipher to ensure that all the computers in the world would never be able to crack the code in practical lengths of time given our present knowledge of such ciphers and their properties.

But exchanging data files still does not exhaust the potential of having a computer at both ends of the line. What other activities involve participation by people at each end of the line? (Remember: we are still using simple modems with a manual protocol at the start of communications.) A computer at each end and a person operating the computer sounds like defining characteristics of a new class of challenging computer games.

For one degenerate case, let us suppose that each player has as his goal to "take over" the other player's computer, using a commonly defined operating system nucleus and a set of rules governing legal moves. The result would be a very abstract, possibly quite exciting (and possibly quite dull) 2 processor remote version of the classic called core war. [Core war is a game surreptitiously played by systems programmers on large installations, where a player's goal in each fixed time slice of real time is to propagate his program elsewhere in memory, while doing as much "damage" (read: clearing to zero) as possible at random places in the

106 luly 1978 e BYTE PuWicilions Inc

Circle 70 on inquiry card.

hopes of causing the opponent's program to blow up.] The game of core war is rarely mentioned with more than a whisper, and thus tends to be lost amid the din of easier and less abstract games such as Star Trek, Adventure or Dungeons and Dragons. But, just as a 2 computer version of a classic is possible, these contemporary games might well be adapted to a 2 sided mode employing two computers and two teams of players.

Games border on the world of simulations, and simulations border on the world of games. The use of two local processors across the phone lines (or in the same room sans modems) has much potential. Suppose each computer is running a simulation of a plane in flight. A natural variation would be to loosely couple the state variables between the similar programs across the link, so that the two "pilots" could attempt formation flying and maneuvers. The key software which is needed is of course a simulation program with direct memory outputs to a display on each computer, and the ability to keep track of the "other guy" from the point of view of the local simulation. For most one player versus the computer games, the random number sources of data typically used could be replaced by parameters received across the communications line from the second computer. At 300 bps (30 characters per second, roughly) the potential for some 2 party interaction is definitely present, relying upon local simulations in each computer for most of the actions observed on each screen.

But enough of this blue sky. How much does the equipment cost? All of these suggestions could be implemented using a typical personal computer which has a spare serial lO port with RS-232 levels (the more floppy disk drives the better of course, with zero as the minimum acceptable number). The cost for the modem, based on two advertisements in the May 1978 issue of this magazine, would be either $139 or $129 depending upon whose modem you buy. The basics require no particular attention to the phone line itself, other than making sure you have a standard handset which fits the acoustic coupler. And of course, having made the investment you also get access to the local time sharing service, which may have such juicy tidbits as cross assemblers and compilers which are not yet up and running on your own system. But this is merely a taste of the possibilities of telecommunications: even more function can be had at a slightly higher expense through the use of modems which feature automatic dialing, automatic answering and telephone company compatible "data access arrangement" (DAA) features.

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July 1978® BYTE Publications Inc

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Circle 311 on inquiry card.

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Automatic Communications:

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The protocols appropriate for an acoustically coupled modem are heavily biased by the need for manual operations. Just as the audio cassette recorder is the poor second cousin of the floppy disk as a mass storage medium, the acoustically coupled modem works for telecommunications but has many fewer features of merit than the more expensive modem options.

The first extension to consider is that of a form of the modem which is wired permanently to the phone company's network via an appropriately approved data access arrangement or DAA. Given this extension alone, there would apparently be no great improvement in function relative to the simple acoustic modem.

Thus we must consider the second extension, use of an auto answer option through the data access arrangement. Here, with appropriate software, your computer gets a signal from the interface which tells it when someone is calling. The computer can then reply with a signal which "lifts the phone off the hook" by changing appropriate electrical levels in the interface which simulate that normally manual action. The computer can then proceed to verify that there is indeed a modem on the other end and commence its automated version of that conversation between X and Y given a little earlier. For thorough description of how such protocols work, consult any text book on systems software for timesharing systems: this model is used by your friendly timesharing service to receive calls from its users with ordinary modems at the other end.

The third of these three extensions of the basic model is the auto dial function. Here the intent is to allow your computer to place the call automatically, an event which implicitly assumes the number being dialed can receive such calls unless the modem is disconnected after the call is made.

This more general function can be had at reasonable prices. The board used by Ward Christensen and Randy Suess costs about $300 assembled and tested, plugging into an S-100 bus slot. Another brand, also assembled and tested, but complete with a Bell approved data access arrangement module, runs about $500 and also plugs into an S-100 bus slot. (The difference between buying your own data access arrangement module or using a phone company version is one of paying monthly installments forever or paying a lump sum of about $100 to $150 once.)

108 |ul> >9;6^BYU rublicitioniinc

Circle 298 on inquiry card.

Circle 136 on inquiry card.

With the economics of the auto dial and auto answer versions and data access arrangement settled, what are the possibilities which may be fulfilled? First, there is the matter of regular correspondence with a close friend on the other side of the continent. If you communicate via the simple model of the unautomated link, your prime time for originating a call may be different from the hours of prime functioning as a human being. The phone company rates are much lower in the wee hours of the morning. So, let your automated computer servant sit up late and take advantage of the cheap rates to telephone your correspondent's computer, send the mail you left for him or her and of course receive the mail left for you. More than one correspondent? Simply keep a list of phone numbers associated with the names, and call all of the ones which have been left messages on a disk file or in memory. Don't care to waste phone charges? Well, use the auto answer feature to wait for your correspondent's calls. (This concept of using the auto answer and auto dial features to implement Telemail service is one of the pet projects of Ken Bowles at the University of California at San Diego. We can expect to see a protocol established from that source, written in PASCAL of course, which will be widely available for a nominal charge.)

Let's extend the model a bit to the world of games so often frequented by the personal computer user. But now, consider the N party game, a sort of computerized version of Dungeons and Dragons viewed as a prototype of the N player simulation game. Now, the phone network and dialup features can be used to some advantage: instead of one week's long conversation on a party line (the brute force approach), each player node in the game has a computer with a local model of the game plus interaction models which involve dialing up other players in the game for information or to send game messages which affect the other players. To be less than prohibitive in line costs, it would have to be done locally within a "free" dialing zone of your local exchange. It is a challenging problem to even think about defining such a game, let alone playing it. It is a suggestion which is quite within the capabilities of a dedicated group of N enthusiastic participants. Who will be the first to define and implement such a discipline?

And then, of course, there is the less esoteric but quite useful concept of the local computer club bulletin board, as prototyped by Ward Christensen and Randy Suess. Here, both the auto answer and the auto dial modes can be used to advantage. The auto answer mode is of course currently being

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employed in the interactive message center concept: users can call in from anywhere and leave messages which are either broadcast, or specific to particular users. The club can also prepare a file which is sent to every active user upon logging into the system.

The concepts of auto dialing and autc answering can also be applied to personal use independent of the use of the modem if provision is made to manually switch from modem data to voice data. The auto answer feature is of course typically used in a standard telephone answering machine, but by having your computer answer the line and listen with one of several voice response boards on the market, you might be able to call up your house and have various options such as lights, radios or sprinklers change state in response to voice command. If the voice recognition method of remote control does not work then consider using a touch tone telephone to send a coded pattern of numbers which are detected by another special demodulator after the phone is answered.

Auto dialing coupled with the usual voice mode enables you to build a file of frequently called numbers, a "little brown disk" instead of a little black book. These numbers could then have symbolic names like "FIRE," "MOTHER," "SUZY," "JUDY,"

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Circle 35 on inquiry card.

Circle 61 on inquiry card.

Circle 101 on inquiry card.

etc. When a phone conversation is desired, dialing could be done symbolically by selecting a name with one character referring to a menu list on your display. Of course there are certain things one would not want to do with an auto dial feature, such as create intrusive automatically dialed junk phone calls.

Summarizing the State of the Art...

Computer to computer communications via the dialup phone network are a very real possibility for the personal user. The communications can be as simple and inexpensive to implement as an acoustic coupler on an ordinary telephone, or slightly more elaborate (but still less than $500 for an S-100 bus computer) with automatic answering and dialing features. However you implement your link to the outside world from a personal computer, the applications of the system expand considerably."

How Much Is That Turtle in the Window?

As noted with a photograph and some background information on page 6 of the March 1978 BYTE, personal computer users will soon be able to add an absolutely fascinating new peripheral: an electromechanical "turtle." Recent word from Cambridge is that the Terrapirr turtle was scheduled for a mid May press conference announcement by Terrapin Inc, 33 Edinborough St, 6th Floor, Boston MA 02111. (This note was written April 24 1978, following a phone conversation with David McClees of Terrapin.)

Using simple programming concepts in versions of the LOGO language, it is possible to teach young children many of the concepts of computer science using the mechanism of the turtle to emphasize points. Also quite possible with such a mobile robot appendage are various other applications from delighting friends at an adult or child's party to implementing the world's least expensive plotter output using the tail dragging capability of the turtle's solenoid controlled pen. Sensors on this inexpensive robot are four microswitches which can determine one of eight possible directions when the unit runs into an object.

How much for that "turtle in the window" at your local pet store? While final prices have not yet been set, the kit version is expected to be about $300. To be complete, Terrapin Inc will also sell an assembled version for $500 or so."

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Mail to: Information Unlimited (authoriied distributor) P.O. Box 55B, Hsbron. Indian* 46341

n Model NS 3 for North Star BASIC (requires 24K RAM). $75.00

LJ Quantity discount schedule for dealers

[J More information (I'm running disc BASIC

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Circle 73 on inquiry card.

July 1978 e BYTE PuWkaliom Inc 111

Lsngusges Fopuff)

Pat Fitzgerald

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BASIC to Assembly Language Linkage

Listing 1: PDP-ll assembly language listing of program to output a quotation mark.

177564

TPS =177564

177566

TPB =177566

000050

.=50

000050

037426

-WORD SEXF

037426

.=37426

037426

105767 SEXF: TSTB TPS

140132

037432

100375

BPL SEXF

037434

012767 000042 140124

MOV #042,TPB

037442

000167 140404

JMP 52

000052

.END 52

;teleprinter status ;teleprinter buffer ;link between BASIC and ;external function ;start address of ;external function ;is printer ready?

; if not branch

;move ASCII code for quotation

;mark to buffer and print .•return to BASIC

Listing 2: Driver program for the assembly language program in listing 1.

10 PRINT "IN BASIC THE QUOTATION MARK (";

2 0 LET T = EXF(l)

30 PRINT") IS A DELIMITER"

Listing 3: Sample run of the BASIC program of listing 2. This is one simple solution to the problem of printing a quotation mark in a BASIC interpreter, lacking appropriate escape mechanisms.

IN BASIC THE QUOTATION MARK (") IS A DELIMITER

Frequently one needs to use a BASIC interpreter to do things it was never designed to do. Getting around the problem can require a great deal of ingenuity. A case in point is David Chapman's article, "All This Just to Print a Quotation Mark?", in May 1977 BYTE.

Several versions of BASIC allow assembly language programs to be added to the BASIC interpreter; these programs are linked to BASIC at load time and usually cannot be deleted without reloading BASIC. Using this technique provides a very simple method of getting around the problem described by David Chapman. The assembly language listing is given in listing 1 and the BASIC language program is given in listing 2. A run of the program is in listing 3. It appears that a relatively simple solution to the problem has been found.

The version of BASIC I use is single user Digital Equipment Corporation's BASIC V008A for the PDP-ll series of minicomputers. This BASIC allows the user to call the assembly language program by use of an EXF function. Obviously in other

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Circle 36 on inquiry card.

versions of BASIC the calling procedure will be different. The EXF function call can be used as an expression or as an element of an expression anywhere that an expression is legal in BASIC syntax.

The assembly language program is called by use of the EXF function. The argument for the quotation mark program is a dummy one and any number would suffice. However this is a trivial use of the power of the linking method. More useful programs can be written to allow BASIC to be used in a variety of applications from real time control of instruments to reading data from cassette transports. It can also be used to add powerful functions to increase the number crunching ability of BASIC. In short the uses of this tool are only limited by the user's imagination.

One particular use we can make of the assembly linkage is a program to retain a BASIC program in the machine when the power is turned off. On the PDP-11 series when BASIC is restarted, information necessary to recall the user program is lost from two of the volatile registers

(although the main core memory returns its information). However, use of the assembly language program shown in listing 4 allows the contents of these registers to be saved on power down and restored at power up.

To use this program when you have temporarily finished with the BASIC pro

Listing 4: A nontrivial use of BASIC to assembly language linkages. This PDP-11 assembly program saves the PDP-11's registers and restores them so that the program may be used after a restart occurs.

000001

R1 = %1

;define registers to

000005

R5=%5

;be saved

000006

SP=%6

;register 6 to be stack

000050

.=50

037406

.=37406

037406

010146

START

.MOV

Rl,-(SP)

;save Rl and R5

037410

010546

MOV

R5,-(SP)

;on stack

037412

010667 000016

MOV

SP,SAVE

;save stack

037416

000000

HALT

;EXIT AND RE-ENTRY POINT

037420

016706 000010

RSTRT

:MOV

SAVE,SP

.-restore stack and

037424

012605

MOV

(SP)+,R5

;registers 1 and 5

037426

012601

MOV

(SP)+,R1

037430

000167 140416

J MP

52

;back to BASIC

037434

000000

SAVE:

.WORE

0

000052

.END

52

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luly 1978 <&J BYTE Publications Inc 113

gram, you type "Print EXF (N)" where N is an arbitrary number. When you wish to reuse the program, you start at address 037420 rather than the conventional 000000 which would destroy the user program. The machine responds by typing the number N. In this version of BASIC the linkage between the interpreter and the assembly language program is maintained through location 50; this address must contain the start address of the assembler language program. Return to BASIC is achieved by a jump to location 52. Several arguments can be used in the EXF function, but it is the user's responsibility to evaluate each argument after the first. By this technique an assembly program with several entry points can be called up from a BASIC program to do a multitude of tasks not provided for in the BASIC language.

Of course this requires that the programmer learn the assembly language. Fortunately for the PDP-11 user an excellent introductory manual has been provided by R W Southern (see references).

Moral

Try using assembly language programs before attempting complex contortions within BASIC."

REFERENCES

Chapman, David, "All This Just to Print a Quotation Mark?", May 1977 BYTE, page 132.

Southern, R W, PDP-11 Programming Fur)damentals, Algonquinote 12, Algonquin College Bookstore, Ontario CANADA, 1972.

Languages Forum is a feature wliich is intended as an interactive dialog about tlie design and implementation of languages for personal computing. Statements and opinions submitted to tfiis forum can be on any subject relevant to its purpose of fostering discussion and communication among B YTE readers on the subject of languages. We ask that all correspondents supply their full names and addresses to be printed with their commentaries. We also ask that correspondents supply their telephone numbers, which will be printed unless we are explicitly asked to omit them.

BASIC is BASIC is ...

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Circle 4 on inquiry card.

Fooling

with the Stack Pointer

I think Dr Borrmann ("Relocatability and the Long Branch," page 26, October 1977 BYTE) used the right word when he said he was "fooling with the stack pointer." Using the stack pointer as a general data pointer is bad programming practice; when the system uses NMI interrupts for real time clock maintenance it is simply intolerable. In this case it is not even particularly necessary: the same two subroutines can be implemented in a stack-safe way for only eight more bytes, as follows:

Tom Pittman

POB 23189

San Jose CA 95153

Label Op Code

Operand

Commentary

LONGBS STX

XSTOR

[save X for later]

DES

make room for copy of return

DES

TSX

point to it in X

PSHA

save A on stack

LDAA

3,X

low byte of return address

STAA

1,X

ADDA

#2

point to actual return

STAA

3,X

LDAA

2,X

high byte of return

STAA

o,x

ADCA

#0

finish add

STAA

2,X

BRA

BPUSH

skip over start of LONGBR

LONGBR STX

XSTOR

PSHA

BPUSH PSHB

save b on stack

TSX

point to top of stack in X

LDAA

3,X

get address of offset . . .

LDAB

2,X

. . . into A&B

LDX

2,X

also into X,

ADDA

1,X

so to add offset

ADCB

o,x

to its address

TSX

get back to stack

STAA

3,X

put sum there

STAB

2,X

PULB

restore saved A&B

PULA

LDX

XSTOR

[restore old X]

RET

[go to address]

Dr Borrman illustrated a very good idea with a poor program. However, it was a good article, bringing to people's attention the fact that the 6800 alone of all popular processors is capable of self-relocatable code. Something that Dr Borrmann perhaps did not notice is that the subroutine LONGBS (and its chain of BRA stepping stones) is superfluous. At least where the subroutines

now

sour

with

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*CP/M IS a trademark of Digital Research

Circle 308 on inquiry card.

BYTE )uly 1978 115

BSR

LINKn

BRA

EXITn

LINKn

BSR

LONGBR

FDB

SUBR-*

EXITn

are to be included in the program, it is probably more economical to do the subroutine calls this way:

[Instead of JSR LONGBS] [jump over linkage] [or JSR if LONGBR Is in monitor] [relative address of subroutine]

There is also the technique of using the indexed addressing mode with JMP or JSR when X is not needed in the call itself. Once in the program you compute the address of the first of a dense block of subroutines. Then each time you need one, the following linkage is used (notice that LONGBR is not needed):

LDX JSR

AFIRST =address of first subroutine

SUB-FIRST, X

The easiest way to compute the address of FIRST is to jump to a BSR just before it as shown next:

BRA

INIT

(part of initialization)

SAVEIT

PULA

get high byte

STAA

AFIRST

save it in RAIVl

PULA

now low byte

STAA

AFIRST+1

(continue with main program)

INIT

BSR

SAVEIT

push address onto stack

FIRST

(first subroutine)

If every subroutine knows its stack depth, you can leave the return address generated at INIT on the stack, then use the following calling sequence:

TSX LDX JSR

depth,X SUBR-FIRST

point to stack

get saved address of FIRST

X

Of course these will not work if you need the index register to pass an argument to the subroutine."

More On Varistors:

A Supplier of Some Note

Comments

William G Morris

General Electric Research

and Development

POB8

Schenectady NY 12301

I don't know which brand of varistor Stephen Sorger of W N Phillips Inc (Letters, April 1978 BYTE) was using when he experienced "aging," thermal "runaway," and a "fire hazard," but it certainly was not a General Electric GE-MOV"^ varistor. As a typical example, the V130LA10 GE-MOV varistor will run at full rating to 85 °C ambient, which is 15°C greater than Intel specifies as maximum temperature for the 8080. This varistor also exhibits an observed failure rate of less than 0.2% per 1000 hours during accelerated testing at 100°C ambient.

The reader should be reminded that transient suppression is essential to reliable operation of microprocessor systems, particularly in industrial environments, but also in hobby applications. Varistors continue to represent the most cost effective method of achieving transient suppression.

The V130LA10 GE-MOV varistor, which can be used directly on 110 VAC lines, is available for $1 to $2 from most industrial electronics suppliers. Additional information is available from General Electric Company, Electronics Park, Syracuse NY 13201."

-r^'Wi

$95 Stand Alone Video Terminal

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^

t. a «. T W « ^"^ ^ » « » • • « fcT

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abcdefyhi jklj"inopqrstuyyxyz<I>^i

SCT-lOO FEATURES:

64 .X 16 lii.^ ^.

Serial ASCII or BAUDOT with multiple Baud rates »$187 Assembled or $157 Kit (Partial Kit $95) \ • Full cursor control with scrolling and paging "■ On board power supply

I Many additional features Call or write today. MC/VISA accepted

I XITEX CORP. P.O. Box #20887

I Dallas, Texas, 75220 • Phone (214) 386-3859 / Overseas orders and dealer inquiries welcome

116 luly 1978 © BYTE PuUicUMm Inc

Circle 400 on inquiry card.

Beck fieviews

Instant Freeze-Dried Computer

Programming in BASIC

by Jerald R Brown

Dymax, POB310, Menio Park CA 94025

$6.95

How quickly the personal computer owner trades the student's notebook for the teacher's chalk. Says the friend, "Neat, you got a computer. How do you get it to do X or Y?" Or you modestly back yourself into a corner; "Programming isn't hard. I could teach you BASIC in a few hours." In my case it was a deal with my neighbor's recent high school graduate to teach him programming in return for his doing some of my more routine programming chores. But however you got the teaching job. Instant Freeze-Dried Computer Programming in BASIC is in my opinion an interesting, involving and entertaining text you can use to ease the teaching task.

The book resembles a half inch thick collection of BASIC oriented flashes that somehow escaped from the pages of Ripley's Believe It or Not. We see the scene of the keyboard LET fading into the sunset beyond the hills, captioned by "And so, in the name of Efficiency and Ease, the LET was banished forever from Statementland. . . ." Throughout each page the student is exhorted to either read the explanatory text, or, more often, "do it": the signal for you to actually type out one of the hundreds of brief examples on your waiting terminal. The layout is designed to be both a text and a practical workbook. For example, immediately after you learn to loop with the GOTO statement, half inch type warns you to "WAIT! STOP! HALT! CEASE! DESIST!" before running, so the saving properties of the Control-Ccan be explained to keep you from the terror of the infinite loop.

The examples are so clear that not even a computer could complain of ambiguities. The actual keys punched are pictured using the standard key markings of the ASR-33 Teletype. The printed listing for each example explains why you typed this and why the computer typed that.

Besides being an excellent teaching text, the book has the two necessities that make it a handy manual to keep forever, plus several bonuses. The necessities are a set of concise summary boxes at appropriate spots throughout the text gaudily surrounded by polka dots; and a good index that not only

tells you where the concept is taught, but the precise location of the summary box. The bonuses are the examples cnosen by the author: a broad set of games, pictures, string techniques and useful business programs, all indexed and ready to run.

The dialect of the BASIC taught is both a strength and a weakness of the text. Altair 8 K BASIC, revision 3.2 (essentially the same as DEC BASIC Plus), is that ubiquitous version that started so many of us hackers off in BASIC and served us so well. But revision 4.0 is now out, and, especially in its extended version, it far surpasses 3.2 8 K BASIC in flexibility and power. But of course, the further you go from standard BASIC the more machine dependent you become. For the beginner, or those writing for a variety of interpreters. Brown's choice was a wise one.

All said. Instant Freeze-Dried Computer Programming in BASIC is the most painless and involving text for that language yet on the market.

Jay P Lucas

3409 Saylor PI

Alexandria VA 22304 a

Address Correction

David Clapp, who reviewed Z-80 Programming Manual by IVIOSTEK (June 1978 BYTE, page 118) has changed his address to: FOB 501, Streetsboro OH 44240.*

A

SOFTWARE SYSTEMS SPECIALISTS

Growth corporation has immediate openings AT ALL LEVELS for candidates with a BS or MS in Engineering/Science and a bacl<ground in the following areas:

■ Microprocessors ■ Minicomputers

■ Real Time Systems ■ Operating Systems

■ Event-Driven Applications ■ Diagnostic Programming

■ 8080 Assembler, PLM

TECHNICON is the industry leader in the manufacture of State-of-the-Art automated laboratory instruments. Located in suburban NY, we provide a professional working environment, along with competitive salaries and a full range of companypaid benefits. Send resume including salary history in confidence to:

Manager, Technical Staffing

Tomorrow's Technology Today

Iliil lechnicon IIIIH Tarrytown, N.Y. 10591

An Equal Opportunity Employer M/F

Circle 373 on inquiry card.

)ulv 1978 © BYTE Publications Inc 117

eVTE's Ells

Portia Isaacson to Edit New Bool< Series

Announcements in BYTE's Bits are usually confined to products and services rather than details of who is doing what in the personal computing industry. We could never hope to find room to print all the people oriented press releases that come our way every month. Because of the contributions she has made to personal computing, however, we are making an exception here to report that Portia Isaacson has now joined book publisher Prentice-Hall as series editor and advisor for the firm's new Personal Computing Book Series.

Dr Isaacson is currently chairperson of the ACM Special Interest Group in Personal Computing, editor of a monthly "Personal Computing" column in Datamation, acting president of the Computer Retailers Association, an Electronic Data System fellow, and coowner of the Micro Store. Named as an honorary fellow of the Asso

ciation of Computer Programmers and Analysts in 1977, she also chaired the 1977 National Computer Conference. Dr Isaacson has been associated with Textron, Lockheed Electronics, and Xerox Corporation and is a former university professor. She will author the first book in the Personal Computing Series, 777e Microcomputer in Business.*

Heard on a BOMB Card

"If this feedback helps you why is this card not postage paid? 1 really do not know why 1 put a stamp on this every month. You really do not want this card back, do you?"

Why does anyone write a letter to the editor? It costs a minimum of $.13 and has no guaranteed or measurable result for the sender. Formalized rating feedback is quite adequately provided by those readers who are opinionated enough to return a filled out BOMB card. If we received as much as 10% of the 135,000 or so cards mailed with the May 1978 BYTE, the analysis would require a nearly full-time person. By providing the filter of requiring a person to back his or her opinion with a stamp, the numbers are kept within manageable limits. . .CH"

At the suggestion of a reader, this emergency equipment now hangs on a certain editor's wall at BYTE. The hexadecimal abacus was created by Blaise Liffick, and the now obsolete scientific and engineering calculator at one time was the primary computer of yours truly. . .CH"

S-100 BUS COMPATIBLE. The EMM 1104 single card plug-in memory has been field tested and proven in a variety of systems including the Poly 88, IMSAI, MirS. COMPAL-80, TLD and CREMENCO. 16K BYTES ON A CARD. Convenient plug-in card, fully burned-in, tested and guaranteed by one of the industry's largest memory suppliers. NMOS STATIC RAM. The 4K static RAMs have been proven in applications ranging from single chip memories to IBM 370 add-on systems. They are fast,

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See your dealer, or contact us for complete information.

S-100 Bus Compatible Memory 16K bytes on a card

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eVTPs Bugs

DeMorgan Gets Half-Bombed

An error appeared in one of the definitions of DeMorgan's two laws in Dan Bunce's "Some Musings On Boolean Algebra" (February 1978 BYTE, page 26, second paragraph). The last sentence of the paragraph should read: ^igure_3a also gives us the other law, p \/ q = p A Q'" Thanks go to Steve Shade, Lehigh University, Bethlehem PA 18015, for spotting this error."

Microbot Bug

A minor bug appeared in listing 1 of John Webster's "Robot Simulation on Microcomputers" (April 1978 BYTE, page 1 36). The assembler code at address 0017 should read: "LXI B, 0A040H" instead of "LXI B, 0A004H." The hex code listing is correct as it stands."

Correction

The address for Pickles and Trout on page 51 of Dan Fylstra's "The Radio Shack TRS-80: An Owner's Report" (April 1978 BYTE, page 49) should read: Pickles and Trout, POB 1206, Goleta CA 93017, (805) 967-9563. Our apologies to Messrs Pickles and Trout."

118 July 1978 <D BYTE Publicilions Inc

Circle 132 on inquiry card.

Ppogpsmming

iHEADER PROGRAM TO HOI^E BASIC OVER NORTH STAR DOS

Ouickies

Beating North Star— MITS Incompatibility

Alan R Miller New Mexico Tech Sorocco NM 87801

If you have a North Star floppy disk and you want to use it to load MITS extended BASIC, there may be a slight problem. The North Star disk operating system requires 2.5 K bytes of memory starting at hexadecimal address 2000. MITS extended BASIC also uses this same area. The solution is simple: load BASIC in the old way (cassette or paper tape), but don't start it up. Next, load the 23 byte automove program in listing 1 at hexadecimal 4000. Use it to relocate BASIC at hexadecimal 4020. Jump to hexadecimal E900 and reload the disk operating system. Finally save the combination automove and BASIC (hexadecimal 4000 to 7FFF for version 4.0; hexadecimal 4000 to 6FFF for earlier versions) on the North Star disk with file name MBASIC.

When you want to load MITS BASIC from disk, type GO MBASIC and the disk will copy BASIC into memory above the disk operating system and jump to the autoload routine. This routine will in turn copy BASIC into its proper location, then jump to it. The disk operating system will, of course, be overlaid by BASIC. When you're through with BASIC, jump to the disk bootstrap to recopy the disk operating system back into memory. With BASIC versions 4.0 and above, type:

DEFUSR=&HE900: X = USR(9) [carriage return].

For earlier versions type:

POKE 65,0: POKE 66,233: X = USR(9) [carriage return]."

tNEU MEXICO

TECH. SOCORRO. NM 9890J. 505-835-5619

BASIC

EQU

4020H

SSTART OF UPPER BLOCK

BASEND

EClU

7FFFH

(END OF UPPER BLOCK

BEGIN

EQU

0

;START OF LOUER BLOCK

4000

210000

start:

LXI

H.BEGIN

(DESTINATION ADDRESS

4001

112040

LXI

D.BASIC

(START OF UPPER

4006

01FF7F

LXI

B.BASENE

(END OF UPPER

4009

lA

NEXT!

LIlAX

D

(GET BYTE FROM UPPER BLOCK

400A

77

MOW

M.A

(PUT IN LOUER BLOCK

400B

23

INX

H

(INCREMENT POINTERS

400C

13

INX

n

400D

79

MOW

ArC

;CHECK FOR END

400E

93

SUB

E

(SUBTRACT LOUS

40or

78

MOV

A.B

4010

9A

SBB

D

(SUBTRACT HIGHS

4011

D20940

JNC

NEXT

(CONTINUE IF NOT DONE

4014

C30000

JMP

BEGIN

(DONE. START PROGRAM

Listing 1: Program to move previously relocated MITS BASIC back where it belongs when using a North Star floppy disk. To move the original program, the parameters must be changed. BASIC must be set to hexadecimal 0000, BASEND to 3FFF, and BEGIN to 4020.

modem / 'mo • dam / [modulator + demodulator] n - s : a device for transmission of digital information via an analog channel such as a telephone circuit.

those of us who live on the North American continent are blessed with an incredible non-natural resource consisting of a gigantic web of tiny copper wires linking virtually all of our homes and businesses together into the greatest telecommunications network in history. The Bell System and over 1600 independent telephone companies have been stringing wires and microwaves nearly everywhere for up to 100 years. Now, the 80-103A Data Communications Adapter brings this amazing network to S-100 Micro Computers.

The

80-103A Data

Communications

Adapter is more than

just a modem. It is a complete

data communications sub-system

combining on a single S-100 board

functions which formerly required a

modem, an automatic calling unit, and serial

and parallel interfaces. This fully programmable

unit gives you flexibility never before available at such

a low cost. Fully assembled, tested, and burngd in with

full documentation and our standard 90 day warranty, the

iO-103A is available at retail computer stores across the country

for only 279.95

D.C. Hayes Associates Inc.

P.O. BOX 9884 • ATLANTA, GA. 30319 • (404) 231-0574

Dislfibutea in Canada by TRINTRONICS LIMITED, Toronto

Circle 155 on inquiry card.

July 1978 & BYTE PuUkaliom Inc 119

Continued from page 11

RSX-11 and DOS-11 variants of the same editor and can testify to tine usefulness of the scope support features built Into the newer versions. One goes through a rather large annount of hassle with DEC to get the software for RTII (pricing is never very clear), but the result is fairly worthwhile. If you guys ever get a version of TECO running, I have an ELIZA demo that runs in it, just to show you a bit of what can be done with an editing language.

Glenn C Everhart

211 Great Rd

Maple Shade NJ 08052

IS THERE ANY CP1600 INTEREST?

Have any of your multitude of readers expressed an interest in the General Instrument CP1600 chip and their GIMINI microcomputer? I have been Interested in this processor ever since Its development and would like to communicate with others on the subject. I was recently talking to one of the people at General Instrument's Hicksville plant and he was telling me about their latest offering, which is a single card 32 K byte (addressed as 16 K words)

implementation of this processor including read only memory operating system. This card is to be, in most cases, available as a fully assembled, burned in and tested card for original equipment manufacturer type applications. He also said that it might be possible to discuss a hobbyist type kit, unassembled, perhaps with fewer chips and capabilities and also less expensive. I would like to hear from anyone else who is interested in this powerful 16 bit processor (which uses a very PDP-11 like instruction set) and possibly talk again to General Instrument about interest in the hobbyist kit version.

Brian D McCullough

Site 9, Box 37

RR2

Sherwood Park, Alberta

CANADA T8A3K2

MULTIPROCESSORS

ARE BECOMING EASIER TO DESIGN

The article, "The Intelligent Memory Block" by K Castleman in the March 1978 BYTE, page 186, was an interesting and an enlightening system design concept. However, his premise that the current development of multiprocessing

$7 95

T.Y. CROWELL

10 East 53rd St., New York, NY 10022

CCMPUTIER CAPIERS

From the acclaimed New Yorker series —now expanded for book publication.

Thomas Whiteside

"Anyone contemplating a life in strictly modem crime

or who is worried about those who are should read

Thomas Whiteside's guide."—john kenneth galbraith

An alternate selection of Book-of-the-Monfh,

Fortune, and Macmillan Book Clubs.

2nd printing before publication.

systems is lagging is no longer relevant. This is because of the mechanisms on many new microprocessors.

National's 8060 and Motorola's 6801 and 6809, for example, have the necessary on-the-chip hardware for bus access control. This allows for two or more microprocessors to be interconnected to perform different tasks on a time and memory share basis. Intel's new 16 bit microprocessor, 8086, is interesting because of its software control feature in multiprocessor applications. A special 1 byte prefix attached to any instruction can compel the processor to assert a bus lock signal for the duration of the instruction operation, thereby allowing processors to share resources. By using these new microprocessors the memory block can now be intelligent but with a lot less hardware and timing stringency.

John C Peterson

Jet Propulsion Lab

Pasadena CA 91103

FOR SOME, HIGH PRICE=NO SALE

Thank you very much for your editorial "Don't Ignore the High End . . . .or My Search for Manuscript Editing Paradise" which appeared in the March 1978 BYTE, page 6.

I feel compelled to write to you because my thinking has been parallel to yours on this same topic and for the very same reasons.

I started out with the idea that electric typewriters have been around for many years; there is a market for them and the manufacturers have been able to make profits.

These days we have a lot of very good and very cheap electronics so that it seems reasonable to expect electric typewriters with inbuilt memories and editing capabilities at reasonable prices. The price would also be increased by video displays and magnetic tape storage devices, but I do not expect that it would be anywhere near the $8000 which you mention. The potential market for reasonably priced goodies may well include all those people around the various university campuses who type and retype dissertations, thousands of articles for publication in journals (including BYTE) and term papers. If I could get one with insert and delete capabilities for around $700 I would go out tomorrow morning and get one right away. But that day seems to be rather remote at present.

Philip S Barker

59 Acadia Bay

Winnipeg Manitoba

CANADA R3T3J1

There is a bit of a difference between an output peripheral (the typewriter) and a complete computer system with soft copy displays, magnetic auxiliary storage and lots of memory.

120 July 1978CIBYTE Pubiications Inc

Circle 81 on inquiry card.

620/L VARIAN COMPUTER INFORMATION AND PARTS NEEDED

We have a VARIAN 620/L which has been loaned to our computer center by one of our teachers. We are writing to find out if there are any readers of your publication who can help us locate additional plug in boards, either stuffed or unstuffed, for this machine so that we can mal<e more effective use of it. We would appreciate hearing from anyone who may be willing and able to help with any aspect of this machine.

Norman Lee, Asst Prof

Electronics-EDP

College of The Albemarle

Elizabeth City NC 27909

DRAMA REQUIRES SPEECH AS WELL AS ACTION

I was delighted to see the article by Gerrard, Ghent, Hemsath and Seawright (June 1978 BYTE, page 153) describing a simple modification to the Processor Technology VDM board which results In a greatly enhanced graphics capability for the small computer user.

It may be of interest to a number of readers that this same modification is also quite useful for displaying and editing the control parameters for the Computalker Model CT-1 Speech Synthesizer. With a vertical resolution of 208 lines, it is possible to display up to three CT-1 parameters simultaneously with 6 bits resolution on each. The horizontal resolution of 64 is sufficient to see more than Vi second of speech data at a time, plenty of display for good editing.

We are currently exploring the possibilities of using such a graphics display in connection with a digitizer pad, which will make it much easier to produce good quality speech output with the Computalker board.

Lloyd Rice, partner

Computalker Consultants

POB 1951

Santa Monica CA 90406

(213)392-5320

WORD OF A BETTER SORT

As a computer science major interested (when I find the time) in getting into personal computing, I enjoy reading BYTE. In general, the material is worthwhile and educational, but in your April 1978 issue I was greatly disappointed to find one of the worst methods for sorting an array of items that I have ever seen published. Rene Pittet's algorithm, presented in "Programming Quickies," page 148, is a slow variant of the ubiquitous bubble sort. I am writing this letter to infornn your readers that there are much better sorting methods around, including some no more difficult to code or to understand.

A well known method (which is

about four times as fast as the one Pittet presented) is called straight insertion sort. To understand how it works, observe that at the beginning of each iteration of the FOR-NEXT loop, the first 1-1 elements of the array are already in sorted order. The body of the loop merely inserts the Ith element into its correct position in that initial sorted segment. My code segment, which follows, replaces the actual sorting part of Pittet's code.

Insertion sort is probably the method of choice when less than 30 items are being sorted — it is easy to write and to debug and incurs very little overhead. However, it can be shown that the amount of time required to sort N items using this algorithm is proportional to N*N. Thus, if sorting ten items take 100 units of time, 1000 items will take about 10000 units of time! Many algorithms exist which require an amount of time proportional to N times the logarithm of N. I refer the interested reader to a book, which all hobbyists should read anyway, by Kernighan and Plauger: Software Tools. They describe the quicksort algorithm, the generally recognized method of choice in a wide variety of applications. Mathematically inclined readers who want to know "everything you ever wanted to know" about sorting (and searching) should refer to The Art

171 KEH STIllGHT lISnTIOl SUIT: PJTS THE ZLEIIEIIS

172 BE!1 1(1) THVOOCR i (!) IITO iSCEHDIir. OlDEi. 17J lER 1: LOOP COUITIi - ELENEVT OP I TO BE 17« lEII IISEBTEO iEIT

17S REH J: LOOP COUBTEE USED TO 5BABCH POI iE

17k EEa ELEKBIT LESS THiB B

177 BEn K: t*l(l)) THE BUNBEP ("RET"} BEIRG IBSEBTED

laO POB I ' 2 TO If

190 R > A (1)

200 J « 1-1

20^ REN BHILE Jk(J) > K

210 IP 1(J) <• R THEB 2'>0

220 * (J*1) ■ I (J)

2J0 J - J - I

235 PER UBTIL J = 0

21*0 IP J > 0 THEB 20S

250 Jt [J*1) * R

260 BRIT 1

of Computer Programming, Volume 3: Sorting and Searching, by Donald E Knuth.

Neal D McBurnett

POB 4173

Brown University

Providence Rl 02912

WHY NOT JUST USE THE PHONE?

I was pleased with Mike Wilber's article on CIE standards ("CIE NET: Part 1, The Beginnings" February 1978 BYTE, page 14) and look forward to seeing more in the same vein. However, I was not equally taken with Jeff Steinwedel's article ("Personal Computers in a Communications Network" February 1978 BYTE, page 80) on the

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Gold plated 86-pin connectors at $5 70 ea

G $64 95 plus $2 pill tor ASCII Keytioard kit a J14 95 for ELF II Tmy BASIC cassette i»——

a I mnt my ELF H wired and tasted witli the power transformer. RCA 1802 User's Manual and Short Course on Microprocessor I Computer Programmini for tl49.95 plus (3 p&h. Ibtal enclosed (Conn, res add tax) ( D Check here if you are enclosing

Sbaaniirltli

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gIwT NARIT" ( KlBia Board.

Learning Breakthroughi

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Written For Anyone! Minimal Baclrground Needed! Wby speed a small fortaaa aa a parsoRal ceaipBtar ultbaat kaevlai how to usa its advaflcad capabilities? We'll teach yea haw ta aiaka ELF II respaad ta year aaads, witbeat waltlei lar saataaRa to develop the soffvara. Itaa laarn, in BOR-tecbBlcal laaiaaia. aach of ELF ll's 91 iastrBCtions sa you'll andarstaad aieiytblBi EtF II caa da... aad boa to (at ELF II to do it. It's year cbaace ta atastar aa adtaacad parsoaal ceaipatar talckly aad paialassly, avea if yaa'va aavsr asad a coaipatar bafore!

- SPECIFICATIONS

ELF II feataras aa RCA COSNAC COS/MOS l-bit ailciaprocasser addrassabla ta Mk bytai «ltb BNA, latarrapt. It ta(istars, ALU, 2S( byta RAM, fall bai keyboard, twa dlflt be> eatpat display, 5 slat plB|-ta aipaflsiaa bas (less ceaaactars), stabia crystal clack far tJaiiBi parpasas aad a deabla-slded, platad-tbreagb PC board plas RCA 1111 tidee IC ta display aay SBiataat af aiaaiary or a yidaa ataaltar ar TV scraaa.

EXPANSION OPTIONS ELF IIGIART BOARD™ with cassatta I/O, RS 232-C/TTr fO, 1-bit P I/O, decoders far 14 separate I/O instractloas and a systeai aieaitar/edltar • 4k Static RAM. Addrassabla ta any 4k page ta i4k • Pratatype (Klafal Beard accapts ap to 39 IC's • Geld plated B6-plB caRRBCtar • Expaasioa Paver Sapply (Kot required aaiass addiai 4k RAMI • All af the abaie PC boards plag directly iota ELF ll's aipaaslaa bas.

ELF II TINY BASIC CaaiBiaads iRclada SAfE, LOAO, ±, x. -f, ( ), 2S latiables A-Z. LEI IF/THEK. IRPUl PRIRi; GO TO, GO SBB, RETURN, ERD, REM, CLEAR. LIST, RUR. PLOT, PEER, PORE. CeaiBS tally dacafliaated. (4k Rteaary reqairad.l

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July 1978 e BYTE Publications Inc 121

How to say

low-cost data tablet/digitizer

in two words.

Bit Pad Bit Pad Bit Pad Bit Pad Bit Pad

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Bit Pad is the low-cost digitizer for small computer systems. Better than a joystick or keyboard for entering graphic information, it converts any point on a page, any distance into its digital equivalents. It's also a menu for data entry. You assign a value or an instruction to any location on the pad. At the touch of a stylus, it's entered into your system.

Who can use it? Anyone from the educator and the engineer to the hobbyist and the computer games enthusiast. The data structure is byte oriented for easy compatibility with small computers, so you can add a power supply, stand alone display, cross-hair cursor and many other options.

Bit Pad by Summagraphics. The leading manufacturer of data tablet digitizers. Bit Pad. The only words you need to say when considering digitizers.

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use of RF in a data exchange network. His generalities do no justice to tine enormous technical, political and financial complexity of such a system. It is unfortunate that someone who must know quite a bit on this subject would author oversimplifications which could lead less well informed persons to believe that such a system is really a practical option.

Anyone who plans to propose that the FCC allocate 1 MHz of precious VHF or UHF spectrum for a short haul, fixed, unattended, personal radio communication service should be prepared to be laughed out of Washington. First, just where does Mr Steinwedel suggest that this 1 MHz come from: amateurs, government, broadcasters? Don't count on it! The fact is that there is nothing like a 1 MHz block available below 900 MHz. Second, all services are allocated frequencies on the basis of international standards and demonstrated need. How can anyone demonstrate the need for a frequency hungry radio network to link homes around town so we can all play Star Trek together? How would he reply when asked, "Why not just use the phone?" Third, Mr Steinwedel totally ignores the high cost of such a system. This is probably due to the fact that amateurs don't have to pay first class technicians to maintain their equipment. Why do you think the cost of mobile telephone is so high? Finally, the suggestion that the FCC would authorize this service to employ totally unsupervised transmitters exhibits unfamiliarity with one of the prime principles of FCC regulation. That is, who is going to pull the plug when the thing gets stuck in transmit mode? Every chapter of the FCC Rules and Regulations expounds on this principle at length under the heading of "Operator Requirements." The cases where the FCC has authorized totally unsupervised transmitters are so few as to not be worth noting. In short, why don't you just use the phone?

I don't want to give the impression that I am totally against digital radio communications. It is fine by me if amateurs wish to combine hobbies. I personally would love to help set up an intercity tropo or satellite link for CIE use. However, I would not be so bold as to suggest that it would be cheaper than "Ma Bell."

Anyone who wishes to explore the possibilities of digital exchange and calling by radio should obtain a copy of the International Telecommunications Union CCIR Study Group 8 Draft Recommendation #493 which proposes some international standards for similar systems. I would also suggest that anyone interested in writing CIE standards should first take a long look at standards accepted by the ITU and other organizations so that international compatibility can be maintained.

Donald R Newcomb

819 Bayou Blvd

Pensacola PL 32503"

122 July 1978 © BYTE Publications Inc

Circle 352 on inquiry card.

College Sports Report

Grinnell Wins Second Midwest Regional Programming Competition

Grinnell College of Grinnell lA barely nosed out DePauw University of Greencastle IN in the Second Midwest Regional Programming Competition held at Taylor University, Upland IN, April 1 1978. The host team, Taylor, finished third and Wabash College of Crawfordsville IN was fourth. Grinnell's 2 person team led by Scott Parker of Champaign IL and sponsored by Prof Mark Grundler defeated DePauw's squad by only three points in the 4 person, 4 hour competition using Taylor University's DEC timesharing system. However Evansville University used their IBM 360 over telephone lines for the competition.

Each team had only one 300 character per second printing terminal on which to write, test and debug their programs. A team of six judges led by chief judge Bruce Gaff of Plycom Industries (Plymouth IN) and Jere Truex (Upland IN) reviewed the solutions written in BASIC and indicated if the solutions were correct or incorrect. The scoring method included the number of problems, the time required to complete the solution, and the number of judged runs submitted.

The four problems posed included writing check amounts in words, screening inaccurate data from an electronic instrument for accuracy, connecting pairs of points in a geometric plane, and retrieving prices from descriptions in a catalog.

Although 14 teams from seven midwestern states were expected, schedule changes and other factors caused some teams to miss the competition. In addition to the four teams already mentioned, others competing were the University of Wisconsin/Platteville, Asbury College of Kentucky, plus Grace College and Rose-Hulman Institute from Indiana.

Next year the Midwest Region will be held at Rose-Hulman or Taylor University. It is hoped that a National BASIC competition between regional champions will be held at a later date. Taylor University had two freshmen on their third place team and other schools had freshmen participating also, so it Is anticipated that next year's competition will be even more strongly contested.

Taylor's young team included senior Steve Olsen from Wyckoff NJ, junior Mark Tomlin of West Milton OH, plus freshmen David Woodall of Marengo IL and Stan Rishel of Kalamazoo Ml. The alternate members were freshmen Cory Waller of Franklin Lakes NJ and Mark Collins of Indianapolis, who missed the competition because of illness."

DATALYZER ... a 24 channel Logic Analyzer for your SlOO Bus

24 Channel LOGIC ANALYZER, complete with 2 cards and 3 sets of probes.

Features

— 24 channels with 256 samples each.

— Display of disassembled program flow.

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— Selectable trigger point anywhere in the 256 samples.

— 0-16 bit trigger word format or external qualifier.

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Designed to plug easily into your S-100 Bus, the DATALYZER is a connplete system — for only $595. Display of disassembled program flow is a standard feature, not an extra. And the low price includes 30 logic probes, so you can hook up immediately, without additional expense.

The DATALYZER is available in kit form ($595), and as a fully assembled device on two PCB's ($695). Operators' manual $7.50. A substantial warranty, and the Databyte, Inc. commitment to service make the DATALYZER a worthwhile investment.

Databyte, Inc.

7433 Hubbard Avenue Middleton, Wisconsin 53562 Tel: (608) 831-7666

Circle 86 on inquiry card.

)uly 1978 ©BYTE Publications Inc 123

How to Choose a Microprocessor

Lou Frenzel Heath Company Benton Harbor Ml 49022

All personal and hobby computers are microprocessor based. That is, they use a single processor integrated circuit chip. One of the most important decisions you will ever make in purchasing a personal computer is choosing the type of microprocessor. The semiconductor manufacturers have provided computer designers with a wide range of microprocessing units having varying degrees of power and sophistication. As a result, there are at least a half dozen different processors available in hobby computers. This wide variety of products mal<es your choice somewhat flexible, or at least it seems that way. In reality, having so many processor styles to choose from, your decision becomes much tougher. If you are a beginner, it may be particularly difficult to make an intelligent choice. The purpose of this article is to provide you with some guidelines in making this important decision. The emphasis is on how to choose the best microprocessor for you when purchasing a personal computer.

What's Available

Below is a list of all of the available microprocessor architectures and their primary manufacturers.

Intel 8080, 8085, 8048, 8086

Motorola 6800

MOS Technology 6502

Zilog Z-80, Z8000

Signetics 2650

RCA 1802

Fairchild F8, 9440

MOSTEK 3870

Intersil 6100

Texas Instruments 9900

National Semiconductor SC/MP, PACE, 8900

DECLSI-n

Data General microNova

General Instrument 1600

With this wide variety, is it any wonder that it is a difficult choice? Yet with all of these available devices, the choice narrows down rather quickly when several important factors are considered. What makes things even more confusing is the fact that many of the above microprocessors will undergo changes and improvements. Semiconductor manufacturers will also develop and introduce even newer improved microprocessors. The whole microprocessor business is a dynamic one. Changes occur almost daily. The biggest dilemma is not so much the changes themselves but the rapidity with which they occur. Today you may make a decision to use a particular microprocessor only to find that six months later the choice is apparently incorrect because a newer, better, improved device has become available. There is no complete solution to this problem. The rapid changes in this field will continue to occur. For that reason, you must make a choice and stick with it. You must attempt to select a device that has the greatest longevity potential as well as one that meets the criterion for performance in your application. You must not let the rapidly changing technology paralyze your decision making process. It is best to choose among the presently available devices and take your chances with the future. To obtain the most value from your personal computing system, you must select a microprocessor that meets your immediate needs but offers future potential as well.

Selection Criteria

There are many factors that go into the process of selecting a microprocessor. You should consider all of these factors even though some of them affect you only indirectly. You should also be influenced by the factors that ordinarily would interest

124 July 19780BYTE Publications Inc

only the designer. Below are listed some of the key elements in choosing a microprocessor.

Cost

Cost is always a major consideration in choosing a microprocessor. However, of all the factors involved, this is one that the user should be least concerned about. Cost is primarily the concern of the computer manufacturer. Most microprocessor integrated circuits are in the same price range; and the cost of the microprocessor itself is only a fraction of the overall cost of the computer system. The cost of memory and peripherals is far more than the cost of the processor. Thus for purposes of our discussion here, cost is irrelevant.

Speed

One of the factors considered in the evaluation or comparison of computers is processing speed. This is the rate at which instructions are executed. While speed is primarily a function of the clock frequency and the upper frequency limit of the microprocessor itself, it is also affected by the memory speed and the architecture of the processor. Most modern microprocessors are not known for their processing speed. After all, most microprocessors are metal oxide semiconductor (MOS) circuits which are inherently slower than bipolar (TTL) circuits. Over the years great improvements have been made in the speed of MOS circuits. The slow "P channel" circuits have been gradually replaced by smaller and faster "N channel" circuits. Continuing developments in the N channel process promise even further improvements in speed. Speeds approaching bipolar levels are achievable. If processing speed is the most important criterion, then bipolar circuits should be selected over MOS microprocessors. Speed is of little or no consideration in choosing a microprocessor-based personal computer. Most MOS microprocessors used in personal computers execute an instruction within several microseconds which is fast enough for most applications.

While processing speeds can vary as much as four to one among MOS microprocessors, the difference is almost unnoticeable. For

From the machine and assembly language programmer's point of view, the Signetics 2650 processor shown here is often considered to be a superior machine. But it has never become popular in the personal computing field, most likely because it entered the 8 bit marketplace later than the major contenders. This photograph was supplied by Signetics.

The Digital Group leaves out no major microprocessor choice. While their emphasis is on the Z-80 processor, they cover all bases with options for 8080, 6800, 6502 and Z-80 processor boards. This photo, supplied by Digital Group, shows a board which features the 8080processor.

July 1978 ©BYTE Publications Inc 125

Circle 43 on inquiry card.

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example, most hobbyists use the BASIC language. The speed of the microprocessor will definitely determine the length of time that it takes to execute a program. However, with an interpretive language such as BASIC, an order of magnitude difference in execution speeds is frequently almost unnoticeable to the user. While it may take 200 iis to execute a program on one computer and 20 /is on another, the user is often totally incapable of recognizing the difference.

The real value of speed comes when your application requires it. If your applications involve lengthy, complex mathematical operations or highly complex real time functions, speed may be an important consideration. Otherwise, speed is one factor which you could practically ignore in the selection of a personal computer. Few personal computer manufacturers know how to specify it, let alone mention it.

Computing Power

Computing power is a rather nebulous designation that refers to the power of the instruction set and architecture of the computer. Computing power also effectively involves speed as discussed above. Yet computing power is far more important than raw speed in determining the capabilities of a microprocessor.

It is difficult to provide any specific guidelines for determining whether one microprocessor is more powerful than another. However, as a general guideline there are several factors to look for in determining which microprocessor has the greatest power. These factors are: number of instructions in the instruction set, number of working registers, and number and type of addressing modes. Those microprocessors with the greatest numbers of instructions, registers, and addressing modes are essentially the more powerful microprocessors. They can accomplish more complex operations in less time than other microcomputers with lesser characteristics.

It is the wide variation in architectures which makes the choice of a microprocessor interesting. In some cases, a superior instruction set, more flexible register organization and more addressing modes can offset the superior computing speed of another microprocessor with a simpler architecture. There are never any clear cut answers to the question of which microprocessor is the most powerful since usually the answer lies in a specific application. When a particular application can be defined, the choice of microprocessor can be optimized. However, when choosing a microprocessor-based general purpose computer which must be

126 July 197S e BYTE PuUicatisns Inc

Circle 140 on inquiry card.

Circle 265 on inquiry card.

useable in a wide range of applications, the speed and computing power consideration becomes fuzzy at best.

Second Sources

Another way to assess the value of a microprocessor is to consider the second sources. Second source refers to a manufacturer other than the original manufacturer, producing the same device. When a semiconductor manufacturer introduces a new microprocessor, he attempts to capture as much of the marl<et as possible with various features and pricing strategies. However, one of the strategies that works best is if competing manufacturers choose to make the same device. These secondary manufacturers will compete with the primary manufacturer. Despite this competition, it is usually the original manufacturer who benefits from this situation. It provides alternate sources. The competition creates pricing advantages. In addition, the reliability of supply is improved. One way to determine the popularity and widespread use of a microprocessor is to determine its second sources. The more second sources that a device has, the more widely it is used and the more competitive is the pricing. Don't overlook this as a way of choosing a microprocessor.

Popularity

It may seem almost ludicrous to include such a general and seemingly meaningless criterion for selecting a microprocessor as popularity. Yet this rather inexact factor is important. Most people tend to want to go along with the crowd. They want to select devices that are well known and widely used by others. For that reason, you cannot overlook the popularity factor. Most people feel that a device that is popular and widely used must have something going for it. This tends to make their own choice easier. In effect, they are relying upon the decisions of many others to back up their own decision. This is why Chevrolet sells more cars than any other US manufacturer. Popularity in computing also has benefits with regard to availability of software.

The choice of a microprocessor is also largely emotional. Even though a device may not have the benefits of software availability, speed and computing power, the device may be highly regarded. This may be because of the reputation of a particular manufacturer or a particular unique feature. Many times the features or benefits are perceived rather than real. A strong sales pitch by a trusted friend or respected source can also easily sway an individual's choice. In

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luly 1978 e BYTE Publlcationi Inc 127

Circle 321 on inquiry card.

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selecting a microprocessor, you are often buying mystique or potential rather than real practical computing capability. The thought of having the newest, best, fastest, most powerful microprocessor is a strong selection inducement. While these factors will no doubt influence you, you should attempt to be more practical, realistic and analytical in the selection of a microprocessor for your own personal computer.

Documentation

Documentation refers to all of the written material available for a particular microprocessor. This includes magazine articles, books, courses, manufacturers' literature and any other printed sources. Good documentation is hard to come by and often it will make the difference between failure and success in getting your system to work. You will get more value from your own investment if you have plenty of written sources to refer to and to help you in applying it. This is particularly true if you are a beginner. The more sources of information you have for the microprocessor, the easier it will be for you to learn to use it. You should always consider this factor before making your final decision.

Upwards Compatibility

Upwards compatibility refers to the future of a given microprocessor. It tends to indicate that a particular microprocessor will eventually be upgraded or replaced by a compatible device. Computer manufacturers found out early that upwards compatibility was an extremely important part of their development and marketing strategy. The upwards compatibility factor is tied to software. Individuals who purchase computers proceed to develop considerable amounts of their own application software. If at a later date they decide to replace that computer, they must take into consideration the status of their applications software. If the replacement computer is upwards compatible with the previous computer, their present software will run on the new computer. Because of the significant amount of time and money invested in software, the desirability of upwards compatibility is extremely important. If an entirely different microprocessor or computer is selected, it may be necessary for the users to completely convert or abandon their present software. This is highly undesirable since it involves throwing away a considerable investment.

When considering a microprocessor, you should examine the concept of upwards compatibility. Will the microprocessor you

128

July t978«jBYTE Publiciliom Inc

Circle 319 on Inquiry card.

Circle 183 on inquiry card.

select eventually be replaced and upgraded by a compatible improvement? If so, it is probably a good choice. This means that you will obtain valuable usage from your present computer but then ultimately upgrade to a more powerful system at a later date without any loss of software capability. Most of the major microcomputer manufacturers are quickly learning the importance of the upwards compatibility concept.

Software

It seems almost unnecessary to mention the importance of the software factor in choosing a microcomputer. Even a beginner quickly learns that the microcomputer hardware itself is useless without good software. This means not only good systems software that allows you to develop your own applications programs, but also the availability of a wide range of "canned" or predeveloped programs which can be run on the computer. Most computer hobbyists want to write and develop their own programs. But the value of their systems is higher if they can also readily obtain other software that will run on their computers. All things considered, software and Its availability is by far the most important decision making factor in choosing a microprocessor.

There are two software considerations which you should make. First, how easy is the microprocessor to understand and program? Second, how much software is available for that particular device? In the first case, the simplicity of the instruction set and architecture makes a great difference in learning to use a microcomputer. If the instruction set is straightforward and the architecture textbook-like, the microcomputer will be easy to program and use. Even a beginner will learn to use it quickly and obtain satisfactory results.

In the second case, how much software is available for the microprocessor? If the microprocessor is popular and very widely used, chances are there is a tremendous amount of software available. Programs are listed in magazine articles or are available for sale. Regardless of the source, if software is available for the microprocessor, then the choice is a good one. The lack of available software is a clear indication that the processor is not widely used and that you will have to develop most of the software yourself should you choose it. Software should be your single most important consideration in choosing the microprocessor. All other factors, speed, cost and computing power are practically irrelevant or at least far less important than the software consideration.

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)uly 197g®BYTE Publicilions Inc

129

(o)

(b)

(c)

Shown at (a) is the Heathkit H8 computer, which uses the 8080 processor to provide generai purpose computing capability. It Is typical of a number of units based on the popular 8080, Z-80, 6502 or 6800 processor integrated circuits. Other examples of personal computers Include the Cromemco Z-2 (b), and the Equinox 100 (c).

The Big Four

Of all the microprocessors listed earlier, four are clearly the most popular and widely used. It is probably safe to say that these four devices account for more than 90 percent of all microprocessors used in personal computing systems. It is strongly recommended that you choose one of these four devices when selecting your microcomputer.

The microprocessors most widely used in hobby and personal computers are the 8080, the 6800, the 6502 and the Z-80 in that order. You won't go wrong if you choose one of these four microprocessors. A considerable amount of software is available for each and there is evidence to support the concept of upwards compatibility. Let's take a look at each of these devices and analyze its present capabilities and future potential.

8080

The Intel 8080 microprocessor was the first of the second generation 8 bit microprocessors. Because it was first, it readily captured a large portion of the 8 bit processor market. Later second generation microprocessors such as the 6800 had a more difficult time in penetrating the marketplace simply because of the great lead that Intel held. The 8080 was announced in 1973 and even today despite inroads by other 8 bit microprocessors, the 8080 is still "king of the hill."

While the architecture, speed and computing power of the 8080 are not spectacular when compared with other chips, it is nevertheless a useable device. It has proven its worth and value time and time again not only in dedicated industrial cohtrol applications but also in stand alone general purpose microcomputers. It is so widely used and well documented that it is by far one of the best choices you can make. In addition, there is more software available for the 8080 than for any other 8 bit microprocessor. While exact data is difficult to obtain, an estimate I have seen claims that over 60 percent of all 8 bit microprocessors in use are 8080s.

Another factor that the 8080 has going for it is that upwards compatible devices are available. Intel's new 8085 microprocessor is an improved 8080. By using the 8085, you can develop a microcomputer with greater capabilities than the 8080. The 8085 uses fewer support chips since the clock and system controller functions normally required for the 8080 are effectively built into the 8085. In addition, the 8085 uses a single power supply eliminating the additional two supplies required by the

130

luly 1978©BYTE Publicitions Inc

Circle 82 on inquiry card.

8080. An added bonus is that the 8085 operates at a higher speed and has several more instructions.

Another upwards compatible device for the 8080 is the well known Z-80. This device is a newer and more powerful microcomputer with far greater capabilities than the 8080. Nevertheless, the Z-80 was designed to include the 8080 instructions so that software written for the 8080 will also run on the Z-80. The 8080 instruction set is in effect a subset of the Z-80 instruction set. The Z-80 is not only faster but has nearly twice as many instructions making it a far more powerful microprocessor. Like the 8085, the Z-80 requires fewer external support chips and only a single 5 V power supply in contrast to the 8080.

Evidence of the popularity of the 8080 can be demonstrated simply by listing the number of personal computer manufacturers who use the 8080. A probably incomplete list of manufacturers of 8080 systems includes:

Digital Group

E&L Instruments

Equinox

Heath Co (H8)

IMSAI (8080)

MITS (Altair 8800b)

PolyMorphic

Processor Technology

Vector Graphic There are more 8080 based personal computers than any other type.

Another consideration is the number of second sources available for the chip itself. As indicated earlier, the number of second sources is a clear evidence of the popularity of a particular microprocessor. Semiconductor manufacturers typically will not gear up to second source a device unless there is a large demand and an identifiable market for that device. A list of suppliers of the 8080 is given below.

Intel (the original 8080 design)

Advanced Micro Devices

Texas Instruments

National Semiconductor

NEC (Nippon Electric)

Siemens

Again, there are more second sources for the 8080 than for any other 8 bit microprocessor.

Another factor to consider is the bus design associated with the 8080 based microcomputers. The popular MITS Altair or S-100 bus is used by most of the manufacturers incorporating an 8080. The S-100 bus is in effect an 8080 bus. The signals defined on that bus are peculiar to the 8080. The S-100 bus over the past several

I

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Circle 137 on inquiry card.

luly 1978 8BYTE Publications Inc 131

years has become nearly a standard. While not an official standard, it does nevertheless provide the user with a wide choice of options and accessories for his 8080 based microcomputer. However, keep in mind that the Altair bus became a de facto standard by virtue of being the first widely sold design. Many manufacturers jumped on the Altair bus bandwagon when they started because it had a built-in marketing advantage; this helped snowball interest in the Altair bus. While the Altair (S-100) bus is certainly not an optimum choice, it is strong inducement to many individuals simply because so many people are using it and so many accessory products are available. By choosing an 8080 microprocessor you will no doubt at the same time be choosing an S-100 bus. That isn't all bad. Keep in mind, however, that several 8080 designs on the market do not use the S-100 bus. Notably these are the Heathkit and Digital Group designs.

6800

The second most popular and widely used microprocessor is the Motorola 6800. It was announced almost a year after the 8080. Despite its time lag behind the 8080, the 6800 has come from behind to capture a rather large following. While it is still not as widely used as the 8080, it is a clear-cut second place with many followers and supporters.

The architecture of the 6800 is extremely simple. It is a classic, almost textbook-like design. Its instruction set is easy to learn and understand. And at the same time, it incorporates a variety of addressing modes. While it is slightly slower than designs like the 8080 or Z-80, the 6800 makes up the lack of speed in its superior instruction set, architecture and addressing modes.

A wide variety of software has been developed for the 6800. This software is widely available to most 6800 users.

The popularity of the 6800 can be illustrated by the number of hobby and personal computer manufacturers using the 6800. A probably incomplete list of these is given below.

Southwest Technical Products

(SwTPC 6800) Wavemate

Electronic Products Associates MITS (Altair 680b) Digital Group Motorola MSI Heath Company

A list of second sources for the 6800 chip is given below.

Motorola

American Micro Systems Inc

Fairchild

Hitachi

Unlike the 8080, the 6800 does not appear at present to offer upwards compatibility. It is possible that a more powerful 6800 will be offered in the future. However, improved versions of the 6800 have been announced by Motorola. They include features such as on-chip clock and memory and higher speed versions. These improved versions will help lengthen the life of the 6800.

All in all, the 6800 is a well established microprocessor. You will certainly not go wrong in choosing this device in your microcomputer.

6502

The MOS Technology 6502 is essentially in third place in the hobby and personal computing field. This device is very similar to the 6800. There are a number of differences in that the 6502 does feature an on-chip clock, only one accumulator, and different indexed addressing modes. It is widely used in hobby and personal computers.

Due to the large number of KIM-1 computers in the field, the 6502 does have an enthusiastic following of users and an independent users' publication.

Some of the personal computers using the 6502 are listed below.

Ohio Scientific Instruments Apple Computer MOS Technology (KlM-1) Commodore PET Microcomputer Associates JOLT

At the present time there are three sources for the 6502. These are MOS Technology, Synertek and Rockwell.

While the 6502 is way down the list in terms of popularity when compared with the 8080 and 6800, it is still a widely used device. Like the 6800, it is simple to learn and use. It is a practical choice for a personal computer.

Z-80

The Z-80 is one of the most popular and certainly the most talked about 8 bit microprocessor of 1976 and 1977. While it was introduced a number of years after the 8080

132 )uly 1978©BYTE Publications Inc

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I Infinite Programming Possibilities |

I Microcomputer Handbook by Charles J SippI defines tine j present state of computer technology very well, con1 centrating on both hardware and software. Lucid and i complete glossaries are combined with a variety of I illustrations. Topics covered include: microcom\ puters-where they are, what they are doing, and

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Top-down Structured Programming Techniques. What is [ structured programming? Clement L McGowan and | John R Kelly answer this question in their lively, : well-written book. Top-down Structured Program-: ming Techniques. Discover the three basic types i of flowcharts and how to optimize them. One j section deals with the best ways to manage pro- j grams being written by a team of programmers, j An important feature of this book is its univer- j sality: practically any program in any language | can be improved by using the ideas described | in it. 288 pp. $15.95 hardcover. j

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Circle 35 on inquiry card.

BYTE Julv 1978 133

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Several firms manufacture microprocessor trainers like t/iese. The unit at (a) is an E&L Instruments IVII\^D-I 8080 based trainer, shown with a tape recorder for mass storage and documentation. The unit at (b) is the Heath kit ET3400 trainer, based on the 6800 design. The unit at (c) is the MOS Technology KIM-1 single board 6502 computer, probably the most widely sold board in personal computer experimental circles. The unit at (d) is a Motorola 6800 training kit available from the manufacturer. (These photos supplied by the respective manufacturers.) The training computers tend to have limited memory and limited peripheral capability, but excellent documentation designed to train technical people in the operation of a particular computer and in general principles of computer controlled systems.

and 6800, it has managed to capture a significant portion of the microprocessor marl<et. It has also been widely accepted in hobby and personal computing. Because it is essentially an improved and more powerful 8080, the Z-80 can be considered a part of the 8080 movement. Nevertheless, it deserves some attention on its own.

Some of the personal computers using the Z-80 are listed below.

Technical Design Labs Cromemco Digital Group Radio Shack

The Z-80 also has two primary suppliers. These are ZiJog and Mostek.

Since the Z-80 will run most 8080 software, it is an excellent choice with respect to software. Besides the upwards compatibility and software factors, the Z-80 is also far more powerful. It runs at a higher speed, has a larger instruction set and more sophisticated addressing modes. The Z-80 is perhaps the best 8 bit microprocessor currently on the market.

Despite these advantages, the several Z-80 based processor boards developed as replacements for S-100 based microcomputers have not been all that popular. It is difficult for the owner of an 8080 based Altair bus microcomputer to justify a three or four hundred dollar expense simply to replace an 8080 processor with a Z-80. While you still maintain software compatibility, the Z-80 provides the additional benefits of greater computing power and speed. However, most hobbyists do not require the greater power and computing speed. The capabilities of the less powerful 8080 are more than adequate.

Choosing a microprocessor for a microcomputer design is an agonizing process. Yet once all of the factors are considered, the choice narrows down rather quickly. For a general purpose microcomputer, most designers circa 1975 to 1977 quickly identified the four choices given above. Choosing among them then becomes somewhat subjective. I was personally involved in making

134 July 1978 © BYTE Publications Inc

Circle 6 on inquiry card.

a decision for tiie microprocessor of the H8 Heathkit computer. When that choice was made in early 1975, the Z-80 was not available. The 6502 was a fairly new device and no second source was available. This narrowed the choice rather quickly to the 8080 and 6800. At that time the 6800 had not penetrated the 8 bit market as much as it has now. As a result, not as much software and documentation support were available. Because of this, the 8080 became the most obvious choice in our planning. Today, even with the greater penetration of the 6800 and the announcement of the 6502 and the Z-80, the choice of the 8080 for the Heathkit H8 was still a good one. The 8080 still has sufficient computing power for nearly any hobby and personal computing application. But today with more choices available, the 6800, Z-80 and 6502 are certainly viable alternatives. At some point in the decision making process, technical capabilities, specifications and other factors become meaningless and the choice is made strictly on subjective or emotional grounds.

What About the Others?

What about all those other microprocessors which are available to the hobby and personal computing user? Why shouldn't a hobbyist consider these devices as well? The answer is a difficult one. First the other microprocessors are certainly capable of producing the same or even improved performance over the most popular devices in use. However, since they have not been widely adopted by microcomputer manufacturers, most of them are simply not available.

2650

The Signetics 2650 is a good example. This device was announced well after the 8080 and 6800. However, it is a superior design in many ways. The 2650 is in effect more like a minicomputer than a microprocessor. It is extremely powerful in that it has a superior architecture and powerful instruction set. It also operates at a high rate of speed. Yet this device never really caught on. Today there are no widely used hobby and personal computers available using this device. As a result, there is limited software available for it. For the homebrew experimenter this device may be an excellent choice provided he is willing to develop his own hardware and support software.

SC/MP

The National SC/MP is another very interesting 8 bit microprocessor. It is perhaps one of the simplest and lowest cost

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Circle 291 on inquiry card.

luly 1978©BYTE Publications Inc 135

Circle 330 on inquiry card.

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devices available. Because it is so simple it does not offer the computing power of the other devices. Nevertheless, it is extremely easy to learn and use.

The main reason why the SC/MP has not been widely used is that again no hobby and personal computer manufacturer has selected it for its processor. National Semiconductor does provide several development kits that have found some interest in hobby and personal computing fields. In addition, National has developed a BASIC-lii<e language called NIBL that was developed with the hobbyist in mind. For the homebrew enthusiast, the SC/MP is a good choice.

1802

The RCA 1802 is another interesting 8 bit microprocessor. This is a CMOS device which has extremely low power dissipation. Its low power dissipation has led to incorporation of the 1802 design into one well known experimenter's project, the next series of AMSAT radio amateur satellites. Again, no hobby and personal computer manufacturer has selected this as the primary processor of a general purpose computer. The architecture and instruction set of the 1802 is peculiar and thus more difficult to use than other devices. Little or no software is available. Nevertheless, the 1802 is relatively easy to use and the homebrew hobbyist may find it a desirable choice. RCA makes several development kits that serve as a good starting point, one of which is intended as a low cost hobby computer.

F8/3870

The F8/3870 microprocessor is another widely used 8 bit microprocessor. The F8 is effectively a two chip microprocessor featuring a ROM on one chip. The 3870 is MOSTEK's version of the Fairchild F8 in a single chip form. Neither of these devices has caught on for hobby and personal computer use. Only one hobby and personal computer manufacturer ever announced an F8 based machine and the company which manufactured it appears to be no longer in business. Both the F8 and the 3870 microprocessors were not designed for general purpose computer application. Instead, they were designed to be hardwired digital logic replacements. These are the microprocessors that were designed to be buried inside of equipment as controllers. As a result they make very poor choices as general purpose digital computers.

The same is true of the new Intel 8048/ 8748. Like the F8 and 3870, the 8048 incorporates all circuitry on one chip. This includes the processor, clock, both pro

136 luly 197g«>BYTE Publicdiions Jnc

Circle 294 on inquiry card.

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(a)

(b)

Digital Equipment Corporation, tine largest minicomputer company, introduced the LSI-i i microprocessor based single board computer to extend its minicomputer line downward into the microcomputer world. This PDP-i 1/03 system (a) is the DEC finishedpacliage based on the LSI-I I. The Heath Company offers a version of the LSI-I J (b) which is called the HI J, which is available at lower cost in partial kit form along with extensive documentation aimed at the personal computer kit builder and experimenter. These photos are supplied by Digital Equipment Corporation and Heathkit, respectively.

grammable and read only memory, as well as Input and output interfaces. The 8048 was designed as a hardwired logic replacement and not for general purpose digital computer application.

What About 12 and 16 Bit Microprocessors?

Without question the trend in microprocessor development is toward larger, more sophisticated designs. While most microprocessor activity is centered around 8 bit devices, there is clear evidence that single chip 16 bit microprocessors will

eventually replace the 8 bit units. As semiconductor technology improves, it will be just as easy to manufacture a 16 bit microprocessor as it is an 8 bit device. When that time comes, the price differential will be minimal. As a result, most purchasers of new equipment will go to the more powerful 16 bit device over the 8 bit device, even though the computing power available is overkill for the application.

There are a number of 16 bit microcomputers and one 12 bit device now on the market. In terms of overall microprocessor usage, their popularity is small. But it is growing rapidly as more devices are developed. As these devices are incorporated in designs, the demand will go up and prices will decline.

Some of the manufacturers making a 16 bit microprocessor are given below.

National Semiconductor PACE, 8900 General Instrument 1600 Data General microNOVA Digital Equipment Corp LSI-11 Texas Instruments 9900 Fairchild 9440

At present there are few hobby and personal computers based on 16 bit microprocessors. Notably those that are available are the Heathkit H11 which is based on the popular DEC LSI-11 and the Technico 9900, based on the TMS-9900 part from Texas Instruments.

The reason why 16 bit microprocessors haven't caught on in personal computing is that they have not been widely adopted elsewhere. The price is significantly higher than 8 bit devices and little or no software is available. 16 bit microprocessors are far more powerful and can process data much faster than an 8 bit microprocessor. However, for most personal computing applications such power is not necessary.

At this time, the most widely used 16 bit microcomputer is the DEC LSI-11. This particular computer has a wide following among hobbyists because of the great DEC software base. It is an ideal choice for the advanced user.

None of the other available 16 bit microprocessors has yet caught on. The first 16 bit microprocessor available was National Semiconductor's PACE. Despite its early lead, PACE never became popular.

The newer Texas Instruments 9900 16 bit microprocessor shows promise of becoming one of the more popular 16 bit microprocessors. This device may eventually become the 8080 of the 16 bit microprocessors. This device is gaining acceptance in many areas. It is a powerful, general purpose

138 luly 1978©BYTE Publicatiominc

device. In addition, much of the software available for Texas Instruments minicomputer line is compatible and could possibly be converted in the future for use on this device. Finally, Texas Instruments is one of the largest and most aggressive semiconductor manufacturers. They have the manufacturing and marketing power to support and promote this device. Watch for it in future designs.

The Micro NOVA is another very powerful 16 bit microprocessor. It can effectively run all of the software available for the popular Data General NOVA line of minicomputers. However, this device like some of the others has not caught on. It is an expensive device and not widely available. While the architecture is straightforward and easy to learn and the Data General software base is tremendous, it is doubtful that Data General will promote this device for the personal computing market or make such software available at competitive prices. (However, Data General is promoting the Micro-NOVA through selected retail stores and electronics distributions. Fairchild's 9440 MPU uses the Data General architecture and will run the software. Although it is expensive, someone may eventually use the 9440 in a personal computer.

The Intersil 6100 is a 12 bit CMOS microprocessor. Its claim to fame is that it has the architecture and instruction set of the famous DEC PDP-8/E minicomputer. It will also run software written for that machine. This gives the 6100 an excellent software base. But despite the software advantage the 6100 hasn't caught on in personal computing. One reason is the high price associated with 6100 based computers. These include Intersil's own Intercept series and a machine made by PCM. For the prices of these machines, a user can buy a used but real DEC PDP-8. In any case, the 6100 is a good chip with much potential.

Summary and Conclusion

The message in this article is relatively clear. If you are choosing a microcomputer for hobby and personal computer applications, your best choice lies in the 8080, Z-80, 6800 or 6502 based machines. This is the mainstream of personal computing. The 8080/Z-80 combination probably has the edge over all of these.The biggest question is who is going to make the 16 bit microprocessor. Will it be the new Intel 8086? or will Zilog's Z8000 win? We will have to wait and see.

Finally, the message here is that "a processor alone does not a computer system

Another 16 bit minicomputer architecture available In microcomputer form Is the Data General Corporation's MicroNOVA shown here in a picture supplied by Data General. In the foreground is the processor chip standing alone; in back of the integrated circuit is a printed circuit board version of the computer Intended for use In dedicated applications. In the background can be seen the MicroNOVA fully integrated minicomputer system. These products are available at several retail computer stores and at several electronics distributors.

make." When it comes right down to it, the type of processor is almost irrelevant to the user who is programming in BASIC or PASCAL or some other high level language. Overall, it is the software that gets the job done. If you base your choice of a personal computer system on the availability of good system and application software, you will not go wrong, whatever low level machine architecture is used."

luly 1978 © BYTE Publications Inc 139

»^nt;itr iH3 on inquiry card.

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Continued from page 46

The integrated circuit manufacturer can sell parts that would otherwise have to be thrown away, and the designer can buy state of the art parts for prices far below those of the equivalent 16 K part.

The design task breaks down into the following steps:

1. Select the memory chip. For reasons stated earlier, the MK4115 (or equivalent) is the clear choice.

2. Decide how to handle refresh.

3. Analyze the timing requirements for the memory and the processor.

4. Merge these two timing diagrams so that they work together.

5. Design the circuitry.

6. Lay out the circuit board.

Refreshing Strategy

When should you refresh? There are two types of refresh used in a dynamic memory system. Burst refresh suspends all other memory activity and quickly refreshes all the required locations at the top memory speed. This burst occurs once every refresh interval (generally every 2 ms).

A preferable approach in a microprocessor system is to use a distributed refresti approach, in which refresh cycles are interspersed with processor access cycles. In this manner the refreshing action is evenly spread over the 2 ms refresh interval.

Let's examine some refresh alternatives:

1. Use a 2 ms timer to interrupt the processor and tell it that the memory requires refresh. The processor interrupt routine then counts out the proper memory addresses and returns to normal processing.

2. Use a timer with an interval of 2 ms divided by the number of required refresh cycles, and perform item 1 on a distributed basis.

3. Interleave the refresh operation with normal processor timing: For example, notice (as the Z-80 designers did) that the processor address lines serve no useful purpose on the tail end of an instruction fetch cycle. During this time the processor must decode the instruction fetched from memory in anticipation of executing it. Why not put the refresh cycle (which needs the address lines) into this time slot?

Items 1 and 2 above require processor overhead (processing time) since the interrupt system is used to provide programmed refresh. Of the two, the distributed approach is preferable because it produces less of a timing discontinuity in the background pro

140 luly 1978 (^ BYTE Publications Inc

Circle 1 79 on inquiry card.

Circle 120 on inquiry card.

gram execution while the interrupt is being serviced. Item 3 is best in all respects, since no direct processor intervention is required to perform refresh. This is the so-called "transparent" or "invisible" refresh. This approach has already been implemented in some small system designs. It does, however, have some drawbacks in Altair (S-100) bus products. In examining the details of this approach, we'll describe an even better method of achieving "Altair (S-100) refresh." This discussion assumes an 8080 or equivalent processor.

Catching the Bus

The only time the processor can guarantee that the address bus is not needed is the second half of an instruction fetch cycle. This point in time is signified by the processor control signal called Ml, which means "memory cycle one" of any instruction. Every instruction execution starts with an Ml memory cycle, in which the instruction is brought into the processor from memory. Depending on the instruction, further memory cycles might be required to finish execution of the instruction. During these subsequent cycles, the Ml signal is inactive. For example, the 8080 STA (store A) instruction operates as follows:

1. Ml: instruction word fetched from

memory.

2. M2: first half of the storing location

read from memory.

3. M3: second half of the storing loca

tion read from memory.

4. M4: accumulator contents written

into memory location specified by data brought in by steps 2 and 3.

The STA instruction is a 3 byte instruction, and M2 and M3 are needed to read in the additional two bytes of the instruction. M4 does the actual execution of the instruction, storing the accumulator. In this example, the Ml control signal is active only for step 1. The actual Ml cycle is divided into five processor cycles, called time states or "T-states." By the end of T3, the processor has received the first byte of the instruction and now requires two more time states, T4 and T5, to figure out what to do. This is the logical time to force a memory refresh (to be exact, T4 and T5 of Ml).

This is all very nice, but what happens when the processor is halted? During HALT, the signal needed to locate the point in time for refresh. Ml, is not there. In fact, most of the processor signals are not there. This is also true for processor RESET, wait states, and direct memory access cycles. This means

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Circle 383 on inquiry card.

July 1978©BYTE Publications Inc 141

Circle 405 on inquiry card.

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that the design must do something special for these cases.

What is really needed is an approach independent of processor control signals for refresh. The only signals on the Altair (S-100) bus that are present under all circumstances (except power off) are the processor clock signals 01 and 02.

Plan Ahead - Backwards

Here's the plan: the memory design should contain a self-contained refresh system that uses only 02 for its operation. The control is arranged so that the memory is normally refreshing, and it is the exception cycle that diverts it away from refresh to perform a processor access. This emphasis is "backwards" from most systems, which treat the refresh operation as the exceptional case. Now the card merrily refreshes itself until called on by the processor. If the processor "goes away," for example, in a prolonged wait state (a method frequently used to implement single-step and other front panel operations), the refresh continues.

When the processor needs to access the memory card, it must do it on a synchronous basis. This means that the processor timing on a memory access into the dynamic memory card is designed to not jeopardize a refresh cycle in progress (it is synchronized with the refresh timing). Imagine the processor crashing in on a refresh cycle, and 64 data locations in the memory not being properly refreshed and going to indeterminate states. This is the kind of "soft error" that occurs only when you demonstrate the system ("It worked perfectly on the bench.. ."), and promptly goes away when you try to fix it.

Programmable IVIemory Timing

Let's take a detailed look at the dynamic memory integrated circuit itself, and at exactly what signals are required to make it work. The integrated circuit described could be any of the various 16 K parts of the MOSTEK MK4116 type; or, with one small exception, any of the 4 K parts of the MK4027 type.

Since 16 K is equal to 2^^, the part requires 14 address lines to uniquely select any of its cells. Allowing one line for DATA IN and another for DATA OUT, this adds up to all of the pins of the 16 pin package. That's fine if the chip doesn't require power supplies or read and write control, but unfortunately, it does. This dilemma is solved by using a multiplexed address approach. Only seven pins are used for address inputs, and the address is loaded in two parts. One

142 luly 1978 % BYTE Publicitions Inc

Circle 388 on inquiry card.

Circle 95 on inquiry card.

of the big benefits of this approach is that, when the technology jumped from 4 K to 16 K, an additional two address lines could be had with only one additional pin. On the 4 K parts, this "unused" pin is a Chip Select input, which is used to select only one bank of parts that share the same output bus. As we'll see, the 16 K part does the chip select function without a chip select pin.

Two control pins called RAS and CAS strobe the two 7 bit parts of an address into the memory part. These signals stand for Row Address Strobe and Column Address Strobe. They are active low signals, which means that they are normally at a high logic level, and are "strobed" by going into the low state momentarily.

The sequence of events necessary for a memory cycle is as follows (see figure 3):

1. Set up the low order 7 bit address on the address lines. This requires setting the address multiplexer to state 2 (for example).

2. Wait a suitable time for the address lines to settle. There will be a certain delay through the multiplexer, as well as some line settling time.

3. Drop the row address strobe (RAS) to the low state. This latches the low address into the part. Both RAS and the column address strobe (CAS) start out high.

4. Wait the "row address hold time," which specifies for how long after RAS drops the address lines must not change. This requirement is due to the setup time of the on-chip latches.

5. Set up the high order 7 bit address on the address lines. This requires selecting multiplexer state 3 (for example).

6. Let the lines settle.

7. Drop CAS to the low state. This latches the high address into the part. Don't remove the addresses until after the "column address hold time."

When the logic level of the column address strobe drops, the output lines go from a high impedance state to a valid data state after the interval called "CAC" for Column ACess time. This is one way of specifying the access time of the memory part.

These seven steps are the same for either a memory read or write cycle, the only difference being the treatment of the RW pin which controls the choice of Read or Write operation. If this pin is held high throughout the cycle, a read operation is performed. To do a write, the RW pin is pulled low sometime after RAS. Exactly when it is pulled low determines whether the outputs become valid for the old data in the selected cell.

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Circle 40 on inquiry card.

luly 1978©BVTePublicaIianslnc 143

Circle 202 on inquiry card.

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or whether they stay high impedance throughout the write operation.

The chief difference between the 4 K and 16 K part timing is in how the data outputs are treated when the column address strobe becomes inactive (high). In the 4 K part, the data outputs remain valid until the Column Address Strobe again makes a negative transition, in the 16 K part, they enter the high impedance state when the column address strobe goes high, effectively disconnecting the data output from the external bus in a system.

Maintaining Control

There are several ways to control these strobe lines during refresh. The simplest way is to perform a full memory read cycle (row, then column address strobes) and not turn on the data input bus drivers; this does the refresh without affecting the external data bus. The problem with this method is that it is not the lowest power approach. Remember that for refresh only the row addresses (the least significant half of the address lines) are needed. The dynamic memory designers have provided for a mechanism called "RAS-only refresh" in the spec sheets, which consumes less power than a full row and column address cycle. In this method, the refresh counter address is applied to the address lines, and the row address strobe is made active (low voltage level). No other address bits or strobes are needed for this special refresh cycle.

The chip select function in the 16 K memory is performed in effect by row and column address strobe timing (remember that the chip select pin was sacrificed for an additional address pin in the transition from 4 K to 16 K). The method is quite simple: only those devices that receive both row and column address strobes in a memory cycle will activate their outputs; otherwise they will be in a high impedance condition. This means that it is possible to select one bank of programmable memories out of many whose outputs are tied together by (a) feeding a continuous row address strobe signal to all parts, and selectively feeding a column address strobe to only the selected bank, (b) the opposite (feeding a continuous column address strobe and selecting a bank with row address strobe), or (c) both (selecting a bank with choice of column and row address). The manufacturers' literature frequently refers to this as "decoded RAS" or "decoded CAS."

There is a slight power advantage to feeding the column address strobe to all devices and decoding the row address strobe to do bank selecting. However, a refresh cycle

144 |uly 1978 © BYTE Publication! Inc

Circle 76 on inquiry card.

using ihe row address strobe only uses less power than a "RAS-CAS" refresh cycle using both strobes, as noted above. It turns out for logic simplicity (a real consideration in view of the small amount of Altair (S-100) bus card space available) that the decoded column address strobe method of selection is the optimum choice. It also happens to fit beautifully into the 8080 system timing. It is now apparent that the programmable memory address pins must be fed from three different sources: for a processor access, the low address half and high address half constitute two of the sources; and for refresh, the refresh counter address constitutes the third. To select these three groups of address lines, a TTL multiplexer (74153) may be used. This is a dual one-of-four selector that accepts four inputs and feeds a common output. The input which is

selected depends on a 2 bit code (called the select bits) input to the multiplexer. These signals are labeled MUXI and MUX2 (see figure 4). For the 8 K part, which requires 14 address lines, the multiplexer has to be seven bits "wide" so that the switching is done seven bits at a time. This means that three and one half 74153 integrated circuits are required.

Processor Timing

Turning our attention now to the 8080 system control signals, the dynamic memory timing must be "dovetailed" into the 8080 system timing. Figure 4 shows the timing for an 8080 fetch cycle.

Lines 1 to 4 are control lines common to any 8080 system: the two clock signal inputs 01 and 02, the address bus (actually

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0 DATA INTO eoeo 7m'i)mtmnmmmmnmm^'^uo mmtmunKm 0 s^N \ nm

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Figure 4: Master timing diagram lor on 8080 dynamic memory fetch cycle using the Altair (S-WOJ bus. Lines 1 thru 4 show the control lines common to all 8080 systems: the two clock signal inputs (<pl and <p2), the address bus and the processor SYNC output. Lines 5 and 6 are the control lines to a one-of-four multiplexer. Line 7 shows the state of the multiplexer selected by the two control signals IVIUXI and IVIUX2. Lines 8 and 9 are the row address strobe (RAS) and the column address strobe (CAS), respectively. Lines 10 and 11 show the processor timing requirements for accepting data read out of the memory. Line 12 is the write line (WL) from the 8080 used to enable a memory write into the programmable memory.

July 1978SBYTEPubH[alionilni.

145

Circle 283 on inquiry card.

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16 lines), and the processor SYNC output. Lines 5 and 6 show the control lines MUX2 and MUX1 to a one-of-four multiplexer, and line 7 shows the state of the multiplexer selected by the two control signals IVIUX2 and MUX1. Lines 8 and 9 show the principle memory timing signals the row address strobe (RAS) and the column address strobe (CAS); lines 10 and 11 show the processor timing requirements for accepting data read out of the programmable memory. The "valid" indication on the waveform of line 10 shows when the eight data lines into the processor must be stable for a successful memory read. The DBIN signal (line 11) is a signal issued by the 8080 to notify the input buffers to turn on in preparation for receiving input data. Line 12 shows the write line (WR) from the 8080 which is used to enable the write operation into the memory.

Working Together

Lines 5 thru 9 of figure 4 constitute the actual memory system design, the result of trading off memory, Altair (S-100) bus and processor parameters, and verifying that all the processor and memory timing considerations are met. The ultimate criterion of a good design is that it can pass a "worst case" analysis — every specification for the 8080 and the programmable memory can be the worst specified in the data sheets, and the system will still work. In fact, a good figure of merit for a digital design involving complex timing (such as this one) is how far beyond worst case the specifications can be for the system to still function properly. This is known as margin. The better the margin, the better the designer sleeps at night, and the better guarantee that the system will work over a long production run.

Notice the similarity between 02 and RAS (lines 2 and 8) of figure 4. RAS is simply 4>2 with certain positive parts missing. Whenever the 8080 starts an instruction fetch cycle (signalled by SYNC), the RAS line must make its negative transition during MUX state 2 and stay there throughout the memory cycle. If the 02 pulse during T2 were allowed through, the memory timing requirements would not be met. To inhibit this 02 pulse, SYNC is delayed slightly and used to gate off the unwanted part of 02. Notice that this gating signal is MUX1 (line 6). SYNC is delayed very simply by feeding SYNC to the D input of a flip flop and clocking the flip flop with the leading edge of 01.

Before this cycle gets underway with row address strobe line RAS dropping, the address lines to the memory must be set up

146 (uly 1978 6 BYTE Publicitionsinc

Circle 318 on inquiry card.

to receive the low order part of address lines from the processor. The multiplexer must therefore switch from state 0 (the refresh select state) to state 2 (processor-low address state) prior to the fall of RAS. This is accomplished by the signal IVIUX2, which is turned on by the leading edge of SYNC. This edge gives the address lines more than enough time to settle before they are sampled by RAS.

After the row address strobe part of the cycle is satisfied, the multiplexer switches to state 3 (the other half of the processor address lines), and column address strobe is activated. The column address strobe line goes low when three signals are asserted as follows:

1. 02 high.

2. MUX1 high.

3. The bank of programmable memories is selected.

The third control, often called "this memory," performs the chip select function by feeding the column address strobe to only one bank of programmable memories at a time.

Looking now at lines 9 and 10 of figure 4, we can calculate the access time margin of the memory system. The data out of the programmable memory becomes valid sometime after CAS makes its negative transition. The data into the processor must be stable and valid at the time shown in line 10. Counting the time from CAS-low to the earliest time data must be valid, the programmable memory access time should be 6X55 ns (each division is 55 ns), or 330 ns. In a system, this time is reduced by approximately 50 ns to allow for the delays through the data buffers and line settling time. Let us say that the CAS to data access time (CAC) must be 330-50 or 280 ns. The specification for the slowest IVIK4n5 gives a maximum t^;\c °f ^^^ "5' ^ ^^''y comfortable margin. (If the margin point seems to be overstressed, its importance will be seen in the section on Altair (S-100) bus compatibility).

To complete the cycle, the CAS line must be held low until the processor is definitely through with the data lines. This is indirectly specified in the 8080 data sheet as being the time that DBIN goes high. Since this point is anywhere from 25 to 140 ns after the rising edge of 02 in T3, the CAS line is held low until the falling edge of 02 in T3. Note that the RAS line makes its lowto-high transition well in advance of CAS's going from low to high. This is permitted in the newer dynamic memory parts but would not be acceptable in the older ones, such

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July 1978 Q BYTE PuWicilionsInc 147

80 percent of dynamic

memory design is printed

circuit board layout.

as the MK4096 dynamic 4 K (both column and row address strobes had to go high together). By the time the RAS line makes its next negative transition, the multiplexer has switched back to state 0, selecting the refresh address, and another refresh cycle begins.

The processor access cycle chain of events is initiated by the 8080 SYNC signal. Anytime the SYNC signal is not there, the circuitry automatically reverts to refresh operation. (Multiplexer state 0 selects the refresh counter, the RAS line continuously cycles, and the CAS line remains inactive (high) for the RAS-only refresh operation.) This implements a strategy that maintains refresh on a fail-safe basis.

The refresh counter is clocked by a signal which is suppressed during a processor access cycle, so that none of the refresh addresses is skipped. A refinement detail of the design is a flip flop which eliminates some of the redundant refresh cycles to conserve power. This is possible because the latter scheme considerably "over-refreshes" the memory, since a full 128 row refresh is performed in much less time than the 2 ms the specification calls for. Refreshing more frequently than the specification requires has no effect on proper memory operation.

For a write operation, the 8080's write line (WR) is timed such that it can be fed unmodified to the memory's read or write control (RW) pin. The write operation is

RAS

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terminated by the WR line going low to high, or the CAS line going low to high, whichever occurs first.

Now, the Hard Part

You might think that the design is complete when the final schematic is drawn. Not so: it is about half complete. As any dynamic memory system designer will tell you, 80 percent of dynamic memory design is printed circuit board iayout. These parts don't just sit there like their static counterparts, responding with data whenever addressed. The dynamic part is actually a sophisticated analog part inside, aside from being a dense memory array. The circuitry that senses the charge on the storage capacitors must resolve millivolt levels in the presence of continuously running 12 V clocks. The power distribution system and power supply noise decoupling are therefore the most critical elements of a good dynamic memory design. This consideration has killed more dynamic designs than any amount of poor circuit design.

The dynamic memory has four power pins; 12 V, 5 V, ground and -5 V. The 5 V supply is connected only to the output transistors (to provide TTL compatible outputs), and draws next to nothing in power. The —5 V supply provides high current ptz/jes of very short durations. Since these pulses are bipolar in nature, the actual DC current for the —5 V supply is also very low. It is the 12 V supply and ground system that need special layout consideration.

The four power pins are located on the four corners of the dual in line package, which somewhat simplifies a good power distribution layout. The best layout for power is one in which all power pins are fed from a horizontal and a vertical direction. This is known as "gridded" power distribution, since each power pin is placed at the intersection of a grid of power lines that simulates a plane surface. Wherever possible, the power lines should be as wide as the array density will allow. When density considerations prohibit wide power buses on all four supplies, the 5 V and —5 V supply buses can be fed with smaller traces (but should still be gridded).

The second important consideration is power supply bypassing. The current drawn by the 1V1K4116 is shown in the waveforms of figure 5. Notice that all the current is drawn as a result of RAS and CAS transitions. The factor which sets the MOSTEK 4116 apart from all other 16 K devices is that after the RAS and CAS current demands, the Iqq (12 V current) drops to nearly 0. The fact that other parts drop to some continuous current (on the order of

148 July 1978 ©BYTE PuWiclIions Inc

20 mA) when the RAS line and CAS line are inactive (high) accounts for the wide difference in power dissipation between the MK4n6 and the others. MOSTEK does it by turning off the sense amplifiers when they are not needed, and the rest of the semiconductor world is presently designing (or redesigning) to duplicate this feature.

Looking at the most critical current waveform of figure 5, Iqq, it is seen that the instantaneous current drawn is about 100 mA maximum. TOO mA per device times 32 devices (in a 32 K memory comprised of 8 K parts) is 3.2 A at 12 V. Before running out to buy a water pump to cool the 12 V regulator, notice that the 100 mA is drawn for only a very brief time. Suppose you connect a capacitor between 12 V and ground, let it charge up during the low current demand time and supply the instantaneous current pulses when needed. This is the role of the so-called "bypass" or "decoupling" capacitors. The value needed for these capacitors can be readily calculated by estimating the area under the curves in figure 5. Using the formula C=(iAt)/Av, the capacitance can be calculated for any allowed drop in the 12 V supply (Av). The MK4116 allows a 10 percent tolerance on all supplies, so a good conservative number to use for the 12 V supply is about 2 percent or 0.24 V. Estimating iAt (the area under one of the current waveforms) from figure 5 to be about 50 ns times 100 mA, the formula yields a value for C of approximately 0.02/jF. (0.1/iF capacitors should work fine.)

The reason for the above exercise is that even though the data sheets may say so, not all dynamic memories are identical. The primary difference between today's dynamic memories is in the current waveforms, and only two manufacturers (MOSTEK and Intel) even publish them.

For the bypass capacitors to be effective, they must be located as close to the memory power pins as possible, so that the inductance of the printed wire feeding the instantaneous current to the part does not interfere with this current supply. Note that for exactly the same considerations as the 12 V supply, the —5 V supply should be adequately "bypassed" with capacitors. The bypass capacitors should be evenly distributed throughout the memory array.

An often neglected detail of dynamic memory layout is that the ground system between the address line drivers and the memory array must be very heavy. As the number of integrated circuits in the memory array increases, the requirements on the

address line drivers become more stringent. Each address pin contributes a capacitance of about 4 picofarads, and they are all tied together in the array. If you follow any address line through a printed circuit board memory array, you'll see that it takes a rather long and usually discontinuous path. For this reason, series damping resistors should be placed between the address buffers and the memory array to help damp out the undershoot and overshoot caused by the layout discontinuities.

It is quite a trick to achieve optimum power distribution layout on an Altair (S-100) bus format card. The system ground pin comes in at only one corner of the card, and it must be routed in a "web" for a good board level ground distribution. Additionally, the required on board regulators use up a lot of space which, along with the permissible heat dissipation, puts an upper limit on the number of chips that can exist on a card. The message here is that a good memory design requires extreme cooperation between the designer and the printed circuit board layout person.

Ah, That "Altair (S-100) Compatibility"

If you have plowed your way through the timing diagrams and technical discussion of this article, you can now appreciate the fact that the question, "Is it Altair (S-100) bus compatible?" is one that cannot be answered with an unqualified yes or no. The memory system is designed to be Altair (S-100) bus compatible, but when you plug it into a Stromdecker X-3 mainframe, running a Fantastroid Z-SOQ processor card with memory-managed-phantomindirect-parabolic-vectored-restart implemented, it might not work. The design philosophy is to use as few of the Altair (S-lOO) signals as possible, to account for unforeseen variations in various systems. Back to figure 4; the only timing lines the memory counts on being there are (?il, 02, SYNC, DBIN (actually MEMR, memory read) and WR (actually memory write). In the case of the memory write line, any Altair (S-100) design should derive the memory write signal from SOUT and WR, since early designs put the gate to do this on the front panel board, and you therefore cannot guarantee that the signal MEMW will be there in all systems.

Some analysis of the interlocked timing of figure 4 reveals that the card will work with any implementation of 01 and 02 that meets the 8080 specifications. The 01 and 02 timing shown in figure 4 is that

luly 1978©BYT[ Publications Inc 149

Imagine pulling out four

8 K static memory cards

and plugging in a single

32 K card that uses less

power than one of the 8 K

cards. This can be done

with today's dynamic

memories.

provided by systems using an 8224 clock generator with an 18 MHz crystal; this is the most popular Altair (S-100) implementation. Will it work with Z-80 processor cards? Maybe. The Z-80 requires only a single clock, has no SYNC output, and times its read and write operations slightly differently than the 8080. Designers of Z-80 based Altair (S-100) cards realize that there is a big compatible world out there that they must back into, so they attempt to synthesize 8080-type signals out of the Z-80 system timing. How successfully they emulate the 8080 (meaning how accurately they reproduce signals such as 01, </)2 and SYNC) determines the degree of compatibility in a system of Altair (S-100) cards.

Incidentally, a final look at figure 4 illustrates the elusiveness of the memory "access time" specification. How many times have you seen ads that say something like "300 ns memories," and wondered what this actually means in an 8080 system? Figure 4 shows that the access time is not itself a figure of merit. The actual memory timing must be compared with the system timing requirements to make any sense. The general idea in a dynamic memory design is to crowd the multiplexing of row and column address strobe events as close as possible to the processor addresses becoming valid, so that the maximum memory access time is allowable. One thing /5 certain — faster memories always cost more than slow ones, so a cost effective design should accommodate the

slowest available. The access time margin is so wide in figure 4 that the system could actually run much faster and still retain comfortable margins.

Final Thoughts

The design presented here is intended primarily to show the important areas of consideration in a dynamic memory design. The general concepts can be applied to any processor and memory interface, using the same methodology of carefully analyzing the specific timing requirements of the system and the programmable memory components, and then merging the two together. Exactly how this is done is the exciting part of digital design, where the designer can be creative. It is most important to first examine the system requirements and keep the memory faithful to these specifications.

A dynamic design pays handsome dividends in a system. By using low power Schottky TTL (74LS family), the 5 V current requirement is kept so low that the 5 V regulator on the card does not even need a heat sink. The 12 V regulator requires a modest heat sink. The total power requirement of the board can be generally less than any static board, regardless of density. Imagine pulling out four 8 K static cards and plugging in a single 32 K card which uses less power than one of the 8 K cards. This type of performance is possible only with today's high performance dynamic memories."

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BYTE

Circle 302 on inquiry card.

BYTE July 1978 151

Ted Williams Steve Conley Dept of EE University of Arizona Tucson AZ 85721

A High Level Language

for 8 Bit Machines

i Assignment

A. VAR =exp

II Branch

A. IF ^ VAR relation exp

B. ENDIF

III Loop

A. DO

B. UNTIL (3 VAR relation exp

C. ENDDO

IV Subroutine

A. CALL (3 NAME

B. SUBROUTINE NAME

C. RETURN

V Input and Output

A. READ/3 channel, VAR1, VAR2,

B. PRINT (3 channel, ( VAR 1 quotes

VI Leaving Interpreter EXIT

Variable VAR is set to the value of the expression on the right side of the equal sign.

The code following, up to the corresponding ENDIF, is executed only if the variable value satisfies the relation.

Indicates the portion of code to be executed if the earlier IF statement is satisfied.

The code between a DO and an ENDDO is executed repetitively until the variable satisfies the inequality. More than one UNTIL may be included in one DO loop.

A CALL executes the code following the SUBROUTINE statement with the same name until a RETURN is encountered.

READ specifies a transfer from the device specified by channel, conversion to floating point, and transfer to the locations in memory specified by the variable names.

PRINT sends data to a specified output device in binary coded decimal form, prints ASCII code between quotes, and sends a carriage return for each "!".

Causes the interpreter to return to the monitor.

Interpreters such as BASIC or APL do not translate the high level source code into machine language. Rather, they scan the line of code and then perform a set of operations based upon the instruction and data stored in tables from previous instructions. Thus an interpreter saves the time consumed by translation, but no machine code is saved for later execution. The main advantage of an interpreter is the ease of error correction. The results of each line of code can be printed and the exact source of difficulty can be pinpointed. The price paid for this feature is memory. The source code, data, tables and the Interpreter program must all be resident in memory at the same time.

Tab/e J: The interpreter instruction set allows the evaluation of expressions, conditional branches, loops, subroutine calls with multiple returns, and 10 instructions. Keywords are indicated by boldface type in this table. The variable names must contain six or less alphanumeric characters and start with a letter. Expressions (exp) may contain numbers, operators, variables, functions and parentheses. Any of the following relations may be used: >, > =, <, < =, =, > <. |3 indicates mandatory space. All other spaces are ignored by the interpreter. The only limit to the number of loops that may be nested is the amount of memory space available for storage on the stack. Everything past a semicolon on a line will be ignored as a comment. Each statement must be terminated with a carriage return.

152 July 1978eBYTE Publications Inc

Programs also run slower because the code within loops must be reinterpreted on each pass.

The language proposed here is suitable for use with both an interpreter and a compiler. If both are available then the time consuming process of compiling is avoided until permanent machine level code is required; furthermore, the debugging of a developing program may be done quickly and easily with an interpreter in an interactive mode.

The purpose of this article is to introduce readers to concept interpreters and to present an example of an interpreter for a high level language.

The interpreter instruction set is shown in table 1. In addition to evaluating expressions, the interpreter can also perform conditional branches, loops, subroutine calls with multiple returns, and 10 instructions. These instructions are sufficient to execute very complex tasks. In fact, the language is devised to encourage a top down approach to writing code so that it is easy to understand, debug and modify. More complex groupings such as an IF THEN ELSE construction might yield slightly shorter programs if included in the language, but the convenience of using such structures does not seem to warrant the considerable effort required for implementation. Good programming techniques are essential to useful code.

Some other simplifications are made just to simplify this interpreter. No integer variables, arrays, complex variables or double precision variables are included. All numbers are considered to be floating point numbers with a 4 byte mantissa and a 1 byte exponent. Also the subroutine calls do not pass arguments. Since all the variables are global symbols, local variable names within a subroutine may not duplicate those in another routine. These restrictions are made so that the code for the interpreter would fit on a small machine and so that the main features of the interpreter will not be obscured.

The interpreter program is written in terms of a universal set of instructions, MACL1. These macroinstructions can be translated into machine code instructions for a variety of microprocessors if the expansions for each macroinstruction are defined for your microprocessor. The translation of the interpreter into machine code is simplified by the use of a program called a macroprocessor. Otherwise it can be done by hand.

High Level Language Statements

AREA=0

X=1

Y = (Xt2) -^ (2*X)-i-3

DELTX=0.1

IND=11

Notes

initialization

DO

X=IND*0.1

YPLUS=(Xt2)+(2*X)+3 I

AREA=AREA+DELTX* (YPLUS+Y)»0.5 / UNTIL IND>=100

IND=IND+1

ENDDO

PRINT 1, "The area is", AREA

EXIT END

loop condition counter is "IND"

start of DO loop

; sum areas using trapezoidal integration rule

UNTIL evaluates loop reiteration condition

ENDDO tests loop reiteration condition

output message and AREA through channel 1

go back to monitor

Listing 1: This example program, written in the high level language of this interpreter, is a trapezoidal integration routine for the function Y=(X\2)+(2*X) 3.

P2=3.14159»0.005

READ 2,A

IF

A<SIN (P2)

PRINT 1,A "A IS TOO SMALL

EXIT

ENDIF

IF

A>SIN(100*P2)

PRINT 1,A, "A IS TOO BIG",!

EXIT

ENDIF

LOW=1

Hl = 100

DO

UNTIL HI<=LOW+1 IVIID=INT( (HIH-LOW) 12) IF A>SIN(P2*IVIID)

Hi=MID ENDIF

IF A>SIN(P2*MID)

LOW=MID ENDIF

ENDDO

IF a=sin(p:

l*LOW) HI = LOW ENDIF

IF A=SIN(P2

!*HI) LOW=HI ENDIF

XL0W=SIN(P2*L0W)

XHI=SIN(P2

♦HI)

PRINT1,XLOW,XHI,A

EXIT

END

Listing 2: This example program gives the flavor of a longer program with references to various mathematical routines. Indentation is done to emphasize program structure.

luly 1978©BYTE Publicaliom Inc 153

The following sections discuss the implementation of each of the five types of instructions and show the function of the instructions in flowchart form. Two examples shown in listings 1 and 2 illustrate the simplicity of the resulting high level language.

Interpreter Organization

The basic elements of the interpreter and the utilization of memory are shown in figure 1. Besides the source code and the interpreter routines, there are four tables, two stacks and a workspace for control pointers. The workspace is used for pointers to keep track of positions in the various tables, limiting addresses for the tables, scratch area for temporary results, and addresses for 10 channels.

The stacks are used for saving subroutine

return addresses and for evaluating equations as described in our discussion of the assignment operations section. The four tables are for remembering:

1. where previously defined variables are stored.

2. where subroutines are located in the source code.

3. where subroutines are located in the interpreter code.

4. the location of routines to perform the operations (+, —, *, /, t) and functions defined for this language.

The tables are searched by a linear search routine which starts with the portion of the table most likely to contain the item. The ASCII byte string in the name list is compared with the desired name. The end of a name or symbol in the table is denoted by a

CODE TO BE INTERPRETED

CONTROL POINTERS

INTERPRETER

STATEMENT EVALUATION

SEMANTIC LOOKUP

i TABLE

C

R

F

I

A

^

V

F

1

T

A

L

u

R N

L

TOKEN

f

f

f

t

POINTER

POINTER

SEMANTIC

•

PLOT

^~—•

DONE

EXPRESSION EVALUATION

SYMBOL VALUE TABLE

TOKEN

POINTER

NYSM

•

X

•

>|

i

1

0

p

0

E S

P s

R T

E T

A A T C 0 K R

R A A C N K D

TOKEN

POINTER

*

» '

SIN

• -^

Figure 1: A map detailing ttie utilization of memory by the Interpreter. Part of the memory consists of four tables that are used to look up values of previously used variables, locations of subroutines in source code, locations of machine language subroutines for the interpreter, and locations of routines for symbols and functions defined by the Interpreter. The two stacks are used in the parsing of equations and when a subroutine is called or returned from. The two largest areas of memory contain the source code and actual machine code for the Interpreter.

154

July l97g©BYTEPublicj|iam Inc

one in the most significant bit, called a terminator. When a terminator is reached in the name list, the pointer in the corresponding address table or value table is incremented to the next item. When a name is found, the pointer in the corresponding list points to the location where the value for the symbols table or the address is located. The desired name or symbol is always added to the list to make sure that the search does not run off the end of the table. After the search, the name pointer can be checked to see if the search went beyond the current length of the list. This technique is faster than putting an end check into the search routine.

The subroutines in the high level source code are not the same as the routines used by the interpreter for performing operations and functions. The first set of subroutines contain source code and the second set contain machine code for operations executed by the interpreter.

Operation

.JSR

.JSR

.POP .MOV

.JSR

Operand

Igvarad

level

wdeval

(wptr), wdeval

Ifinstm

Description

Get variable address. Use current line pointer to fetch variable name. See if name is in name table. If it is, transfer its address to (wptr). If it is not, add name to table. Transfer symbol address from symbol value pointer to workspace at (wptr). Update the line pointer up to the equal sign.

Subroutine EVAL evaluates the right side of the expression and returns the value on the stack.

Put result from EVAL call into workspace.

Transfer the result from EVAL call to the location specified by the contents of (wptr).

Scan the rest of the line of code skipping over the comment field up to the carriage return and update the current line pointer.

Table 2: An outline of the EQN routine. The routine first gets the variable address, then evaluates the right side of the expression and puts the value into the workspace. It then skips over the comment field to the carriage return, updates the line pointer, and decodes the next line of code. This outline flows from top to bottom, with the "operations" and "operands" intended to be used with a macroassembler.

Interpreter Operation

Initialize: The initialize portion of the interpreter has two functions. It loads the source code from a peripheral and it initializes the workspace. As it loads, it also scans the source code looking for subroutine statements. The name of each subroutine is put into the subroutine name table, and the corresponding position in the code is put into the subroutine address lookup table shown in figure 1. The initialize routine is entered from the system monitor, and the initialize routine returns control to the system monitor.

Scan: The scan portion of the interpreter receives control from the monitor and scans the code starting from the current contents of the line pointer. Depending upon which of the 12 instructions of table 1 is encountered, this routine jumps to one of the routines as shown in figure 1 in order to execute one line of code. If an end of file (EOF) character or an error is encountered, the scan routine transfers back to the monitor for text editing, reloading or further execution.

A trace option is included in the scan routine which prints the name and value of all assignment statements as they are executed. This option is included for debugging and tutorial purposes.

Assignments: If the scan routine detects an assignment statement then the interpreter jumps to the EQN routine of figure 2. The EQN routine operation is outlined in table 2 as a list of operations and operands.

The EQN routine uses the routine EVAL

LI mode: In this mode an operand, unary operator, left parenthesis, or function is expected.

If this token type is received

Then perform operation

operand:

stack the operand. If the operator stacked is not a "(", perform the indicated binary operation. Proceed to mode L2.

operator:

must be unary. Stack operator and stay in mode LI. Push a 0 onto the stack if operator is a minus sign.

function:

push variable near operand stack. Push $ onto operator stack to indicate a function. Stay in mode LI.

right parenthesis:

error.

left parenthesis:

push it onto operator stack. Stay in mode LI.

L2 mode: In this mode an operator, right parenthesis, or carriage return is expected.

If this token type is received

Then perform this operation

operator:

push operator onto stack. Go go mode LI.

operand:

error.

left parenthesis:

error.

right parenthesis:

pull operator from stack. If it is a "(" unstack it and return to mode L2. If it is a $ perform the function, then return to unstack operation.

carriage return:

check operator state. Operand stack should have exactly one value. Convert value to floating point. Return to EQN routine.

Table 3: The Bauer-Samelson algorithm to determine the order of operation of an expression. The algorithm starts in the LI mode looking for an operand. The execution of the expression starts in the Innermost parenthesis and works from left to right without any consideration for precedence.

July 1978 © BYTE Publicitions Inc 155

( EVAL j

PUSH ONTO

OPERATOR STACK

-®

GET NEXT

CHARACTER

PUSH'( ONTO

OPERATOR STACK

PUSH '0 ONTO OPERAND STACK

PUSH

ONTO

OPERATOR

STACK

OUTPUT ERROR I

( RETURN j

CONVERT NUMBER TO BINARY FLOATING POINT

GET

NEXT

CHARACTER

PUSH

OPERATOR

ONTO

OPERATOR

STACK

-hS)

PULL NEXT

CHARACTER

OFF

OPERATOR

STACK

PULL NEXT

CHARACTER

FROM

OPERAND

STACK

OUTPUT ERROR 5

OUTPUT ERROR 3

( RETURN )

Explanation of error messages used in this flowchart

Error 1:

An operand, "(", or unary operator ex

pected at this point.

Error 2:

Variable name exceeds six characters.

Error 3:

An operator, ")", or terminator expected

at this point.

Error 4:

A left parenthesis not found to balance

this right parenthesis.

Error 5:

A carriage return was encountered pre

maturely. Check for missing right

parenthesis.

OUTPUT ERROR 2

( RETURN )

CONVERT VARIABLE TO NUMBER ON OPERAND STACK

Figure 2: Flowchart of the modified BauerSamelson algorithm. The table of error messages summarizes all the errors that may be encountered while an expression is being evaluated. For an algorithmic explanation of the flowchart see table 3.

PULL FUNCTION NAME OFF OPERAND STACK

DO FUNCTION

OUTPUT ERROR 4

( RETURN )

( RETURN )

156

)ulv 1978 ©BYTE Publlcitiom Inc

Equation: X = +4.t VAR (CR)

Present

Character

New Operand

New Operator

Mode

Obtained

Stack

Stack

LI

+4.

4

=

L2

t

4

=,t

LI

VAR

4,VAR

=,t

LI

(unstack)

4tVAR

=

L2

CR

4tVAR

Equation: X =

(+4* -VAR +COS(SIN(

-Y))) (CR)

Present

Character

New Operand

New Operator

Mode

Obtained

Stack

Stack

LI

(

=,(

LI

+4

+4

=,(

L2

*

44

= ,(,*

LI

-VAR

4,0,VAR

= ,(,*,

LI

(unstack)

(4*-VAR)

-,(

L2

+

( )

=,(,+

LI

COS(

( ),COS

=,(,+,$

LI

SIN(

( ),COS,SIN

= ,(,+,$,$

LI

-Y

( ),COS,SIN,0,Y

= ,(,+,$,$,

LI

(unstack)

( ),COS,SIN,(-Y)

= ,(,+,$,$

L2

)

( ),COS,SIN(-Y)

=,(,+,$

LI

(unstack)

(no change)

L2

)

( ),COS,(SlN(-Y)

= ,(,+

LI

(unstack)

( )

=,(

L2

)

( )

=

LI

(unstack)

no change

L2

CR

exit

Listing 3: Two examples of parsing done by ttie EVAL routine. The first equation is performed sequentially from left to right since there are no parentheses to change the order of execution. The second expression contains parentheses to modify the order of execution. The first operation performed is the sine of — Y. The cosine of that value is then determined. The value of VA R is then subtracted from that value and added to +4. The symbol t /5 used to designate exponentiation.

to evaluate the right side of the equation, then the value returned on the operand stack is transferred to the location assigned the variable. The FINSTM routine skips over any comment field up to the carriage return.

EVAL: The EVAL routine uses a slightly modified Bauer-Samelson algorithm to determine the order of execution of an expression. [For a thorough discussion of this method see February 1976 BYTE, page 26.J The execution starts in the innermost parentheses and works from left to right without any consideration for precedence. Since many different types of precedence have been used in other languages, confusion is likely. This procedure minimizes the size of the stack and conforms with the conventions of APL and most assemblers. Precedence is established by parentheses which make the ordering unambiguous.

The algorithm is shown in table 3 as an action table with two modes LI and L2. The algorithm starts in the LI mode, expecting an operand, which is a variable or a name. If an operand is found, the algorithm goes to

the L2 mode, expecting an operator. After an operand is found, any operators at the top of the operation stack are executed. A flowchart of the algorithm is shown in figure 2.

Two examples of parsing by EVAL are shown in listing 3. The t symbol is used for exponentiation. In mode LI, the -•- and — are considered unary operators, but if they are encountered in mode L2 they are considered binary operators. This distinction is the rationale for operating in the two modes. The errors described in the table of figure 2 cause the interpreter to terminate execution, print the line of code up to the error, and print an error message indicating the difficulty.

IF: The routine shown in figure 3 first compares the variable with the expression and then the interpreter executes the code up to the corresponding ENDIF statement, but only if the variable meets the conditions specified by the IF statement. This routine uses the EVAL and SEARCH routines.

A flowchart of the SEARCH routine is

( '' )

GET

VARIABLE AND ITS VALUE

SET

INEQUALITY

FLAG

CALL EVAL

EVALUATE EXPRESSION

/equality\y ssatisfied >■

NO

ES

CALL SEARCH

LOOK FOR END, ENDIF, OR IF

1

CALL FINSTM

SKIP THE COMMENT FIELD

/^ GO TO A ^^ SCAN J

Figure 3: The IF routine evaluates the expression and then checks to see if the inequality has been satisfied. If the inequality is not satisfied it will perform the operations between the IF statement and the line containing the ENDIF statement If the inequality is satisfied then the interpreter skips over the instructions and goes to the line of code directly after the ENDIF statement.

luPy 1978IDBYTE Publications Inc 157

shown in figure 4. The SEARCH routine scans the line of code trying to find an ENDIF statement. If another IF statement is encountered the subroutine calls itself to try to first find another ENDIF before it goes back to searching for the first ENDIF. If one ENDIF statement is not found for each IF before an END or ENDDO statement, an error is announced.

An IF and its corresponding ENDIF may not straddle an ENDDO. If this were allowed, the data stored on the stack by the DO loop might not be unstacked as the DO loop is exited.

Search: Each line of code is inspected until an END, ENDIF or IF is encountered. An IF causes the search to initiate another search for an ENDIF, an END causes an error, and an ENDIF causes a return.

Figure 4: The SEA RCH routine inspects eacli line of code until an END, ENDIF or IF command is encountered. An IFstatement causes the search to initiate another search for an ENDIF. Note that this means that the routine will be calling itself recursively, so care must be taken in allocating and preserving local data within SEARCH during recursion. An END statement causes an error and an ENDIF statement causes a return from the SEARCH routine.

( SEARCH )

I IS

I EXPRESSION END, ENDIF,

GET NEXT EXPRESSION

<-^ TE

ST^\.

MO

ENDDO OR IF

! '® EXPRESSION

I

TEST

CALL SEARCH

RECURSIVE SEARCH

[IS I

[EXPRESSION j_ (END OR ENDDO 1. J

TEST

\YES

OUTPUT

-^ ? ^

y

ERROR

1

NO

( RETURN j

Figure 5: The DO routine will perform the operations between the line of code containing the DO statement and the line of code containing the ENDDO statement until the inequality is satisfied. When the inequality is satisfied the interpreter will exit the DO loop and perform the first line of code that follows the ENDDO statement. *

( - )

PUSH LINE POINTER ONTO STACK

CALL FINSTM

JUMP OVER

COMMENT

FIELD

CALL SCAN

EXECUTE INSTRUCTION

PULL OLD LINE POINTER FROM STACK

STORE LINE POINTER IN LINE POINTER REGISTER

CALL FINSTM

JUMP OVER

COMMENT

FIELD

CALL SCAN

EXECUTE INSTRUCTION

GET VARIABLE NAME VALUE

1 UNTIL ^INSTRUCTION_|

1

SET

INEQUALITY

FLAG

CALL EVAL

EVALUATE EQUATION

DETERMINE VALUE OF INEQUALITY

NO

^Tn-^^

/equalit'n.y e s

PULL LINE POINTER OFF STACK

riNCREMENT "] ' LINE POINTER ' 1 TO FIRST 1

SEARCH

FOR

ENDDO

1 LINE AFTER | |_ENDDO J

VES

1"

\^/

LINE

POINTER.

ENDDO+I

NO

1

j^ ^\

10

J

\ "V y^

1

Nc^

JUMP OVER

COMMENT

FIELD

1

OUTPUT

ERROR

MESSAGE

1

V scan" J

( RETURN )

158 luly 1978©8YTE Publications Inc

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START OF

RETURN

ROUTINE

CED

f END j

GET

SUBROUTINE

NAME

FIND

SUBROUTINE LOCATION IN LOOKUP TABLE

GET

VARIABLE

VALUE

/end ^

V ERROR y

JUMP OVER

COMMENT

FIELD

GET

VARIABLE

VALUE

PUSH CURRENT LINE NUMBER ONTO STACK

LINE

POINTER:SUBROUTINE LINE NUMBER

RESET

LINE POINTER

OUTPUT

ERROR

MESSAGE

EXECUTE INSTRUCTIONS

CLEAR SYMBOL TABLE AND STACKS

JUMP OVER

COMMENT

FIELD

SKIP OVER

COMMENT

FIELD

(GO TO \ MONITOR^

PULL OLD LINE POINTER OFF STACK

f GO TO ^ V MONITORy

JUMP OVER

COMMENT

FIELD

EXECUTE

INSTRUCTION

Figure 7: The END statement should be the very last statement at the end of a program or subroutine. If during normal operation an END statement is encountered, there has been an error in execution. This END ERROR routine is used before the interpreter exits to the monitor program.

d

PULL LOOP

ADDRESS OFF STACK

-*r

SCAN NEXT LINE OF CODE

OUTPUT

ERROR

MESSAGE

TURN J

Figure 6: Flowchart for the CALL and RETURN routines. The interpreter allows multiple return statements and allows the subroutine to have a return from within a DO loop. Subroutines may be nested with the only limit being the amount of memory space that is available for use by the stack.

Figure 8: The EXIT routine transfers control back to the monitor program. The line pointer is reset to the beginning of the program, the stacks are reset to their original values, and the symbol table is cleared.

DO: The flowchart of the DO routine is shown in figure 5. The DO loop routine stores the line pointer on the stack. The line pointer will be used later by the ENDDO macroinstruction to determine where to return in the source code. The use of a stack allows nested DO loops. The lack of statement labels excludes the possibility of errors caused by not nesting DO loops within each other (which is possible in a language like FORTRAN).

The UNTIL instruction provides the means of exit from a DO loop. When the variable satisfies the inequality, the program moves to the code past the next ENDDO statement. For a DO loop of fixed length the variable must be initialized prior to the DO statement and incremented within the loop.

Subroutine Call: The CALL routine shown in figure 6 determines the location of the subroutine code in the code list by looking up the location in a table. The table of locations is built for later use during the initialization process before any code is executed. The location of the current position in the code is saved in the stack. Usually the operand stack is used.

The RETURN routine recovers from the subroutine by loading the old line address from the stack into the line pointer. A RETURN from within a DO loop presents a special problem which is resolved by searching for any lone ENDDO statements and pulling the loop address off of the stack.

END and EXIT: The END routine is shown in figure 7. The END routine denotes the end of the program or subroutine. Its main purpose is to prevent the program execution from proceeding into another routine, causing an error.

The EXIT routine shown in figure 8 is responsible for transferring control back to the monitor and mopping up chores such as resetting the line pointer to the beginning, resetting stacks, and clearing the symbol table. It normally would not clear the subroutine table as the code may be rerun later.

Conclusion

The interpreter is especially adapted to interactive programming. The language

160

|ulv 1978©BYTt Publkalions liic

Circle 190 on inquiry card.

presented here is tailored to structured programming techniques which can yield clear, precise code. Our implementation of the interpreter is written in a macrolanguage which may be adapted to any microprocessor by defining each macroinstruction in the assembly language of the microprocessor. A compiler for the same macrolanguage was also written so that a resident machine language version may be made when it is required.

The main features of this interpreter are: the structured language, the methods for evaluating expressions, and the methods for handling lO. Much of the detail in handling data is taken over by the interpreter so that only the fundamental considerations must be considered in writing a program."

BIBLIOGRAPHY

1. Bloom, A IVI, "The ELSE must go to," Datamation, pages 123 to 128, IVlay 1975.

2. Maurer, W D, "Processing Algebraic Expressions," BYTE, pages 26 to 30, February 1976.

3. Kerninghan and Plauger, The Elements of Programming Style, McGraw Hill, New York, 1974.

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July 1978 © BYTE Publications Inc 161

How To Get

Larry Weinstein Objective Design Inc POB 20325 Tallahassee FL 32304

Your Tarbell Going

General Theory

The function of the Tarbell cassette interface (referred to as the "Tarbell") is to enable a computer system to save the contents of memory on audio tape. The purpose of this article is to explain how the Tarbell interface works and to suggest some improvements to its design for readers who have had difficulties with the unit.

The Tarbell is intended for use with inexpensive cassette recorders: the inputs and outputs are matched for the typical Aux In, Ext Spkr and Earphone connections. The computer interface to the Tarbell is on a byte level, with the bytes and commands passed by 10 instructions on the Altair (S-100) bus.

ANALOG SECTION

CASSETTE

Figure 7: Block diagram oftfie Tarbeli cassette interface board.

The Tarbell converts digital information to an audio form that can be written on magnetic tape. In turn, it recovers the digital data from the audio signal. These are the primary functions; the rest have to do with the "housekeeping" involved with the Altair (S-100) interface.

Figure 1 shows a simplified block drawing of the Tarbell.

A cassette recorder has definite frequency limitations. The higher the frequency, the less accurate the signal reproduction will be. On the other hand, speed of operation is critical for the success of a storage medium. The Tarbell makes its compromise at approximately 1500 bps. This is determined by the interface clock.

The rate of data flow to the cassette must be known if the data is to be recovered. At first it might seem that we could use the same clock to move raw data to and from the tape. The problem is that a cumulative error will quickly build up when a long stream of data is read. There are two solutions to this. First, write the data only in small groups (say ten bits) with definite start and stop points in each group. This is called asynchronous recording. Second, write long uninterrupted data streams and include some clock information with the data. This is called synchronous recording.

The Tarbell generates synchronous data streams. Some clock information is added to the data by a technique known as phase encoding. To phase encode, one simply performs an exclusive OR operation with the clock and data (see figure 2). The Tarbell block diagram now takes on the form of figure 3.

162 )ulv 1978 e BYTE Publications Inc

Note that phase encoding does not mean that the decoding circuitry is free from the tasl< of generating a matching clocl<. This will still be a critical part of the operation. We have simply eliminated the possibility o^cumulative timing errors.

Assembly

The Tarbell cassette interface board is plated through but does not use a solder mask or silk screen printing. A 30 page manual is included with all needed parts. The kit does not include sockets for integrated circuits.

Assembly is not difficult. The original design lacked several pull up resistors and small capacitors, which led to noise problems. Subsequent revisions have incorporated these parts without any major board changes. Consequently, some of these parts are in unlikely places. A careful examination of the assembly drawing is required. If you have access to a copying machine, I suggest that you copy the parts list, assembly drawing, and two schematic pages to facilitate construction. Repeatedly flipping back and forth in the manual becomes tiring and one does not feel so bad about checking off items in pencil on a working copy as construction progresses.

There is a 50 k potentiometer on the board that is inappropriate. It is of the thumbwheel variety, and is too big: you cannot insert a board in the Altair bus slot directly in front of a Tarbell. There are also electronic problems with this part, which we will get to presently.

Operation (Digital Sections)

For output, bytes are loaded into a shift register. A timer clocks data out of the register into an exclusive OR gate. The same timing signal goes into the other input of the exclusive OR. The result is that a phase encoded signal is written onto the tape. A status bit informs the computer program that the last bit is being transmitted and the next byte can be loaded.

For input, the decoded clock signal feeds the data into a shift register. For startup, the register is examined for a sync byte. When this pattern is detected, a modulo 8 counter

CLOCK

0

0

0

0

1

DATA

PHASE

ENCODED RESULT

Figure 2: Phase encoding. Tine Tarbell interface uses this technique, which involves performing an exclusive OR operation with the clock and the data.

is enabled. This counter flags the computer program after eight new bits (byte) are loaded into the shift register. The sync byte pattern (hexadecimal E6, or binary 11100110) is hardwired into the interface. A cassette with a sync stream written on it is supplied. An LED on the Tarbell is supposed to light up when the aforementioned sync code is detected. The setup operation consists of adjusting the cassette volume control and the 50 k pot until the LED remains on with a steady light. Here is where the difficulties begin.

CLOCK

SHIFT OUT

ANALOG SECTION

ENCODE

-o

SHIFT IN

BUS INTERFACE

?^

^Z

DATA

-<:]

CASSETTE

BUS INTERFACE

Figure 3: A more detailed block diagram of the Tarbell cassette interface showing the phase encoding and decoding procedures.

luly 1978 © BYTE Publications Inc 163

74L86

CLOCK DATA

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\ IKA

IIKii

@ OUTPUT TO CASSETTE AUX INPUT

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Figure 4: Output section of the Tarbell interface. Tlie circuit contains a simple low pass filter with a cutoff frequency of 1.5 kHz. The filter eliminates the high order harmonics to produce an approximate sine wave, which is then recorded onto the cassette.

The presence of a steady sync light is a good indication, but it does not guarantee the ability to read long files. A single missed clock pulse in the sync stream will almost certainly go unnoticed. However, a single missed clock pulse during the reading of a data file will cause the subsequent bits to be read incorrectly. Also, the sync stream does not have a 010 pattern in it, which turns out to be a prime candidate for dropping a clock pulse.

With some cassette players and Tarbell combinations, the control settings are noncritical. The lack of a good setup indicator isn't important in these cases. On other cassette players the settings are critical; extremely so. Here, the absence of a source of feedback for the setup is sorely missed.

Our early experiences with the Tarbell were problematical. As we began to look

RECOVERED DATA

CASSETTE C6 INPUT .02

*0N SOME MODELS,THIS MAY BE A 2.4K RESISTOR

Figure 5: Input circuitry of the Tarbell cassette interface (internal details of the 8T20 circuit have been included for clarity). The incoming sine wave signal is transformed into a digital signal by the comparator circuit inside the 8T20 (see figure 6).

164 July 1978 e BYTE Publications Inc

more closely at the device, we ran into more questions than answers. For example:

A. Why do different Tarbell units have different levels of reliability?

B. Why do seemingly equivalent tape decks yield different performances?

C. Why will a very cheap cassette machine outperform one costing many times more money?

D. Why do some very good cassette tape brands fail to do well with the Tarbell, while others, even less expensive ones, do a fine job?

E. Why must (as the manual recommends) the tone control be placed at maximum treble? With the highest frequency we wish to have on the tape being 1500 Hz, the results should be better with the tone control on a high bass setting.

F. How were the resistance and capacitance values in the analog sections chosen?

With these questions in mind, we took a closer look at the Tarbell and came up with the following information.

The critical part of any tape storage system is the analog input section. The entire digital data and clock recovery circuit of the Tarbell is constructed from a single IC (the 8T20) and a few passive components.

Figure 4 gives the output section. This is really a simple low pass filter with a cutoff frequency of 1.5 kHz. The filter eliminates the high order harmonics of the output digital signal. The result is a sine wave, or nearly so.

The input section of the Tarbell is shown in figure 5. We have drawn out the internal 8T20 circuitry. Data on the 8T20 in the early Tarbell manuals was absent.

To recover the data, it is first necessary to convert the sine wave recovered from the cassette unit to a digital signal. Assume for the moment that the sine wave is symmetric about 0 V. A comparator with one input grounded (a zero detect circuit) would then produce a digital signal that matches the original one (see figure 6).

Once the input signal passes through C6 (a 0.2 juF capacitor in the Tarbell input section), it loses any DC level. The DC level is then set by the 9 k and 5 k voltage divider resistors inside the 8T20. To convert the signal properly, the positive input of the 8T20 comparator must also be set to this voltage. This is accomplished by the voltage divider formed by Rl and R3. As figure 5 shows, R2 and diode CRT play a part in

this circuit by providing hysteresis: When the output of the comparator is high the divider circuit is electrically equivalent to figure 7a. When the output is low, the circuit is roughly equal to that of figure 7b. The effect of this is to eliminate oscillation about the bias point.

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Figure 7: Equivalent circuits for the voltage divider input circuit (Rl, R3, R2 and Dl) in figure 5, plus the resulting output waveform. Figure 7a shows the equivalent circuit for the case when the comparator is high, and figure 7b shows the equivalent circuit when the comparator is low. Figure 7c is the output waveform. This hysteresis effect is designed to eliminate oscillation of the comparator if a signal "hovers" about the bias point.

July 1978 e BYTE Publications Inc 16S

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ORIGINAL DATA

~L

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ORIGINAL CLOCK

M0N0STA8LE TRIGGER

ENCODED SIGNAL

RECOVERED CLOCK

^ PULSE IS 75% OF CLOCK PERIOD,T^

Figure 8: Recovery of the clock from the encoded signal. The encoded signal Is formed by performing an exclusive OR operation on the data and the clock. To recover the clock, a one shot with a duration of exactly 0. 75 clock cycles fires on every transition of the encoded signal.

RESULT OF ALL Is OR ALL Os

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TRANSITION IN ORIGINAL DATA

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CLOCK RECOVERY OUT OF SYNC

NOW IN SYNC

Figure 9: Automatic synchronization of the one shot (monostable) pulses and the signal transitions (see figure 8). As soon as a I to 0 or a 0 to I transition takes place In the data, the recovery one shot is forced to "fallin line."

Figure JO: Complete timing diagram for signal processing In the Tarbell interface.

HEXADECIMAL 22

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®THIS LOW FREQUENCY WAVE WILL OFTEN BE LOW IN VOLUME AND DISTORTED, RESULTING IN A DROPPED CLOCK AND LOSS OF SYNCHRON IZ ATION

166 lulv 197S ' BYTE Publicalion* In

SYMMETRIC SINE WAVE INPUT TO COMPARATOR

DC "TRIGGER" LEVELS, WITH HYSTERESIS, INPUT TO COMPARATOR SHOWN INCORRECTLY SET FOR SINE WAVE, TRUE DC LEVEL

SINE WAVE DC LEVEL

SYMMETRIC RESULT OF MATCHED DC LEVELS INPUTS TO COMPARATOR

ASYMMETRIC RESULT OF MISMATCHED DC LEVELS,WITH HYSTERESIS

Figure 11: Effect of mismatched comparator input DC levels.

CI 6 reduces any very high frequency noise coming in on the line. C6, besides serving as a coupling capacitor, also forms a filter with the 8T20's internal 5 k resistor. The effect is to reduce the low frequency part of the signal. It is also an effective 60 Hz and "wow" filter.

Once the original digital signal has been recovered, we can proceed to reconstruct the clock signal, and from that, the data. On every transition of the digital signal, a monostable is triggered (see figure 8). The timing of the pulse is critical. It should be 75% of the period of the output clock. (You may have to study figure 8 carefully in order to understand how this recovery process works.)

Next, examine figure 9. It shows the automatic synchronization process of the monostable pulses and the signal transitions. As soon as a 1 to 0 or a 0 to 1 transition occurs in the original data, the recovery monostable is forced to "fall in line." For this reason, some kind of start byte is required ahead of the normal sync byte when using the Tarbell. The entire process is shown in figure 10.

The major problem with this circuit is its sensitivity to waveshape and amplitude. The primary cause of this rests in the way the DC levels are set for the comparator. The 8T20 specifications give the reference voltage available at pin 7 as a nominal 1.4 V, with minimum and maximum values of 0.8

and 2.0 V, respectively. Since the "+" input to the comparator is set by an independent voltage divider, an error of half a volt is possible. Figure 11 shows the effect of mismatched DC levels. As you can see, the more closely these DC levels are matched, the better off you will be.

The timing distortion produced by this effect can be compensated for by the proper setting of the monostable, up to a point. However, the more the timing is off, the more critical the pot setting will be.

The monostable pulse time is determined by C7 and R8, a 50 k pot. The timing is defined by the relation:

Tw=(C)(R)(ln2)

For the given Tarbell output frequency we require a pulse of (.67 ms) (0.75) = 0.5 ms. Therefore, the R/C relation is R= .72/C,with R in kilohms and C in microfarads. For a .033 mF capacitor, R should be 21.85 kf2; for .039 ixV, it should be 18.5 kfi. A large fixed resistor in series with a 5 ki2 trimpot would do a far better job here.

The next factor affecting this timing is in the cassette transport itself. Flutter, a high frequency variation in tape speed, will cause the sine waves to vary in period. Figure 12a shows the effect of flutter.

The shape, symmetry, and amplitude of the wave will also affect this timing. Inexpensive tape machines generally use tone controls that work in tandem with the

|uly 1978 ' BVT[ Publications Inc 167

02a)

(12b)

(12c)

(12d)

(12e)

J"

1

Figure 12: Factors causing timing distortion in Tarbell processed signals. Figure 12a shows tfie effects of flutter, orhigfi frequency variations in tape speed. Figures 12a, 12b and 12c illustrate the effects of shape, symmetry and amplitude, respectively, of the signal waveform on the digitized output. Figure 12 shows how changes in signal amplitude caused by the low pass filter in the input circuit (see C6 in figure 5) can affect pulse width.

HYSTERESIS PRESENT

Figure 13: Effect of the presence of hysteresis: a sudden unexplained dip in DC level.

Figure 14: High amplitude signal with steep sides resulting from a high treble setting on the cassette recorder.

volume control. Each will affect the other. The effects of these factors are shown in figures 12b, c, and d.

The high pass filter created by C6 in the Tarbell causes the amplitude of the input signal to vary according to frequency. The result is shown in figure 12e. This frequency change area is already a sensitive point; the mismatch of amplitudes compounds matters.

We noticed one additional effect in a Tarbell unit, for which we have no explanation as yet. The input appears as in figure 13 whenever the hysteresis circuit is connected. With the hysteresis removed the wave oscillates about a fixed center line.

Bearing all of this in mind, we're ready to try for some answers.

Tarbell units with the more closely matched DC level inputs to their comparators will be less sensitive to all of the factors that can cause problems. A very slight difference, even 200 mV, is significant.

Also, the higher the input signal ampli

168 July 1978 e BYTE Publicitiominc

tude, the less likely any of the waveshape factors are to have any effect.

Why do some Tarbell units work in the higher end of their volume range but not at the very top? This is due to the connection between the volume and tone controls. When the volume is at maximum, especially where the treble control is also at an extreme, the waveshape is severely distorted.

When the tone control is at maximum, the amplitude of the signal is increased and the waveshape is affected. The general outcome is a wave with steep sides about the "zero level" (see figure 14). The amplitude increase and steep sides tend to produce a more accurate digital signal.

A high bass setting reduces the amplitude of the wave with a greater effect on the higher frequency section. With some cassette players, a full bass setting can produce up to a 3 dB per octave loss beginning in the area of a few hundred Hz. It is the overall signal loss that makes a high bass tone setting unacceptable.

Figure 15: Suggested changes to the Tarbell front end circuitry.

CASSETTE INPUT

(OR USE LOGIC PROBE HERE)

o

REMOVING RESISTOR MAY IMPROVE PERFORMANCE

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-REMOVE HYSTERESIS

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Circle 287 on inquiry card.

July 1978©BYTE Publications Inc 169

Listing 1: The author's test tape for the Tarbell cassette interface.

The presence of even mild dropouts on the cassette tape will also cause problems. A 1 ms loss of a few decibels of output level wouldn't be noticed in audio work, but could mean the fatal dropping of a clock pulse when recording digital information. Thus, some cassette tapes that pass audio tests with flying colors may be unacceptable for digital applications. (We have had excellent results with Scotch low noise, high density C-60 tape.)

As for the differences in cassette decks, there are many possible factors: probably the main one is the amplitude of the output signal. However, the amplitude effect is closely tied to the waveshape, and a pure sinewave does not always yield the best results. In other words, high cost and accurate reproduction do not guarantee good performance.

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Corrections

A few simple changes in the Tarbell input section will significantly improve performance. (Refer to figure 15.)

First, remove the hysteresis circuit, either by cutting the trace on the rear of the card that connects R2 to CRT, or by simply removing one of these two components. If you are a diehard believer in hysteresis, replace R2 with a 47 k or larger resistor. Bear in mind that the 8T20 specs give a ±4 mV input threshold.

Next, replace R1 with a 5 k or 10 k pot. This will enable you to set the "-i-" input level to match the signal DC level.

Set up the Tarbell with its cassette player. Place a logic probe on pin 1 or 9 of the 8T20 (or add a resistor and LED as in figure 15). With the cassette player off, adjust the R1 replacement pot near the area where the light switches from on to off.

Set the tone and volume controls to their halfway points. Use the program in listing 1 to generate a test tape. Note that a special test byte (hexadecimal 22, binary 00100010) alternates with sync.

Now play back the tape with the test program running. A signal (light, beep, etc) implies an error. First adjust the 50 k Tarbell pot. You should be able to get a steady sync light with few or no error signals. From there, adjust the volume and tone controls until you can run a long test without a single error signal. As with a well running Tarbell, you should have a large range of acceptable cassette settings.

Our experiences with Tarbells with these few changes have been excellent. They are totally reliable. Further, tapes written on other systems, can generally be read without readjusting the various control settings.

Conclusions

With revision D of the board, the noise prone floating inputs have been tied down (or up). But the input circuit i-j still lacking. The 8T20 internal bias resistors are clearly intended for use with a TTL input, not an analog one. The lack of adjustment on this bias will continue to cause problems, necessitating fixes such as the one given.

On the plus side, the Tarbell is a continually evolving and improving device. The responsiveness of its manufacturer (Don Tarbell) is unsurpassed in the industry.

1 70 )uly 1978 © BYTE Publications Inc

The board is available, has no "exotic" components, and is simple to set up and use. The cassette writing scheme which the Tarbell executes is one of several cassette methodologies now being used in the personal computing field. Several versions of this type of recording method are now available in the hobby market. The 1500 bps

speed is acceptable for work with small to medium length data files. For program loading, it is excellent.

We'll take this opportunity to cast our vote for phase encoding at 800 bits per inch as a cassette standard and recommend it, from whatever manufacturer, for small computer systems."

Manufacturer's Reply

Thanks for the opportunity to reply to Larry Weinstein 's article.

First, to reply to the questions posed: A, B, C, and D are somewhat, related. The main source of reliability problems we have found on the interface is faulty integrated circuits. These are sometimes difficult to isolate, especially when the problem is not occurring all the time. Tape drives vary considerably in their performance characteristics. The main requirements for our interface are a frequency response to 8000 Hz, and an output amplitude of at least 5 V peak to peak. We haven't found any recorders that have these characteristics that haven't worked with the interface. Some expensive recorders, sadly, don't have the above minimum requirements.

As mentioned in question E, the highest frequency the interface works with is apparently 1500 Hz. A certain number of harmonics above this, however, are required to accurately reproduce the phase shifts that this method uses. That's why it's usually better to have the tone set high. To answer question F, the parts values were generally first chosen by a combination of calculation and experience. They were then tuned empirically (ie: diddled on the breadboard) for optimum operation.

I don't think of C6 as a filter capacitor so much as I think of it as a differentiating capacitor. Its main purpose in my mind, in addition to removing the DC component, is to translate the peaks of the Input waveform into zero crossings. In this way, the circuit becomes less dependent on input amplitude. Although the worst case tolerances of the components in the input sec tion theoretically could cause a problem, our experience is that they don't. Out of the

many units that have been returned for repair, none required adjustment or replacement of these components to make them work. On the other hand, it is true that replacement of Rl with a potentiometer could mean the difference between operating or not operating with a marginal recorder. The reason that a pot was not used in the design Is that I felt the fewer pots there were to adjust, the better off the user would be.

We don't put a fixed resistor in series with the 50 k pot because we want to allow the user to adapt to much faster or slower speeds, as his requirement dictates. The reason for the hysteresis is to reduce the effects of noise on the input signal. With a sufficient amount of input amplitude, the percentage of distortion introduced by the hysteresis is minimal. IVIany computers have a fairly high level of noise, and so do many recorders. If you have a very clean system, you may not need the hysteresis, and can remove it as he suggests. This will also allow you to work with lower amplitudes, such as are generated by tape decks without amplifiers.

In spite of the above comments, I feel that Mr Weinstein's article is a valuable one, and is accurate, on the whole. His test program, especially, is excellent. I hope, however, that readers will not try the changes suggested in the article unless they actually are having problems. I would also like to take this opportunity to announce that the 90 day, no fault warranty on this product has now been extended to six months, and to encourage customers to send their boards back for a quick repair.

Donald E Tarbell

Tarbell Electronics

20620 S Leapwood Av, Suite P

Carson CA 90746

luly 1978 (S BYTE Publicitions Inc

171

Now, a book

for the practicing

professional...

"This is the best liandbook of data communications system technology that this reviewer has yet oicoiintered." — Arvid G. Larson in ACM Computing Reviews February 19 78

Digital Press announces the publication of TECHNICAL ASPECTS OF DATA COMMUNICATION by John McNamara.

Written for the practicing professional, TECHNICAL ASPECTS OF DATA COMMUNICATION details the nuts-and-bolts problems and solutions in configuring communications systems. It features: • comparison of protocols (DDCMP, BISYNC, SDLC) • extensive explanation of interface standards (CCm/V.24, RS232C, RS422, RS423) • six comprehensive appendices (how far/how fast?, modem options, codes, UART, format and speed table for asynchronous communication, channel conditioning) • 20 milliampere loop • telephone switching systems • error detection

• 382 pages • 125 figures • 70 pages of tables • index • hardcover

mma

Digital Press Educational Services Digital Equipment Corp. Crosby Drive, Bedford, MA 01730

I would like to order copies of

TECHNICAL ASPECTS OF DATA

COMMUNICATION at $19.95 per copy,

n Check enclosed D Money Order enclosed

(Note: Minimum order for Digital Press to

process purchase order is $35).

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AddressCity

_State_

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Prices apply in U.S. only. B78

172 (uly I9780BYTE Publications Inc

Event Ousus

This month we begin a formal Event Queue, a calendar of coming events which we t^now about as of press time. In order to gain optimum coverage of your organization's meetings, computer conferences, seminars, workshops, etc, notice should reach our office at least three months in advance of the date of the event. Entries should be sent to:

Event Queue BYTE magazine 70 Main St Peterborough NH 03458

Each month we publish the current contents of the queue for the month of the cover date, and the two following calendar months. Thus a given event may appear as many as three times in this section if it Is sent to us far enough in advance.

July 17-19, Data Processing Operations Management, Houston TX. This seminar will offer the senior data processing professional an opportunity to gather the latest management skills. The curriculum is designed toward practical, applied data processing management techniques. Contact Philip M Nowlen, Program Chairman, Director, Center for Continuing Education, University of Chicago, 1307 E 60th St, Chicago IL 60637.

July 17-21, Coding and Information Theory, UCLA, Los Angeles CA. This course will present the fundamentals of representation, storage and transmission of data. Protection against storage and transmission errors using error detection and error correcting (including hamming) codes will be developed. Efficiency enhancement through information compressing codes, predictive run encoding and Markov chains (probabilistic finite state machines) will be discussed. Contact Short Course Program Office, 6266 Boelter Hall, UCLA Extension, Los Angeles CA 90024, (213) 825-3344 or 825-1295.

July 25-26, Workshop on Use of Computers in Teaching Statistics, University of New Hampshire, Durham NH. Workshop participants will be scheduled for hands-on use of the following packages: Minitab II, IDA, SAS, SPSS and BMDP. Contact Dr Jerry Warren, Director, The Office of Academic Computing, 304 McConnell Hall, University of New Hampshire, Durham NH 03824.

July 26, Third Annual Indy Microcomputer Show, Holiday Inn, Indianapolis IN. There will be exhibits, demonstrations and technical seminars addressing the engineering, industrial, scientific, business and personal applications of microcomputersystems. Contact Thurman H Gladden, Naval Avionics Center, D-810, 600 E 21st St, Indianapolis IN 46218,(317)353-3208.

July 31-August 4, Digital Filters, University of Toronto CANADA. This course will provide a practical introduction to the subject of digital filters. Topics will include the frequency approach, Fourier series and integrals, nonrecursive filter design, theory of recursive filter design, discrete Fourier transforms, fast Fourier transform implementation, estimation of power spectra and nonlinear phenomena due to quantizing signals. This course will be of interest to those who use linear combinations of data. The emphasis is on its basic nature and practicability. Contact Nonie Watanabe, Short Courses, 6266 Boelter Hall, UCLA Extension, Los Angeles CA 90024.

August 7-9, Third Jerusalem Conference on Information, Jerusalem ISRAEL. The conference will cover a broad range of topics on computing applications, science and technology. Primary emphasis will be on the role of computers in the transfer of technology between large and small countries. Contact Robert W Rector, Executive Director, AFIPS, 210 Summit Av, Montvale NJ 07645,(201) 391-9810.

August 7-9, Laser Beam Information Systems, Minneapolis MN. This seminar will cover the growing application of laser technology in image and data manipulation in the form of scanning, transmission, reproduction and control. The principles and practice of laser beam information systems will be covered in preparation for direct application to such fields as facsimile, computer memory and display, target identification, reconnaissance, photocomposition and image manipulation. Contact Philip M Nowlen, Program Chairman, Director, Center for Continuing Education, the University of Chicago, 1307 E 60th St, Chicago IL 60637.

August 7-11, Coding and Information Theory, University of Toronto CANADA. See July 17-21, UCLA, for information.

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Circle 250 on inquiry card.

August 21-25, Digital Filters, UCLA. See July 31-August 4, University of Toronto, for information.

August 21-September 2, Courses on Microcomputer Interfacing and Analog Signal Conditioning, Virginia Polytechnic Institute and State University, Blacksburg VA 24060. The objective of these programs is to provide an educational experience for scientists, engineers, teachers, managers or technicians in the areas of microcomputer data acquisition, instrumentation, and measurement systems ranging from the analog sensor through the analog data channels to the microcomputer. The courses provide a combined lecture/ laboratory experience. Continuing education units are provided for each course. Contact Dr Linda Leffel, Center for Continuing Education, Virginia Polytechnic Institute and State University, Blacksburg VA 24061, (303) 951-5241.

August 24-27, PC '78, Philadelphia Civic Center, Philadelphia PA. The first day of PC 78 (August 24) will be an industry trade show which is open to dealers, the industry and exhibitors' guests. For the remaining three days the full Personal Computing Show and Personal Computing College will be running. Over 80 hours of free seminars are planned. Contact John H Dilks III, Rt 1, POB 242 (Warf Rd), Mays Landing NJ 08330.

August 29-31, Data Processing Operations Management, New York NY. See July 17-19, Houston TX, for information.

September 6-8, COMPCON Fall '78, Capitol Hilton Hotel, Washington DC. Sponsored by the IEEE Computer Society, this conference will cover computers and communications, interfaces and interactions. Such topics as microprocessors in communications, multiple computer systems, advances in communications technology and many others will be discussed at this conference. Contact Kenneth H Crandall Jr, COMPCON Fall '78, POB 639, Silver Spring MD 20901.

September 11-15, Coding and Information Theory, Georgia Institute of Technology, Atlanta GA. See July 17-21, UCLA, for information.

September 18-22, Digital Filters, Georgia Institute of Technology, Atlanta GA. See July 31-August 4, University of Toronto, for information.

September 29-October 1, International Microcomputer Exposition, Dallas Convention Center, Dallas TX. This exposition will be directed toward all levels of technology from the professional engineer to the beginning computer hobbyist. In addition to the seminars, a panel of experts will be available to answer questions. Contact Beverly Tanner at (214) 271-9311."

PROGRA9I

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And at an affordable price. The fvlodu-Learn™ home study course from Logical Services, Now you can learn microcomputer programming in ten comprehensible lessons. At home. In your own time. At your own pace.

You learn to solve complex problems by breal<ing them down into easily programmed modules. Prepared by professional design engineers, the Modu-Learn^" course presents systematic software design techniques, structured program design, and practical examples from real 8080A micro-computer applications. All in a modular sequence of 10 lessons . , . more than 500 pages, bound into one practical notebook for easy reference. You get diverse examples, problems, and solutions. With thorough background material on micro-computer architecture, hardware/software tradeoffs, and useful reference tables. All for only $49,95.

For $49.95 you learn design techniques that make software work for you. Modu-Learn™ starts with the basics. Our problem-solution approach enables you to "graduate" as a programmer.

Circle the reader service number below to receive our free descriptive brochure and course outline. Use your Master Charge or VISA card to order today. Call Pat at [408} 245-8855,

Circle 21 5 on inquiry card.

P.O. Box 60968 Sunnyvale, CA 94088 408-245-8855

SERVICES

luly 1978 e BYTE Publications Inc 173

Continued from page 63

X *

M2

M2

Ml

M2

Tl I T2 I T3 1 T4 I Tl I T2 I T3 | Tl | T2 | T3 | T4 | Tl | T2 | T3 | Tl | T2 | T3 | T4 Tl j T2

J ^ r

J—^ r

J—\ r

J ^ r

"1^

"VJ"

"A r

"A_^

"Y^

X SELECT

"A r

1 r

Y SELECT

J V.

J V.

Y *

EXTRA WAIT STATE

Figure 3b: Ml, TlIMl, Tl, one of the seven interprocessor Tstate alignments shown in table 1. Synchronization Is achieved after three clocfi cycles In this example. A complete discussion of the M and T states can be found in the Z-80 technical manual. (Note that, even though the arbiter activates the wait lines at periods during synchronization, this has no effect on the processors because the lines are not sampled until the falling edge of T2.)

Inter-processor State Relationship

Synchronization Pattern M1,T1/M1,T3 M1,T1/M2,T3

Wait States

T States Until Synchronization

M1,T1/M1,T1

V

0

1

3

M1,T1/M1,T2

V

1

0

3

M1,T1/M1,T3

V

0

0

0

M1,T1/M1,T4

V

0

1

6

M1,T1/M2,T1

V

0

2

7

M1,T1/M2,T2

V

1

0

3

M1,T1/M2,T3

V

0

0

0

Table 3: Timing analysis for two Z-80 processors in parallel. The seven possible interprocessor state relationships are shown at left. The center column lists the two possible classes of operation for the parallel processors: the first (Ml,T1 IMl,T3) occurs when both processors are performing an op code fetch at the time of synchronization; the second is the case when one processor Is performing an op code fetch while the other Is performing a memory read or write. The wait states column indicates how many wait states each processor must undergo until synchronization occurs. Note that in two of the cases, the shared memory arbiter (see figure 2a) need not be employed, since the two processors fall into synchronization spontaneously.

suit, enabling IC3b; ie: granting processor Y's request.

System Timing

In order to choose a memory that is subject to overlapping access requests from more than one processor, system timing must be carefully examined. Important considerations in this design include the control logic propagation delay and the "window size" provided by the processors for read or write accesses to the common memory.

In the single processor system, the smallest memory access window of any Z-80 instruction occurs during the op code fetch cycle. The effective length of that cycle is a few nanoseconds less than 1.5 clock cycles (1.5 <I>). However, the dual processor configuration reduces the window size for two reasons: (1) the delay in processor selection (ie; the data gating signal) incurred by the control logic and, (2) the overlap of the memory request signals from opposing processors that is required to permit full speed operation by the processors. Further, the memory cycle time requirement becomes more stringent, accommodating from more than two clock cycles in a 1 processor system to less than one clock cycle in this system.

174

|uly 1978 O BYTE Publications Inc

SHARED MEMORY ADDRESS BUS

MAI5-MA0

NOTE:

MAIS IS NOT CONNECTED

The clock that drives the processors operates at 2.5 MHz, defining a basic cycle time of 400 ns. With this information it is now possible to calculate the operating characteristics required of the shared memory.

As stated earlier, the memory access window depends on the control logic switching delay and the request signals overlap. It has been shown (see figure 3) that the smallest window occurs at times of bus request conflicts, and that this window has a length of one clock cycle. The equation,

then, for actual window length is:

La = *-S"T^-Td

where:

$ = 400 ns (1 clock cycle)

6 = maximum delay in falling edge of

MREQ T = maximum propagation delay of

control logic Tj = maximum propagation delay of

Figure 4: Block diagram of the shared memory. The memory is arranged in a square array of 64 static programmable memory integrated circuits with 4096 bits per circuit.

decoding logic

luly 1978 © BYTE Publicilions Inc 175

Examining the control logic timing shown in table 2, we observe that the maximum timing delays from either MREQ line going active until the arbiter sets the corresponding SELECT line active are as follows:

IC In Signal Path

Maximum

Propagation

Delay (ns)

74S04 74S10 74LS126

Total Arbiter Delay:

5

5

+18

28 ns

Substituting into the equation for L , we obtain:

L = $-5

a

Tc-Td

= 400-20-28-Tj = 352-Tj ns

The switching delay of the decoding logic, T^ (SELECT active until the memory receives the signals), further reduces the memory access window. Referring to figures 2b and 4, the signal path Tj is:

Tj = 7408 + max [74S157 (select), 74S157 (enable)]+ 74S138 = 19 + max [15, 11]+ 12 = 46 ns

Finally, L, =

352-T^ 306 ns

This allows plenty of time for a memory access operation; so much time, in fact, that we do not need the faster and more expensive bipolar programmable memory.

We must also consider the memory cycle timing (L ), reduced by this two processor system to "l> — 6 :

L = $-6 = 400-20 = 380 ns

It is good design practice to calculate delays in the system using the maximum time figures rather than typical ones, and to adjust the results by including a safety margin. Accordingly, we specify the following requirements for the shared static programmable memory:

• Access time 280 ns or less

• Cycle time 350 ns or less

Conclusions and Possible Applications

The principle advantage of two (or more) parallel processors performing complementary tasks is the cost savings. For example, let us say that we operate a packet switching network in which multiple microprocessors perform the relay functions of each node, such as the TELENET of Telenet Communications Corporation. Our responsibilities include insuring data reliability (eg: using cyclic redundance coding (CRC), checksum, etc), doing format checks, and recognizing the destination of the traffic and routing it to another node in the network. Further, this service must be provided at high speed.

Clearly, for one processor to perform these and other nodal functions without some delay, high performance and high cost systems would be required. Conversely, multiple microprocessors could perform all of these tasks in parallel at a significant reduction in cost.

For the experimenter, a multiprocessor system doesn't appear to offer much beyond an interesting diversion in design engineering. As mentioned earlier, the benefit from this type of design is increased throughput (by virtue of the reduced per unit cost). This is an idea that has little significance for persons with a dedicated system.

One possible application does come to mind, however. Many 8080 system owners are upgrading to the Z-80 for the expanded instruction set, but for some, direct replacement of a processor board is not possible. Why not consider adding a Z-80 with your current system acting as a front end? Admittedly, it seems like a bit of overkill, but it is an inexpensive way ($8 for the interface circuitry of this design) to upgrade. Of course, after installing another processor, the owner must write an operating system to accommodate the addition; but that's part of the continuing challenge to be found in the world of microprocessors."

REFERENCES

Z80-CPU Technical Manual, Zilog, 170 State St, Los Altos CA 94022, 1976.

176 )uly 1978 © BYTE Publications Inc

85/P =8085 + PASCAL

The new 85/P programmer's workbench from Northwest Microcomputer Systems Inc combines the throughput of the 3 MHz Intel 8085A and the power of PASCAL.

Designed for the serious applications programmer, the system features include; 8085A processor, a PASCAL compiler and interpreter, CP/M supporting BASIC,

COBOL and FORTRAN, direct memory access, two Shugart floppy disk drives with 1 M bytes of online storage, 54 K bytes of 450 ns user available static programmable memory, a Hall effect keyboard with 103 keys, two serial ports (RS232C), two parallel ports (16 bits), and a 24 by 80 character 12 inch (30.5 cm) video display, all enclosed in a single cabinet.

The system provides the full PASCAL environment including a 725 line per minute compiler and interpreter, random and sequential files, a screen oriented editor, interactive source linked debugger, plus full documentation and a 90 day warranty. Pricing for the complete system is $7495. A variety of other packages are available, including a screen oriented accounting package and a word processor, from Northwest Microcomputer Systems Inc, 121 E 11th, Eugene OR 97401."

Circle 602 on inquiry card.

New 2708 Erasable Read Only Memory Programmer

New 6800 Industrial BASIC

?>„ ■■;,.., ill,

i?-; 11 .11 tlJK

OIHPMT ni-

■

)if ^w

/f'

^?■ '

'' ^

^w . ,

Wintek 4 K BASIC is a 6800 BASIC interpreter optimized for industrial applications. Features of the package include control of interrupts, direct memory read and write, assembly language subroutine capability and flexible lO. The package is oriented toward process control and monitoring. 4 K BASIC retains all the advantages of an interactive high level language, including rapid coding and debugging, easy maintenance, and advanced control structures.

The interpreter may reside in programmable memory or in programmable

read only memory for instant power on operation. If the BASIC program is also stored in programmable read only memory, the interpreter will immediately enter the RUN mode, allowing unattended operation in dedicated applications.

4 K BASIC is available on cassette at $95 or in programmable read only memory on a Wince read only memory module for $299. The source listing is available for $95. For further information contact Wintek Corp, 902 N Ninth St, Lafayette IN 47904.■

Circle 603 on inquiry card.

A new 2708 erasable read only memory programmer has been announced by Smoke Signal Broadcasting, POB 2017, Hollywood CA 90028. Designated the POP-1, the unit lists for $149 and is designed to interface to the company's P-38-1 and P-38-FF erasable read only memory boards, which are SwTPC SS-50 bus compatible products. Complete software is provided on audio cassette. An adaptive programming technique is used that allows most 2708s to be programmed in 15 seconds. A separate selfcontained power supply is used for the programming voltage insuring sufficient current capability to program erasable read only memory from any manufacturer."

Circle 601 on inquiry card.

Text Processing System for Microcomputers

The Diaspar Text System is said to be a package of four programs which form a commercial text processing system. Text files are stored on diskettes using a named file structure with passwords. According to the vendor, hardware needed for this product is an 8080 based microcomputer with 32 K of main memory, a screen terminal, floppy disk and a printing terminal. Software required is the CP/M operating system and CBASIC runtime package. The system comes on standard diskettes with a user's manual for $195 from Diaspar Data Systems, POB 888, San Juan Capistrano CA 92675."

Circle 604 on inquiry card.

July 1978 © BYTE PubNcations Inc 177

Whafs New?

Miniature Switching Power Supplies

of INTEREST to DESIGNERS

Keeping Connected

Tlie new 2505 MODCON series is available in double row configurations of

10, 20, 40, 60, 80 and 100. These modular high density receptacle connectors are designed for board to board interconnect applications. The connectors are easy to mount using box form contacts that mate with conventional 0.025 by 0.025 wiring posts on 100 inch center to center spacing. The series operates in temperatures between —55 to -H50° C. Operating voltage is 800 V DC at sea level; insulation resistance is 5000 M n minimum at 500 VDC; current rating is maximum 3 A; and contact resistance is 10 mO at 3 A. Contact Stanford Applied Engineering,340 Martin Av, Santa Clara CA 95050."

Circle 629 on inquiry card.

New Probe Extends AQ6800 Microprocessor Analyzer to 6802 Use

This buffered probe extends the capabilities of the AQ6800 Microproc

essor Analyzer to 6802 microprocessors. With the PRB68/02 probe, the AQ6800 displays all address, data and status information of any 6802 microcomputer system, and provides direct user interaction with all memory locations, 10 ports, and internal microprocessor registers. The probe clips directly to the 6802 microprocessor chip in the system being tested. Interactive features include the ability to examine or modify the contents of all 6800 or 6802 internal registers, plus the program counter, manual or breakpoint program halt, single step operation, execution of single byte instructions independent of normal program flow and many other control capabilities. The probe is priced at $295 and the AQ6800/02 system, complete with probe, is $1950. Contact AQ Systems Inc, 1736 Front St, Yorktown Heights NY 10598."

Circle 630 on inquiry card.

200 and 400 W Open Frame Switching Regulated Power Supplies

The OL-200 is a four output unit which supplies 200 W of continuous power, -^5 V at 25 A (maximum) from one output, -5 V at 4 A, and ±12 V at 4 A each. The OL-400 is a five output unit that is capable of supplying a continuous 400 W, ±5 V at 45 A from one output, ±12 V at 10 A each from two outputs, and -5 V and +24 V at 4 A each from the remaining two outputs. Each unit is capable under transient conditions of handling three times

the rated current. Both units can be adapted to provide voltages specified within ±70 V and up to 4 A per output for the OL-200 and 10 A per output for the OL-400. Input voltages are also user selectable. Both units will operate from either 115 VAC or 230 VAC and are equipped with brownout protection that allows them to operate without performance degradation at line voltages as low as 95 VAC (115 V option) or 190 VAC (230 V option). Both power supplies can provide 16 ms of continuous power after full loss of input. Standard features include an input EMI filter, a series thermistor that reduces input line surges at turn on, reverse voltage protection, and protection against system shorts. The OL-200 is priced at $248 and the OL-400 at $395 in quantities of 100. Contact Boschert Associates, 384 Santa Trinita, Sunnyvale CA 94086."

Circle 631 on inquiry card.

Three 12 V, 15 V and 24 V units, with efficiencies from 75 to 85 percent, have been added to Gould's MMG line of 5 V, 25 W switching power supplies. The new units operate from 110 and 120 V or 220 and 240 V ±10%, 50 or 60 Hz, and currents from 1.4 to 2.5 A. Optical coupling is used to provide 4 kV rms insulation (5.7 kV peak) between input and output. Units can be used in series or parallel operation without special interconnections.

Remote sensing is available from terminals on the printed circuit board adjacent to the output connections for control of voltage at the load instead of at the power supply. Standard features include overcurrent and overvoltage protection. Gould MMG switching power supplies carry a 5 year warranty.

The units cost $135 in quantities of one to nine. Contact Gould's Electronic Components Division, 4601 N Arden Dr, El Monte CA 91731."

Circle 632 on inquiry card.

It's Late in the Learning Curve for 8080s

National Semiconductor Corporation has announced across the board price reductions for its version of 8080A microprocessors. The price of National's plastic package INS8080AN is now listed at $9.98 in quantities of 1 to 24, reduced from a previous listing of $15.50 each. In quantities above 100, the device has been marked down by one third, from $10.80 to $7.10, as quoted in National's latest OEM price list. Contact National Semiconductor Corp, 2900 Semiconductor Dr, Santa Clara CA 95051 .■

Circle 633 on mquprv card.

178

luly 1978©BYTE Publicalions Inc

5 PLETE SATISFACTION IS OUR GUARANTEE YOUR COMPLETE SATISFACTION IS OUR GUARANTEE YOUR COMPLETE SATISFACTION

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'^C/f

74L$00 TTL

74L$00

74L$02

74LS04

74LS08

74L$10

74LJI4

74LS20

74L$21

74L$22

74L$30

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74Lt38

74L$42

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74H73

74L$74

74L$75

74L»76

74L$86

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74L$92

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74LS114

74LJ125

74LS126

74LS132

74L$138

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74L$153 .66

74L$154 1.00

74LJ157

74LS160

74LS161

74L$162

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74LS174

74L$175

74LS190

74L$191

74LS192

74LJ196

74L$197

74L$221 1.06

74LJ257

74L$258

74L$266

74LJ283

74L$365

74L$366

74L$367

74L$368

74L$386

81LS95

51L$96

eiL$97

81LS98

.65

.82 82

.98

.80

55

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16.95 16.95

6.95 13.95 10.95

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9.95

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6.95 6.85

(Continued)

8080 Machine Languages

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SSM 8080 MONITOR VI ON 2-2708 47.00

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Beginning BASIC

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Glossary and Guide Basic BASIC Introduction to BASIC Home Computers; 210 Questions

and Answers

Volume 2: Software Microcomputer Dictionary

and Guide Microprocessor Basics Home Computers: 210 Questions

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Volume 1; Hardware Understanding Integrated

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of Digital Logic Circuits

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74XX

SUPPORT DEVICES

6820 6850 8212 8214 8216 8224 8228 8226 8238

8.00 8.00 3.45 MEMORY

8.00 1702A 3.75

3.75 2708 11.50

3.50 2716TI 22.50

6.25 21L02 450ns 1.25 3.85 21L02 250ns 1.60 7.95 2114 8.50

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24.95 34.95 16.50

''rNew)25Pin—DSub miniature Solder Tail Male 3.00 Female 3.50

100 PIN EDGE CONNECTOR. Imsai spacing 3.50 (New)

7400 7401 7402 7403 7404 7405 7406 7407 7408 7409 7410 7411

7420 7423 7425 7426 7427 7430 743Z 743 7 743S 7439 7440

7482

7483

7485

7486

7489

7490

7491

7492

7493

7494

7495

7496

74107

741L)9

74121

74132 74141 74145 74150 74151 74153 74154 74157 74161 74163 74164 74165 74170 74173 74174 74175 74176 74177 74180 74181 74190 74191 74192 74193 74195 74221 74251 74365 74366 74367 74368

Charge My D M.C, D BAC (VISA)

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Address

City

Satisfaction 100% Guaranteed

California Residents Add 6%

Sales Tax

Note: Minimum Order $10.00, 5% Discount over $100.00 on I.C'^ only.

_State_

-Zip

K^

NEW 1978

IC MASTER

Over 40.000 IC's listed. Over 2,000 pages.

Retail Value

$55.00

Updated every 90 days.

Your Price

$39.99

Check catalogue for more listings on linears, voltage regulators, resistor books, IC sockets and more.

IS OUR GUARANTEE YOUR COMPLETE SATISFACTION IS OUR GUARANTEE YOUR COMPLETE SATISFACTION IS OUR GUARANTEE

Circle 170 on inquiry card.

BYTE )uly 1978 179

Circle 25 on inquiry card.

ATW<

• I#ll

ENTERPRISES

KITS

Available assembled and tested $89.95.

$ 79.95 4K RAM

$ 1 29*95 4K PROlvl Bipolar 512x8 Proms 93448/6341.

$149*95 8K EPROlvl Needs onlv4K space 27I6.

$ 59*95 DIGITAL I/O 8 parallel ports plus le interrupts.

$ 99*95 ANALOG IN 32inputs, 8 bits, 100 microseconds

$ 49*95 PROM PROGRAMMING

$129*95 SERIAL I/O

I DID YOU I KNOW . . .

-| BIG SALE

I 1 each board:

Digital I/O

Eprom programming

8K Eprom Board (without 2716's)

1 I

-| REGULAR PRICE

7 serial ports, fully software controlled To 500 baud.

J $139.85

Burns4 | JUNE ONLY

Can copy to 3. I .

-I $100.00

I Extra zero insertion force sockets $5.00

MOTHER BOARD

8 SLOT 44 PIN BUS

50 Pin Edge Connector

Mother Board $20.00 ea Connectors 2.50 ea

Card guides for above $10.00 per set.

MAKE CHECK OR MONEY ORDER PAYABLE TO:

Kathryn Atwood Enterprises

P.O. Box 5203. Orange, CA 92667

Discounts available at OEM quantities. For orders less than $25 total, add $1.25 for shipping. California residents add 6% sales tax. Estimated shipping time 2 days ARO with money order. For checks allow 7 days for check to clear.

Beckian Enterprises All Prime Quality — New Parts Only — Satisfaction Guaranteed

EPGE CARP COmiaC^: GOLV PLATEV.

BODY: Non brittle, solvent resistant, high temperature G. E. Velox. The finest electrical properties available. CONTACTS: Bifurcated Phosphor Bronze, Gold over Nickel

ALTAin TYPE

Contact Ctrs. .125: Row Spacing, Dip Solder $4.00 ea.

.140

50/100 Dip Solder $4.00 ea. 5 pes,

IMSAI TVPE: Contact Ctrs. .125: Row Spacing, .260

50/100 50/100

Dip Solder Wire Wrap II TurnI (3 Turn)

$4.25 ea. $4.25 ea.

5 pes. 5 pes.

IMSAI Card Guides " .25 per pair to IMSAI Prices

Note Also good for CROMEMCO,

OTHER COmECTORS AVAILABLE .100" Contact Ctti: .140" Row Spacing.

15/30 Solder Eyelet

22/44 Dip Solder

22/44 Wire Wrap (3 Turn)

40/80 Wire Wrap 13 Turn)

$2.30 ea. $2.75 ea. $2.50 ea. $4.00 ea.

5 pes. 5 pes. 5 pes. 5 pes.

$3.80 ea.

$4.00 ea. $4.00 ea.

$2.10 ea.

$2.40 ea.

$2.20 ea.

$3.70 ea.

Note: llJAe Wiap S^xiclnQ -16 .200" (Row Spac-cng) .15b" Contact CVii: .140" Row SjxiCAjig.

18/36 Dip Solder

22/44 Dip Solder

15/30 Wire Wrap (3 Turn)

$2.25 ea. $2.50 ea. $2.00 ea.

5 pes. 5 pes. 5 pes.

156" Contact Ctu: .200" Row S]XLclng.

22/44 36/72 15/30 18/36 36/72 43/86

Wire Wrap 13 Turns)

Wire Wrap (3 Turns)

Dip Solder

Dip Solder

Dip Solder

Dip Solder (6800)

$2.80 ea. $4.00 ea. Sl.eOea. $1.95ea. $4,00 ea. $4.90 ea.

5 pes. 5 pes. 5 pes. 5 pes. 5 pes. 5 pes.

$2.00 ea $2.25 ea. $1.80 ea.

$2.50 ea. $3.80 ea, $1,65 ea. $1,70 ea. $3,65 ea, $4.75 ea.

WE ARE yOUR CONNECTOR SPECIALISTS.

IF VOU VO NOT SEE THE CONNECTOR HERE THAT

VOU WEEP, PLEASE WRITE US. IW MOST CTRCLlUSTANCES,

WE CAN SUPPLV IT TO VOU.

25 PIN VB TVPE SUBUINTATURE CONNECTORS.

CANNON: Gold Plated. The Best You Can Buv.

DB25P Male Plug DB25S Female Socitet DB 51212-1 Hood. (Grey) DB 51226-lA Hood. (Blaclr) D 20418-2 Hardware Set

SAVE: BUV A COMPLETE SET.

Complete Set includes: 1 pe. DB25P: 1 pe. DB25S:

1 PC. Hood of your choice Grey or Btaelt,

1 Set $6.50 ea. 5 Sets $6.25 ea.

Note: For D 20418-2 Hardware Set. add $0.75 ea.

$2.60 ea.

5 pes.

$2.25 ss

$3.70 ea.

5 PCS.

$3.45 ea

$1.00ea.

5 PCS.

$0.95 ea

$1 lOea.

6 pes.

$1.00 ea

$0.80 ea.

5 pes.

$0.75 ea

27OS - PRIME

(450 nS) $14.00 ea.

BOSOA - PRIME

$9.40 ea.

I.e. SOCKETS: VIP SOLVER

Low Profile. 14 pin.a 16 pin. $0.16 ea.

HEAT SHRINK TUBING

I/8"shrinl<sto 1/16" I.D. $0.35 per ft.

CABLE TIES

314" and S'/i" $0.03 ea.

WRITE FOR LARGER QUANTITY VISCOUNTS DEALERS WELCUM

MINIMUM ORPER: $10.00: Add $1.00 (,on i/vcppXng. Ondcru omck $25.00, lue paij thz ilUpp-ing. Catli. Ru-identi add 6% Tax. NO CO.P. SHIPMENTS.

OldeA Tfiom:

Beckian Enterprises P.O. Box 3089 Simi, Calif. 93063

180 BYTE July 1978

Circle 30 on inquiry card.

FOR AL

211-02 (450ns) Static Rams 100 SI $1.10 ea.

Z-KU

Microprocessor 5 @ $20.00 ea.

CUSTOMERS EXCEPT CALIF. CALL TOLL FREE 800-421 5809

1702A E—PROM 8 S> $3.75

8224-4

Clk.Gen.&Dvr. 25 @ $8.75ea.

6502

Microprocessor 5 @ $11.00 ea.

410D (200ns) Static Ram 100 @ $8.75ea.

MICROCOMPUTER COMPONENTS

MICROPROCESSOR-S "'^^^ "^HER COMPONENTS

F8 Z8 0

zaoA

CDP1802CD

26S0

AM2901

6S02

6B0O

SB02

8008-1

8035

80B0A

8085

TMS9900TL

16.95 12.00 28.00 19.95 24.95 22.95 11.95 18.95 25.00 9.9 5 22.00 11.95 27.00 75.00

8080A SUPPORT DEVICES

8212 3.50

8214 9.00

8216 3.75

8224 3.50

8224-4 9.95

8236 3.95

8228 7.95

823B 7.50

B251 9.95

8253 21.95

8255 21.95

825 7 21.95

8259 21.95

B275 75.00

8279 20.00

FLOPPY DISC CONTROLLER

17718 55.95

1 7 7 1 a-0 1 5 7 .9 5

KEYBOARD CHIPS

AYS-2376 13.75

AV5—3600 13.75

PROM'S

1702A

2704

2708

2716

2716 intl

2758

O3601

D3604

5203 AQ

5204 AQ 6834 6834-t 82S2 3B 82S129B B223B

6800 SUPPORT

6810P

6BB10P

6B20P

6821 P

6828P

6834 P

6850P

6852P

e860P

6B62P

6871 P

6875P

6880P

4.00

15.00

12.00

30.00

38.00

26.60

4.50

13.00

5.00

7.50

17.50

14.95

4.00

4.2 5

3,50

4.95 6.00 7.50 J.50 11.25 16.95 9.75

1 1.75 10.00 14.50

2 8.00 8.75 2.50

Z80 SUPPORT DEVICES

3881 12-95

STATIC RAMS 21L02 1.51

21L02 I

21 Lj02 j

410D

1101 A

2101-1

2102

2111-1

21 12-1

2114-3

2125L

2147

) 1.7S 1.60

10.75 lO.OO

1.00 .90

2.95 2.75

1.25 I.IS

3.95 3.50

2,95 2.80

1.18 1.25 1.50 9.25 .80 2.60 1,00 3.2 5 2.69 9.25

31 L

3 106

3107

TMS-4 04 4

4200 A

TMS-4045

5101

74C89

7489

74S201

PBlOl

P8155

P8156

8599

9102BPC

2.35 3.70 3.70 9.00

37.50 2.50 3.9 5 3.95 9.95

12.95

11.00 10.00 8.30 7.40 3,25 3.05 2.25 2.10 4.50 4.00 4.20 3.40

17.00 14.00

21.00 18.00 1.8B 1.7 5 1.6 5 1.4 5

2.00 3.25 3.25 8.95

9.25 7.25 2,85 1.90 3.75 2.B0

CHARACTER GENERATORS

2513 6.75 2513 5v upper 9.75 2513 5v lower 10.95

2516 10.95

MCM6571 10.95

MCM6571 A 10.95

MCM6574 13.25

MCM6575 13.25

WAVEFORM GENERATOR

8038 3.50

MC4 0 24 2.2 5

566 1.50

DYNAMIC RAMS

4160/4116 32.00

1103 1.00

2104 4.00

2107B 4.25

210 7 8-4 3.9 5

TMS4050 4.00

TMS4060 4.50

TMS4070-2 32.00

4096 4.00

4116/4I6D 32.00

MM52 7 0 4.50

MCM6605 S.OO

USRT

S2350 10.75

UART'S

AYS 101 3 A AV5-10I4 A TR1602B TMS6 01 I IM6402 < M6 4 0 3

5.25 8.25 5.25 S.9S 10.80 lO.BO

JADE 8080A KIT

$100.00 KIT

BAHE BOARD $30.00

N8T20 N8T26 NgT9 5 N8T96 NBT9 7 N8T9 8 8 1 LS9 5 81 LS9 7 1488 1489 D3205 D3207A D3208A 03 211 63 2 22 B324 2 03 245 C3404 P3408 A P4201 A MM5320 MMS369 TMS5501 OM81 30 OMB131 OMSB3 3 OM8e35 DM8B3 7 MKS0240 MK50250

3.39 2.10 1.35 1.35 1.35 1.35 2.00 2.00 1.75 1.75 4.00 4.55 14.20 10.00 9.75 10.15 5.60

6.75

.2.00

5.20

7.50

1.9 0

24.9 5

2.9 0

2.75

2.50

2.50

1.7S

20.0 0

15.00

2708 (4 50 ns)

E—PROM

8 @ $11.00 ea.

4096

Dynamic Ram 100 @ $3.50 ea.

E-PROM BOARDS

MM 16 I16N uiri 1/

flAWN'ROM IIGK ,1 E I'HOMI

S9*»l)0 S99'jO

S99 0n

SI woo

TJ-l

Convert T,V. sel to

Video Monitor.

KIT S8.95

STATIC RAM BOARDS

8K

$189,95 $149 75 $169 95 $125 00 2500

2S0ns ASSEMBLED & TESTED

450ni ASSEMBLED 8. TESTED

250ns KIT

450oi KIT

BARE BOARD

6800 ADAPTER lo S100 Syttem

KIT S12.95

16K

2S0ni ASSEMBLED & TESTED $435.00

4S0ns ASSEMBLED 8. TESTED $380 00

450m KIT $335,00

32 K

2&0n<i ASSEMBLED S. TESTED $850.00

450nj ASSEMBLED & TESTED $775.00

450ni KIT $675,00

DYNAMIC RAM BOARDS

On ba«ril R*ti«(h pow»r u provided «iib "u *»>t iiim oi cycle itailing iH)uir«l ■ 8VDC 400MA DC -tSVOC 400MA DC jnd

I8VOC SOMA DC

EXPANDABLE

8K (375nj| KIT

16K (375ns) KIT

24K I375nil KIT

32K (375nO KIT

EXPANDABLE 16K (375ni) KIT 32K (375nil KIT 48K I375nil KIT &4K (375nil KIT

$151-00 $259 00 $367.00 $425-00

$281 00 $519.00 $757.00 $995.00

MOTHER BOARD'S - S 100 Style 13 slot - w/front panel ilot BARE BOARD $35.00

KIT $96.00

22 slot

$149.95

ASSEMBLED 8i TESTED

THE PROM SETTER

WRITE S, READ

EPROM

1702A - 2708 - 2716

5204 - 6834

- Plugi n.<tflly o'lO vUu' ALTAIR iWSAI Com^iiK ' lociuiKs Ma<n Modiiip Bovrt af^a t'lri CPRO'

Soch'i Un.i ■ The EPHOM Soclir' U...I is coii.in lurt ii) "»■ C.m'

pure, through ., 26 O'" connecio^ ' Prograrnmtf>g fs ac<:Ofrtpii\t\ed bv '*^*' Ci*"iijv*i»*f

KIT S210.00

ASSEMBLED $376 00

KIM-1

ASSEMBLED & TESTED $245.00

MEMORY PLUS for KIM-1 8K RAM I21L02) 8K EPROM

ASSEMBLED & TESTED $245.00

211J02 (250ns) Static Rams 100 @ $1.36 ea.

4200A (200ns)

Static Rams

25 S> $10.00 ea.

Z—80A

Microprocessor 5 @ $2 5.00 ea.

74LS36 7 Hex Buffer 100 @> .70?

jadeZ80„,,

-Mth PROVISIONS tor ^\ \

ONBOARD 770B md POWER ON JUMP

$135.00 EA.™« $149.95 EA. —

BARE BOARD $35.00

Z80 "UPGRADE" KIT

Chjnge your JADE 3MHi Z80 lo a 4MHi uersn wiih lhi5 simple kii

only $17.95 with trade $49.95 purchase.

To trade, you must give ui youf 2MHi 280 chi|

and B234 clock dt.ve<

The UPGRADE KIT'' mcludei

ZSOAchip. 1.8K tesiiior

8224 4 clock dii«er 20 p(. capadtoi

36IV!Hf crystal

COMPU.TIME

SlOO BUS COMPATIBLE ^ ' lUU

TIME & CALENDAR

MJcroprocejjors need the power that a leal time cinck can oHet Oaie and time becomes msiantlv available COMPU/TIME does not have lo be mniaiijed eue'v '"^^ the system IS powered up It possesses a crysial connolied time base to obtam superior accurKy and has two seiable coincideriee counters. Time, date, and counterj are set via software.

COMPUTATIONAL FUNCTION Microprocessors need to be comp'imenied by hafdwaie arithmetics to free up memory pages dedicated to float ing point routines and mathmaiical software COUPU/ TIME provides a 40 function calculator anay so f'lai algebraic, Inqonometnc, basic aithmetic proMems can be solved wiihotit the need of ripveloping saplnsiicated software. a.

COIiAPUTIME CTl(

COMPU <inl, C101

TIME only T101

COIUIPU'TIME PC e

iuy It Your Way

$199 KIT $245

$149 KIT $189

$165 KIT $205

d o„[y $80

JADE VIDEO INTERFACE KIT

FEATURES $99.95

S 100 Bus Compatible

32 or 64 Characters per line

16 lines

Graphics (128 x 48 matrix)

Parallel & Compositive video

On board low-power memory

Powerful software included for cursor, home, EOL, Scroll Graphics/ Character, etc.

Upper case lower case & Greek Black on-white & white on-black

full ASCII PROFESSIONAL KEYBOARDS

full 13b Chardcle- ASCH' Ir.-Mode MOi Entodmg'

M03 DIi TTL Compatabic Om'p-.'

T*o-ke/ Rollover'

level and ^^.i^e ^irob«< MODEL

Sh,(T and Alpha Lock' 755

Selec'able Panty

Negai

Logu

156 keys)

PRICING INFORMATION Model 756 (•siembledl i75 9J Model 756K (kii) 64 95

Model 703 Er>closure 29 95

Model 710 Numeric Pad 9 95 Model 7S6MF Mig Fr«n^e 8 95

8212

8 Bit I/O Port

?5 @ $3.00 ea.

74LS368 Hex Inverter 100 @ .70^ ea.

4116 (200ns) 16 K Dyn. Ram 16 @ $24.00 ea

2513 (5v) Character Gen. 5 @ $9.00 ea.

REAL TIME CLOCK FOR S-IU BUS

1 MHZCrvitai Otcillator

Two indepenbeni interrupts

One interrupt uiM 16 b<t counter in

10USEC steps

Other interrupt is <n decade stept trom

100USEC to 10 sec.

Both software programmable

Board can be selected bv 128 device

code pairs

Complete documentation includes sott

vwre to dispiav nme of dav

Double sided solder mask

Silk screen parts layout

JG-HT ASSEMBLED & TESTED S179.

JG- RT KIT $124,95

SARE BOARD miih Man.isl S30.00

TARBELL CASSETTE INTERFACE

• Plugs diieclly into you. IMSAl or ALTAIR"

• FaiiesrtTanslerraie 187 (standard) to 540bytes/second

• Extremely Reliable —Phase encoded (self clocking)

• 4 Extra Stalus Lines. 4 Extra Control Lines

• 37 page manual included

• Device Code Selectable by DlP-switch

• Capable o( Generaling Kansas City tapes also

" No modilication required on audio cassette recorder

JADE KIT* S99.95 ASSEMBLED $175.00

•16 monlh warranlv trom JADEI MANUAL S4 00

JADE PARALLEL/SERIAL INTERFACE KIT sioo S124.95 KIT

2 Serial Interfaces with RS232

interfaces or 1 Kansas City cassette

interface.

Sena! interfaces are crystal controlled.

Selectable baud rates.

Cassette works up to 1200 baud.

1 parallel port.

DATA COMMUNICATIONS ADAPTER

* Comgletelv compatible SOL" Of other SlOOr Trademarkiot 'MITS,

• Oesigoect for um on tlie

ilTh your IMSAl. ALTAIR* icrocomputari 'ProceiiOr T«chnotogv lial IBlaphona ar TWX :ated Irnei, m>Bti ill ed wiihaCBTcouplar.

FCC regulations when i • All digita' rnodulation and damodulation with on board cyrxal dock and procition dlttr rnean thai NO ADJUSTMENTS ARE REQUIRED

• Ball 103 iianda'd fraguartciai

• Automated dial (pulsed) and •ntwar

• Originata and answer mode

• 1 to O' 300 BPS ipee<l lelKt

■ Complaia te" lasi capability

■ Character langtfi, stop bit, and parity

• 90 day warranty and full documentation

PRICES: BABE BOARD ; Ass^mblpil (48 h JG OCA KIT

S49.95 $279.95 $159.95

NUMBER CRUNCHER

The CT200 is a number onenied microprocessor intended lor use in those applications that repuire fast versatile mathematical solutions.

THIS IS NOT A CALCULATOR CHIP, THERE ARE.NO KEY DELAYS

The CT300 tias a unique architecture that is designed lo be a TASK piocessmg system within a system. This unique architeclute will allow the CT200 to work and run with ANY SIOO BUS microp-ocessor system It .s completely cnmpalible with Z80, 4MHZ version also. 8080. 6800, 650? microprocessor A micro incoded instruction set allows programming in a calculatoi like language. The instruction set includes a full set of test and branch instruclions. AM decoding of SIOO bus signals (for select oi control funclionsl is performed with strobed latches to el'imtnate the possiljilitv of glitches

Includes - Maniidl,

PRICE: $249.00 ASSEMBLED & TESTED,

CONNECTORS DB - 25P S3.00 DB - 25S S4.00

COVER

$1.50

44 Pm

44 Pm

86 Pin

86 Pm

PC & EYE

WW

16800) PC

(COSUAC ELFI PC 100 Pm - (Altatrl PC 100 Pin - (Imsai) PC 100 Pm - (Imiail WW

$1.95 $2,50 $5.00 $5.00

$4.50 $3.75 $4.25

Computer Products

5351 West 144ih Street LAWNDALE, CALIFORNIA 90260 (213) 6793313

RETAIL STORE HOURS Monday Pndav 9-7 Saturday 9-5 Discounts available at OEM quaniities ADD $1,50 under 10 lbs. tor shipping. California residents add

6% sales tax.

NEW CATALOG NOW AVAILABLE

Circle 195 on inquiry card.

BYTE July 1978 181

Whafs New?

PERIPHERALS

Floppy Controller Uses New Motorola Chip

Parallel and Serial lO

A new peripheral board, called the Bit Streamer, is now available in assem

bled or kit form from Vector Graphic Inc, 790 Hampshire Rd, Westlake Village CA 91361. According to the company, the Bit Streamer combines two parallel input and output ports, and a serial 10 port using an 8251 programmable universal synchronous or asynchronous receiver and transmitter USART. One parallel port also can be used as a keyboard input port. The USART is designed to interface easily to an S-100 bus structure and is capable of being configured for a wide variety of communication formats. The price is $195 assembled and $155 for the kit. Technical data covering the Bit Streamer and other products may be obtained from the company.*

Circle 624 on inquiry card.

A New Audio Cassette Interface

W c'^^^^^^^

This standard PerCom CIS-30+ interfaces with the MITS 680b computer. The unit interfaces two cassette record

ers and a data terminal to a microcomputer using the 6800 processors. It provides user selected data rates of 300, 600 or 1200 bps. The two cassette interfacing circuits are independent and simultaneous dual tape operations are possible. Optional program control of recorders is available. Cassette data recording is done using the Kansas City Standard (bi-phase-iVl, double frequency). The data terminal communication mode is full duplex. The MITS 680b read only memory monitor may be used for loading running programs, except for flipping the tape switch to on for program loading. The CIS-30+ sells for $79.95 in kit form, and $99.95 assembled and tested. An instruction manual is included. Contact PerCom Data Company, 318 Barnes, Garland TX 75042."

Circle 625 on inquiry card

The new Motorola MCM 6843 floppy disk controller integrated circuit has been incorporated into a low cost but versatile floppy disk controller. The 4'/2 by 6/2 inch (11.4 x 16.5 cm) module interfaces to any full size or minifloppy disk drive. The module supports both hard and soft sectoring, IBM 3740 or user programmable read and write format, automatic CRC generation and checking, and programmable step and settling times. The price is $1 99. Contact Wintek Corp, 902 N 9th St, Lafayette IN 47904."

Circle 627 on inquiry card

Moving Head Disk Controller for LSI-11 Systems

Add a Programmable Scientific Calculator to Your System

0Si

k

T

^^^

c

^B^^^ m^y^

^^

This new microcalculator. Model 85, is intended for operation with an 8 bit microprocessor. The Model 85 requires only +5 V for operation and interfaces

with the microprocessor thru an 8 bit bidirectional lO port. Each entry that would normally be made by a key is replaced with an 8 bit instruction from the microprocessor. The number of input instructions is not limited, restricted only to the user program or the amount of memory in the microprocessor system. Instruction entry to the microcalculator is under microprocessor software control. It accepts instructions, provides a means to detect busy status, and outputs the 14 digit display back to the microprocessor for storage or display. Complete software for controlling the microcalculator in both read and write modes requires less than 256 bytes of microprocessor system memory. The Model 85 has scientific calculation capabilities for handling scientific engineering, mathematical or statistical problems. Priced at $189 from Artisan Electronics, 5 Eastmans Rd, Parsippany NJ 07054."

Circle 626 on inquiry card.

The PX-C45L moving head disk controller enables you to add up to 40 megabytes of storage to DEC PDP-11/ 03, V03 Systems. It is Q-BUS compatible and equipped with a 5 or 10 megabyte disk drive. The controller is compatible with RT-11, FORTRAN, BASIC and other LSI-11 software. When used with a 5 megabyte disk drive, the removable media is interchangeable with DEC RK05 disk media. The unit is supplied in a 19 inch (48.3 cm) rack mountable 5!4 inch (13.3 cm) chassis complete with bootstrap loader, +5 V, 25 A power supply, slides, cardcage assembly fans and a 5 or 10 megabyte disk drive. An 8 foot (2.4 m) flat cable extends to the PDP-11/03 Q-BUS and three prewired Q-BUS 10 slots are available for user peripheral devices. The PX-C45L may be purchased separately or as part of a complete disk system. Contact Xylogics OEM Components Group Inc, 42 Third Av, Burlington MA 01803."

Circle 628 on inquiry card.

182

July 1978©BYTE Publicilioni Inc

Circle 115 on inquiry card.

lectrolabs

Educational Grade VIDEOTAPE Special: 72x2400' 20 boxes/$125.00

The "Pro" fully encoded ASCII Keyboard by Cherry. Auto REPEAT feature, 5 special function keys. 300mA/5V. (Shown as mounted in'The Case'. Below) $119.00, 3/99.00,10+/89.00

USED SYLVAN/A 12" MONITORS You Fix: $24.95 Working: $69.95 Cold Chassis. 25lbs.

The Dumb Terminal for Smart People

80X24 with full 128 char. ASCII UC+LC font with all control characters displayed. 300-19,200 baud RS232. 2nd font addressable from keyboard in you-program-it 2708 for APL, Graphics sets, etc. Plug in monitor I/O connector, 110VAC and you are ready. INCLUDES: 'The Case', Cherry Kbd. A used monitor, ESAT 200A, all options except vector addressable cursor and modem. Bulletproof design and construction. Normally $675.00 What you always wanted your ADM3 to be:

SYSTEM"A" $649.00 10/$5g9.00

■PO Box 6721 Stanford!

(.l^i

THE FANTASTIC!

MEMOREX FIVE-FIFTY

S: 94305

415-321-5601 ^—»•» '<

* Hard and Soft Sectoring

* Single and Dual Density 'Double side configuration as a retrofit at any time. *110l220V.50l60Hz

*Pin for pin computable with Shugart 800,801,850,851 (50 pin edge connector) $536,2/499, 5/475,10/449 25/425,100/405 Double Sided Retrofit $200

MINIDISKETTES (5.25') 1-9 10-24 25-H 10, 16 or Soft Sector $4.79 4.65 4.45

STANDARD (8') DISKETTES Hard or Soft Sector $5.99 5.33 4.79

"The Case" Beautiful and sturdy anodized aluminum case in deep black designed to contain the ESAT 200A, and with a bezel cut out for the Cherry 'Pro' keyboard, (installed as shown above) Choose deep brown, light yellow, or crimson to accent or color code your installation. The only choice for hard-use institutional and educational applications. $69.00, 10/ 59.00

CASSETTES R-300 Certified Phillips Type $5.25 4.99 1-150 Certified for audio decks $4.60 4.30 ('Kansas City' & SWTP formats)

4.35 3.90

SURPLUS Muffin tvpe fans $7.95, Lambda Power Supplies

5V/70A.$ 145.00, 35A.$8'9.00, 16A-49.00, 12V/7.3A-S69.00

OUR CATALOGUE

Contains IC's, T.I. Sockets (1 cent/pin) Advice and much more. It is free.

Ding and Handling: Surface: $o.40/ib. Air: $0:75/ib., 1.00 minimum Tax: 6.5% Insurance: $0.50 per $100.00

Stand Alone ASCII Keyboard

,«-.

I f V f B j N 1 M 1 < I > 1 T "! .M.FT ^ lir

■i34 SIMULTANEOUS OUTPUTS AVAILABLE: THE ONLY ONE ON THE MARKET

1. SERIAL TTL LEVEL

2. BUFFERED 8 BIT (TRI-STATE LATCH) PARALLEL OUTPUT WITH VALID DATA SYNC PULSE AND LEVEL

3. 20 MA OPTO-ISOLATED CURRENT LOOP, POLARITY INDEPENDENT

4. EIA RS232C

liSINGLE +5 VOLT 300 MA (NOMINAL) POWER SUPPLY

(REQUIRED) ^INDUSTRY STANDARD 2 KEY ROLLOVER ENCODER li-ANSI-COMPATIBLE KEY SET; FOR SLIM-LINE "HIDEAWAY" PACKAGING

5 COMPONENT SALES INC. 77B-A BRANMAN, SAN FRANCISCO. CA 3.4103 [41B] 861-134S

oo

ASSEMBLED AND TESTED

Plus $3.00 handling charge. California residents add 6'/2% sales tax.

^SEGMENTED SPACE BAR ALLOWS FAST MULTIPLESPACING WITHOUT REPEAT KEY

irREPEAT KEY REPEATS AT CHARACTER RATE

irUSER SELECTABLE UPPER CASE ONLY (KSR/ASR/33 REPLACEMENT) OR UPPER/LOWER CASE

liFACTORYSETAT 110 BAUD BUT EASILY ADJUSTED BY USER TO ANY BAUD RATE FROM 110 TO 9600 BAUD

^FLEXIBLE PARITY

*LED INDICATOR FOR SHIFT-LOCK KEY ELIMINATES CASE UNCERTAINTY

*24 PIN DUAL-INLINE CONNECTOR

6LOW PROFILE CASE (OPTIONAL) $40.00

^Ml Orders accepted by phone or maU. ■■■■

MASTERCHARGE V VISA JCOD*CHECK*MONEY ORDER

Circle 60 on inquiry card.

BYTE July 1978 183

What's New?

PERIPHERALS

Centronics Announces Front Feed Option for 700 Series Printers

Micromodule Has 16 Keys and IS Displays

An optional front feed device has been Introduced by Centronics Data Computer Corp, Hudson NH 03051. The front feed Is designed for use on eight members of the firm's 700 series of dot matrix printers and permits automatic front Insertion of cut forms and cut multipart form sets. It can be used In any application that requires information for Immediate utilization, Including invoicing, accounting, banlclngand stock certificates. The price for the front feed option is $700."

Circle 639 on inquiry card.

Assembled and Kit Plotters

Plotter kits and plotters completely assembled are offered by Sylvanhllls Laboratory Inc, POB 646, Pittsburg KS 66762. The kits require the purchaser to mount them on a drawing surface and to do the interconnection between the control printed circuit boards and the computer. Plotters require an 8 bit parallel lO port and 5 and 24 V power sources. A basic 8080 software program Is Included In the owner's manual. Applications Include architectural, mechanical, and schematic drawings; printed circuit board artwork; positioning of small objects; computer generated art; games; etc. Sizes available are 11 by 17 inches (30 by 43 cm) at $795 in kit form, 17 by 22 Inches (43 by 56 cm) at $950 In kit form, and 22 by 34 Inches (56 by 86 cm) at $1 300 In kit form."

Circle 640 on inquiry card.

■ B B B

B B B B

B B fl B

B B B B

This new Wince console lO module provides a versatile but inexpensive means of communication between a human operator and a microprocessor. A 16 key keyboard allows entry of parameters such as product codes, gas chromatograph stream selects, etc, and 15 7 segment displays. It allows output of data such as torque, item counts, etc. Also Included is a real time clock for providing Interrupts and displaying time. For further Information contact WIntek Corp, 902 N 9th St, Lafayette IN 47904.»

Circle 641 on inqurry card.

Add Some Color

•*F

«u

The RM 9050 series, a new family of raster scan color Imaging and graphic systems, has been announced by the Ramtek Corp, 585 N Mary, Sunnyvale CA 94086. The RM 9150, 9250, 9350 and 9351 are the first members of a compatible family of solid state digital television image generation systems capable of displaying In color, gray scale and black and white. The series was developed to provide a basic Imaging system plus graphics (plots, vectors and bar charts) and alphanumeric capability.

The basic system Includes scrolling, character scaling, readback, cursor and interactive capabilities. An assortment of custom video boards are available providing enhancement lookup tables and digital to analog converters which can produce from 256 gray levels to 4096 different colors. Keyboards and cursor controllers are available as addon options. Pricing for a basic 64 color system is under $6000 with black and white less than $5500."

Circle 642 on inquiry card

Speed Up DECwrlters

The SuperDEC throughput optimizer Is a printed circuit board designed to replace the existing digital electronics In Digital Equipment's LA361 DECwrlter 11 teleprinter, upgrading It to 1200 bps. Installation of the optimizer takes less than five minutes and Is completely plug compatible with the cables In the DECwrlter. Standard features Include automatic and manual top of form, full horizontal and vertical tabs (addressable and absolute), adjustable right and left mar

gins and an RS-232C Interface. Features not previously offered to DECwrlter users Include a double wide character set, bidirectional printing and 32 user programmable characters. An APL character set, selective addressing and an answer back feature are optional. Price Is $395 with a one year warranty on all parts and workmanship. Contact Intertec, 19530 Club House Rd, GaithersburgMD 20760,"

Circle 643 on inquiry card.

184 July 1978©BYTE Publicaiions Inc

CaIIFoRnIa iNduSTRJAl

Post Office Box 3097 B • Torrance, California 90503

WORD PROCESSING PRINTER

S255.

IBM EXECUTIVE D"

This Rubo Goldbergized printer, when properly interfaced to your data processing system, offers the capability of producing error free duplicate personalized letters. A seven bil TTL signal directs one of the 50 solenoid driven fingers to I depi'ess the proper typewriter key. Expandable incremental spacing allows the operator to software control justified copy. The heart of this machine is an Executive "D" serviceable by any IBM repair center. Shipping east of the Mississippi add $20,00; California add $10.00 all other states add $15.00. (Copy above reduced to half size. )

CONNECTORS

:r

m

your c.ioice

DB25P

male plug & hood

or

0B25S female

^395

Qty. fe. male hd. 10 3.45 2.45 1.15 25 3.15 2.25 1.05 100 2.«5 1.90 .95 500 2.25 1.50 .95 IK 197 1.37 .73

Edge

Connectors

100 PIN

IMSAI/ALTAIR

S-100 • GOLD PLATED • .125 "CENTERS

AHair 140 row. solderlail.. imsai 250 row, sotdeflaiL .. 3 Level Wire Wrap .250 row. SPECIALS W/W same as above without ear5$3.50 3/$10 72 (dual 36) W/W 156" centers . $2.50 3/S6

$5.98 3/$16.50 $4.98 3/$11.95 $4 98 3/$13.00

S-100 Mother Board Quiet

18 slot IMSA

HEXADECIMAL KEYBOARD

$34.95

Maxl-Stivitcfi hexadecimal keyboards

microcompuler syslems Ihat require ■

in standard hen code.

Each assemtjiy consists of 16 hermati

caliy sealed reed switches and TTL'

shot" debouncB circuitry

Reliable low friction acelal resin

piungefa are cfedded for the smooth

operation and long life ot this premlu

keyboard

RoQuires single +5 volt supply.

:fi ScptcH

Diskettes

8inchSoft<IBM) 8 inch 32 sector Mini Soft sec. Mini 10 sector Mini 16 sector

Certified Digital

CASSETTES

Won't drop a BIT!

CALIFORNIA INDUSTRIAL

is an

Authorized

Dealer ot

Scotch Brand

Data Products

21i02

LOW POWER

450 nS

7A%

im

7-1100 7-1107 74109 74110 74116 74120 74121

n^^^

74123 74125 74126 74128 74132 74136 7414! 74145 4 47

400

3

44

44S

7446

7404

19

19

7450

.19

7451

7407

25

7453

7411

7413

49

7414

79

7416

39

7417

39

7425

39

7426

.39

7486

7430

25

7492

7493

7494

39

'495

7440

39

301H

39

350N

«

304H ■

1^

370N

y^

305H

99

373N

119

307H

49

377N

199

307CN

39

3eON

.99

99

CMOS

309K

99

NE566

1?9

NE565H

149

NE565N

1 /4

311H

NE566N

1 i'S

4007

25

99

400B

149

312H

199

709H

39

4009

69

318H

179

709N

;(q

4010

69

318CN

149

710N

/H

711H

w

320K-5 -v 3MK-12 >

14

4015

139

149

4016

69

733H

149

4017

129

320T-12

733N

99

4018

169

739N

1 14

741N

IN

4021

149

4022

125

340K-5

746N

;i9

4023

25

1414N

1/S

1.19

340K-12

1458

(j9

S

.25

UART

4028

125

4030 4032

59 49

340T-12 '

•4.98

SPECIAL

GENERAL INSTRUMENT ASCII Keyboard Encoder AY 5-3600 Prime but house marked only $4.95

TELETYPE MOraL 43

New from Teletype, ihe Model 43 Is capable of printing 132 ASCII characlera pe' line. Send and receive dataat I0of 30 char, persecond Keyboard Qeneralea all 123 ASCII code combi tions RS-232 interface, same as the popui Model 33. Data sheet sen! upon request Manufacturer suggested pr.ce It377 00. • ^ ** ^ *v

IMMEDIATE DELIVERY >1219

TTLmodel with NOVATIONbrand Acoustic Modem. n419

TSP

MAXI-SWITCH

ASCII KEYBOARD

Fully ftCS^.97 Assembled •O^*.^'

Definitely the best small systtmi keyboard that we have seen. Maxi-Switch has incorporated all the important keyboard features at a reasonable price. Full 128 ASCII funetions, "N" key rollover, automatic repeats, user designated special function keys, escape, control ^ lots of others. Data sheet upon request.

FROM ATARI

COLOR TELEVISION R.E MODULATOR 1395

HH

mfinUfiL CRfiPHiTE DiSPLflV DEnERfiTDR

Mprtetn teclinoiogy has P'Q

Generator has the capaOilH) kwer case ASCII set Seii-cf the operator lo alimmalB e. Each umi is manutactureo ti QyGlanaaidssel'fiHlhCiy C£ every Ofder

}r assembly allows

JO

Potter &Brumfield REED RELAY

5voltcoil,pulls3.5v.

.97 .79 .65

Digital Casseite Drive

COMPUTER CONTROLED

•V9.50

This precision I/O assembly features remote software controlled searchi capabilities. Two independent capstan drive motors allow the computer to control direction and speed of the transport.

The assembly consists of a Raymoncl cassette transport, chassis, motherboard and three edge cards: read/write, capstan drive & control card. Current replacement valued at over $700.00. Schematics and complete documentation included. USED, but in excellent condition.

SlOO PROTOTYPE BOARD]

OPIOO-Moilmum design ver SQ'illtv along witti stondora oanress decoding and Dut tenng tor SlOO systems Room for 32 uncommiHeO 16 pin ics. 5 bus buffer & decoding cmps. 1 DIP address select swiicti o 5 volt regu

WWIOO-Wire wrap breodDoora, similar to the GPlOO Allows wire wrap of all sizes of sockets in any sizes of sooieis in any combinotion An extra reguloior position tor muiilDie volioge oopiico

TJujmbwheel switch

Ten position

BCD

'139 «.

r^

o;5eo

Miniature / Switches A

it

$.69

Conductor Fl.

RIBBON WIRE

TWISTED PAIR

Transistors

ea. 10 SO 100

2N2222A.20 .li .16.15 2N30S5 .69 .65 .59 .55 .79 .75 .69.65 159 1(I9J391Z9 .15 .11 .09.07 .15 .11 .09.07

odes

Ml 3055 2N3772 2N3904 2N3906

Di

10 a 100 1N4002 100«. .08 06.05 tN40a5 600>..10.08.07 lN4148sitnal .07.05.04 ittinb, red ea. 10 25 100 LED'S h5.13.11.09

Power Adapter

6vdc,140mA 51.39 7vdc, 1.4 A. 5.50 9vdc. ISmA. 1.19 10 vAc.300mA.

■a

Binding Posts 5-WAY

3.or*1.19

20 100 ».35 .29

SOLDERLESS TERMINAL^

INSULATED 20lor

♦.98

Specify:22-18 16 14

100 soo Ik

.213.679-9001

RELAYS

spot miniature

10 25 100 'l.l'ea $115 104 »9

Coil 12 Volt dc. 7 Amp Contacts P. C. Board Mount

CAPACITORS

ELECTROLrnCS

«a. 10 50

80,000/lOv. 355 3.M 2.95 4500/50V.SW9 135 U9

lOOO/lSv 555 49 45 axial

your choice t OO 1° 50 100 Ik *-9o s.gg .81.73.66 SPDT Miniature Toggles

7101 C&K ON'NONE-ON I

7107 jM ON.OFF(mnt.ON)

7108 CK ON-(moment.ON> I

Rockec IBT . OPOI

Rotary 3P-4-POS.

Rotary 3P-6-POS.

Pu&tiB<NO) S39ea4^$l

.Idisc .01 disc

512 .09 .07 .06 .05 .04

DIP Switch

^Rfl

$149

Heavy dutfgrounded power cord and mating chassis connectors.

PANASONIC

\9S

"A A"

450mA.

DISCOUNT <|

UJire UJfQp<entef

IC SOCKETS

pif

Wire wrap ea. 25 50

low profile

ea. 25 SO

8

17' 16 IS

14

37<36 35

18 17 16

16

38 37 36

19 18 17

24

99 93 85

36 35 34

40

169 155 139

63 60 58

saa.95

50ft.

'.98

soo 1.000 11,000 59. 515. $105.

VISA

Circle 39 on inquiry card.

BYTE luly 1978 185

Whal's New?

PERIPHERALS

Intelligent Parallel Printer Interface Card for Apple II Computer

N

Apple Computer Inc has introduced the Model A2B0002X intelligent printer interface card. The unit gives Apple II owners hard copy from popularly priced printers such as those offered by Axiom, Centronics, Qume, Printronics, OKI Data, SwTPC and other. Users can pro

duce permanent copy of program listings, generate reports, print letters and labels and generate graphics on printers with graphic capability. It comes fully assembled with instructions for connecting it to a printer. The card has a wide line format, capable of handling line widths up to 255 characters per line. It features high speed operation, up to 5000 characters per second, the equivalent of 3700 lines per minute at 80 characters per line. The power requirement is low, as card components are automatically powered down when no printing occurs and no external power is required for the card. It also features a general purpose 8 bit parallel output port. The card comes with firmware in read only memory, printer configuration block, ribbon cable and instruction manual.

The price of the A2B0002X is $180. Contact Apple Computer Inc, 10260 Bandley Dr, Cupertino CA 95014."

Circle 619 on inquiry card.

LSI-11 to Instrumentation Bus

National Instruments, 8330 Burnet Rd, Austin TX 78758, has announced an interface from the Digital Equipment

Corporation LSI-11 to the IEEE standard 488-1975 general purpose interface bus (GPIB). The unit, designated the GPIB11V-1, can be used with either the LSI-11 or Heath H11. The unit is furnished with a 4 meter bus cable and a complete software package including drivers, utilities, and diagnostics. The drivers and utilities are furnished as MACRO source files which can be assembled as FORTRAN, BASIC or MACRO callable subroutines. The interface can be used with such GPIB devices as voltmeters, counters, frequency synthesizers, and other controllers such as the PET microcomputer. The unit, including software and cable, sells for $695."

Circle 620 on inquiry card.

New Improved TV Modification Kit

TUM-41 TU MOD KIT

The TVM-04 television modification kit (see May 1978 BYTE, page 22) has

been superseded by the improved TVM-41, allowing greater monitor bandwidth than with the TVM-04. The new 80 character video generator displays look crisp and sharp. Operation as a monitor or TV receiver is switch selectable. The TVM-41 also extends the number of sets which can be modified to include Hitachi model number P-04, P-05, P-08, PA-4, PA-5, PA-8, P-40, P-41, (all 12 inch) and the 9 inch model 1-28. Total cost for the monitor is about $100, depending on the local price of the TV set. The TVM-41 is priced at $20 including hardware, wire and a five foot video cable for connecting to your video source. For more information contact Pickles & Trout, POB 1205, Goleta CA 93017."

Circle 621 on inquiry card.

"OEM 11" Brochure on Open Frame DC Power Supplies

A new 12 page, illustrated brochure is now being offered by Powertec Inc, 9168 DeSotoAv, Chatsworth CA91311 that describes the company's OEM II series of second generation, open frame DC power supplies. Described in the brochure are Powertec's broad product range of single output low power to 375 W, and multiple outputs dual and triple power supplies. The printed circuit board electronics have been designed to provide high efficiency and low primary power consumption. A listing of specifications is also included. Voltage and current rating charts are listed for user convenience."

Circle 622 on inquiry card.

Glitch Exterminator for the S-IOOBus

Vamp Inc has introduced the Exterminator (VTE-100) which they claim puts an end to bus problems on S-100 computer systems. The VTE-100 is a dual function board serving as a bus terminator and card extender. Bus termination by the VTE-100 is said to clean up noise, cross talk, overshoot and other bus problems that can scramble data unpredictably. The board also serves as a card extender for memory or lO cards which may require analysis or maintenance. The Exterminator, through on board termination, eliminates interference from adjacent boards which may radiate digital RF allowing any memory or lO card to be extended without fear of having the board perform unpredictably. It fuses all extended power buses to protect both the extended card and the power supply from any accidental damage. The fuses also allow for easy access to all power buses to permit the monitoring of current consumption. The Exterminator comes fully assembled and tested for $49.95 plus $2 to cover shipping and handling from Vamp Inc, POB 29315, Los Angeles CA 90029."

Circle 623 on inquiry card.

186

luly 1978©BYTE Publicjtiom Inc

• • •••'

m, m • • • •

• •• • • • ? ?

•••••••••••••••••••••••••••••••••••••I

••••

••••• ••••• ••••• ••••• •••••

I***■••••■

I***

•••••'

^l

KIT FEATURES:

16K E-PROM CARD

IMAGINE HAVING 16K OF SOFTWARE ON LINE AT ALL TIME! S-100 [Imsai/AltaJr] Buss Compatlile!

••.-.••••A

1. Double sided PC board with solder mask and silk screen and gold plated contact fingers.

2. Selectable wait states.

3. All address lines & data lines buffered!

4. All sockets included.

5. On card regulators.

KIT INCLUDES ALL PARTS AND SOCKETS (except 2708's). Add $25. for assembled and tested.

PRICE CUT!

$57.50 kit

SFtCUL OFFED:

WAS $69.95

DEALER INQUIRIES INVITED!

Our 27a8's (ABONS) are when purchased with above kit.

$12.95

■i<M

Swli^

KIT FEAUKS:

ADD

$20 FOR

250 NS

1. Doubled sided PC Board with solder mask and sijk screen lavout. Gold

plated contact fingers.

ill sockets included. Fully buffered on data lines.

Phantom is jumper pin 67. FOUR on card

all address and selectable

7805

regulators are provided (ASONS)

8K LOW POWER RAM KIT-$149.00

S-100 (Imsai/Altair) Buss Compatible! 2 kits for $279

Fully Assembled & Burned In

$179.00

Blank PC Board w/ Documentation

$29.95

Low Profile Socket Set 13.50

Support IC's (TTL & Regulators)

$9.75

Bypass CAP'S (Disc & Tantalums)

$4.50

USES 21L02 RAM'S!

MOTOROLA QUAD OP ■ AMP

MC3401, PIN FOR PIN SUB. FOR POPULAR LM 3900,

3 FOR $1

ALARM CLOCK CHIP

N S MM5375AA Six Digits With full Data New!

$1.95 each

MOTOROLA 7805R VOLTAGE REGULATOR

Same as standard 7805 except 750 MA output. TO-220. 5VDC output.

44c each or 10 for $3.95

FULL WAVE BRIDGE

4 AMP. 200 PIV. 69e 10 FOR $5.75

NOT ASSOCIATED WITH DIGITAL RESEARCH OF CALIFORNIA. THE SUPPLIERS OF CPM SOFTWARE.

450 NS! 2708 EPROMS

Now full speed! Prime new units from a major U.S. Mfg. 450 N.S. Access time. 1 K x 8. Equiv. to 4-1702 A's in one package.

$15.75 ea.

4 FOR $50

00

OUR LATEST COMPUTER KIT!

WHY THE 2114 RAM CHIP?

We feel the 2114 will be the next industry standard RAM chip (like the 2102 was). This means price, availability, and quality will all be good! Next, the 2114 is FULLY STATIC! We feel this is the ONLY way to go on the S-100 Buss! We've all heard the HORROR stories about some Dynamic Ram Boards having trouble with DIVIA and FLOPPY DISC DRIVES Who needs these kinds of problems'' And finally, even among other 4K Static RAIVI's the 2114 stands out! Not all 4K static Rams are created equal! Some of the other 4K's have clocked chip enable lines and various timing windows just as critical as Dynamic RAM's. Some of our competitor's 16K boards use these "tricky" devices. But not us! The 2114 is the ONLY logical choice for a troublefree, straightforward design.

FULLY S-100 COMPATIBLE! FULLY STATIC, AT DYNAMIC PRICES!

16K STATIC RAM KIT, ^ _^

separate 4K

sasgoo

COMPLETE KIT

four

^

SPECIAL

INTRODUCTORY OFFER!

Buy 2 KITS(32K)for $650

450 NS

Blank PC Board with Documentation

$33.00

LOW PROFILE SOCKET SET- $12.00

ASSEMBLED & TESTED - ADD $30.00

2114's 4K RAM's - 8 for $85.00

KIT FEATURES:

1. Addressable as Blocks.

2. ON BOARD BANK SELECT circuitry. (Cromemco Standard!) Allows up to 512K on line!

3. Uses 2114 (450NS) 4K Static Rams. 4 ON BOARD SELECTABLE WAIT STATES.

5. Double sided PC Board, with solder mask and silk screened layout. Gold plated contact fingers.

6. All address and data lines fully buffered.

7. Kit includes ALL parts and sockets.

8. PHANTOM is jumpered to PIN 67.

9. LOW POWER: under 2 amps TYPICAL from the +8 Volt Buss.

10 Blank PC Board can be populated as any multiple of 4K

Z-80 PROGRAMMING MANUAL

By Mostek. The major Z-80 second source. The most detailed explanation ever on the working of the Z-80 CPU CHIPS, At least one full page on each of the 158 Z-80 instructions. A MUST reference manual for any userof theZ-80. 300 pages. Just off the press. $12.95

HEAVY DUTY!

Full Wave Bridge 25AMP 50PIV

$1.25

Tarttalum Capacitors

1 MFD. .35V. By Kemet. Axial Lead. Best Value! 10/$1.

GE 10 AMP Triac

SC146D. House no.

To-220 case. Rated

10amps400PIV.

75c ea. 3/$2.

Digital Research Corporation

** (OF TEXAS! ■

P. O. BOX 401247 • GARLAND. TEXAS 75040 • (214) 271-2461

New! REAL TIME

Computer Clock Chip

N.S, MM531 3. Features BOTH 7 segment and BCD outputs. 28 Pin DIP $4.95 with Data

LSSER

74LS00 — 33c 74LS02 — 35c 74LS04— 35c 74LS08 — 35c 74LS10— 33c 74LS20 ~ 33c 74LS73 — 49c

lESTTL

74LS74 — 49c 74LS90 —69c 74LS138—89c 74LS154—1.49 74LS175—1.10 74LS367—75c 74LS368—85c

TERMS: Orders under SI 5. add 75c. No COD's. We accept VISA, MasterCharge and American Express Cards. Money Back Guarantee on all items! Texas Residents add 5% Sales Tax. WE PAY POSTAGE!

•••:.:•.•

»••••••••«

••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••J

Circle 100 on inquiry card.

BYTE July 1978 187

Circle 297 on inquiry card.

^ YOUR BEST BUY IN WIRE WRAP SUPPLIES ^

PRECUT WIRE

WHY BUY WIRE ON ROLLS' PRECUT a STRIPPED WIRE IS:

• Fail - No more Cutting & stripping by hand

• R*Habl« - Good, clean, uniform strip

• Economical - Cheaper than using bulk wire

Pracul Wirt

Bulk WIra

100 0C3

100 PCS

WireK

oi 3 at S 82 ^ 3-'<c/ti. ol 6' at 1 06 ae/tt1 at (6 95 = 2 1/»/n.

so It roll at 00 It foilai

1 99 ^ 4«/ft.

2 95 - 3C/ft.

« SOKynarsliippad 1 c Colors fled.Blue,Green Wire packaged m ptasti

n eacr> end Lengths are ovetaM Veiiow.Black.Orange.While Dags Add 25«'length for tubes

2'', in 3 in 3'^ in

100

78 82 86 90

500

2 40 260 280 300

1000

4 30/K

4 7t/K S12/K

5 52/K

5SS0

3e9^K 4 22/K

4 55/K 4 8e'K

4* in

5 in 5'^ in

6 in

94 96

1 02 1 06

3 21 3 42 3 65 3S5

5 93/K

6 34/K

6 75/K

7 16/K

5 21/K 5 52/K

5 86/K

6 19/K

6'^in

7-, in 8 in

1 15 1 20 125

129

4 05 4 25 4 45 4 65

7 57-'K

7 98/K

8 39/K BaO'K

6 52/K

6 85/K

7 18/K 7 53/K

8>j in

9 in gwin

10 in

1 32 136 1 40 1 45

4 85

505

5 25

5 51

9 2t/K 9 62'K 10 03/K

10 44/K

7 84/K ei7/K

8 50/K 8 83/K

Addi

nches iO

41

82/K

66/K

WIRE KITS

£J

$6.95

= 2 ?19.W

250 250 100

3- 100 *r 250 2'V

3V 100 5' 500 3

4" 100 6" 500 3'->'

500 4

Choote Or>e Color or Assonmeni

250 4',.

250 5'

100 5/

1 250

250 6

100 6 -■ 100 7 Hon Bulk

WIRE WRAP SOCKETS

10-24 25-99 100-249 250-999 1K-5K

18pin?0p.r. 22 pin ■ 24 pin 28 pin 40 pin

Gold 3-lev*l CloMd Enlry Sockelt d & Side SlBCkaDle All pncM include gold

Tin sockeli and 2-ievei sockets available

^ INTERCONNECT CABLES^

bon caDle conneclors 'or connecUng Ironl panels, or board to board

Boards lo

SINGLE ENDED

DOUBLE ENDED

I4p,n 16 pin

24p>n

14 pm

16 pin 24 pm

124 1 34 1 33 1 44 152 165 1 91 2 06

205

2 24 263

3 40

2 24 2 33 2 52 291

2 45 3 37 2 55 3 92 2 76 4 31 317 508

WIRE WRAP TOOLS

$34.95

With Free Wire Kit (S6 95 Value) HOBBY WRAP Model BW 630

Batteries & Charger $11.00

WSU 30 Hand Wrap-Unwrap Strip Tool 5 95

WSU 30M, for Modified Wrap 6 95

BT 30 Extra Bit 2,95

WIRE WRAP BOARDS

14

5J

WW 1024 Connector

H-PCB 1

3662

3682

4x4'.',

4x6

4x10

44 44 44

Buses on both sides

Blank

Buses on one side

4 76 625 10,50

4 50 6,85 10,00

4 00 5,50 9,50

3,00 3,00 300

36822 4066-4 3719-1

4x6 4x6 4x6

44 72 72

Buses on one side Buses on bolh sides Blank

950 13 60 900

900 13,00 8,50

825 12,50 800

3 00

4 00 4 00

3719-4

4350

8800V

4x10 7.9'', 10x5.3

72 80 100

Blank

Buses on both sides

Buses on bolh sides

11.00 17 50 19,50

1050 16,50 17,96

10,00 16 00 16 96

4 00 700 500

169P84

8v,x 1 7

Blank

626

5.75

5,26

SOCKET SAI ^'

14 p 16 p

24 p

n Gold WVW Socket n Gold WW Socket n Gold WW Socket

30

,32 ,75

27 pe ,29 pe ,65 pa

400 350

117

44 p

n ST Edge Cerd Cddnector

1.75

1 50pe

10

100 pin ST Edge Card Connecior 3.SO 3.00 par 10

lOOpin WW Edge Card Connector 3.50 3,00 par 10

Prices good through 8/1/78 vvhen purchased with Wire Kit —1 or -2

PAGE DIGITAL ELECTRONICS

Ordering Information:

Orders under S2S and COD'S, add $2

All others, shipped ppd m US via UPS 135 E. Chestnut Street 5

For Blue Label (Air) or 1st Class, add $1 Alt^^w^nln r^nlif^^^',.^ omic

weacceptv,Mj,Mas«rch.rg, Monrovia, California 91016

Most orders shipped same day

Dealer Inquiries Invited

Phone (213) 357-5005

P.O. Box 4430X Santa Clara. CA 95054 For will call only: (408) 988-1640

^^^^For will call only: (408) 988-1640 ^^^^^^2322 Walsh Ave.^

^^B^^ ELECTRONICS

"^^^ CRYSTALS

1 MHz 4.50 2.0100 MHz

1,95

2 MHz 4.50 2.097152 MHz 4.50

MICROPROCESSOR

2708 14.65

2104A-4

4.95

4 MHz 4.25 2.4576 MHz

4.50

6800

19.50

DH8577 290

2107B

4 95

5 MHz 4.25 3.2766 MHz

4,50

8.95

8223 290

2111-1

4 95

10 MHz 4,25 5,0688 MHz

4.50

m

29.95

2716 28,95

2112-2

3.95

18 MHz 3.90 5.185 MHz

450

8212

2114

8.50

20 MHz 3.90 5.7143 MHz

4.50

8214

8.00

IC SOCKETS

MK4116

27 50

32 MHz 3.90 6.5536 MHz

4.50

8216

2.90

2513B

6.30

32768 Hz 4.00 14.31818 MHz 4 25

8224

2,95

PIN 1 UP PIN lUP

21L02-1

1.49

4.50

8228

5.35

MM5262

.40

3.5795 MHzl.20 22 1164 MHz 4,50

8251

9.25

14 ,18 28 .42

MM5280

3.00

60 Hz Cryital Time Bate Ktl

S 4.40

8253

10.00

16 -20 36 .58

MM5320

9,95

30 MHz Fffiquencv Counter Kit

S47.7S

18 .27 40 .61

PrHCslv Kit to 350 MHz

$19.95

CDP1802CD

19.95

22 30

PD4110-3

4.00

CDP1802D

25,00

PD411D-4

5.00

CDP1861

12.96

P5101

13.95

6620

4200A

12.95

6850

12 95

82S25

290

Extender .Board w/connectot

Video Interlace board kit

125.00

PROM

16K EPROM board kit w/o PROMS 74 50

3.95

16K Static RAM board kit

395 00

N82S23

2,95

North Stir Hoppy Dlik Kit

>665 00

N82S123

3.50

Additional Drive Kit

N82S126

3-75

MOSMEMONT RAM

INTERFACE

Parstrofllct IMA Logic

8.75

2102AL-4 1,60

8T28

2.75

Model 10 Trigger Expandef Kit

^8^s^37

8.75

21F02 1-85

8T97

1.69

Model 150 Bus Grabber Kit

S369.00

New Cosmac Super "ELF"

RCA CMOS expandable to 64K microcomputer w/H EX lieypad input and video output for graphics. Just turn on and start loading your program using the resident monitor on ROM. Pushbutton selection of all four CPU modes. LED indicators of current CPU mode and four CPU states. Single step op. for program debug. Built in pwr. supply.

256 Bytes of RAM, audio amp. & spkr. Detailed assy. man. w/PC board & all parts fully socketed. Comp. Kit $106.95. High address display option 8.95; Low address display option 9.95; Custom hardwood cab.; drilled front panel 19.75; Nicad Battery Backup Kit w/all parts 4.95; Fully wireij S, tested in cabinet 151.70; 1802 software club. 10-12 pg. monthly publication 12.00 per yr.

Auto Clock Kit $15.95

DC clock with 4.50' displays Uses National MA-1012 module with alarm option. Includes light dimmer, crystal timebase PC boards. Fully regulated, comp. instructs. Add S3.95 for beautiful dark gray case. Best value anywhere.

4K Ell Expansion Board Kit with Cassette l/F $79.95

Available on board options; 1K super ROM monitor S19.95. Parallel I/O port $7.95. RS232 l/F $3.50. TTY 20 ma l/F $1.95. S-100 Memory l/F $4.50.

Tiny Basic for ANY 1802 System

"oltZ Monitor mil ^'"^ E" ™"«'= «*» 30%off.

Object code listing or paper tape with manual

$5.50

78 IC Update Master Manual

1978 IC Update Master Manual $30.00

Complete IC data selector 2175 pg. Master reference guide. Over 42.000 cross references. Free update service through 1978. Domestic postage $3.50, Foreign $6,00. Final 1977 Master closeout $15.00

Video Modulator Kit $8.95

Convert your TV set Into a high quality monitor without affecting normal usage. Complete kit with full Instructions.

RCA CosmacVIP Kit $275.00

Video computer with games and graphics.

Sinclair 3V2 Digit Multimeter

Batt. oper. ImV and 1NA resolution. Resistance to 20 meg. 1% accuracy. Small, portable, completely assem. in case. 1 yr. guarantee. $50.05

FREE; Send for your copy of our NEW 1978 QUEST CATALOG.

lericard and e 24« stamp

188 BYTE luly 1978

Circle 307 on inquiry card.

ELECTRONIC SYSTEMS

Dept. B P.O. Box 21638 San Jose, CA 95151

FOR CATALOG INCLUDING PARTS LISTS AND SCHEMATICS. SEND A SELF ADDRESSED ENVELOPE WITH 2i«r POSTAGE.

RS-232/TTL INTERFACE*

UART &BAUD RATE GENERATOR*

Part no. 101

• Converts serial to parallel and

parallel to serial

• Low cost on board baud rate generator

• Baud rates: 110, 150, 300,600, 1200, and 2400

• Low power drain +5 volts and -12 volts required

• TTL compatible

• All characters contain a start bit, 5 to 8 data bits, 1 or 2 stop bits, and either odd or even parity.

• All connections go to a 44 pin gold plated edge connector

• Board only $12.00; with parts $35.00

8K

STATIC

RAM

Part no. 300

• 8K Altair bus memory

• Uses 2102 Static memory chips

• Memory protect

• Cold contacts

• Wait states

• On board regulator

• S-100 bus compatible

• Vector input option

• TRl state buffered

• Board only $22.50; with parts $160.00

, and

Part no. 232

• Converts TTL to RS-232, converts RS-232 to TTL

• Two separate circuits

• Requires 12 and +12 volts

• All connections go to a 10 pin gold plated edge connector

• Board only $4.50; with parts $7.00

DC

POWER

SUPPLY*

Part no. 6085

• Board supplies a regulated -^5 volts at 3 amps., +12, -12, and -5 volts at 1 amp.

• Power required is 8 volts AC at 3 amps., and 24 volts AC C.T. at 1.5 amps.

• Board only $ 12.50; with parts S42.50 excluding transformers

TIDMA'

Part no. 112 a^'^f

• Tape Interface Direct Memory Access

• Record and play programs without bootstrap loader (no prom) has FSK encoder/decoder for direct connections to low cost recorder at 1200 baud rate, and direct connections for inputs and outputs to a digital recorder at any baud rale.

• S-100 bus compatible

• Board only $35.00; with parts $110.00

Part no. Ill

TAPE INTERFACE*

• Play and record Kansas City Standard tapes

• Converts a low cost tape recorder to a digital recorder

• Works up to 1200 baud

• Digital in and out are TTL-serial

• Output of board connects to mic. in of recorder

• I^phone of recorder connects to input on board

• Requires -^5 volts, low power drain

• Board $7.60; with parts $27.50

• No coils

Part no. 107

RF MODULATOR*

• Converts video to AM modulated RF, Channels 2 or 3

• Power required is 12 volts AC C.T., or +5 volts DC

• Board $7.60; with parts $13.50

Apple II Serial I/O Interface *

Part No. 2

• Baud rates up to 30,000

• Plugs into Apple Peripheral connector

• Low-current drain

• RS-232 Input and Output

SOFTWARE

• Input and Output routine from monitor or BASIC to teletype or other serial printer.

• Program for using an Apple II for a video or an intelligent terminal. Board only — $15.00; with parts — $42.00; assembled and tested - $62.00.

RS-Z32/TTY* INTERFACE ^

Part no. 600 J^^

• Converts RS-232 to 20mA^^ current loop, and 20mA current loop to RS-232

• Two separate circuits

• Requires +12 and -12 volts

• Board only S4.50, with parts «7.00

TELEVISION TYPEWRITER

Pari no. 106

• Stand alone TVT

• 32 char/line, 16 lines modifi cations for 64 char/line included

• Parallel ASCII (TTL) input

• Video output

• IK on board memory

• Output for computer controlled curser

• Auto scroll

• Non-destructive curser

• Curser inputs: up, down, left, right, home. EOL, EOS

• Scroll up, down

• Requires+5 volts at 1.5 amps, and -12 volts at 30 mA

• All 7400, TTL chips

• Char. gen. 2513

• Upper case only

• Board only 839.00; with parts 8145.00

MODEM

Part no. 109

• Type 103

• Full or half duplex

• Works up to 300 baud

• Originate or Answer

• No coils, only low cost components

• TTL input and output-serial

• Connect 8 ohm speaker and crystal mic. directly to board

• Uses XR FSK demodulator

• Requires +5 volts

• Board $7.60; with parts $27.50

To Order:

Mention part number and description. For parts kits add "A" to part number. Shipping paid for orders accompanied by check, money order, or Master Qiarge, BankAmericard, or VISA number, expiration date and signature. Shipping charges added to C.O.D. orders. California residents add 6.5% for tax. Parts kits include sockets for all ICs, components, and circuit board. Documentation is included with all products. Dealer inquiries invited. 24 Hour Order Line: (408) 226-4064.* Designed by John Bell.

Circle 125 on inquiry card.

BYTE )ulv 1978 189

What's New?

PERIPHERALS

Isolated Digital Output Board for Intel Microcomputers

A Video Camera Kit

This 202 video camera kit may be used for visible or infrared viewing and surveillance with an infrared light source, and is excellent for standard surveillance work because of its light weight (under one pound) and small size {VA by 6V2 inch boards). A 5 V, 1 A power supply is needed. The kit includes all semiconductors, boards, data sheets, diagrams, resistors, capacitors, and an 8 mm lens. The kit sells for $349 from Solid State Sales, POB 748, Somerville, MA 02143.

Circle 61 5 on inquiry card.

Video Terminal Offered by Phone 1

The new model PI-11 video terminal features the following: 80 by 24 screen, local editing, upper and lower case display, dual screen intensity, full or half duplex operation, numeric cluster keyboard, and 300 bps acoustical modem. The unit sells for $1075 complete and $800 for the terminal alone. Contact Phone 1 Inc, 1330 E State St, Rockford IL61108.

Circle 616 on inquiry card.

Module Interfaces Voice and Instruments to Synthesizers

PITCH FOtLOWER

The Aries AR-333 pitch and envelope follower is an electronic module that interfaces external signal sources, such as voice, single note instruments, and tape recorders, to most synthesizers. A one octave change of input signal produces a 1 V change in pitch control output for controlling VC oscillator frequency, filter frequency, etc. Linear and logarithmic envelope follower outputs allow control of synthesizer functions by the amplitude of the input signal. On the front panel, a trim pot lets you adjust the tracking sensitivity of the pitch control output, and permits use of the module with different synthesizers without retrimming oscillators. The front panel also provides a tuning control for adjusting oscillator frequency which allows tuning to the pitch of other instruments, and a retriggering sensitivity control for picking up accents. A low distortion compressor output is also provided. The module's 36 db, low noise microphone preamp accepts Vi inch phone plugs. It sells for $349 (kit) and $499 (assembled). An assembled AR-333 with case and power supply (Model GE-101) sells for $550. Contact Aries Music Inc, Shetland Industrial Park, POB 3065, Salem MA 01970."

Circle 618 on inquiry card.

Plug compatible 16 or 32 channel isolated digital output systems are available for the Intel SBC 80 and Intellec MDS microcomputers. Isolation eliminates ground loop problems and protects the processor from real world transients. Memory mapped MP801 (16 channel) or MP802 (32 channel) systems are contained on a single printed circuit board and provide all control and timing circuitry. Channels are implemented by dry reed relays protected by metal oxide varistors and can handle up to 10 W. Relays provide low "on-impedance," high output current and isolate output channels from the computer bus (to 600 VDC) and from channel to channel (300 VDC). They are treated as memory by the processor, eight output channels occupying one memory location. Prices of the 16 channel MP801 are $295 and $475 for the 32 channel MP802 in quantities of one to nine. Contact BurrBrown, International Airport Industrial Park, Tucson AZ 85734.»

Circle 61 7 on inquiry card.

Attention Readers, and Vendors.. .

Where Do New Product Items Come From?

77!e information printed in tlie new products pages of BYTE is obtained from "new product" or "press release" copy sent by the promoters of new products. If in our Judgment the neat new whizbang gizmo or save the world software package is of interest to the personal computing experimenters and homebrewers who read BYTE, we print the information in some form. We openly solicit such information from manufacturers and suppliers to this marketplace. The information is printed more or less as a first in first out queue, subject to occasional priority modifications.

190

luly 1978©BYTE Publicjtions Inc

c^^ri.1 T-W7 n/./^n A "Smart" VIDEO BOARD ^^^^ Ihe tW-2001 KIT At A "Dumb" Price!

'^ A VIDEO BOARD + A MEMORY BOARD + AN I/O BOARD - ALL IN ONE!

■ STATE OF THE ART TECHNOLOGY USING DEDICATED MICROPROCESSOR I.C. 4^ 1 QQ O ^

■ NUMBER OF I.C.s REDUCED BY 50% FOR HIGHER RELIABILITY ■ MASTER PIECE ^fl? J- 3/ 3/« 37 tJ

OF ENGINEERING ■ FULLY SOFTWARE CONTROLLED Priced at ONLY Basic Software Included

SPECIAL FEATURES: ■ Programmable no. of scan lines OPTIONS:

■ S-100 bus compatible ■ Underline blinking cursor Sockets SI0.00

■ Parallel keyboard port ■ Cursor controls: up, down, left, 2K Static Memory

■ On board 4K screen memory right, home, carriage return (with Sockets) $45.00

(optional)* relocatable to main ■ Composite video 4K Static Memory

computer memory *Min. 2k required for operation of this board. (with Sockets) S90.00

■ Text editing capabilities (soft- DISPLAY FEATURES- Complete unit, assembled ware optional) _ .^^ ,. , ., .g^„ . ^ and tested with '

■ Scrolling-UD and down through " 128 displayable ASCII charact- 4K Memory S335.00

icroumg. up dnu uown uiruugn ers (upper and lower case alpha- „ . , „^.. „^^ ^^

video memory numeric, controls) Basic software on ROM . S20.00

■ Bhnking characters a 64 ^j. 32 characters per hne Text editor on ROM .... S75.00

■ Reversed video Oumper selectable)

■ Provision for on board ROM ■ 32 or 16 lines

■ CRT and video controls fully Oumper selectable)

programmable (European TV) ■ Screen capacity 2048 or 512 DEALER

' ?rn dot^maTrlx""' INQUIRIES WELCOMED

8080 SUPPORT

8212 S3.00

8214 7.95

8216 3.50

8228 5.95

8251 7.95

8555 8.50

1/4W RESISTOR

10 Ohm- 1.5m

$1.75/100

of one value

Pole lOPos. ROTARY SWITCH

3 for $1.00

Pole 8 Pos. T05 Miniature Rotary Switch 3 for $1.00

MINIATURE

Slide Switch

DPDT

$.15: 10/$1.00

Push Button Momentary

Switch 3 for $ 1.00

a

080 A

CPU

$7.75

RAM-2II4

lKx4 450ns $8.00

RIBBON CABLE

32 Conductor

26 AWG - $.60/Foot

HEXADECIMAL LABEL KEYBOARD

Matrix coded output

Interfaces with 74C922

for binary code

Zero bounce

Est. life: 100 million

Remove back to stick on

SHIPPING: Keyboard and Video Board: $3.50; others: $1.25 California residents add 6% sales tax

ELECTRONICS WAREHOUSE Inc.

1603 AVIATION BLVD. REDONDO BEACH, CA. 90278

TEL. (213)376-8005 WRITE FOR FREE CATALOG

Minimum Order: $10

•JfONLY

ASCII 3rd GENERATION

KEYBOARD KIT *68.00

TTL Logic Circuits

Power: +5V 275mA

Upper and Lower Case

Full ASCII Set (Alpha Numeric, Symbols, Control)

7 or 8 Bits Parallel Data

Optional Serial Output

Selectable Positive or Negative Strobe, and Strobe Pulse Width

'N' Key Roll-Over

Fully Debounced

Carriage Return Key

Repeat Function Key

Shift Lock, 2 Shift Keys

4 User Defineable Keys

P.C. Board Size:

17-3/16" x 5"

OPTIONS:

Metal hnclosure Painted IBM Blue and White)

$25.00

18 Pin Edge Con.

S2.00

I.C. Sockets

$4.00

Serial Output (Shift Register)

$2.00

Upper Case Lock Switch for Capital Letters and Numbers

$2.00

KIT INCLUDES: Keyboard, P.C. Board, all required components & assembly manual.

NOTE: If you have this 63 Key Teletype Keyboard you can buy the Kit without it for only $44.95.

Circle 130 on inquiry card.

BYTE July 1978

191

What's New?

Full Character Line Printer

PERIPHERALS

The Writehander: a New Typing Keyboard for One Hand

A typing keyboard has been designed that permits typing all 128 characters of the ASCII code with one hand and is particularly useful with computers and terminals that accept ASCII coded parallel input. To use the Writehander, the typist places four fingers on four

press switches and the thumb on one of eight press switches. The four finger switches operate as the lower four bits of the 7 bit ASCII code, selecting the group of characters (out of 16 groups) that contains the desired character. The group contains a choice of eight letters, numerals, symbols, etc. The thumb then presses the particular switch that selects the desired character from the choice of eight. A computer is not required to operate the terminal. The Writehander will directly operate terminals such as the Diablo HyType, Teletype ASCII modified Selectric, or a video monitor that accepts parallel 7 bit ASCII signals. Required power is 200 mADC from 5 V regulated or 7 to 25 V unregulated. The unit connects to the terminal through a ribbon cable that has lines for the 7 bit ASCII code, a 1 bit fixed parity, strobe and acknowledge signals and the power and common lines. The price of the Writehander is $98 and it can be obtained from the NewO Company, 246 Walter Hays Dr, Palo Alto CA 94303."

Circle 646 on inquiry card.

Line Printer with Graphic Capabilities

IKi mt

_ ^^'**^«^_ .f f

The Model 160 Malibu Line Printer is a commercial grade dot matrix machine which operates bidirectionally at 165 characters per second and has graphics capabilities. The printer's features include logic seeking capabilities for fast throughput, reinking rollers (said to increase ribbon life up to 50 million characters), and jumper selectable primary voltage (110 to 220 V, 50 to 60 Hz). Standard software supports the 96 character ASCII set, but the user may easily change the characters to exotic languages, scientific symbols, or whatever can be printed with a 9 pin head. The tractor operated paper feed allows groups of dots to be placed immediately adjacent to one another either horizontally or vertically, giving graphics capabilities at 3000 dot locations per

square inch. The Malibu accepts paper from 4 inch (10 cm) to 15 (37.5 cm) inch width and prints up to 132 characters per line. Normal line feed is 1/6 inch (0.4 cm), but increments of 1/60 inch (0.04 cm) are possible under software control. All circuitry is designed into three circuit boards which plug into the mother board. An optional Altair (S-100) interface card is available, making the printer immediately operable with many popular computers. An RS-232 option with a Z-80 processor on board allows the printer to accept serial input (up to 9600 bps) or parallel ASCII input with handshaking. The Malibu printer is priced at less than $2000 from Malibu Design Group Inc, 21110G Nordhoff St.Chatsworth CA 91311."

Circle 653 on inquiry card

The FUTRA Model 10 Line Printer incorporates a belt impact, full character (not dot matrix) 80 column printing mechanism. The unit operates at a minimum print rate of 150 lines per minute using the 64 ASCII character set or a minimum of 84 lines per minute using a full 96 ASCII character set and can produce up to four copies including the original. The input is an 8 bit parallel which can be interfaced to a 3P-^S or similar interface card. The unit has a buffer size of one full line (80 characters) and a maximum data input rate of 75,000 characters per second.

The Model 10 is priced at $2695 and comes with pin feed paper handling mechanism, format control unit (top of form), either 64 or 96 ASCII character set and parallel interface. Options are an off line test print excercisor, $75; and serial interface (RS-232c, 20 mA current loop, TTL direct interface with 1010 byte buffer), $595. Contact FUTRA, 3421 Onyx St, POB 4380, Torrance CA 90510, (213) 371-8138."

Circle 583 on inquirv card

Fast Cassette Interface

The Wince Cassette Interface dumps and loads programs at a data rate of 2400 bps. It also supports the 300 bps Kansas City standard. The unit interfaces directly to a Motorola 6850 ACIA and includes an RS232 interface at data rates from 150 to 9600 bps. The interface board is priced at $139 in single quantities from Wintek Corp, 902 N 9th St, Lafayette IN 47904, (31 7) 742-6802."

Circle 584 on inquiry card.

192

July 1978©BYTE Publicilioni Inc

DIODES/ZENERS

SOCKETS/BRIDGES

TRANSISTORS, LEDS, etc.

1N914

lOOv

10mA .05

8-pin pcb .20 WW .35

2N2222

NPN (2N2222 Plastic .10)

.15

1N4n05 1N4007

600v lOOOv

1A .08 1A .15

14-pin pcb .20 WW .40 16-pin pcb .20 WW .40

2N2907 2N3906 2N3904

PNP

PNP (Plastic - Unmarked)

NPN (Plastic - Unmarked)

.15 .10 .10

1N4148

75v

10mA .05

18-pin pcb .25 ww .75

2N3054

NPN

.35

1N4733

5.1v

1 W

Zener .25

22-pin pcb .35 ww .95

2N3055

NPN 15A 60v

.50

1N753A 1N758A

6.2v lOv

500mWZener .25 .25

24-pin pcb .35 ww .95 28-pin pcb .45 ww 1.25

T1P125 LED Green, D.L.747

PNP Darlington Red, Clear, Yellow 7 seg 5/8" High com-anode

.35

.15

1.95

1N759A

12v

.25

40-pin pcb .50 ww 1.25

MAN72

7 seg com-anode (Red)

1.25

IN 5243

1N5244B

1N5245B

13v 14v 15v

.25 .25 .25

IVIolex pins .01 To-3 Sockets .25

MAN3610 MAN82A

7 seg com-anode (Grange) 7 seg com-anode (Yellow)

1.25 1.25

2 Amp Bridge 100-prv .95

MAN74A FND359

7 seg com-cathode (Red) 7 seg conrvcathode (Red)

1.50 1.25

25 Amp Bridge 200-prv 1.95

CMOS

- T T L

4000

.15

7400

.10

7473 .25

74176 .85

74H72

.35

74S133

.40

4001

.15

7401

.15

7474 .30

74180 .55

74H101

.75

74S140

.55

4002

.20

7402

.15

7475 .35

74181 2.25

74H103

.55

74S151

.30

4004

3.95

7403

.15

7476 .40

74182 .75

74H106

.95

74S153

.35

4006

.95

7404

.10

7480 .55

74190 1.25

74S157

.75

4007

.20

7405

.25

7481 .75

74191 .95

74 LOO

.25

74S158

.30

4008

.75

7406

.25

7483 .75

74192 .75

74L02

.20

74S194

1.05

4009

.35

7407

.55

7485 .55

74193 .85

74L03

.25

74S257(8123)

1.05

4010

.35

7408

.15

7486 .25

74194 .95

74L04

.30

4011

.20

7409

.15

7489 1.05

74195 .95

74L10

.20

74LS00

.20

4012

.20

7410

.15

7490 .45

74196 .95

74L20

.35

74LS01

.20

4013

.40

7411

.25

7491 .70

74197 .95

74L30

.45

74LS02

.20

4014

.75

7412

.25

7492 .45

74198 1.45

74L47

1.95

74LS04

.20

4015

.75

7413

.25

7493 .35

74221 1.00

74L51

.45

74LS05

.25

4016

.35

7414

.75

7494 .75

74367 .75

74L55

.65

74LS08

.25

4017

.75

7416

.25

7495 .60

74L72

.45

74LS09

.25

4018

.75

7417

.40

7496 .80

75108A .35

74L73

.40

74LS10

.25

4019

.35

7420

.15

74100 1.15

75491 .50

74L74

.45

74LS11

.25

4020

.85

7426

.25

74107 .25

75492 .50

74L75

.55

74LS20

.20

4021

.75

7427

.25

74121 .35

74L93

.55

74LS21

.25

4022

.75

7430

.15

74122 .55

74L123

.85

74LS22

.25

4023

.20

7432

.20

74123 .35

74H00 .15

74LS32

.25

4024

.75

7437

.20

74125 .45

74H01 .20

74S00

.35

74LS37

.25

4025

.20

7438

.20

74126 .35

74H04 -20

74S02

.35

74LS38

.35

4026

1.95

7440

.20

74132 .75

74H05 .20

74S03

.25

74LS40

.30

4027

.35

7441

1.15

74141 .90

74H08 .35

74S04

.25

74LS42

.65

4028

.75

7442

.45

74150 .85

74H10 .35

74S05

.35

74LS51

.35

4030

.35

7443

.45

74151 .65

74H11 .25

74S08

.35

74LS74

.35

4033

1.50

7444

.45

74153 .75

74H15 .45

74S10

.35

74LS86

.35

4034

2.45

7445

.65

74154 .95

74H20 .25

74811

.35

74LS90

.55

4035

.75

7446

.70

74156 .70

74H21 .25

74S20

.25

74LS93

.55

4040

.75

7447

.70

74157 .65

74H22 .40

74S40

.20

74LS107

.40

4041

.69

7448

.50

74161 .55

74H30 .20

74S50

.20

74 LSI 23

1.00

4042

.65

7450

.25

74163 .85

74H40 .25

74S51

.25

74LS151

.75

4043

.50

7451

.25

74164 .60

74H50 .25

74S64

.15

74LSI 53

.75

4044

.65

7453

.20

74165 1.10

74H51 .25

74S74

.35

74LS157

.75

4046

1.25

7454

.25

74166 1.25

74H52 .15

748112

.60

74LS164

1.00

4049

.45

7460

.40

74175 .80

74H53J .25

74S114

.65

74LSI 93

.95

4050

.45

7470

.45

74H55 .20

74LS367

.75

4066 4069/74 C04

.55 .25

7472

.40

74LS368

.65

4071

.25

IVICT2 .95 LINEARS, REGULATORS, etc.

4081

.30

8038 3.95

LIVI320T5 1.65

LM340K15

1.25

LM723

.40

4082

.30

LM201 .75

LIVI320T12 1.65

LM340K18

1.25

LM725N

2.50

MC 14409 14.50

LM301 .45

LM320T15 1.65

LM340K24

1.25

LIVI739

1.50

MC 14419

4.85

LIV1308 (Mini) .95

LM324N 1.25

78L05

.75

LIVI741 (8-141.25 1

4511

.95

LM309H .65

LM339 .75

78L12

.75

Ll\/1747

1.10

74C151

1.90

LM309K(340K-5>85

7805 (340T5) .95

78L15

.75

LM1307

1.25

LIV1310 .85 LM311D(Mrni) .75

LM340T12 .95 LM340T15 .95

78M05 LM373

.75 2.95

LM1458 LM3900

.65 .50

9000 SERIES

9301 .85

95H03

1.10

LM318(Mini) 1.75

LM340T18 .95

LM380(8-i4PiN).95

Ll\/I75451

.65

9309 .35

9601

.20

LM320K5{7905)1.65

LM340T24 .95

LM709(8,i4PiN).25

NE555

.35

9322 .65

9602

.45

LM320K12 1.65

LIVI340K12 1.25

LM711

.45

NE556 NE565 NE566 NE567

.85

.95

1.25

.95

MICRO'S, RAMS. C

PU'S,

E-PRC

74S188 3.00 1702A 4.50

)MS

8214 8224

8.95 3.25

INTEGRATED CIRCUITS UNLIMIT

ED

MM5314 3.00

8228

6.00

7889 Clalremont Mesa Boulevard, San Diego, California 92111

MM5316 3.50 2102-1 1.45

8251 8255

8.50 10.60

(714) 278-4394 (Calif. Res.)

SPECIAL DISCOUNTS

2102L-1 1.75

8T13

1.50

All orders shipped prepaid No minimum

Total Order

Deduct

2114 9.50 TR1602B 3.95

8T23 8T24

1.50 2.00

Open accounts invited COD orders accepted $35-$99

10%

TMS4044- 9.95

8T97

1.00

Discounts available at OEM Quantities California Residents add 6% Sales Tax *1^V ' Z.^^

15%

2107

3-4 4.95

All IC's Prime/Guaranteed. Ail orders shipped same day received.

saui - !t>iuuu

20%

8080 8.95 8212 2.95

2708 Z80P

9.50 10 8.50

24 Hour Toll Free Phone 1-800- 854-2211 American Express / BankAmericard / Visa / MasterCharge

Circle 180 on inquiry card.

BYTE luly 1978

193

/g

aCfipif CT Mates with two rows ot 025" sq. or OUulVCI dia posts on patterns of 100" lilR/IDCDC c^eoters and shielded receptacles JUIVIr tnO Probe access holes in back. Choice

Part No.

924003-18R 924003-06R 92400S-18R 924005-06R 924006-18R 924006-06R

of 6" or 18" length. No. ot Contacts Lengtl)

26 18" 26 6"

40 18" 40 6"

50 18" 50 6"

Price

$ 5 38 ea. 4.78 ea. 8.27 ea. 7.33 ea. 10.31 ea. 9.15 ea.

HIIIMPFR ^"'"^^ '° ^'' tioards for instant JW"'' f" plug-in access via socket-connector IjrJinpoQ jurnpers. 025" sq posts Choice nCMUCno of straight or right angie.

Part No.

923863-R 923873-R 923865-R 923875-R 923B66-R 923876-R

No. ot Posts Angle

26 26 40 40 50 50

straight right angle straight right angle straight right angle

Price

SI .28 ea.

1 52ea 1.94 ea 2.30 ea. 2.36 ea.

2 82ea.

DIP JUMPERS

Males with stanttard 1C sockets

24" lengtt) • Fully Assembled i Tested

PRICE

t 1.92 3.02

40

m end sgl end

924106-24 924112-24 924116-24 924122-24 924126-24 924132-24

334 330 S.20 553

Also Available in 12" and 36" lengths

32

CYlft

CY1.84

CY2A

CV201

CY2 50

CY3.27

CY3.57

CY3A

CY491

CY7A

CY5.18

CY6.14

CY6.40

CY6.55

CY12A

CY14A

CY19A

CY18 43

CY22A

CY30A

CRYSTALS I

TKESE FREaUENCIE!; ONLY J; FREQUENCY CASE

1 00OMH2

1 8432MH2

2 0OOMH2 2.010I^Hz 2500MH2

3 2768MH2 3579545MH; 4.000MH! 4.916MHz 5.000MHz

5 185MHz

6 144MH2 6400MHz 6 5536MHz 10 000MH2 14 3I818MH; 18.000MHz 18.432MHz 20 000MH2 32 OOOMHz

HC33

5 95

HC33

595

HC33

595

HC33

1.95

HC33

4.95

HC33

495

HC33

495

HC18

4 95

HC18

4 95

HC18

4.95

HC18

4 95

HCt8

4 95

HCie

4 95

HC18

4.95

HC18

4.95

HC18

495

HCt8

4.95

HC18

495

HC18

4.95

HC18

4 95

TRIMMERS

10MM size trimmers -.394" Dia.

Part No. 1-9 10-24 25-49 100 + TR-11 (valve) 35 .30 25 20

Resisrance values . 10Q. 500 IK ?K. 5K 10K ?0K. 50K. lOOK. ?00k 1 meg

TRIMPOTS

Single-Turn - 1/2 Walt

Square - Top Ailjust - 3/B" Size Pan No. 1-9 10-24 25-49 50-99

63P(value) .99 .89 .80 .70

Resistance Values-50. too 500 IK,2«,5K. 10K.?OK 50K lOOK, 200k, 500K, 1 meg

^j

15-Turn - 3/4 Watt

Rectanguiar Side Adjust 3/4" x 1/4" Size Pari No. 1-9 10-24 25-49 50-99

43P(value) 1.35 1.25 1.20 1.15

50. 100.500, IK, ?K,5k, I0K.Z0K,50K, lOOK, 200K, 500K, 1 ™g

1/16 VECTOR BOARD

Par! No 64P44 0S2XXXP 169P44 062XXXP 64P'14 D62WE B4P4-1 062Wt 169P44 062WE t69P84 062WE 169P44 062WEC1

Rsn

?07

fiSO

?m

7 00

hlM

7,00

9 23

Model P180 Includes 2-100' spools #28 AWG wire wrap wire

Supplies insul. pingandpreci

Model P180

$24.50

REPLACEMENT WRAP BIT forPISOSlit N Wrap No. P180A $12.95 each

Replacement wire-wrap wire for P180 #28 AWG (pkg ot 31 $2.75 each

W2B-2-A green W28-2-B red

W2S-2-C clear W2a-2-D blue

INSTRUMENT/ CLOCK CASE

IniectJon molded unrt. Complete with red Oe;el

$3.49

CPU 8080A CPU

MICROPROCESSOR COMPONENTS

8212 8214 8216 8224 8228 8251 8255

8-8it Input/Output Pfionty Interrupt Control Bi-Directional Bus Driver Clock Generator/Driver System Controtler/Bus Driver Prog Comm. Interlace Prog Periph. Interlace

$29.95 CDP 1802 CPU

10,95 Z80 CPU

4.95 3650 MPU

7.95 MC6800 MPU

4.95 MC6810API 126 x 8 Static Ram

5.95 MC6820 Penph. Interlace Adapter

5.95 MC6821 Periph, Interface Adapter

9.95 MC6830L8 1024x8 Bit ROM

10-95 MC6850 Asychronous Comm. Adapter

S19.95 24.95 26.50 19 95 5.95 7.95 11.50 14.95 14,95

[The Incredible "Pennywhistle 103"

25B

2101

2102

2107/5280

2111

?112

2114

2)14L

2114-3

21UL-3

7489

aioi

21L02 74200 9342!

FUM'S

1 Static X 1 Dynamic 4 Sialic « T Static I 1 Dynamic : 4 Static I 4 Sialic 1 Slatic 450n5 1 Sialic 450ns Low Power 1 Static 300i!s 1 Static 300(15 Low Power 4 Sialic [ 4 Static (4 Static 4 static

S ! 49

MK4027 (UPD4U) 1 MK4116iUPD416| 1 TMS4044-45NL 4

DYNAMIC 16 PIN DYNAMIC 16 PIN STATIC

"STna

2513(2140) 2513(3021) 2516 MM5230N

1802M !80M 2e50M

ROMS

Characlei Generator (upper case] Cli a racier Generator (lower case) ChariCier Generator 2048 Bil Read Only Memory

USER MANUALS CDP1S02 Manual 2S0 Manual 2650 Manual

1702A

5203

B2S23

82S115

B2S123

743287

2708

2716 T.I

2716 Intel

6301-1

6330-1

;41li6 7418H

MM5013N

MM5016H

MM5017N

2504T

:?518

■^519

2522

2534

2525

2527

2528

2529

2048 X 204B « 32x8

16K

PROMS

Famous

Famous

OpenC

Bipolar

Tristdte

Static

EPROM

EPROM

EPflOM

Ui Stme Hi(jc)..(; j6 I 1 Onen C Bmnij'

12 > ' ni Ocen CoHecioi

56 1 1 TTL Open Collaaor

SHIFT REGISTERS 1024 Bit Accumulator Dynamic 500/512 Bil Dynai-ic Dual 50O,'5l2 eit Uvnamic 1024 Dynamic Hex 32 BiI Sialic net ■lO Bii Static Dual t.i: Bil Siaik' 512 Oynamtf 1024 Dynamic Dual 256 Bit Static Qua' 250 Static Dual 24n Bit SUlic OuaU 80 'in Static 1024 Static Fito" 4X4 Rflgistfi'

UARTS 3QK BAUD

S 5 95

TELEPHONE KEYBOARD CHIPS

Ay-5-9100 $14 95 flY-5-9200 14 95 Ay-5-9500 4 95 Ay-5-2376 14 95 HD0165 7 95

74C922 9.95

SPECIAL REQUESTED ITEMS

(CM CHIPS

ICM7045 E24.95 ICH7205 19 95 ICM7207 7 50

ICM7208 19.95 ICM7209 6 95

NMOS READ ONLY MEMORIES

MCM6571 S13M) MCM6574 13 5(1 MCm57^ 13 50

MISCELLANEOUS

MC3061P 'jICUOBI ' "1[;i-lU8L8

PARATRONICS

Logic Analyzer Kit Model 100A

$229.00/kit

pV GAME CHIP SET

I AY-3-3500-1 Cliia:intl 2.01D MH2 Crystal $7.9S[

95H90 s:'-- 00 .'set

I I I I I

1111 • «■« 1

Analy/es any type ot digital system

Cfi'-'ci'^ data rates in excess o( 8

million words per second I Trouble Stiool TiL. CMOS, OIL. RTL

Schonky and MOS tamilies . Displays 16 logic states iiplo 8 digits wide I See ones and zeros displayed on your

CRT. ocial 01 hrtxadpctmal \o«"'^t

■ Tests circuits unOei acr'jai ope-aling conditions

■ Easy to assemble — comes with step-by-step construction manual which includes 80 pages on logic analyzer operation.

(Model 100A Manual ■ $4 951

,»^r'|^t1HiP""»

Some applications are

- Troubleshooting microprocessor address, mstruction, and data flow

~ Examine contents ot ROMS

- Tracing operation of control logic

- Checking counter and shift register operation

- Monitoring 1/0 sequences

- Veritying proper system operations during testing

PARATRONICS TRIGGER EXPANDER - Model 10

Adds 16 additional bits. Provides digilsl delay aid qualilication of input cl and 24-bit trigger word, — Connects direct to Model lOOA for integrated ui

I 1G Kit - S229.00

Ba»plate - S9 95

Model 10 Manual

3Vi-Dlglt Portable DMM

• OverloaO Protected

• 3 high LED DiSDlay

• 8aMerv or AC oppralion

• Aiilo 7e;oiny

• lin-j IVa 0 I Cfiin ffiSolulrO'i

• Ovtiange ifdding

• 10 meg input impendence ■ DC Accuracy l-o typical Rang*s; DC Voltage - 0-lOOOV AC Voliage O-lMOV

Freq Responw 50-400 h2 DC/AC Current 0-lOOmA ResislacCB 0-Ki meg ohm Size 6 ■: .44 < ?

Accessories: AC Adapter BC-28 S9.Q0 Rechargeatile

Batteries BP-28 20.00 Carrying Case LC-28 7.50

"95

100 MHz 8-Digit Counter

20 Hz-100 MHz Range , four power souces, i e

battenes ' 10 or PZOV witn

* charger l?V w tti auio

lighter adaqter and eiteinal

7,2-lOV power supply

"'x-io" $134.95

• 6' LED Display

■ CrystaI-cpntrolled timet

• Fully Aulomatie

■ Portable — completely self-contained

« 5 63'

ACCESSORIES FOR MAX 100:

MotillB Chargar Eliminator

use power Iron) car bahery Model 100 — CLA S3.9S

Charger/Eliminator

use 110 V AC Moilel 1D0 - CAI S9.35

63-Key Unencoded

I KEYBOARDS I

Hexadecimal Encoder

This Is a 63-key, terminal keyboard newly manufactured by a large computer manufacturer. It is unencoded with SPST keys, unattactied to any kind ot PC board. A very solid molded plastic 13x4" base suits most applica

tion. IN STOCK $29.95/each

19-key pad includes 1-10 keys, ABCDEF and 2 optional keys and a shift key. $10.95/each

$5.00 IVIinimum Order - U.S. Funds Only California Residents - Add 6% Sales Tax

Spec Sheets - Ki

I978A Catalog Avallable-Ssnd 3S<stamp

JSameco

PHONE

ORDERS

WELCOME

(415) 592-8097

MAIL ORDER ELECTRONICS - WORLDWIDE

1021 HOWARD AVENUE. SAN I:ARL0S. CA 94070

Advertised Prices Good Tliru July

$129.95

Kit Only

The PennywlHStle 103 is CKRshle ol recorrlmg ^nXi to ana Trom audio laps withDu: nilical soeeil requireinenls lor tue fetonler and il is able lo roinmiiincate liracHv with another modern and teminal lor teleptione tiamimnq snri coimmitiicabon; toi ttie deal In addition, it is free ot critical aHju^lieiits am is tiiiill with non-precision readily availaQle parts Data Transmlnian Method . ,Frequency Shitl Keying Itill-ilupiex ihallOuole'

selecJaDtei

MaKimum Data Rata 300 Baud

Dala Format , , Asynctironous Seiial netufn to 'nsrlt level lequnei

hetween eacb cbaracteri Receive Channel Freijuencies . .2025 Hz lor space 3?35 Hz lor narK Transmil Ctiaitnel Fteguencies . .Swilcn selectalile Low inornali lQ7fi so^ce

1370 TiatW High 025 spate "i'-'S km fleceivG Sensilivity .46 ilb ti accousiically en..' , i

iio-ninal ftiljustsbie I'O i' t ih n

Receive Frequency Tolerance Oigital Data Inlerlace

to .'ll 'II

.Frequency reterence auion^licaiiv .t.i|.isls

alio* 'or opeiation belwee'i 1800 h/ rfiti ?.lf)D H .EIA RS-33?C or ?Q ■nA cufiRm iQOi t'Bi'KWi

opioisolaled and iion w\fu

120 VAC single Dhasf! 1

..All c

I All c

■ipotie

■myle b

R"qiiiie . fl V0^^ Audio Oscillator fieguency Goiintef and O' QscHmscope te

the 3

rd

Hand

$9.95 each

'Leaves two hands 'ree (nr

working * Clamps on edge ot bench, lable

or work bench ■ Position board on angle or flat

position fo' --oldenng or clipping ' Slufrty .-^iii tii'ium consfr^'Ciion

tor hobbyist, -nanulacturer or

.school rooms

DIGITAL STOPWATCH

■ BNgni 6 Digii LEO Display

• rtmes 10 S9 minutes 59 59

• CfVEtai Controlled Time Ba't

■ Tfiree StopwatcWs m One

limes Single Event — Split S Tiyii .Sim4 5 t? 15 « 90 i4';ounceii

• Uses 3 Penlite Cells

Kit - $39.95

Assembled — $49.95 Heavy Duly Carry Case$5.95

Stop Watch Chip Only (7205) (19 95

3y2DIGIT DPM KIT

W

j^W

New Bipolar Unit • Auto Polarity

• Auto Zeroing • Low Power

. .5" LED • Single IC Unit

Model KB500 DPM Kit $49.00

Model KB503 5V Power Kit $17.50

JE700 CLOCK

MAN n I] h 1] f "lout diid

KIT ONLY $16.95

JE803 PROBE

Ifie Lo:|i{, Prnlif .s ,i unit *ni( ri iv fo' tne -tiosi p.ir' indesoenjibte m irouDie ihooliig logic lamiiips ni DH RlL CMOS It de'ivc'; tne oowei n needs to oceiale directly o't ol ine riicuil unoei tesi dia*inija scani 10 mA mai- ituses^MANi readDui to indicate any n' trie toiiowinq slates 3^ tnesesymUois 'Hi i iiOWi mPuLSl' P Tus Probe can dPiect niQ*! ttpauenr-y ouise<. m 45 Mh? II c?r> I tip used ,11 MOS Ipvci-, ii

$9.95 Per Kit

printed circuit board

VI 5V 1A Supply

This IS a standard HL oowf supply uS'ing tbe well knni LM309K regulator ^CtoproviOeasoltO 1 AMPo'curreniai volts We try to make things easy lot yoo by p'Ovidn everyttiing you nepc! in one package including Ihe Itanlwa

'"°°' JE225 $9.95 Per Kit

PROTO BOARDS

PROTO BOARD 6

S15.95

[6 long X 4 wide)

wnHnnninmi

PROTO CLIPS

14 PIN S4 50

16 PIN 4 75

24 PIN 8 50

40 PIN 13.75>

194 BYTE July 1978

SN7400N SN740m SN7402N SN7403N SN7404N SN7405N SN7406N SN7407N SN7408N SN7409K SN7410N SN74nN SN741;N SN7413N SM7414N SNM16N SN7417N SN7430N

SN7421N SN74Z2N SN7423N SN74Z5N SN7426N SN7427N SNM?9N SN7430N 5N7432N SN7437N SN743SN SN7439N St4744(M SN7441N SN7442f( SN7443N SN7444N SNT44SN SN744eN SN7447t, SN7448M SN74S0N SN74S1N SN74S3N SN7454N SN7459A SN7460N Sn;470N

CD4000 CD4001 CD4M2 C04006 CIM007 CD4009 CO40I0 C04011 CD401? CO4013 CD40)4 CO4015 CD4016 CO4017 CD401B CD4D19 CD4020 CD40J1

C04o;2

C04K3 CO4024 Cn402S CD40?6

74C02

74CM 74C08 7-1C10 74C14 74C20 74C30 74C4! 74048 "IC73

lM3uU»i

LM301H

IM301CN

LM302H

I.M304H

IM305H

LM307CN H

LM30eM

LM308CN

LU309H

LM309K

LM3tKN

LM3ltH

LM3nN

LM317K

LM318CN

LM319N

LM320K-&

LU320K-5 2

LM3raK-12

LM320K-15

LM320K-18

LM320K-24

LM3MT.5

LM3aT-5 2

LM320T-8

LM3!l)T.t2

LM3MT-15

LM320T-ia

LM320T-24

LM323K 5

LU324N

LM339N

LM340K-5

LM340K-6

LM340K-8

LM340K-12

LM340K IS

LM340K-1B

LM340K 24

LM340T-5

7400 TTL

SN7472N

SN7473N

SN?474N

SN7475N'

SN7476N

SN7479N

SN74eON

SN74e2K

SN7483N

SN7485N

SN74B6N

SN74B9N

SN7490N

SN7491N

SN7492N

5N74g3N

SN7494N

SN7495N

SN7496N

SN7497N

SN74tOON

SN74I07N

SN74I09N

SN74116N

SN74121W

SN74122N

SN74I23N

SN74125N

SN74126N

SN74132fc

SN74136N

SN 7414 IN

SN74142N

SN74143N

SN74144N

SN74145N

SN74I47N

SN74t4aN

SN74150N

SN7415tN

SN74I53N

SN74154N

SN74155N

SN74157N

C/MOS

CD402e CD4rr?q CD4030 CO4035 CD4040 CD4041 C04042 C04043 C04044 CO4046 CD4047

ca*tm

CD4049 C04050 CD4051 CD4053 CD4056 CD4059 CD4060 CD4066 CO4068 CP4069

74C00

74C89 74C90 74C93 74C95 74C107 74Ct51 74C154 74C157 7-1C160 74C161

300

2 15

3 ?5 3^5

LINEAR

LM340T 8 ' 25

LM340T 1? 1 25

LM340TI5 1 25

IM340T.16 1 25

LM340T-24 I 25

LM350N 1 00

LM351CN 65

LM370N 1 15

lM3r3N 3 25

LM377N 4 00

LM380N t 25

LU380CN 99

LM381N 1 79

LM382N t 79

NESOIN B 00

NE510A 6 DO

NES29A 4 95

NE531H 3 00

W536T em

NE540L 6 00

NE55DN 1 30

NESSSV 99

NE556 99

NEseoe 5 00

NE56ie 5 00

NES628 5 00

W565H 1 75

NE£fi5N 1 25

NE566CN 1 75

NE567H 1 25

NE567V 99

NE570 10.50

LMr03CN/H 45

LM709H .29

LM709N 29

LM710N 79

LM71IN 39

LM723H 55

LM723N 55

'^B

3N74160N St474161N SN74162N SN74163N SN74164N SN74165N 5NM166N SN74167N SN74170N SN74172N SM74173N SN74174N SN74176N SN74176N SN74177N SN74179N SH74iaON 5N74181N SN74182N SN74t84N SN74185N

SN74iaaN

SN741SeN SN74190N SN74i9tN SK74192N SN74193N SN74194N SN74195N SN74196N SN74197N SN74198N SN74199N SN74200N SN74^51N SM74279N SN742B3N SN74284N SN742B5N SN74365N SN74366N SN74367N SN7436BN SN74390N SN74393N

C04070

CD407I

CO4072

CD4076

CD4081

004082

CO4093

C04098

wet 4409

MC14410

MC144n

MCU4t9

MC14433

UC14506

MCI 4507

MCI 4563

MCI 4583

CO4508

CD4510

CD45n

CD45I5

CD4518

CD4520

CD456

BUGBOOK®

Continuing Education Series

S17.00 par tat

fits Msigncd to

THE S5S nMER APPUCATIONS SOURCEBOOK WITH EXPEWMENTS bf HMirdM. Barlln W3HB

jrjpus

pho'ogrsDfiV.

THIS ifoiurrw Hill intiodura you tD in< tituilous wm c^p — tni inlgpfm Mnntsn diu ttrirunSs dc ind your micocompuU' curiifli loopj. tnil th« RS IIK inlerfKt sbndarii Piniculifly

fT05

■M, Wt4HYJ. MwMui k. IHm Hare IS the tnwli inn puts i all logWu' BesKHs nivmo muctt > (MM ire Dwr imre arc i saxes ol natnmtnis rn lafiy^ tne ruMr comtfatety ItlHOW tna Xidy 10 go BOW cfuo p.n Oy p« and mlroUUMS you 10 ma Miit 60 rmcrocompum arcuils D3fiy un-qua lastt* iniartjcaa syflam It is ^acofimeralafl iha —■ -— "" "■■

KM BUGROOK III

1e 8UDB0OKS I & II

WITi euGBOOK III

IHSTRUCTOH'S MANUAL

Nacasuiv N>i insirucnO'i ol Bugbooii > and i enpanntants suggesnansloitu'lher tMing p dliilil aiedrDflics * musl lo'sal'-laacning im

BUGIDOK V and VI

S19.D0 H' nl

OP AMP MANUAL by Hmird M. Birlln W3HB tg.QO gugbooK vi loun).

at 2S

S3.00 t, OnM ~G Urawi, l>IMr H taqr, JMMhta A. tltM

J^J']? EipanmanS ui i»||m Bacl'omcs aOSOA micnicomouiar prograip WMA mcrocomuula' inlailidng *n intaijiJtBO iMKoacli lo salt tiasic digital g4«c1ron>cs. Dteaaboiriling 3M 8060* mtarlacmgipFognmrning

- —-' - was tfia digital concapW ol BuflboM V into a treMirwni ol

nuKr orogiaipming tnfi interfacing Dalai) 9r Utornarv

T4Cie5

74Ct64 74C173 74C192 74C193 74CI95 74C922 74C923 74C925 74C926 80095

LM733N LM739N LM741CM LM741CN

LM74

)4N

LM747H

LM747N 79

LM748H 39

LM748N 39

LU1303N 90

LM1304N 1 19

IM1305N 1 40

LM1307N 85

LMiSlON 2 95

LM1351N '65

LMI4UN 1 75

l.M145eCN.'M 59

MC1488 1 95

Mcuag t 95

LU1496N 95

LM1556V 1 75

MC1741SCP 3 00

LM2901N 2 95

LM3053 t 50

LM3065N 69 LM3900N(3401| 49

LM3905N 89

LM3909 1 25

MC5558V 1 00

lM7525N 90

LM7SMN 75

80386 495

LM75450 49

75451CN 39

75452CN 39

75453CN 39

75454CN 39

75491 CN 79

75492CN 89

75494CN 89

nC415i 5 95

RC4I94 5 95

RC4195 4 49

OBUO

BD80 mtgi

aisa<nW|i languipt programs

jf tnlanng. 4ebui)gi"9 '"'' storing

U CMOS-M - DESIGNERS PRIMER

AND HANDBOOK Naw axpindad vanion

%t.SO

COMPLETE MANUAL FOR OIGITAL CLOCKS by John Waiu and John Briuks

Famiiidrizes lecnmcis.-i oi riobbyis! *itti basic meones ijemna oigitat cloWs Includes trouWe stiooling gmOes Sasic clijiaclerisiics of clocks, soldefing tBChniques. clock component data sJieeis anfl construclioti tips.

■4LS0O .4LS02 74LS03 74LS04 74LS05 74LS08 74LS10 74LS13 74LS14 74LS20 74LS26 74LS27 74LS2a 74LS30 74LS32 '4LS40 74LS42 74LS47 74LS51 74LS55 ^741573

74LS00 TTL

74LS74 74LS75 74LS76 74LS83 74LSa5 741586 74LS90 74LS92 74LS93 74LS95 74LS96 74LS1D7 74LS109 74LS112 74LS123 74LS132 74LS136 74LS138 74LS139 74LS151

74LS155 741S157 74LS160 74LSibl 74LS16? 74LS163 74LS164 74LS175 74LSI8I 74LS19C 74LS19I 741S192 74LS193 74LS194 74LS195 74LS253 74LS257 74LS260 741.S279 741S367 74LS368 74LS670

XC209 XC209 XC209 XC209

XC22 XC22 KC22 XC22 SSL 22

Green Oiange Veiiow TOO <ha

R«J G'een Vellow OfBoge

DISCRETE LEDS

XC526 )(C526 XC526 XC526 XC526

XC556 XC556 XC556 XC556 XC556 XC556

Green YellOM Oiange

.190" dia

Red 5-SI

Gteen 4 Si

Velio* 4 SI

Oranoe 4/Sl

.085' dis. MV50 Red 6^1

ITT dIa. MV10 Had 4/S1

Fiat

s.'siw

DISPLAY LEDS

MAN 1 MAN 2 MAN 3 MAN 4 MAN 52 MAN 71 MAN 72 MAN 74 MAN 81 MAN 82 MAN 84 MAN 3620 MAN 3630 MAN 3640 MAN 4610 MAN 4640 MAN 4710 MAN 4730 MAN 4740 MAN 4810 MAN 6610 MAN 6630 MAN 6640 MAN 6650

POLARITY

Common Anode-red 5 I 7 DolMitnx-red Common Cainode-red Common Calhode-red Common AnoOa-gteen Common Anode-ret) Common Anode-red Common CatlwdeieO Common Anode-ye I k)* Common Anode-yelUoi Common Cathode-yelkiw Common AnolB-orange Comtnon Anijae-orange • I Common CatMOeHMsnge Common Anode-orange Common Cathode-orange Common Anode-red -i Common Anode-red Common Callwde-'eO Common Anode-yettow Common Anode-orange-D D Common An ode-orange Common Cathode-orange-D Common CaIhoOe-orange ■ Common Anode-ofange

560

TTPE

MAN 6660

MAM 6710

MAN67M

MAN 6740

MAM 6750

MAN 6760

MAN 6780

OL70i

OL702

0L704

DL707

DL741

DL746

DLr47

0L749

01750

DL33B

FN070

fND359

fND503

FN0507

50B2-7300

5082-7302

5082-7304

5082-7340

POLAMTV

Common Caltiode-orange Common Anode-red-D.D Common Anode-reO * 1 Common Calfwde-red-O D Common CathoiJe-red • 1 Common Anode-red Common CattvxJe-red Common Anode-red =1 Common Cattiode-red Common CatHde-red Common Anode-red Common Anode-feO Common Anode-reO t i Common AnoOc-red Common Cathode-red = 1 Common Caihode-red Common Cathode-red Common CattMKJe Common Anode Common Cathode (FNDSOO) Common Anode (FN0510I 4 X 7 Sgl DIgit-RHDP 4<7Sgl. Digil-LNDP Oyerrange cti,iracier (-11 4 t 7 Sgl Oigil'Hexadecimai

RCA LINEAR

CA3013 2.15 CA3082 2 00

CA2023 2.56 CA3083 160

CA3035 248 CA3086 85

CA3039 1,35 CA3089 3.75

CA3046 1 30 CA3130 1 39

CA3059 3 25 CA3140 1 25

CA3060 3 25 CA3160 1,25

.85 CA3401 49

2.00 CA3600 3.50

CA3080 CA3081

CALCULATOR CHIPS AND DRIVER

FCM3617 S5 00

MM5-25 2 95

MM5736 t 95

MM573B 295

OMa864 2 00

DM8865 1 00

75 75 7 95

CLOCK CHIPS

WIRE-WRAP KIT — WK-2-W WRAP . STRIP . UNWRAP

• Tool tor 30 AWG Wire

• Roll ol 50 Ft, White or Blue 30 AWG Wire

• 50 pes eadi r , 2 , 3 « 4 lengths pre-stnpped wire

$12.95

WIRE WRAP TOOL WSU-30 WRAP • STRIP • UNWRAP $6.95

WIRE WRAP WIRE — 30 AWG

25 ft. mm, $1,25 50ft $1,95 100 ft $2.95 lOOOtt $1500 SPECIFY COLOR — White - Yellow Red - Green - Blue - Black

WIRE DISPENSER — WO-30

• 50 f1, roll 30 AWG KYNAR wire wrap wire $3.95 63.

• Cuts wire to desired length

• Stnps 1" of insulation Specify — Blue-Yellow-Whtte-Red

REPUCEMENT DISPENSER SPOOLS FOR WD 30

Specify blue, yellow, white or red $1.98/ipool

MM5309 MM53n MM531? MM5314 UM5316 UM5318 MM5369 MU5841 7001

14 Din ST S27

16 Din SI 30

IB Din ST 35

?4 pin ST 49

: SOLOERTAIL — LOW PROFILE (TIN) SOCKETS

I so 1M ' ^4

20 OTW 28 pin LP 45

27 36 pin LP 60

30SOLOERTAIL STANDARD (TIN) ^o d" lp 63

28 pin ST S 99

9374 - /-segmenj liti driver

40 pin SI SOLOERTAIL STANDARD (GOLD)

J^ 40pinSG 1

WIRE WRAP SOCKETS (GOLD) LEVEL #3

35 ^^^^^ I^HI D'h WW

50 PCS

ASST. 1 ASST. 2 ASST. 3

RESISTOR ASSORTMENTS $1.75 PER ASST.

66 OHM 82 OHM 100 OHM 120 OHM 150 OHM

ISO OHM 220 OHM 270 OHM 330 OHM 390 OHM

470 OHM 560 OHM 680 OHM 820 O™ 1K

1 2K 1 SK 1 8K 2 2K 2 7K

3 3K 3 9K 4 7K 5 6K 6 8K

lOOK 270K

330K 620K 2 2M 5 6M

ASST. 8R Includes Resistor Assortments 1 -7 (350 PCS,)

1/4 WAH 5% 50 PCS

1/4 WAn 5% 50 PCS

1/4 WAH S% SO PCS.

U4 WAH i-x. 50 PCS.

1/4 WAH 5% MPCS.

1/4 WATT 5% 50 PCS.

1/4 WAn S% SOPCS.

$9.95 ea.

$5.00Minimum Order- U.S. Funds Only California Residents - Add 6% Sales Tax

Spec Sheets - 2U

1978A Catalog Available-Send 35^ stamp

Jameco IMlisUilsUUS

PHONE

ORDERS

WELCOME

(415) 592-8097

MAIL ORDER ELECTRONICS - WORLDWIDE 1021 HOWARD AVENUE. SAN CARLOS. CA 94070

Advertised Prices Good Thru July

XR2206IU $14.95

Function Generator Kit lincludes chip, PC Boaril antt instructions)

EXAR

XR2206KB $19.95

funclion Generaior t<it (includes alt components 9 C Boarr^ and msimcttons)

XR-L555 $1.50

Micro-Power version ol the popular 555 Timer and directly mtercrianoeable. Dissipates 1/15th ttie power and operates down to 2,7 volts Pertect tor battery operation and CMOS circuits.

XR2242CP $1.50

Precision limmg circuit 'or generating timing pulses in minutes, hours and days or up !o 1 year by using two Reduces cost of time delay circuits. Basic 555 Timer witti built-in 8-bil Counter

4 40

XR205 i 8 40

XR210

XR215

XR320

XRS55

XR556

XR567CP

Xfl567CT

Xfl1310P

XR1468Cfi

XH1438

XR1489 XR1800 XR2206 XR22Q7 Xfl220B Xfl2209 XR2211 XR2212 XR2240 XR2264

KR2556 )(R2567 XR3403 );fi4136 XR4151 XH4194 XR42U,; XR4212 XR4b58 XR4739 XH4741

TYPE

1N746 1N751A 1N752 IN 753 1N7M tN959 irt965B 1N5232 1N5234 1N5235 1N5236 1N456 1N45B 1N4e5A tN4001 1N4002 1M003 1N4004

ZENERS

VOLTS W

3 3 400m

5 1 400m

5,6 400m

6.2 400m

68 400n

82 400m

15 400in

5,6 500m

62 500m

68 500m

7 5 500m

■ DIODES —

PRtCi TYPE

4 1 00 1N4005 4:1 00 1H4006 4'1 00 1N4O07 4/1 00 1N3600 IN4148

RECTIFIERS

VOLTS W

600 PIV 1 AMP 800 PtV 1 AMP 1000 PIV 1 AMP 200m

'1 00

■1,00 m4305

28 1N4734

28 1K4735 ■

28 1N4736

28 1N4738

■1 00 1N4742

75

10m 10m

50 PIV 100 PIV 200 PIV 400 PtV

AMP

AMP AMP

12 100 1N1185

12.'1 00 INllSe

50 PtV 35 AMP

100 PIV 35 AMP

ISO PIV 35 AMP

200 PIV 35 AMP

■JOO PIV 35 AMP

SCR AND FW BRIDGE RECTIFIERS

C36D C3eM 2N2328 MDA 9KI-1

5A @ 400V 600V 6A @ 300V ,2A @ 50V

35A

MOA 980-3 12A@200V

CI0681

MPSA05

MPSA06

TIS97

TIS98

IIS133

TIS135

40409

40410

40673

2N91S

2N2219A

2N2221A

2fl2222A

2N2369

2N236gA

MPS236g

2N2484

2N2906

JN2907

2N2925

MJE2955

2N3053

TRANSISTORS

2N3055

MaE3055

2N3392

2N3398

PN3567

PN3568

PN3569

MPS3638A

MPS3702

2N3704

MPS3704

2N3705

MPS3705

2N3706

MPS3706

2N3707

2N3711

2N3724A

2N3725A

2N3772

2N3B23

2N3903

5.1 00 5/1 00 5/1 00

2N39D4 2N3905 2N390G 2N4013 2N4123 PN4249 PN4250 ^N4400 2N4401 2N4402 2IM403 2N4409 2r«6086 2N5087 2^15088 2M5089 2N5129 PN5134 PN5i38 2NS139 2NS210 2N5449 2NS951

3/1.M 6/1,00 4/1 00

5/1 00 4/1 00 4/t,00 4/1 00

5/t 00 5'1 00 5/1 00

CAPACITOR;

CORNER

10-9!

10 pl 22 pf

47 pt 100 pt 220 pl 470 pt

OOlmt 0022

0O47!Ti« 01 mf

1/35V 15/35V 22/35V 33/35V .47/35V ,68/35V 1 0/35V

100> .03

m^f .05

0047;iF 05

04 03 OVF 05

04 03 022Hf 06

04 03 047,if 06

04 ,035 1«F 12 10Q VOLT MTLAR FILM CAPACITORS

022mt

047mf

10

.07

27

22mt +20% WPPED TANTALUMS (SOLID) CAPACITORS

28 23 17 1 5i3SV 30 26

28 ■>'■. 17 2 2/2SV 31 27

28 23 17 3 3/'25V 31 27

28 ,23 17 4.7/25V .32 28 28 ,23 17 6e/25V .36 31

.28 23 17 10/25V 40 35

28 23 17 15/25V 63 .50

MMIATUflE ALUMINUM ELECTROLmC CAPAaXOftS

47/5CV 1 0/50V

3 3/50V

4 7/25V 10/25V 10/50V 22'25V 22/50V 47/2 47/50V

100/25V 10D/50V 220/25V 220/50V 470/25V ■

iooo/iev

2200r16V

AxiRl LMd

Ridlil Lwd

1 0./I6V 1 0/25V 1,0/50V 4 7/16V 4 7/25V 4 7/50V 10/16V 10/25V 10/50V 47/50V 100/16V 100/25V 100/50V 220/16V 470/25V

Circle 200 on inquiry card.

BYTE )uly 1978 195

Whsl s Sew?

PUBLICATIONS

Literature Available for Individuals Interested in Voltage Control Equipment

New BITS Catalog Offered

The new BITS personal computer publications catalog is now available from BITS, 70 Main St, Peterborough NH 03458. The 13 page illustrated catalog is a comprehensive listing of over TOO personal computing books, all evaluated by the editors of BYTE. The books cover such topics as: fundamentals for the novice and knowledgeable; reference and resource publications; the art of computer programming; programming languages; the computer artist and musician; building your own computer; fun, games and foolishness; and many other areas of interest to the personal computer user. Write for your free catalog."

Circle 598 on inquiry card

Computer Interconnections From Hewlett-Packard

A new application note. Computer Interconnections, describes methods by which Hewlett-Packard HP 1000 computer systems and HP 9825 desktop computers can be interconnected to serve together in a wide range of instrument control measurement and analysis applications. It is available free of charge from Hewlett-Packard. The application note, AN 201-6, describes linking the two computers via different communications techniques: HP-IB (HewlettPackard's implementation of IEEE standard 488-1976), RS 232C and an HP 3070A terminal. Example programs and flowcharts depicting program-to-program communications for ihe different networks are included. Contact Inquiries Manager, Hewlett-Packard, 1507 Page Mill Rd, Palo Alto CA 94304.*

Circle 599 on inquiry card.

Electrical Engineering Fundamentals

A Programmed Review for Electrical Engineering is a review of electrical engineering fundamentals. Its primary emphasis is on solving the type of problems found on the Professional Engineering Examination. Each problem has been selected to illustrate a specific concept. Background material, in the form of tables, formulas, charts and graphs, provides all the necessary information to solve the problems. At least one solution is given for each problem. The book covers all the basic principles of electrical engineering. Special consideration is given to two significant areas: the field of digital logic and the study of engineering economics. An introductory section includes addresses of state licensing boards and guidelines for exam preparation. An extensive bibliography rounds out the volume. The book is written by James H Bentley and Karen M Hess PhD and is published by Van Nostrand Reinhold, 450 W 33rd St, New York NY 10001. The price is $14.50."

Circle 600 on inquiry card.

Hand Portable 10 Channel Printing Data Logger Catalog

A recently published 12 page brochure describing a high resolution printing data logger, Model PDL-10, is available from Datel Systems Inc, 1020 Turnpike St, Canton MA 02021. The PDL-10 offers a simple, low cost approach to measuring, scanning, and logging analog voltages. Ten input channels are provided, along with a 4'/> digit panel meter, a 7 column thermal printer for instant hard copy printout, scan electronics, and a 99 minutes or seconds scan interval clock. Input connections are made through convenient rear panel terminals. This color brochure details electrical and physical parameters, operating instructions, block diagrams, application notes, and ordering information."

Circle 601 on inquiry card.

This 60 page powerstat variable transformer catalog PI 78 consolidates descriptive and technical data on the complete product line. It gives ratings, dimensions, performance curves and schematic connection diagrams in an easy to read format, and includes metric equivalents for universal use and easy reference. For a free copy write to the Superior Electric Company, 383 Middle St, Bristol CT 06010."

Circle 602 on inquiry card

New Software Buyer's Guide

A new publication. Packaged Software Buyer's Guide, is said to include 44 pages of important software information and can be helpful to any businessman who is contemplating purchasing such a system.

The guide is reported to give the prospective software buyer an in depth analysis of the following subjects: how to buy a software package for small business computers; how to buy a general ledger software package; the accounts receivable package; the accounts payable package; the payroll software package; and the inventory control package. Price is $15 from MIC, 140 Barclay Center, Cherry Hill N) 08034."

Circle 603 on inquiry card.

Computer Accessories Catalog

This catalog contains a wide variety of word and data processing supplies and equipment including: magetic tapes, cassettes, cards, cartridges, floppy disks, disk packs, paper tapes, rolls, continuous forms, thermal quiet paper, storage cabinets, containers, racks, reels, vertical format tapes, punches, splicers, automatic winders and more. Available from Computer. Accessories Corp, 21 1 New York Av, Huntington NY 11743."

Circle 604 on inquiry card.

196

)uly 1978©BYTE Publications Inc

S-100

32K STATIC MEMORY BOARD

features:

1. FULLY STATIC - usable with all DMA devices.

2. BUFFERED - with noise suppressed control inputs.

3. MODULAR - populated in Ik Increments.

4. RELIABLE - single source +5V regulator

5. PROM COMPATIBLE - monitors available on request.

AVAILABLE EITHER IN COMPLETE KITS OR ALREADY ASSEMBLED UNITS WHICH HAVE BEEN FULLY TESTED AND BURNED IN.

BARE BOARD $38°°

KIT

ASSEMBLED

8K

J270OO

$296'»

16K

$440«)

$465"

24K

$580M

$6120i>

32K

$695»»

$740«'

niCES QUOTED ARE FOR SOOns MEMORIES KITS MID ASSEMBLED UNITS INCLUDE DOCUMENTATION

DEC* LSI-11 16K MEMORY BOARD

• QBUS—FULLY "BUFFERED AND STATIC NOISE SUPPRESSED

• MODULAR •PROM COMPATIBLE

• ADDRESSABLE TO 128K WORDS

• MAPPABLE IN 4K INCREMENTS

ASSEMBLED,

StN $1199'"'

COMPLETE

"" $110900

LAROeST 4 FASTEST STATIC MEMORY AVAILABLE

SlOO EXPANDABLE MOTHER BOARD

• 8SL0T EXPANDABLE BACKPUNE—in line male and female connectors enable backplanes to be plugged together, or the female may be used In place of an extender board. QUIET—ground plane decouples all signal

lines. RELIABLE—SAE 8100 phenolic body, gold contact connectors.

COMPLETE

$66

00

ASSEMBLED

$8900

UNIVERSAL "U DESIGN" WIRE WRAP BOARDS

ALL BOARDS ARE G 10 GLASS EPOXY HAVE Vcc AND GROUND PLANES. PUTED THROUGH HOLES, 4 GOLD PLATED EDGE CONNECTORS

No. 1 BEST ON THE MARKET MICRO CPU CARD WITH S ISO 8US. 3 ON BOARD REGULATORS FITS ALL STAN DARD IC SOCKET CONFIGURATIONS 1700+ HOLES SI'E 5 ilO »„„„!

$23«

No. 2

UNIVERSAL BOARD FITS 86 PIN

SOCKET mlH 0 10' CONTACT

SPACING MADE BY LEADING COM

PUTER MANUFACTURER AS IN HOUSE'

BOARD 1600+ HOLES

SIZE 4 7/8 <;S/8' 57''

SlOO EHENDER BOARD

wilh connector

A MUST for trouble- , 11 7 95

shooting your Computer boards * A /

BUILD YOUR OWN

LOGIC PROBE

24 TO-92, SMALL SIGNAL DARLINGIONS » • qi: AND 24 LEDS.-ALL FUNCTIONAL only ^4'

MAXI SWITCH KEYBOARDS

UNENCODED MOUNTED ON GIG 6USS EPOXY BOARDSA BUCK METAL FRAME KEEPS KEY SWITCHES SECURELY IN PLACE.

No. 1

-53 key main keyboard -10 auxiliary & cursor control keys -11 key numeric pad Bank of 5 auxiliary power and control, rocker arm switches one of them lights up.

$3995

WIRE WRAP SOCKET CONNECTOR FOR NO. 1 KEYBOARD $295

BUILD YOUR OWN

PAPER TAPE READER

l/IO" CENTER STACKABLE

PHOTO TRANSISTORS

10/$96o

GOLD WIRE WRAP SOCKET STRIPS

MAKE UNIVERSAL END AND SIDE

STACKABLE WIRE WRAP BOARDS

12 PIN„

3 LEVEL 48C

14 PIN,„

2 LEVEl 4gC

3 LEVEL 56c

7 PIN STRIP TOP VIEW

No. 2

'53 key keyboard

1 auxiliary power/control

DPDT rocker arm switch

$29"

BEIGE METAL FRAME MOUNT FOR NO. 2 KEYBOARD $995

SOCKET CONNECTOR FOR NO. 2 KEYBOARD

$29

TTL COMPATIBLE REED RELAY

400 OHMS $149 7/$975

OUR NEW ASCII KEYBOARD

HAS ON BOARD UV PROM, A MAIN KEYBOARD SECTION OF 58 KEYS, A HEX PAD OF 15 KEYS AND 16 MORE PERIPHERAL KEYS. 89 KEYS TOTAL & ASCII ENCODED for only $99"

POWER SUPPLY PARTS

DIODES

EDGE VIEW METER

CHARGE DISCHARGE SCALE READS 20.0,40 MOVEMENT -1-60, I20mA «'OAQ

0 135 OHMS ■^i.*^

4K STATIC RAMS

2114 650ns TMS40454 450ns HM 472114 300ns

600m« J6.25 300nm SIO 95 200mw $11 95

l.a SOCKETS

LOW PROFILE-SOLDERTAIL

8 PIN

14 PIN

16 PIN

22 PIN

24 PIN

28 PIN

40 PIN

GOLD

INLAID

10/11,59

10/11,89 10/J1,99 5/$l,69 5/$l,89 5/J1-99 4/Jl,99

TIN

10/$1,35 10/11,49 10/11,59 5/Jl,49 5/tl,59 5/H,69 4/$l,69

MINIATURE

16 BUnON PADS

4i4 MATRIX ENCODED «>-I 05

$is

lor that pmlessioral loach CARBIDE DMU. Rin For P.C BMIID WORK

ASSORTMENT OF SIZES FROM NO, 55 TO NO, 70

5MIX/J7« 10MIX/$12«9 lOOMIX/JSS"

IN4001 50V al lA IN4003 200V al lA IN4007 lOOOV al lA IN250 GOV al 20A IN3909 50V al 30A

6c 8c 12c 95c J1,Z5

BRIDGES

FAST RECOVERY AVALANCHE BRIDGE IN4436.T 200V al lOA FULL WAVE MINI BRIDGE' WITH TAB PR lOE lOOV al 12A

J425 TERMINALS $3 75

5% ZENERS

IN4733A 5 1V 1« IN4739A 9 1V 1» IN4744A 15V 1»

39c 39c 39c

VOLTAGE REGUUTORS

UA723 VARIABLE 2V to 3 7V 78L05 5V at lOOmA TO 92 340T 6 6V at 1 AMP TO 220

PWSIIC 38c

MEIAL

69 c 3/98C 2;98c

PASS nANSISTORS

MIE3055 lOA PLASTIC 2N3055 lOA TO 3 2N5301 30A TO 3

89c

95c

Jl 95

PROTECT YOURSELF, INSTALL AN ELECTRONIC CROWBAR CIRCUIT IN YOUR POWER SUPPLY CROWBAR SCR C220O 400V at lOA

SI 75

OPTO DEVICES

PHOTO TRANSISTORS

SIMILAR TO FPT 100

4/98c

PHOTO DARUNGTONS

MOTOROLA

4/98c

ULTRA HIGH

SPEED

PHOTO DETECTOR

0 5ns RISE TIME

$3's

EXIREMELY

SENSITIVE

IIGHI ACTIVATED

SCR

t'lggeoble by

flashlight at several tiun (Jred yards

$2»

INFRA RED DETECTOR

ULTRA LOW LEVEL PIV 7V

I ma

$495

HEWLETT-PACKARD

JUMBO-RED

HIGH EFFICIENCY

OH BOARD SUIUS

INDICAIOI

LED

6/$l»o

SOUR CELLS

2ii2cm I30ma

$1" ea. 10/$99(i

LED LAMP

EXTREME WIDE ANGLE VIEWING

3/98C 10/$2«5

GOLD

EDGE CARD CONNECTORS

No. 1 SAC185/2 2

SINGLE ROW, IS PIN CONNECTOR WITH 0 156" CON TACT SPACING

99c i

No. 2

SAC22S/2 2

SINGLE ROW, 22 PIN CONNECTOR WITH 0 156 CON TACT SPACING

99c i

No. 3 2VH31/ICB6

31 SOLDER LUG CONNECTOR WITH 0 125- CONTACT SPACING

99c

HIGH VOLTAGE DIODES

EPOXY 1500V at 1 AMP 10/Jl 99

EG250 2500V at 350mA 95c

HV60EL 6KV at 25iiiA $1 95

SUBMINIATURE 20KV at 100mA S2 95

3-1/2 DIGIT LCD.'s

LIQUID CRYSTAL DISPLAY

No. 1

0 4' CHARACTER

WITH CONI^ECTOR

$6

95

No 2

IMIS MiNIAIUFtI I C D IS IDfAl FOB POCKEl SI?EO INSIRIIMIMS

$395

WIRE WRAP POST

? LEVEL

10 98c 100 17 40

I000'J64 00 3 LEVEL 10 Jl 25 100 $8 60

!000'$7? 00

HI-REL GOLD

WIRE WRAP SOCKET PIN

10/51"

1000/$79«>

LIST PRICE 29c

OP AMPS

SINGLE

709 II

741 1:

DUAL

MC1458

QUAD

LM3900

39c

49c

DIODES

IN9I

IN270

IN914

IN3600

IN4148

15c 12c 15c 15c lOc

TMNSISTORS

2N2222 12c

2N3904 12c

2N3906 12c

2N3053 49c

D/A CONVERTER

SIGNETICS NE5008

$9«

SUB MINIAIURE

CRYSTAL FILHR

455 KHZ

WITH DAIA

$295

NO BACK ORDERS FREE DELIVERY BY UPS <"< ^s orders only

YOUR PARTS OR IMMEDIATE REFUND OR OY SURFACE MAIL, IF SPECIFIED — CALIF, RES ADD 6% SALES TAX

MONEY BACK GUARANTEE (mds and led devices excluded, $20 MINIMUM

FOR UNDER 8 HOUR PROCESSING SEND MONEY ORDER, CERTIFIED OR CASHIERS CHECK, SORRY' WE CANNOT ACCEPT PURCHASE ORDERS. CODS, PHONE ORDERS OR CREDIT CARDS

FOREIGN ORDERS

CANADA PUFRIO RICO U S possessions add us $3 M AIL OTHER ADD U S t' 00

IMMEDIATE SHIPPING ON CHASE MANHATTAN FIRST CITI2ENS CASHIFRS CHECKS S CANADIAN POSTAL MONEY ORDERS

LEDS

YELLOW. GREEN. OR

AMBER

(SPECIFY COLOR)

3/88C

LOS ANGELES (213) 967 46)1

LMN ELECTRONICS

1042 E GARVEY AV, W COVINA CA

(VINCENT & SAN BERDO FWY )

tUE -^ SAT 10 fl - ClOSID SUN i MON

DROP INTO ONE OF OUR LOCATIONS

PORTLAND

1503) 646 4044

WIZARD OF PARTS

8225 SW CIRRUS Dfi BEAVEfiTON ORE (KOU BUS CNTR WASHINGTON SQUARE)

F. Reichert Sales

1110 E. GARVEY AVE. W. COVINA, CA. 91790

DENVER

1303) 573 5214

ELECTRONIC LOLLIPOP

5643 N BROADWAY DENVER, CO il2S & SSIh AVE )

ALL ITtMS SUIIECT TO PRIOR SALE

Circle 207 on inquiry card.

PRICES SUBJECT TO CHAmE BYTE July 1978 197

Circle 247 on inquiry card.

CLjbBrc[m boards

MB-1 MK-8 Computer RAM (not S-100), 4KX8 uses 2102 type RAMs. PCBD only $22.00

MB-3 1702A EROM Board, 4KX8, S-100 swilchable

address and wait cycles, kit less PROMS $58.00

MB-4 Basic 4KX8 ram, uses 2102 type rams S-100

buss. PC board $24.96

MB-6A Basic 8KX8 ram uses 2102 type rams, S-10Q

buss, PCBD $24.95

MB-7 16KX8, Static RAM uses uP410 Protection,

fully buffered. KIT $375.00

MB-8A 2708 EROM Board, S-100. 8KX8 or 16KX8 kit without PROMS $75.00

MB-9 4KX8 RAM/PROt^ Board uses 2112 RAMS or 82S129 PROM kit without RAMs or PROMs ,$72.00 10-2 S-100 8 bit parallel I/O port, % of boards is for

kludging. Kit $46,00 PCBD $24,95

10-4 Two serial I/O ports with full handshaking 20/60 ma current loop: Two parallel I/O ports.

Kit $130. PCBD $24.95

VB-1B 64 X 16 video board, upper lower case Greek, composite and parallel video with software, S-100,

Kit $125.00 PCBD $24.95

Altair Compatible Mother Board, 11 x 11'72 x Vb". Board only . $40.00. With 15 connectors . $90.00

Extended Board full size. Board only $ 9.00

With connector $13.00

SP-1 Synthesizer Board S-100

New Low Price Kit $135.95

82823

$1.50

PRIME

DEVICES

823123

1.50

82S126

1.95

8080A

$11.50

82S129

1.95

8212

3.75

828130

3.00

8214

6.50

82S131

3.00

8216

3.95

MMI6330

1.50

8224

4.00

4N26

.75

8228

6.95

4N27

.75

8251

9.95

4N2E

.75

8255

9.95

LM323

2,96

21L14

8.50

/YfTnC/inc. WAMECO INC.

MEM-1 BKXB fully buffered, S-100, uses 2102 type

rams, PCBD $24.95

Mather Board 12 slot, terminated, S-100, board

only $30.95

CPU-1 8080A Processor board S-100 with 6 level

vector interrupt PCBD $24.95

RTC-1 Realtime clock board. Two independent interrupts. Software programmable. PCBD ..$23.95

EPM-1 1702A 4K Eprom card PCBD $24.95

EPM-2 2708/2716 16K/32K

EPROM CARD PCBD ...$24.95

SHORT MOTHER BOARD Short Version of QM-IA

8 Slots PCBD $25.95

2102AL-2 Prime 260 NSEC $1.70

2102AL-4 Prime 450 NSEC $1,30

2708 Prime (National) $10.00

1702A-6 AMD Prime , $3 50

1702A Intel Not Prime (2US) $2.00

2501B $1.50 1488N $1.50

2502B 1.50 1489N 1.25

2504 1.50 MC4044 2.25

2507V 1.60 8038 3.90

2510A 1.50 5320 5.95

2517V 1.50 5554 1,90

2518B 1.50 5555 2.50

2519B 1,50 5556 2,50

2621 1,50 6055 1,25

2522 1,60 5312 4,00

2525 1,50 MH0026 1,50

2527 1.50 MH0026 1.75

2532V 1.50 MH0028 1.90

2529 2.75 5262 .50

2533V 1.95 2101 3.50

m

419 Portofino Drive San Carlos, California 94070

Please send tor IC, Xistor and Computer parts list

MIKOS PARTS ASSORTMENTS

All piece parts for assembly of Wameco and 8SM PCBD's. All Factory Marketed Parts. Order PCBDs right.

Mikos #1 Parts for MEM-1 PCBD with prime

2102AL-4 450 nsec rams. Less PCBD $105,00

Mikos #2 Parts for CPU-1 PCBD with prime 8080A

8212's and 8214, Less PCBD $62.00

Mikos #3 Parts for MEM-1 PCBD with prime

2102AL-2 250 nsec rams. Less PCBD $128.00

Mikos #4 Parts for QM-IA with super low loss gold

plated connectors. Less PCBD $52.00

Mikos #5 Parts for RTC-1. Less PCBD $40.00

Mikos #6 Parts for VB-1B less molex connectors and PCBD $65.00

82S06

$1.00

8T26

$2.00

82S07

1.00

8T28

2.00

828 50

1.00

8T34

2.50

82S62

1.00

8T37

250

75324

1,50

8T38

2.50

75325

1.50

8T74

1.50

8T01

2.50

eT80

2.50

8T09

1.25

8T90

2.50

8T10

2.50

8T95

2.30

8T13

2.50

8T96

2.45

8T14

2.50

8T97

1.50

8T20

2.50

8T98

2.00

8T23

3.00

8T110

2,00

8T24

2.50

567

1.50

Check or money order only. If you are not a regular customer and your order is large please send eitlier a cashier's check or a postal money order, otherwise there will be a delay of two weeks for the check to clear. All items post paid in the U.S. Calif, residents add 6% tax. Money back 30 day guarantee. We cannot accept returned IC's that have been soldered to. Prices subject to change without notice. $10 minimum order. $1.00 service charge on orders less than $10.

COMMERCIAL GRADE EQUIPMENT- HOBBYIST PRICES!!

TAPE DRIVES

MODEMS AND PHONE COUPLERS

lAMPEX MODEL TMX TAPE DRIVES with built-in NRZl formatter. 806 BPI, 9 track, 12 IPS, 8" reel includes 8 bit CPU controller diagram and 8080 interface instructions. Ideal for microcomputerist who wants back-up mass storage and access to IBM-tvDe svstems via standardized W mag tape.. .3750 •AMCOMP SERIES 2700 TAPE DRIVES: current model, vacuum column control; like new:

(2) MODEL 2749 - 45 ips, 800 BPI, 7-Track, 10" reel $1500

(3) MODEL 2769 - 125 ips, 800/1600 BPI, 9-Track, 10" reel. . .$3000 •TAPE DRIVE FORMATTERS, "Pertec Standard Interface":

(3) AMCOMP SERIES 2900 NRZl/Phase Encoded, 25-125 ips..01500 (1) PICO MODEL 1011, NRZl, 800 BPI FORMATTER/

CONTROLLER for PDP-11 $2000

MODEMS, Full-Duplex, Auto Answer circuitry, by VADIC CORP.

BELL 103 Type (300 Baud) Circuit Card only $75

BELL 103 Circuit Card, Power Supply, Case, Connectors $125

BELL 202 Type (1200 Baud) with Reverse Channel Transmission from $125

DB-25 MALE CONNECTOR + 2 wire cable to Phone Jack $4

PAPER TAPE READER (ADDMASTER 601-1): 150 cps, LED sensors read 5-8 level tapes, bi-directional stepper njotor, includes TTL serial interface

plus 8080 parallel interface instructions. Requires -i-5V & 24V $90

DATATEST PROGRAMMABLE AUTOMATIC CIRCUIT CARD ANALYZER

MODEL 4000A S2000

MODEL 4700 $6000

DIABLO SVSTEMS Spare Circuit Cards for HyType Printer, Series 20 h- 40

Disk Drives; complete but defective or below current revision level, $20

ASai ENCODED KEYBOARD from HyType Termmal, never used $60

TELEPHONE ACOUSTIC COUPLER $30

SELECTRIC TERMINALS

• SELECTRIC I/O TERMINALS (by GTE/INFORMATION SYSTEMS). In' eludes 8080 interface plus software ASCII translation and I/O driver routines 15" carriage, interchangeable type spheres & carbon/fabric ribbons. Built-in modem optional,

MODEL 5541 (IBM Corresoondence Code. 2741-tvDe terminal) $895

MODEL 5550 (Corres. Code w/350 char, line buffer memory + built-in cassette drive for data storage/off-Mne printing/word processing. . '.$1495 MODEL 5560 (ASCII Code, with cassette tape drive) $1495

• IBM SELECTRIC TYPEWRITER with magnets, switches & magnet driver PCB (from GTE/IS Terminal) plus instructions for 8080 printer/driver interface.

Typewriter mechanism complete, cleaned & adiusted $325

Aluminum Case & Power Supply (-I-24V, ±12V, +5V («' 5V) S75

• CONVERT IBM OFFICE SELECTRIC to I/O Typewriter; solenoids, switches, wire harness, magnet driver PCB plus instructions + 8080 Interface Diaa. $150

• IBM PIN-FEED PLATENS for 15" SELECTRICS (13 1/8 pin-to-pin) new $50

• IBM SELECTRIC APL TYPE SPHERES (Specify EBCDic or Correspondence Code), new $15

• FORMS TRACTORS, Moore Variable-width "Form-A-Liner" new $50

for 15" Carriage IBM SELECTRICS used $30

■ DIGITAL CASSETTE DRIVE (from GTE/IS Terminal) 2400 baud, FWD/ REWIND/STOP circuitry, plus tape head, but no read/write electronics. . .$25

■ INTERDATA 8-BIT MINICOMPUTER (Model One), includes full front panel, 4K core memory (16K addressable), plug-in teletype port; optional serial I/O + Tape Drive Controller PCB's.software $300

■ RIBBON CABLE 50 Strand X 4' long terminated with 3M edge connector (.10" spacing) + paddle card $3

• AC LINE FILTER 10AMP RFI (110/230V) with Line Relay + Fuses new$15

Call or write for details, quantity discounts, order forms, AH orders shipped from stock — no back orders, no substitutions. All equipment is shipped insured FOB Palo Alto vuithin 7 days after check clears or COD jprder is received. M/C & VISA cards accepted.

PACIFIC OFFICE SYSTEMS, IXC.

2600 EL CAAIIXO REAL. SUITE 502

PALO ALTO. CAIJF. 94306

Tel: (415) 321 - 3866

90 day warranty against defects in material or workmanship on all used equipment. Full documentation included PLUS interface instructions where indicated. Availability subject to prior sale. Prices may change without notice.

198 BYTE luly 1978

Circle 296 on inquiry cartd.

Close-out Purchase by MiniMicroMart

Save up to 50%

on the famous TDL SMB System Monitor Board

iiu!iua»uiiiiiiiTmTWHmiTmimiii»iiii

TWO SERIAL PORTS, PARALLEL PORT, MONITOR ROM, 2K OF RAM,

AND CASSETTE INTERFACE ON ONE BOARD. FEATURE ARTICLE IN APRIL BYTE

AVAILABLE BARE BOARD, PARTIAL KIT, COMPLETE KIT, OR ASSEMBLED AND TESTED

SMB Bare Board w/const, manual. 05-1002-0 $ 49.95 SMB Board, all IC sockets, addressing and buffering components, ppwer-on jump circuits and

FEATURES

Does power-on jump to monitor

Two fully programmable serial ports (110 to 9600 baud RS232or20-milloop)

Programmable 8-bit I/O port

Provision for 1200-baud audio cassette interface

Provision for 1K or 2K on-board static RAM

Provision for 2K ROM (TDL Zapple Monitor or, with minor changes, one 2708 or 2716 EPROM)

support circuitry for ROM/RAMs 05-2002-1 99.50 SMB Board, same as above but incl. all components

for one parallel/one serial interface05-2002-2 119.50 SMB Complete Kit, incl. parallel port, two serial

ports, audio cassette interface . . 05-3002-0 147.50

SMB Assembled and Tested 05-4002-0 197.50

Zapple Monitor ROM for above .... 05-9002-0 29.95

IK RAM (two EMM 4148's) for above 05-6002-0 29.95 Add $2.00 for shipping and insurance.

RAMS/EPROMS

Prime 2708 EPROMs full spec, 450ns

$9.95 each

EM M4200 4K Static RAMs $10.95 each

T. . 4K Static RAMs

4Kx1 TMS4044's

(as usecJ in Heath boarcis)

$8.98 each

1Kx4TMS4045's

$9.89 each

4Kx1 TMS4027-25's (16-pin)

$3.95 each

CLOSE-OUT SPECIALS

S-100 16K Static RAM Boards

for EMM 4200's (bare boards)

$24.95

S-100 1702 EPROM board

(holds 8 PROMs) complete kit

$49.95

S-100 4K Static RAM Board

Kit(less2102's)

$19.95

ASCII Keyboards

Used surplus

Excellent condition

Control functions

Upper/lowercase

Ready to use

$49.95

Teletypes (used)

- IMMEDIATE DELIVERY

KSR-33's from $495.00 ASR-33's from $695.00

CONTACT US FOR

ADD-ON MEMORY

FOR TRS-80

LOTS OF OTHERS

Write for close-out and surplus catalog for fantastic prices on TV Typewriter III boards and kits, cursor boards, screenread boards for above (can also be used with SWTP CT-1024); also, 25 x 40 video boards, UART boards, and Baudot-to-ASCII conversion boards.

S-100 Prototype Boards

General-Purpose

$18.95

Wire-Wrap Version $19.95

IBM 735 I/O Selectrics (used)

from $395.00

MiniMicroMart, Inc.

Circle 251 on inquiry card.

1618 James Street, Syracuse NY 13203 Phone (315)422-4467

BYTE luly 1978 199

Whafs New?

SYSTEMS

Microprocessor Card for S-100 Bus

INFO 2000 Disk System Upgrades Heatiil<it H8 to Z-80

A complete dlsl< system for tlie Heathl<lt H8 lias been announced by the INFO 2000 Corporation, 20630 S Leapwood Av, Carson CA 90746. The INFO 2000 Disk System is designed to upgrade the 8080 computer to a Z-80 system by replacing the Heathkit 8080 processor board with the INFO 2000

Z-80 disk adapter board. The complete disk system for the H8 computer includes PerSci dual diskette drives, power supply, case, intelligent controller, adapter, cables and disk monitor in erasable read only memory. The adapter board contains the Z-80 microprocessor and all support chips, 7 K of erasable read only memory, 1 K of scratchpad programmable memory for the disk monitor, and all necessary logic for interfacing the disk system to the Heathkit H8. With the addition of the system and installation of its adapter board, the H8 computer can operate in either of two switch selectable modes. One mode enables continued use of the H8 erasable read only memory monitor with the existing Benton Harbor software. The second mode supports the disk monitor, and other software adapted to the system for use with all their disk systems. Cost for the complete system is $2750 with a 90 day warranty. A 5% discount is offered when payment in full accompanies order."

Circle 634 on inquirv card.

Microcomputer System Features Dual Disk Drives

The GNAT-PAC System 9 which integrates the GNAT microcomputer system with dual standard floppy disk drives is now available. With disk storage of up to 1 million bytes, the System 9 is

intended for use in small business applications, communications, or process control. The standard computer hardware includes the 8080A processor, 32 K bytes of programmable memory, 16 K bytes of read only memory with 2 K bytes of programmable read only memory, 4 RS-232 serial lO ports, and floppy disk controller. Dual disk drives provide 500 K bytes of disk storage per drive. The System 9 is packaged in a 10'/2 inch high cabinet (26.67 cm) and includes card rack, fan, 11 slot mother board, RFI line filter, wiring and power supply. Software includes a monitor, loader, disk operating system with assembler, editor and dynamic debugger. FORTRAN, BASIC and other high level languages are available. Price is $5500 from GNAT Computers Inc, 7895 Convoy Ct, Unit 6, San Diego CA 92111."

Circle 635 on inquiry card.

The 6800-CPU microprocessor card for the S-100 bus brings all the advantages of the 6800's architecture to the S-100 user. The software support for the 6800 is now available to the S-100 bus user. For the small business user or personal computer user, this microprocessor card provides full turnkey operation and maximum system compatibility as well as an RS-232 20 mA interface (bps rate selectable with a DIP switch), paper tape reader control. Motorola MIKBUG read only memory operating system, power on reset, on board dynamic memory refresh, slow memory interfacing and three state data, address, and control lines. Prices are $179 in kit form and $269 assembled, burned in and tested. Contact Datatronics, 208 E Olive, Lamar CO 81052.»

Circle 637 on inquiry card.

Single Board Microcomputer Holds 8 K PROM plus 8 K Volatile Memory

The Little Brain I is a microcomputer using the 6802 processor mounted on an

S-100 board which includes as much as 8 K words of ultraviolet erasable read only memory and 8 K words of fully static programmable memory plus an RS-232C channel on a single board. The Little Brain I has on-board voltage regulators, fully buffered address, data and control buses along with a 128 word scratchpad memory. Custom programming services are available. The fully socketed version with a 2 K monitor and debug program and 1 K words of programmable memory sells for $395 and is backed with a one year warranty. Contact BPI Electronics, 4470 SW 74th Av, Miami FL 33155."

Circle 636 on inquiry card.

Ohio Scientific Catalog

Now available from Ohio Scientific is a 1 9 page illustrated catalog detailing a full line of computers, software and hardware for personal and business use. Prices range from $298 for their C2-0 Model 500 which is a complete computer on a board featuring standard 8 K BASIC in read only memory, 6502 microprocessor, 4 K of programmable memory and a serial port up to $3590 for the C3-S1 Challenger 111 System with dual drive floppy, 32 K programmable memory, serial port, cabinets and power supplies. For this free catalog write Ohio Scientific, 1333 S Chillicothe Rd, Aurora OH 44202."

Circle 638 on inquiry card.

200

luly 1978©BYTE Publicilions Inc

FREE PROBES FREE PROBES FREE PROBES

ILM3A 3 dig 1% DC $125.

IlMS.SA ZVi dig .5% DC $147.

IlM40A 4 dig .1 % DC $190.

|lM4A 4 dig .03% DC $227

Rechargeable batteries and charger included

Measures DC Volts, AC Volts, Ohms and

Current

Automatic polarity, decimal and overload

indication > Rechargeable batteries and charger I* Measures DC Volts, AC Volts, Ohms and

Current I* Automatic polarity, decimal and overload I indication I* No zero oNJjustment and no full-scale ohms

adjust

• Battery-operated ~ NiCad batteries; also AC line operation.

• Large LED display tor easy reading without interpolation

■ Sizs: 1.9'Mk2.7'Wk4"0 Parta & iftbor guwanlvad l yav Tilt ataod option % *.»

• Laathwcase

S-100 BUS EDGE CONNECTORS Of*

M5-15 MINISCOPE

ft»cntig—blw Btlfft A Ctingv Unit

15 megahertz bandwidth.

External and Internal trigger.

Time base — ,1 mlcrosec 10 0.5 Sec/dli

sellings •3%.

Battery or line operaiion

Automaric & line sync modes

Power consumclion < 15 watls.

Ilinga i 1%

11

PROBE 1«

PROBE IC Mith the

pufchaseo' SCOPE

and the MENTION ol

this MAGAZINE

> MS-21S Dual Trace Version of MS-1S S39S.00 ^ 3 LEVEL GOLD WIRE WRAP SOCKETS

SIOO-WWG 50/100 Cent. 1 26 ctrs 3 LEVEL WIRE WRAP 025' sq posts on 250 spaced rows. GOLD plated

1-4 59 10-24

$4.00 $3.75 $360

S100-STG 50/100 Cont 125 ctrs DIP SOLDER TAIL on 250 spaced rows for VECTOR and IMASI

motherboards GOLD plated.

1-4 5-9 1024

$4.00 $3.75 $3.50

RG81G 50/100 Com. ,125 ctrs. DIP SOLDERTAILon 140 spaced rows for ALTAIR motherboards GOLD plated. $6.00

S100-WWN 50/100 Com 125ctrs 3 LEVEL WIRE WRAP 025' sq posts on 250 spaced rows NASGLO tin nickel plated

14 59 10 24

S3 50 $3 25 S3 00

SIOO-STN 50'100Cont 126 ctrs DIP SOLDER TAIL on 260 spaced rows for VECTOR and trvlASI motherboards NASGLO tin-nickel plated.

14 69 1024

$3 60 $3 25 $300

R681-3 60/100 Com 125 ctrs PIERCED SOLDER EYELET tails GOLD S7 35

Other Popular Edge Connectors

R644-3 22/44 Cont WRAP tails GOLD $471

166 ctrs WIRE

r^rr special

^^r^^y^^^^AACS2 100 for •14"" - ■ 16CS2 100forM6"

14plnCS2 t0lor'2" 16plnCS2 8lor*2" These low cost DIP sockets mil accept both standard width plugs and chips. Foi use witri chips, the sockets offer a lOw pfoliie height of only 125" above the board.

WRAP POST

for 042 dia. holes

(all boards on this page) T-44pkg 100 S 2.U T-44 pkg

1000 S14.00

A-13 hanflinslallmg

tool S Z.BO

XX)3] A Woodley A^o Sepulveda CAo 91343

TermS( ViSA. MC. BAC check. Money Order. C 0 D . U S Funds Only LA residents add 6% sales tax Minimum orQp $10 00 Orders less than $7b 00 include 10% shipping and hjndlmg. excess refunded. Just in case please'inciude your phone no "Sorry.no over the counter soles" Good thru Aug15. 1978

phone orders welcome (213) 893-8202 oEuanc

ir latest brochure.

lonal inquiries

3/$1.00 An / tin nn

FREE PROBES FREE PROBES FREE PROBES

Circle 304 on inquiry card.

BYTE luly 1978 201

Whsfs New?

2708 and 2716 EROM Programmer for KIM-I

Light Pen Literature Available

A new model LP-316 super high sensitivity light pen for long or different focal distances has been introduced by Information Control Corp, 9610 Bellanca Av, Los Angeles CA 90045. The pen features a finder beam to locate the target, and patented touch sense activation to allow the pen to be held back away from the screen for better visibility. Luminous sensitivity can be adjusted down to 0.5 footlamberts. The LP-316 carries a full year warranty. For more information and a complete catalog of ICC light pens, contact the company."

Circle 645 on inquiry card.

Wide Applications for New 30 MHz Dual Trace Scope

The LBO-520 oscilloscope is a 30 MHz dual trace instrument with a fixed delay line. According to the manufac

turer, it has been designed for applications requiring high accuracy signal viewing, single shot trigger, built-in delay and high sensitivity. It is further reported that the unit has 5 mV sensitivity to facilitate accurate signal viewing from video cameras and other low level sources. The instrument's 1 shot trigger, on both channels, assures instant capture of transient phenomena without guesswork or double takes. A 20 ns per cm sweep capability combined with a rise time of 1 1.7 ns lets the observer view the fastest signals in typical small computer systems with ease. The 120 ns built-in delay line permits easy viewing of the leading edge of a pulse or pulse train for quick determination of signal characteristics. Contact Leader Instruments Corp, 151 Dupont St, Plainview NY 11803."

Circle 646 on inquiry card.

Single Sided Wire Wrap Boards in Metric Sizes

Single sided integrated circuit pluggable wire wrap boards are available in

metric dimensions from Garry Manufacturing Company, 1010 Jersey Av, New Brunswick NJ 08902. Both single sizes (series SMP64) and double sizes (series DMP64) are included in the new line. The SMP64 accommodates 20 16 position integrated circuit chips while the DMP64 size will accept 55 16 position integrated circuit chips. The boards are supplied with either 16 position molded sockets or 16 position patterns of individual socket/terminals for maximum heat dissipation. They are designed to provide wire wrapping terminals on the component side, allowing the wire wrap boards to be spaced interchangeably with standard printed circuit board rack assemblies. The boards are supplied with or without a 64 position right angle lO connector (Garry P/N MPS64-PD). They are available at prices ranging from $2 to $3 per integrated circuit socket position."

Circle 647 on inquiry card.

^m

KM tern

cai

KM KM

K3I

1 11

'4

EM

trm ■m

KM

■M-'--i2m:-^'

3

^^^B>'to U

Optimal Technology Inc, Blue Wood 127, Earlysville VA 22936, announces a programmable read only memory programmer for the KIM-1 microcomputer with provisions for programming both the 2708 and 2716 (5 V only) EROMs. By using the KIM-1 monitor, any programmable memory starting address may be specified up to 65 K. Additionally, any starting address within the address space of the programmable read only memory may be specified along with the number of bytes to be programmed. The programmer has a verify mode which confirms that all bits have been programmed correctly. Completely assembled and tested, the programmer is packaged on a single printed circuit board and the connector is furnished. The program will run on all computers which utilize the MOS Technology 6S0X microcomputer. One and a half lO ports are required. Price is $59.95."

Circle 648 on inquiry card.

New Soldering Flux

The flux is called Spec-Master and is available as a liquid, cored solder, paste solder and soldering paste. It is intended for use where a perfectly clean and safe residue is necessary after only a mild water wash. According to the company, the flux is available in strengths strong enough to solder stainless steel yet safe enough to yield electronically clean surfaces after water washing. It is said to be nonflammable, nontoxic, nonirritating and nonfuming. For further information write: Nokorode Soldering Products Division, M W Dunton Company, POB 6205, Providence Rl 02940."

Circle 649 on inquiry card.

202 luly 19780BYTE Publicilions Inc

POLY PAKS

PACTS wccrsucp

POLY PAKS INTRODUCES THE FIRST MAGAZINE RETAIL STORE FOR THE ELECTRONIC MAIL-ORDER HOBBYIST!

********************************** t "RED** LED READOVrS: t I »low « xoc each t

Sli* D«Mriptton Sale *

.127" MAN-3" Sfoi Jl.OO f

MAN-4* 2 fdi $1.19 1

* Cat. No.

■¥ a 7S1B90 f n TC1503 I a 7tl273 X " 7S3093 Z o 7S3161 X □ 7S3512 ■k Q 7S2949 •{i □ 7S!29S0

id 713483 o 7S2485 f □ 7ft22S6 X 'Common Anodo

MAN-1MAN-72 oquatMAN-74 equal** FND359*FND500* FND507* 727-Dual" 727-DuaI* 747"Common Cathodo

$1.00 $1.19 $1.19 $1X»0 $1.50 $1.50 $2.50 $2.50 $1.95

HEXADECIMAL MICROPROCESSOR n LMlircJ::.%:u^Zper^tlA AND CONTROL r\ jttiK rip-^UtTCy roiir^H^*^ KEYBOARD KIT' Cs^

20keys. 16encoded.4exlernaito «****"«"»"*' •*• * . ^"^

be assigned by user. Output 4 bit "'■■ ^ '"^

binary. Also, an EXCLUSIVE o 4 bit binary/haxadacimal output plus strobe!

FEATURE... 4 leds dispiav the • Newl Improved design! Saves you time!

binary output. TTL/CMOS • Keyboard pre-assemMed onto PC board! compalible. requires +5. - ««. ^

12VDC. Complete kit! Nothing Cat. No. 7»S009 Hexadecimal Kit $34.95

else to buy! With instructions. Cat. No. 755010 Hexadecimal Wlred$39.9S

$ >——»■■■■ ■•■■•••••••••»••■«[

**********************************

DISCRETE LEO'S

6 for $1.19

' . Cat. No.

Description Similar to

Order m multiples o 752135

Jumbo Red MV50S3

i of « of each type! □ 7S1944

Jumbo Yellow XC556Y

D 7S213B

Jumbo Green XC5S6G

njUMBO .34" h ^ 752785

Medium Red XC22

a MEDIUM .24" ^ JJIlS?

■Medium Green XC22G | Micro Red XC209

a MICRO .21" Q 781948

Micro Yellow XC209Y

(T0-18> o 7S2140

Micro Green XC290G

■ COMPUTER IT'Vooo \ GRADE D 13.000

■CAPACITORS^ U:S8S

! Order by C.t. Mo. ' "'JS"

; 7t5U2.ndv.l„.! = JJOJJ

WVCD Sale ■

50 $2.75 a

40 2.25

50 2.75

12 1.50

75 3.95

30 2.S0 ■

30 3.95 ■

li^HIEIIi

KETBOARD& EIVCODER KIT

Cat. No. 755001 KH $69.95

Cat. No. 7S5O02 Wred $7S.OO

Outputs standard 7 bit ASCII; interfaces with most data systems. ■ Uses MOS Encoder ROM! Kejboardpre-asscmbled onto PC board, 2 key rollover, Electronic « 7 led Test Feature! shift lock and carriage return. 4 modes: Normal, control, shift. » ^ ^^^y Iteyboard' ltl'/rV,'^"\'"„';l- Additional.functions can be assigned by user *5 - , Encodes 128 ASCII Characters! 12VDC, 200 ma. Negative or positive logic, jumper selectable ^ |„..rlarP5 with ALTAIR

IMSAI, and more!

LED's display the ASCII code,

e 10 buy! Size: I.T' x 5 1/2 x 1 1/4". S Iba.

■■■>•

Vjwxk Poiver ICs J

3a itjf n ii_H_iDa.]i ir inr.iDanciaG

I l^^\ BRIDGE rectifiers: §

2 AMP 6 AMP 10 AMP 25 AMP Q

PIV («7S1346) (fr7$24S6) (07S2447) (((752273) H

□ 50 $ .59 $ J8 $1.05 $1.20 y a 100 .65 .99 1.15 1.25 Q o 200 .69 1.19 1.29 1.95 t:

] a 400 .89 1.40 1.79 2.95 Q

□ 600 .99 1.69 1.95 3.95 U i □ 800 1.19 1.95 2.25 4.95 H ] o 1000 1.25 2^5 230 5.50 ^ ] Orer by Cat. No. Amperase and VoHase D

OQPnnnaGEXonnnanDiioLDan

5PCCTIIA-TWIST * Twisted pairs of brightly

CABLE

n Cat. No. 753680 48 cond. 2 ft. $1. a Cat. No. 754081 32 cond. 2 ft. $1.98

O-XXK "ouDnnt jLi k laDLir k j ]DnaDi:iCT[XJOCopD[.]ncoiioc kt

RIBBOS CABLE AT THIN PRICES

• Ultra-flat! • 28 AWG!

• Single color! Indexed! Order by Cat. No. 7S3939 and conductors

Cond. Sale

o 20 8 ft. $1.98

n 26 6 ft. $1.98

□ 34 5 ft. 51.98

n 40 4 ft. $1.98

u 50 3 ft. $1.98

Order By Cat. No. 7S3667 & Type No.

Typo Sale

74LS00 $.33

74LS02 .32

74LS04 .35

74LS06 .32

74LS10 .32

74L511 .32

_ 74LS13 .64

D 74LS20 .32

~ 74LS21 .32

74LS22 .32

74LS27 .39

74LS30 .32

74LS32 .39

74LS37 .45

74LS3S .45

74L542 1.19

» L 744.547 .99

* C 74LS74 .49

* C 74LS90 .89 J C 74LS92 .89 J C: 74LS93 .89

* n 74LS109 .58

* a 74LS112 .58 I G 74LS113 .58 J a 74LS114 .49 ********** ***** **** * ** ** ******

Type

Sale

74LS132

1.19

: 74L5138

1.24

74LS139

: 74LS151

1.25

' 74LS153

. 74LS15S

1.2s

' 74LS1G0

1.47

: 74LS161

1.47

: 74LS162

1.47

■ 741.5183

1.47

: 74LS168

1.68

74LS169

1.68

: 74LS173

1.68

' 74LS174

1.05

- 74LS190

1.77

' 74LS191

1.75

: 74L5192

1.75

"^ 74LS193

: 74LS195

' 74LSig7

" 74LS257

1.35

■ 74LS26e

.54

" 74LS366

.66

■ 74L5368

.69

a 74LS390

HAlirDT COMPUTER IHnLTlTESTER

1000 ohms per volt

precision, movement»

diode protected against burnout. Measures DC volts 0-15-160-1000: AC volts 0-15-150-1000; DC current 0-150ma:reaistanceX1000. Sensitivity 1000 ohms/volt AC-DC. Uses penlite cell, not included. Sine 2^/b k .IVi X I^'h'*. Wt. 5 ozfi. Cat. No. 7S3921

»0«00«»»—•■••••••■•••••••••9696»96«

I POLT PAKS "CHIPS" AWAY J I IC ASD CRYSTAL PRICES! I

I Order by Cat No. 794048 and Type No! t

ZType Description *-'- *

• □ICM7205 Stopwatch f DAY3-B500-1 6 TV Games

• □MMSSSO 4'f2 DIgtt DVM

• □8038C Volt Control Osc.

sun • al

aKR2376-139 BCD Encoder Rom IKR2376-ST ASCII Encoder Rom esOMHz Prescaler 350MHz Prescaler Touch Tone Chip Char Gen. (sIm 2513) Freq Counter pair 3h Digit DVM/DMM 60 Hi TImebase IC Timebase Xtal Touchtone Xtal Stopwatch Xtal

1C90DC a95H90DC OMC14410 □ MK2002P O7207A/7208 a|CM7107 □MMS369 □3.579MHz D LOOM Hz □3.2768MHz

—#66•—8»*«690

■6—»>»6 ■••••••—

C-MOS

Type

CD4000

CD4001

CD4002

CD4006

CD4007

CD4O08

CD4009

CD4010

CD4011

CD4012

„ C04013

Q CD4015

a CD4016

~ CD4017

CD40ia

CD4019

CD4020

CD4021

Sale

5.29

.29

1.29

Order By Cat. No. 752320 & Type No. Type Sale

D CD4022 1.19

a CD4023 .29

n CD4024 .79

n CD402S .34

L] CD4027 .69

a CD4028

a CD4029

D CD4030

a CD4033

n CD4035

a CD4040

G CD4041

n CD4042

n CD4046

n CD4049

G CD4066

n CD4071

1.19 .49 1.60

MICROPROCESSORS! memories; SUPPORT!

Order by

ICG800L G 8080A

□ Z80A

□ 8008

□ 1101 o 1103

^ 1702A rJ 2102-Ll

□ 2111 n 2708

11 MK4116 a MK4200P11 n MM5202 n MMS203 n MMS260

□ MMS262

□ 8212

□ 8216

□ 8224 a 8228

□ 8251 a 8255

Cat. No. 7S3459 and type Description 8 bit CPU 8 bit CPU, 2 usee 8 bit CPU CPU

256 X 1 Stat. RAM IK Dyn RAM 256 K 8 EPROM IK X 1 t-o-power RAM 256 X 4 Stat. RAM 8K EPROM 16K Dyn RAM 4K X 1 Dyn RAM, 3S0nsec 2K PROM 2K EPROM IK Dyn RAM 2K X 1 Dyn RAM 8 bit I/O port Bl-dlrect bus driver Clock Gen System cont. Communication Int Periph Inter

Sale

$19.95

11.95

24.95

9.95

.69

1.29

5.95

1.69

5.95

10.95

29SS

3.95

6.95

8.95

.99

.99

3.9S

3.95

4.95

9.95

11.50

11.95 I

SILICON POWER

STVD rectifiers;

Order by Cat. No. Amperage and vottage. 50 AMP (a7S727)

12 AMP PIV (B7S727) D 50 " "" a 100 o 200 G 400 o 600 o SOO

% .29 36 AS

i .75 1.10 1.35 1.75 2J5 2.75

250 AMP (>I7<6SS) »4.95 6.50 7.50 •.SO 10.50 11.50

DIP SWITCHES

Cat. No.

G 75 3668

a 75 3669

G 753021

D 75 3670

n 75 3671

D 75 2677

♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦

□ SN7472 Q SN7473

□ 5N7474 o SN7475 c, SN7476

□ SN7483 ;j 5N7485

□ 5N7486 o SN7490 u SN7492 c SN7493 n SN74107

□ SN74121

□ SN74t23 a 5N74125

□ 5N74132 n 5N74t45

□ SN74151 n SN74153 o SN74154

: SN74157 c SN74161 n SN74164 a SN74174

□ 5N74175

□ SN74181 ^ SN74190

□ SN74191 a SN74192

□ SN74I93 n SN74195 c SN74251

*4444444«

: TTL'S

« Type J

« n SN7400 $C

«. □ SN7401

♦ n SN7402

♦ n 5N7403

♦ a SN7404

♦ o SN7405

♦ a SN7406 I a SN7407 I □ SN7408 « a SN7410 «. □ SN7411

♦ n 5N7413

♦ o 5N7414

♦ 3 5N7417

♦ D SN7420

♦ □ SN7427

♦ n SN7430 I :: 5N7432 i :: 5N7437 i n SN7440 « Li SN7441 « n SN7442

♦ G SN7445

♦ u SN7446

♦ □ SN7447 « □ SN7448

♦ Q 5N7450

♦ n SN7451

♦ a SN7470 ♦♦♦♦♦♦♦♦♦♦♦♦*«

♦♦♦♦♦♦ .26

.49 ♦

.39 ♦

.83 ♦

.89 ♦

.63 ♦

.63 ♦

.93

.88 1.95 ♦ 1.15 ♦

.99 ♦

.83 ♦

.83

.75

139

♦«4444

EECO 10-POSITION BCD THUMBWHEEL SWITCH

l-a-4-M Ut'D encoding: Positions labeled 0-7. F, L. 3 »Or

IF coded for S. L coded for $4. 9 1, While numeriil.f on a black background. Eeco 800 (_] .series. IVa x 1 V4 x V3".<t* Jtt% Cat. No. 753846 91.47

********* LI^£/^P3 *********

Type

□ Cms

M301H. V o LM307H, V, N □ LM308H, V cj LM309K o LM311H, V

GIANT SALE! MICRO-MINI Cat. No. Contacts Sate

TOGGLE SWITCHESo 7|3,36 |Pst 5J^|

» 3A, 125VAC contacts or bettern 755085 SPDT* 139 a Complete with mounting n 754037 DPDT 1.45

hardware! "Center oH

.***i*j;it:?«**:

♦♦♦•♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦♦

: IC SOCKETS :

^ as low as 17^ «>• t

• e Low profile, solder tail. ♦

♦ ti 752123 8pl«minidip$ .17 ♦

♦ n 751308 14 pin dip .19 *

* D 751309 16 pin dip JZ2 T □ 783378 18 pin dip

_._..^************ —.;•»««»»* * ° /»id7» iBptnoip ^9 ^

.******J{Sr'cTHOL* SKINNYTHIMS" J ;»♦♦ ♦♦♦♦♦«:

«Ohiin **^*' ,„.«,lri>.T shi.fl _ ,_, Bt! I

jD lO'/. ■'»"Tn\;ii i>""' "'2'""^ * ♦ MOTHHRBOA

te iK::s fSi-^fc-■';U«i*i5'^*:pi.~X«p."t edge_conne^

«n 2»"D lOK'

M« TS 3863 25 turn upril***- J-r^ _- «

m

IMC 'VPEWEE" ,, BOXER FAN

Quiet!

Oelivera

Audible

n:s^'-s

D S2.50

RD CONNECTOR

106 pins (53 each aide). Use with IMSAI & ALTAIR! 0.J26" pin clrs, goldplated %" wire wrap leads. Open ends, fit wide PC boards. 8 oza.Cal. No. 783987

"MICRO-TONE" 0^88 AUTOPATCH ^^

ENCODER KIT ""

Only 2 l.'» s ! .V8 x i,'2", small

enough t^) mount in a mike! Snap • Complete

action bubble keys contact jn Its own

Features output level control. _,_. _^., ..

xtal controlled d i K i I a 11 y •^"•-*'''W''«*'

synthesized tones, on-chip , Family!

oscillator. Requires 4.5 to 5.5 ^ Frlanos!

VDC. Complete kit! Nothing else

to buyl Wt. 12 oz, •

Cat. No. 754086 hit $26.88 EmerEency!

Cat. No. 754087 wlred$32.9S

I □ LM340T-12V

X D LM340T-15V

« □ LM340K-5V

i a LM340K-12V

« a LM340K-15V

« o LM322N

* a LM324N

* a LM339N

* □ LM377N Z a LM379N

1.19 1.19 1.19 1.19 1.19 1.19 1.19 1.19

1.19 t

1.191 .445 .69* .65 V

1.40 « .39* .22* -29* .42* .29 + .59* .69 X

1A9Z .351

1.19( .69* .75*

1.50«

■-i^^±±*:t****** **

□ LM3S0N a LM381N

□ LM5S5V rj LMS5SV a LM565N o LMS67V L: LM703H

a LM709H. N n LM710N n LM723N n LM741H,V. N D LM747H, N r: LM1458V '- LM1800N I LM3900N 1: LM39009V

LM7S491 ■; LM75492 ;J PA263

10 AMP POWER TAB SCR'S, piv sale TRIACS. QUADRACSrcatHo o !So ^H

SCfl'S 751730 n 200 .88

Order by Cat. No. TRIACS 751448 d 400 1.19

and Voltage QUADRACS 7StS90 g 600 1.59

■■■■■■■■■■■■■■

TRANSFORMER SALE ^^^^

a^of^i

■■■■«■■■

I ;&*"■">« pots- *>*.5o

• Chrome handle and hnoH, **: «> "^

-r?!L!!!!i'*3«08A

Cat. No. n 78 3399 D 75 3814 U 7$ 3412 n 75 4029 ri 7S3875

iXOVAC Primaries

Output V. Al

500m lA 3 00m

Metal encased Open frame Open frame Open frame Isolation

Sate

Each

51.98

52.49

51.95

$2.49

S1.19

■■■■■■■■I

Noi«e ^Level! Sleeve | bearings rated, for lClyea|8^b^e.

XN^WiO Epo%^ Rectifiers

For hTfI andComputersJiSVAC^

Cat. No. n 75 2377

□ 7S2378

□ 7S2379

□ 752380 n 75 2381

□ 752382 D 752383

1N4001 1N4002 1N4003 1N4O04 1N4005 1N4006 IN4007

PIV 50 100 200 400 600 SOO 1000

Price 10 lor $.65 10 for .75 10 lor .85 10 for .99 10 for 1.29 10 for 1.39

10 for 1.49

CATALOG

WRITE POLY PAKS 1978

FOR

FEATURING:

• Computer Components!

• Over 400 Assortments!

• Digital Clocks. DPM's, and Stopwatches!

a H(-FI Stereos-Speakers!

• Solar Energy! Semi's!

• Test Equipment! » Fiber Optics! Plus More n' More!

) COPYRIGHT 1978 - POLY PAKS INC

Terms: Add postatre Rated: net 30 Phone : Wakpfifld. Mass. (617) 245-3829 Retail: 16-18 I'el Carmine St.. Wakefield. MINIMUM ORDER — $6.00

POLY PAKS

P.O. BOX 942-S7

C.O.D'i

rtn P.O. BOX9az-s>7 c:^ LYNNFIELD, MA.

Circle 303 on inquiry card.

BYTE July 1978 203

Circle 353 on inquiry card.

$199.95

AS IS

IBM® Selectric-Based

I/O Writers

Excellent Hobby Printers

$249.95

WORKING & CLEANED

Series 72/731 Heavy Duty 8y2" Flatten

All Solenoids Original Documentation While Supply Lasts

SUPER SALE

These terminals are from a large airline reservation system. They are heavy duty and were under continuous maintenance. The units have been in storage. We make every effort to ensure that all essential parts are included. Most work when plugged in. No warranties are given or implied. Conversion Kits.

1. Conversion instructons, P C board for printer only using software approach $59.95

2. I/O kit makes the unit into a conversational terminal. Instructions, P C board, components for a parallel or RS232 interface. Will work with any IBM terminal $249.95

3. Completely converted unit and assembled interface for I/O using kit $999.95

Card reader by HP with RS232 interface $299.95

Printec line printers, parallel interface $1500.00

Honeywell 516 & 316 mini's, make offer, Cables, used 11 conductor, 100 ft with connectors $9.99

Electronic parts and circuit boards 1/4 lb bag $4,99

Check, Money Order, Cash. Personal checks require 3 weeks to clear. No COD's. Units shipped UPS or PP collect. Prices Net FOB Tulsa

SUPER SURPLUS SALES

P.O. BOX 45944 TULSA, OK 74145 1-918-622-1058

4101 STATIC, ni IMHH «l9i>1 N-MOJ UM

OENERAL DESCRIPTION

P«i1 NumtMr 4«01

ita4KBemicon

ductor random ^

Bccoas memorY ll

organizad as 4096 Vbit words. It it fully static and

' a«ds no clock or rafrash pulsas II raquiraa a

ringia * 5 volt powar supply and is fully TTL com

patibla on input and output tinas. Tha 4601 ia

packaged in a convanient ISpindual-in-lina

package.

FEATURES

■ Singla ^ 5V Powaf Supply

■ 4KX1 Organization

■ Raolacaa 4 t024xl Sialic RAh4a

a Complalaly Static-No Clocks or Rafraah

a 18 Pin Package

a Access/Cycle Times 600 naac mak

■ 250 mw Typical Operating Power

■ Separata Data In and Data Out a TTL Compatible I/O

a Tftree Slate Outputs

a Data Bus Compatible I/O Function

4S04 STATIC, HI IN/OUT 1024i4 N-HOS RAM

GENERAL DESCRIPTION

Part Number 4804 It a 4K semiconductor random access memory organiiedas 1024 4-bii words. It is fully sialic and needs no clock or refresh pulses It requires a Single ' 5 voll power supply and is fully TTL compatible on input and output lines. The 4804 is packaged in a convenient 18 pin dual-m-lme package

FEATURES

■ Single • 5V Power Supply

■ 1Kx4 Organization

■ Replaces 4 1024x1 Sialic RAMs

« Completely Static-No Clocks or Relresh

■ ISPin Package

■ Access/Cycle Times 600 nsec max

• 250 mw Typical Operalir>g Power

• Common I/O Bus

■ TTL Compatible I/O

■ Three Slate Outputs

\Tr/ tPi-tek, inc.

\ >/ 7806 Nwih 27th A«tnue

V Phomix, AriionaSSOSI

INTEGRATED TONE RECEIVER

7806 Noritt 27tli Atranue Pboania, Aritona 85031 16021 8060362

SigiMHo 2S04TA 1024 bit S.R. nwnary (I404A)... .SO

MCM6571PCharacUf GifMrilar 9.^5

MCM6571APCh>ncUfG«Mnlor 9.95

MCI44aai>Tiliphon« Rotary Pulnr tO.S8

MC14419PToud< Pad Convener for 14400 4.2S

MC1441 IP Baud Rata Ganaralor 11.88

MC14412VP CMOS Madam Chip ie.86

MU57109NNumb<r Cruncher Micro 18AS

74C915 7 Segment to BCD Convartar 2.80

74C922 16 Key Kaybaard Encoder 8.35

740923 20 key Keyboard Encoder 8.46

74C925 4 Decade Counter w/latchei 12.00

74C926 4 Decade Counter tw/carry 12.00

740935-1 3'A Digit DVM CMOS ChiD 18.98

IN4003 200V lamp 12/81.00

IN4a04 400 V 1 amp 10/81.00 IN414a Hi Speed Sijnal 15/81.00 1OT/$5.00

D.600 115 V, 100 mA Hi Spaed Signal 20/81.00

D2131 200 V. 2SA Stud SBc

02135 400 V, 2SA Stud 1.00

02138 600 V. 25A Stud 1.S5

D3289R 200 V. 160A Stud Anode S.8S

03909^4 SO V, 46A Fast Recovery 2.00

IN4732A'47A 1W 5% Zaners 4/81.00

13 Assorted Brand New Zener Diodes 1.00

50V 3 amp Epoxy Bridge 79t

200V 30 amp Bridge 2.00

600V 4 amp Epoxy Bridge 1.49

600V 3 amo Stud Bridoe .89

SI-2 2aOV. I.SA Gold Leods 1S/$1.00

01A0030 30V DIAC 10/81.00 VOLTAGE REGULATORS

7a05^060ai2 1S-24TO720 95< 5/84.60

78L05A 12 15 4* 100mA TO-92 Plosflc

78H05KC 5V 5A TO 3

78H12KC 12V 5AT03

78H16KC 15V 5AT03

Lm317K 1.5AArf;usra6/eT0 3

Lm317T 1 SA/<d/u«a6te TO 220

Lm317MP .SAAdiustab/etO-iOi

TL430C Adjustable Zener 7'ft/n* About It

TL497C Siivitching Reg. fit Inductor

RCA CA 3085 100 mA Adjustable

S8.95

4«I1 or 4804 4K RAM's

8/S60.00 16/1100.00

MK5102(N)-5

a Detects all 16 stwKtord OTMF digits

O Rsquires minimum axtemal parts count for

minimum syitw* coat D Uses inexpensive 3.579545 MHi crystal for

rettrvnce a Digital counttr detection with period averaging

insures minimum false response O 16-pin package for hi^ systefn density O Single supply 5 Volts t 10% a Output in either 4-bii binary cod* or dual 2-bit

row/column code D Latched outputs

DESCRIPTION

The MK5102 is a monolithic integrated circuit fabricated using the complententary-symmetry MOS (CMOS) process. Using an inexpensive 3.579545 MHz television colortwrst crystal for refervrKe. the MK5102 detects and decodes the 8 ttandard DTMF frequerKies used in telephone dialing. The requirement of only a single supply and its construction in a 16-pin package make the MKS102 ideal for applicationa requiring minimum size and external parts count.

DETECTION FREQUENCY

OtMri Ml iMn IIO <>ll loiai ntntfllns.

Any iMunai wtH M W cMck, n*t en

50<

9.15

9.15

9.15

, 4.98

3.80

13.95

1.50

9.50

.60

•■mpoiclly ou< o> ilock on an Ham, ■n kKk MMr. it ■>• cannot inip In ] ■ notitiM O' 1M aKMCtM >M«plna «ai Fiin I poftae* MM carfl aiiih ■mien l

I (fitpplnf onty In USA, CanaOa ar iw»k>9 <(irii cUH, ipacUi naiv«>in«, aic • ■capt CanaM an« Manlco) oMlmaM a'

Low Group to

High Group i«

Row 1 - 697 Ht Row 2 - 770 H> Row 3 - 8S2 Hi Row 4-941 Hi

Column 1 - 1209 Hi Column 3 - 1477 Hi

JULY SPECIAL -TIL 31 JULY

MK5I02N-5 $33.00

Spec 40

600 :600 C.T. phone transrormer...$1.50 P. C. BOARD TKMINAL STUIP Motd*d body oncloaAs postivo screw ocfrivotod clomp which will accomodate wire sizes 14-30 AWG. Gvitacts ar>d pins ore solder plated copper. Pins are on .200 in<^ (S.OSmM) for stortdord P. C. mounting. IQAmp rotirig. Compare our prices before you buy.

4pola

TS-2S04

.99

8poU

TS-2508

1.49

12 polo

TS-2512

2.19

0^

204 July 1978 © BYTE PuMiutions Inc

Circle 381 on inquiry card.

S.D. COMPUTER PRODUCTS

AN EMPIRE IND CO

P.O. BOX 28810B

DALLAS, TEXAS 75228

EXPANDABLE EPROM BOARD

16K OR 32K EPROM $49 95 W/OUT EPROM Allows You to Use Either 2708s For 16K ot Eprom or 2716's For 32K of Eprom.

KIT FEATURES:

1 All Address Lines & Data Buffered

2. Quality Plated through P-C. Board Including Solder Mask and Silk Screen

3. Selectable Unit States

4. On Board Regulation Provided

5. All Sockets Provtded W/Board

WE CAN SUPPLY 450As 2708's AT $11.95 WHtN PURCHASED WITH BOARD.

EXPANDORAM

THE ULTIMATE RAM BOARD

32K FOR $475.00

-HSl.OO

. 259.00

367,00

475.00

THE 32K VERSION USES THE MOS

4K LOW POWER RAM KIT The Whole Works - $79.95

Fult Buffered - on board regulated ■ reduced power consumption utilizing low power 21L02-1 500ns RAMS - Sockets provided for all IC's. Quality plated througfi PC board.

I^«*!,.;f.^VA^ .'Ifn" J'^n°..r*^.'^L ^i BOARD TO A MAXIMUM OF 65K

BOUNDARIES AND PROTECTION UTILIZES DIP SWITCHES P t, BOARD COMES WITH SOCKETS FOR 32K OPERATION

SZ81 00 519.00 757.00

995,00

THE 64K VERSION USES THE MOS

TEK MKdlie RAM AND HAS ISK

K tirFPI OF FITHFR BK BOUNDARIES AND PROTECTION &

nrifiK'.; vnilR nPT%N RV MFRF UTILIZES DIP SWITCHES P. C.

?? purchasing" more'RAM JmPS IPrOPE'RMJoN'"'" '°''"' ""

FROM SD COMPUTER PRODUCTS.

LOOK AT THE FEATURES WE HAVE BUILT INTO THE EXPANDORAM!

• NO WAIT STATES REQUIRED

• NO CYCLE STEALING NEEDED

• ON BOARD REGULATION

• CONTROL, DATA S. ADDRESS INPUTS UTILIZE LOW POWER SCHOTTKY DEVICES

• DESIGNED TO WORK WITH Z-80, 8080, 8085. CPU's

ADD $50.00 TO ABOVE PRICES FOR FULLY ASSEMBLED AND TESTED BOARDS

• MEMORY ACCESS TIME IS 375 ns

• MEMORY CYCLE TIME IS 500 n

• POWER REQUIREMENTS ARE:

8 VDC 400 MA DC

18 VDC 400 MA DC

—18 VDC 30 MA DC

• ON BOARD INVISIBLE REFRESH

Low Cost

Cassette

Interface Kit

$19.95

Features Play and record K.C. Standard 2400/1200 Hi tapes, 900 Baud. TTl I/O Compatible, Phase Lock Loop, Both 22 Pin ConneetDt and 8 Pin Moie» Connector. Comes parliilly afisembled OsciMalor and phase lock loop pre luned to K C. Standard. Selector switch sends cassette data ot autiliary input data to mi LEO indicates logic 1 level.

8K LOW POWER RAM $159.95

JLLY ASSEMBLED AND TESTED NOT A KIT isai — AHaif — S-100 Buss compalible, uses io* oowet alic 21L02-500ns tutly butlefeU on board regulated, lalily plated Itirough PC Board including solder mask 0 IS dip s*itcfies tor address seiecl

■Add $30.00 for Q

250ns RAM operation

Z-80 CPU BOARD KIT Complete Kit $139.

:^^jii' '*■

CHECK THE ADVANCED FEATURES OF OUR Z-80 CPU BOARD: Expanded set of 158 instructions, 8080A software capability, operation from a single 5VDC power supply; always stops on an Ml state, true sync generated on card (a real plus feature!), dynamic refresfi and NMI available, either 2MHZ or 4MHZ operation, quality double sided plated through PC board; parts plus sockets provided for all IC's. •Add $10. extra for Z-80A chip which allows 4MHZ operation.

NEW FROM S.D. "VERSAFLOPPY"' KIT

THE VERSATILE FLOPPY DISK CONTROLLER ONLY $149.00

FEATURES: IBM 3740 Soft Sectored Compatible- S-100 BUS Compatible for Z 80 or 8080. Controls up to 4 Drives (smgle or double sided). Directly controls the following drives: 1- Shugarl SA400/4SO Mmi Floppy

2. Shugart SA800/850 Standard Floppy.

3. PERSCI 70 and 277.

4. MFE 700/750.

5. CDC 9404/9406.

34 Pm Connector for Mini Floppy. 50 Pin Connector for Standard Floppy. Operates with modified CP/M operating system and C Basic Compiler. The new "Versafloppy ■ from S.D. Computer Products provides complete control (or many of the available Floppy Disk Drives, Both Mini and Full S\i«. FDI771B-1 Single Density Controller Chip, Listings for Control Software are included in price,

FD 1771B1 CHIP ALONE $39.95

Z80 STARTER KIT LEARN COMPUTERS FROM THE START! SIMPLE, STEP BY STEP LEARNING. CONSTRUCTION, PR0GRAMMi;4G, OPERATION, MEMORIES, INTERFACING, COMPUTING, AND CONTROLLING WITH AUDIO CASSETTE INTERFACE CAPABILITIES. Complete Kit includes: Key board and Display; Z80 Central Processing Unit; Instructions; Operation Manual; Learning GuidesFeatures: Powerful Z80 CPU with 158 instructions • 1024 Bytes (Expandable to 2048 Bytes ON BOARD) of RAM • 2 BiDirectional Input/Output Ports with Handshaking

• Kansas City Standard Audio Cassette Interface for Program Storage • Hexadecimal Keyboard and Display

• Wirewrap area for custom circuitry • S-100 Connector on board tor Memory and I/O Expansion • 2716/2758 PROM Programmer • -'Z-BUG" Monitor ROM (Including: Memory, Port and Register Examine and Change Commands; Breakpoints; Single Step Capability; Audio Tape Load and Dump; Execute user program Commands.) Many more unique features. The best computer educational kit on the market , . . the complete computer and educational package for only (199.00. (Available June 1978)

INTRODUCING THE SBC-100

(The Z-80 Based. S-100 Single Board Computer)

$349.00

FEATURES:

• No Front Panel Needed

• 2-80 CPU (2 or 4 MHZ)

• IK RAM

• 4 ROM/PROM Sockets tor 4K/8K of Memory

• SYNCHRONOUS/ASYNCHRONOUS Serial I/O w.Ih RS 232 and Curreni Loop Inlerface and Software

• Programmable Baud Rate

• Parallel Input Port

• Parallel Output Port

• 4 Channel Timer/Counter

• 4 Vectored Interrupts

RAMS

8/15 95

14 95

8'S4 CX)

MK 4115-8K

74S 200 ■ 256

CPU'S

Z—80 includes manual Z—80A includes manual 8080ACPU6BIT 8008 CPU 8 BIT

PROMS

1702A ■ IK • l,5ui 3.95 or 10/35.

2708 ■ 8K • 450ns 14.95

5204 ^K 7.95

82S129 — IK 2.50

2708U 8K signatics 650ns . . . .9.95

O. E. M. SPECIAL

ASK ABOUT SPECIAL OEM DISCOUNTS ON THE SD COMPATIBLE SET

SDC 100 — SINGLE BOARD COMPUTER

VERSAFLOPPY'" FLOPPY DISK CONTROLLER

EXPANDORAM — 32K RAM

EACH KIT IF PURCHASED SEPARATELY TOTAL S973.00 ORDER ALL 3 KITS TOGETHER FOR

$899.00

Thi» Powerful Threesome Operates Together to Form A Comolete Computer

$349 OO $149 OO $475 OO

for Your System.

Z-80

Programming Manual

IN DEPTH DETAIL OF

THE Z-80 CPU

MICRO-COMPUTER

S. D. SALES SPECIAL $9.95

S.D. NOW HAS SOFTWARE FOR IT'S CUSTOMERS

CP/M DISK OPERATING SYSTEM .

CP M IS a powerful disk operating system which has become an industry standard disk based FORTRAN and BASICS This package includes a CP/M diskette (mmi oi SBC 100/VERSAFLOPPY EXPANtXJRAM board set. Complete documentaljon is n islered trademark of Digital Research Corp . Pacific Grove. CA.

$99.95

t IS compatible with severa full size) adapted for S D ■ eluded ( I CP/M IS a reg

Z-80'DISK BASED ASSEMBLER $69.95

Runs on ANY CP/M based disk system Assembles the official Ziiog-Mostek Mnemonics, Contains ex tensive set of pseudo ops. Available on mini or full size diskette.

VERSAFLOPPY'' CONTROL FIRMWARE . . . $24.95

Provides control for VERSAFLOPPY and boots up CP/M. This runs on Z 80. 8080 or 8085 based computers. Available m 2708 or 2758 prom.

SD MONITOR $49.95

Powerful monitor tor SBC 100 smgle board ■com puters Includes all VERSAFLOPPY control firm ware Comes in 2716 prom. Available in 4-6 weeks

VERSAFLOPPY DIAGNOSTIC PROGRAM . . $24.95

Provides routines which are hetpful m checking out a disk based system Available m 2708 or 2758

COUNTER CHIPS

MK50397 6 Digit tiapsed timer 8 95

MKS02S0 Alirm clocli 4.99

MK50380 Alarm chip 2.95

MK5039S 6 digit up/dn. count. 12.95

MK5002 4 digit counter 8.95

MK5021-Cal. chipsq. root 2.50

*

SUPER FLOPPY SPECIAL

S. D SALES- VERSAFLOPPY S 100 CONTROLLER BOARD PLUS SHUGART SA 400 FLOPPY DISK DRIVE INCLUDING CABLE FOR ONLY

$479.00

*

MICROPROCESSOR CHIPS

8212 ■ 1/0 port

8214 —P.I.C

8216 — Non Invert Bus . . .

8224 — Clock Gen

8226 — Invert Bus

PIO for Z—80 .

CTC (or Z—80

8228 Sys. Controller

8251 Prog. comm. interfact.

8255 prog. prep, intertace. .

8820 Dual Line Recr

8830 Dual Line Dr

2513 Char. Gen

8838 Quad Bus. Recvr, . . . 74LS138N—1/8 decoder 8T97.Hei Tri-State Buffer

1488/1489 RS232

TR 1602B Uart

TR 1863 Uart

FD 17718-1

.3.50 12.95 495 4.95 3.95 14.95 14.95 8.20 10.95 13.50 1.75 1.75 7.50 2.00

1.25 1.50 3.95 8.50 39 95

CMOS

4001 4002 4011 4013 4016 4017 4020 4022 4024 4027

19 19 19 32 32 95 97 97 75 39

4029 4042 4047 4049 4069 4071 4076 14518 14528 14529

!I9 69

1.50 35 23 19 97

1.10 85 85

CALL IN YOUR BANKAMERICARD (VISA) OR MASTER CHARGE ORDER IN ON OUR CONTINENTAL TOLL FREE WATTS LlNEr

1-800-527-3460

Texas Residenu Call Collecl:

214/271-0022

DEALER INQUIRIES INVITEDI

(All prices subject to ctiange wittiout Dnor notice.)

NO CODs. TEXAS RESIDENTS ADD 5% .SALES TAX ADD 5% OF ORDER FOR POSTAGE & HANDLING OR DERS UNDER $10. ADD 75c HAND LINGFOREIGN ORDERS - U. S FUNDS ONLY!

Circle 315 on inquiry card.

BYTE July 1978

205

Unclssaifiei^Ac^B

TRADE: BYTE, volume 1, number 2, good condition, for Dr Dobb's Journal of Computer Calisthenics and Orthodontia, volume 1, number 1, I need the article on NIBL BAS/C for the SC/MP chip. Joe Price, POB 543, Olton TX 79064.

FOR SALE; TRS-80 LEVEL-I BASIC tapes and lists: Star Trek (needs 12 K memory), list $7, tape $9.95: Biorhythm (4 K), list $4.50, tape $7; Lunar Lander (4 K), list $3. tape $5. R Menzies, 7106 Colgate Dr, Alexandria VA 22307.

FOR SALE: ASR 32 Teletype with stand, paper tape punch and reader, documentation; excellent condiiion, $325. David Shorthill, RFD #2, Wells ME 04090. (207) 646-5465.

TERMINAL: Texas Instruments 725, 30 cps, hard copy, built in modem and coupler, rugged portable case. Very quiet, popular professional terminal, $775 plus shipping. Also memory: Solid State Music, 8 K, static, 500 ns (no waits), assembled, works, $150, Wright, POB 7576, Menio Park CA 94025 (415) 854-5678.

FOR SALE: Heathkii computer system. System includes; H8 computer, H9 video terminal, 8 K memory, all standard Heathkit software plus extended BASIC. Completely assembled and tested. Asking $1400. Call or write Paul Randazzo, 37 Maxwell Dr, Wethersfield CT 06109 (203) 529-0530.

WANTED; Back issues of CACM, JACM, and JCCs. W Hutchison, Princeton Arms N 191, Cranbury NJ 08512.

FOR SALE: Shugart SA400 minifloppy disk drive and ten minifloppy disks, $390, (no controller or power supply). Working video interface per February 1976 BYTE, $100. DECwriter keyboard, $50. Power supply, $35. Case, $42. Parts for 6800 processor board including 6800, 2x6810, 2x6820, 2708, wire wrap sockets and support ICs $150. Everything except disk, $310. James Thomas, POB 26, Sandv Spring MD 20860, (301) 774-7686.

FOR SALE: DEC PDP8e modules and peripherals DK8EP, $375. AD8 16 channel A/D $875. DECwriter $1050. Omnibus expanders, power supplies, KL8Es; lots more. Send for list and tell me if you have anything for trade or sale. I will repair any DEC part or build custom interfaces or modules. J Simpson, POB 632, W Caldwell NJ 07006.

FOR SALE: Thinker Toys "Speakeasy" board assembled, RS-232 serial port used, $100. Paul Lamb, 13101 Parson Ln, Fairfax VA 22030.

FOR SALE: The Northstar Users group has over 230 outstanding programs including real estate, investment, business, debugging aids and games, t will copy these public domain disks for $5 per disk plus the cost of a disk (or send a disk). About 15 programs on each disk. For a list of programs and details send SASE to J Dvorak, 704 Solano Av. Albany CA 94706, (415) 527-7730.

Readers who have eQuipment, software or other items to buy, seft or swap should send in a dearly typed notice to that effect. To be considered for publication, an advertisement should be clearly noncommercial, typed double spaced on plain white paper, and include complete name and address information. These notices are free of charge and will be printed one time only on a space available basis. Insertions should be limited to 100 words or less. Notices can be accepted from individuals or bona fide computer users clubs only. We can engage in no correspondence on these and your confirmation of placement is appearance in an issue of BYTE.

Please note that it may take three or four months for an ad to appear in the magazine. ■

FOR SALE Floppy Tape Peripheral complete with 10 board, 8 tapes, new and used. Uses stereo 8 track cartridge. Each cartridge can hold one program per track or 8 per cartridge. Program length limited only by tape length. The used tapes have 5 or 6 programs on each and are included free. They are ready to run and cover Star Trek, Othello, other games and technical programs. Will interface to most microcomputers, schematic included. Will ship UPS. $100, R Mendelson, 27 Somerset PI, Murray Hill NJ 07974. (201) 464 5244.

FOR SALE: Teletype model 33ASR, Excellent condition, $600. ALTAIR 8080a, with 8 K memory, TTY and cassette 10 boards. Factory perfect condition, all MITS, $580. Selectric based typewriter with paper tape RDR/PCH. Nice TTY alternative, $480. All for $1500 Andrew Frankford, 2014 Marietta Av, Lancaster PA 17603, (717) 299-2456.

TELETYPE FOR SALE; (All 8 level ASCII) Model 33ASR (new), $1000, Model 35KSR (new), $1500. Model 35ASR (used, very good), $1500. Model 35 reperf and reader set, $425. Parts for Model 33 and 35 machines, gears, modems. Model 28 Baudot machines. Send SASE for complete list and prices. Lawrence R Pfleger, 2141 N 52nd St, Milwaukee Wl 53208.

PROGRAM EXCHANGE: Programs are now available, in source form, to run on most any home microcomputer. These programs corrte from various sources and are written in BASIC and other languages. In addition, our club needs other programs that you may have developed, making them available to other hobbyists for fun, enjoyment, and practical use. If you can make available such programs we want to hear from you. Please write to us soon. For complete descriptive literature and a list of currently available programs, send $1 to cover copy and mailing costs to: Mikel Home Computing, POB 17105. Irvine CA 92713.

FOR SALE: "Elf" microcomputer trainer, $60 complete. Built from Popular Electronics articles. Carefully wire-wrapped on Vector board; all ICs socketed. Full hexadecimal keyboard in outboard module. Hexadecimal display shows 10 byte and memory address. All modifications fully documented. RCA User's Manual, article reprints, much extra data included. Bob Levine, 32 King St. New York NY 10014.

FOR SALE: MMD-1 by E&L Instruments, $250, Bug Book V included (6 units). Contact (805) 522-5276, after 6 PM.

FOR SALE: BYTE September 75 through December 76 excluding January 76. All in perfect condition. Make an offer. Fred Henry, 104 Heathercreek Dr, Plainfield IL 60544, (815) 436-6111.

FOR SALE: North Star BASIC programs: Correspondence Editor: $5, Stock Market Analysis package: $5, Mailing list and random access package: $3, Spacewar game package: $3, plus; Stock Market data on 30 heavily traded companies on North Star disk. Includes: P/E, price, volume, and percent yield, weekly averages for 1977: only $25 for all 30. Send blank disk, or include $5.25 for disk. Write for complete list. Herbert Schildt, 1007 N Division, Urbana IL61801.

TRADE: 12 slot ALTAIR 8800A with HD power supply plus 10 slot IMSAI for factory assembled Altair 8800B. Both units fully socketed and factory checkout. Ken Roberts, 10560 Main, fel5, Fairfax VA 22030. (703) 591-6008 or (703) 378-7266.

FOR SALE: PORTACOM briefcase ASCII printing terminal w/modem, keyboard, instructions, $595. DEC PDP8es, modules, ASR33s, ham gear, free lists, buy, trade, repair, design also. K2DCY, 11 Squire Hill, N Caldwell NJ 07006.

FOR SALE: Digital Group Z-80 four board system including CPU, 10, TV cassette and mother board assembled. Two 8 K memory boards, one with ICs, both with sockets, unassembled. Complete assembly plans and documentation. Going to college, must sell. $750. Richard Yero, 12323 Algonquin Rd, Palo Park IL 60464 or call (312) 448-2609 after 4:00 PM or weekends.

FOR SALE. Altair 8800a with IMSAI 20A power supply installed in original cabinet. With serial 10 board, Tarbell 1 702A prom board, and 4 to 32 K programmable memory. Everything works 100% and software is included. Tell me what you want and I will quote a price, or make me an offer. For more information call (518) 456-8717 or send SASE to Michael Favitta, 4 Sherwood Forest Rd, Albany NY 12203.

FOR SALE. NCR high speed paper tape punches, 110 V, 60 Hz, used but overhauled about 100 cps (according to technical manual), self-contained cabinet, tape spooling mechanism built-tn, eight tracks, weight 40 lbs. Delivery within 5 weeks after your order comes in (ie: 5 weeks till you have it). Price $200 including freight, collective orders from clubs (minimum 5 punches) $150 per punch plus $100 for freight. Order accompanied by crossed checks should be sent to TIME OUT, Siegfried Manfred Rambaum, Rossdoerfer 44, 6100 Darmstadt, GERMANY.

FOR SALE: Control Data 200 UT remote batch/ interactive terminal, equipped with a 14 inch CRT, 63 character keyboard, 300 CPM card reader, 300 LPM-136 column line printer and 4800 baud communications capability. Complete original service and operation documentation included. Excellent condition, currently under CDC maintenance contract. Contact: Bob Levy or Bob Minor (301) 565-9544 8750 Georgia Av, Silver Spring MD 20910.

FOR SALE: Motorola MEK6800O2 evaluation kit, 8 K Solid State Music Memory board. Includes

4 slot Altair (S-100) extender board, cabinet,

5 V 6 A power supply, Mik-Bug firmware, 8 K (SwTPC) BASIC, 8 K (SwTPC) Text Editor and Assembler, 4 K Tiny Assembler, PCC's BASIC games, (the evaluation module has an integral Key board/Cassette interface) and COMPLETE SYSTEMS/Family Documentation. Must sell! Asking $350 — will take best offer. Amn Trotz, Psc Box 1116, Wurtsmith AFB Ml 48753.

FOR SALE: Lunar Landing simulation program for any Radio Shack TRS-80 computer. On cassette, ready to load. Send check or money order for $7.50 to J Quistgaard, 715 S Alder St, Port Angeles WA 98362.

FOR SALE: Heathkit H-9 video terminal, expertly assembled, $600. Also, box of ten 8 inch Data Packaging (DPI) floppy disks, never used, $50. I pay shipping, Andy Thornburg, 400 E Jackson St, DeSoto IL 62924.

WANTED: Card extender or connector (male and female ELCO PNOO-7015-059-000-002) for DATA POINT 3300-101 59 pin. Cecil T Rutledge, 2726 Sandy Ln. Fort Worth TX 76112.

FOR SALE: Altair 8800B computer with 32 K 200 ns static programmable memory, two serial ports, one parallel port, PROM board, ACR cassette interface, floppy disk drive and controller, panel mounted baud rate switches for fast device change, extended BASIC on cassette, disk extended BASIC, and DOS, along with 30 floppy disks. $5000, Steve Mastrianni, 2952 Mam St, Coventry CT 06238. (203) 742-6727 or (203) 664-2401.

Apple II Software cassette: 16 K Blackjack mutlicolor card display, 2 player paddle input, full Las Vegas rules, optional autoplay by computer, sound effects, documentation included, $10. George W Lee, 18803 S Christina Av, Cerritos CA 90701.

FOR SALE: All issues of BYTE from September 1975 to August 1977. All issues completely intact and in mint condition. Best offer over $60 within one month after ad's appearance. Richard Fermoyle, 7597 NW 73rd Ter, Tamarac FL 33319.

FOR SALE: One Compucotor 8001 color terminal with BASIC SOOT, background color option 32 K programmable memory (8 K for CRT), floppy tape bulk storage. CPU operating system includes memory manipulation and paper tape 10 subroutines. One free serial 10 port. In perfect operating condition, $2995. Contact D Brovwi, (803) 771-6087, 1308 Shirley St. Columbia SC 29202.

206 July 1978 © BYTE Publicitions Inc

VISIBLE

OR

INFRA RED

USED FOR CHARACTER

RECOGNITION FOR

COMPUTERS WITH

EXTERNAL CIRCUITS

MAY BE USED IN

A VACUUM, UNDER WATER, HIGH ALTITUDE

IN MAGNETIC ENVIRONMENT BECAUSE THERE IS NO

HIGH VOLTAGE OR MAGNETIC DEFLECTION

MINATURE SOLID STATE

202 VIDEO CAMERA KIT

FEATURING A. . . 100 x 100 BIT SELF SCANNING CHARGED COUPLED DEVICE

THIS UNIQUE UPDATED CAMERA KIT

FEATURES THE FAIRCHILD CCD 202C IMAGE SENSOR

ADVANTAGES

• IN THE FUTURE WE WILL SUPPLY A

COMPUTER VIDEO INTERFACE CARD

• All clock voltages operate at 6V reguiring no adjustments

• Higher video output signal

• We supply the power board, so only a 5V 1 Amp power source is needed

• The circuitry has been simplified for easier assembly

• Two level TTL output is supplied for interfacing

FEATURES

• Sensitive to infra red as well as visible light

• May be used for IR surveillance with an IR light source

• Excellent for standard surveillance work, because of light weight and small size

• All components mounted on parallel 33/4"x6V2" single sided boards

• Total weight under 1 lb.

SURPLUS CENTRONICS PRINTERS

306

'1,150 *900

^QdQoo ,.„

^^0^M ^^ IVI I We supply all semiconductors,

... ^ . , _i X i boards, data sheets, diagrams.

Add $75. ° to assemble and test resistors and capacitors, and

SMM lens.

Add $2.00 Postage and Handling sorry we do not supply the

case, batteries and 5V supply.

UNIVERSAL 4Kx8 MEMORY BOARD KIT

$69.95

32-2102-1 fully buffered, 16 address lines, on board decoding for any 4 oi 64 pages, standard 44 pin buss, may be used with F-8 & KIM

EXPANDABLE F8 CPU BOARD KIT $99.00

featurint] Fairbug PSU 1 K-ot siaiic ram, RS 232 interface, documentation. 64 BYTE teqis.er

4K BASIC FOR FAIRBUG F8

on naner rai>P $25 00

C/MOS (DIODE CLAMPED)

4001 ■■ IB 4016 - .29 4027 - 37 4053 -• 1.10

4002- ,18 4017 - .90 4028- .80 4055- 1.25

4006- .95 4018- .90 4029- .95 4066- 70

4007 - .18 4019- 37 4030- 33 4071 - .18

4009 • 37 4020 - .90 4036 - .97 4076 - .97

4010- 3? 4021 .90 4042- .65 4518- 1.00

4011 - .18 4022- 90 4046- 1.35 74C10 .22

4012- .18 4023- .T8 4047- 150 74C193 .95

4013- .29 4024- 75 4049- ,34

4015 - .74 4025 ■ 18 4050 - 34

2TO»HK ePROM 1460 nl) $ 9.75

2622 STATIC SHIFT HE6 t 1.95

2513 CHAHACTEH G6N t 6.7B

2B1S HEX 32 BIT SR ..._ ., % 2.20

5203-2K CPROM ^ S 4.60

2102 1 (450ni) S .99

21L02 1 USOnil S 1.26

WM5370 4KXI DYN S 3.4S

MK 40O8P ^ S 1.95

2101 1 254 ■ 4 STATIC • 2.46

2111 1-256 X 4 STATIC t 3.45

2112 1 256 M 4 STATIC „ • 2.76

S2B0/21D7e 4K DYNAMIC BAM .„.. t 4.36

TMS 4060L , $ 3.96

5204-4K "ROM _ „ S10.9&

82S23 „ S 1.95

AY 6-1013 UAHT ^ $ 6.96

B703C TELE DYNE 3 STAGE

eiNAHY a BIT A/D CONVERTER S13.SD

90eOA . . «H.95

AP SOARD5 USED FOR 50LDERLCSS BREADBOAR Dl NG 264L - 128 FIVE-TIE POINT ,,„ cr,

TERMINALS $12.50

212H —POWER BOARD $ 2.50

2248L- 96 FIVE TIE POINT *, „ „„

TERMINALS $10.00

209R - POWER BOARD $ 2.25

IC TEST CLIPS TC-1^~ S4.S0 TC-16 - t4-75

CTS 206-8 ei9hi position dip switch .... $1.90

CTS-206-4 tour position dip swuch . . . .Si.45 LIGHT ACTIVATED SCR'j TO 18. 200V 1A $ 1.10

SILICON SOLAR CELLS 2%" diametef .4V at 500 ma $4.00

FND 359C.C..4"$.50 LED READOUTS

FCS8024 4 digit DL-704C.A. .3" $ .85

C.C. 8" airplay $5.95 DL747C.A. ,6- $1.65

FND 503 C.C, ,5" $ .85 FND 800 C.C. ,8" $1.95

FND 510 C.A. .5" $ .85 FND 807 C.A. ,8" $1.95 DL 704 .3" C.C. $ .85

PRINTED CIRCUIT BOARD

7WATTLD 65 LASER DIODE IR $a95

2N 3820 P FET S 45

2N 5457 N FET $ 45

2N2646 UJT $45

ER 900 TRIGGER DIODES 4' SI.00

2N 6028 PROG UJT S 65

MINIATURE MULTI-TURN TRIM POTS 100, IK, 2K, 5K, 10K. 25K, 50K, TOOK, 200^:. 500K. IMeg, 2Meg, $.75 each 3/$2.Q0

CHARGED COUPLE DEVICES CCD 321 AH2 512 Analog Shiit Register . $95.00

CCD201C 100x100 Image Sensor $95.00

CCD 202C 100x100 Imago Sensor $145.00

VERIPAXPC BOARD $4.00

This board is a 1/16"singla sided paper epoxy board, 4>'j"x6%" DRILLF.D and ETCHED which will hold up to 21 single 14 pin IC's or 8,16 or LSI DIP IC's with busses for power supply connactor,

FP 100 PHOTO TRANS . . . S 50

RED, YELLOW. GREEN or AMBER

LARGE LED's .2" ... 6/$1 00

TIL-nS OPTO-ISOLATOR $ .75

MOLEX PINS 100/$].00

1 ooa/$8 00

10 WATT ZENERS 3.9. 4.7. 5.6. 8.2,

18,22,100,150 or 200V , ea. $ .60

1 WATT ZENERS 4.7, 5.6,10. 12. 15

18 or 22V ea. S .25

MC6860 MODEM CHIP $9.95

MCM6571A 7x 9characiergen ... $10.75

TRANSISTOR SPECIALS

2N6233-NPN SWITCHING POWER $ 1-95 MRF-8(»4a CB RF Transistor NPN $ 1-50

2N3772 NPN Si TO-3 . $ TOO

2N1546 PNP GE TO-3 $ .75

2N4008 PNP yi TO :i S 1 00

2N6056 MPIM Si TO 3 D,iihniHo-i S 1.70 2N5086 PNPSi TO-92 . . . 4/S 1.00

2N3137 NpN Si RF $ .85

2N3919 NPN Si TO 3 RF . --. SI 50

2N1420NPNSiTO54 3/$ 1.00

2N3767 NPN Si TO-66 ... S .70

2N2222 NPN Si T018 . . , 5/S 1 00

2N3055 NPN Si TO 3 ... S .50

2N3904 NPN Si TO-92 . 5/S 1.00

2N3906 PNP Si T0 92 . . . 5'S 1.00

2N5296 NPN Si TO-220 S .50

2IM6109 PNP Si TO-220. ... S .55

2N3638 PNP Si TO 5 5/S 1.00'

^SESEMS

600

.20

».oo

DIP SOCKETS

B PIN .17 24 PIN .35

14 PIN .20 28 PIN .40

16 PIN ,22 40 PIN .60

18 PIN .25

5ANKEN AUDIO POWER AMPS

Si 1010 G 10 WATTS. ... $ 7.80

Si 1020 G 20 WATTS ' . . $15.70

Si 1050 G 50 WATTS $28.50

TANTULUM CAPACITORS

TTL IC SERIES

Silicon Power Rectifiers

PRV 1A 3A 12A 50A 1 ^■fA 241;A

100 06 .14 .30 .80 3 70 s.qq

200 07 .20 .35 1 IS 4.25 6.^0

400 09 25 50 1.40 6.50 9.50

600 11 .30 .70 1 80 8.5Q 12.50

BOO 15 ,35 .90 2.30 10 50 16,50

1000 20 .45 1.10 2 75 12 50 20.00 SAD 1024-B REDICON 1024 stage analog "Bucket

B-^iaade" shift regiitar. $16.95

IN 4148 MN914I 15, Si 00

RS232 DB 25P male $2.95

CONNECTORS D6 ^5S female ... $3.50

REGULATORS

309K $ ,95 340K 12,15

723 S .50 Of 24V. .... $ .95

LM 376 .... $ -60 340T 5, 6, 8, 12 320K 5, 12 15.18 or 24V $ .95

or 15V. .. $1-00 78 MG $1.35

'°Ir^2-4V,... $ .95 ^^ MG $1.35

7400

.13

7445

,65

74151

7401

.13

7446

.68

74153

7402

.13

7447

.58

74154

7403

.13

7448

.68

74155

7404

.15

7450

.15

74157

7405

-13

7472

74161

7406

-16

7473

.28

74163

7407

,20

7474

.28

74164

7408

.18

7475

.45

74165

7409

.18

7476

.30

74170

7410

.13

7480

.31

74173

7411

IB

7483

.65

74174

7412

.13

7485

.87

74175

7413

.36

7486

.28

74176

7414

.60

7490

,42

74177

7416

.22

7491

.58

74180

7417

.25

7492

.43

74181

7420

.13

7493

.43

74190

7425

25

7494

.67

74191

7426

.22

7495

.65

74192

7427

,19

7496

.65

74193

7430

.13

74107

,28

74194

7432

.22

74121

75325

7437

.21

74122

38

74196

7438*

.21

74123

,45

74279

7440

.13

74125

.40

74367

7441

.70'

74126

40

75491

7442

.37

74150

.94

75492

DATA CASSETTES

$

44 Pin Solder Tail .156" Conn.

IVIM 5387AA new clock chip which v drive LED's 1 2/24 hrs., 1 supply & al

NO. 30 WIRE WRAP WIRE SINGLE STRAND 100'$1.40

22UF 35V 5/Sl.OO 47UF 35V 5/S1 00 68UF 35V 5.S1 00 1UF 35V 5,S1 00

2 2 UF 20V5'S1 00

3 3UF 35V 4 S1 00 4.7UF 15V 5,'$1.00

6 8UF 35V 4.S1 00

lOUF 10V $ .25

22UF 25V S 40

15UF 35V 3/$l,00

30UF 6V 5/$1.00

47UF 20V $ .35

68UF 15V $ .50

LINEAR CIRCUITS"

LM30a LM311 LM31S LU319 LM324 LM339 LU 358 LM 370

- 1,26 -2.50 -2-50

ALCO MINIATURE TOGGLE SWITCHES MIA 106 SPOT . .... $ 1.05

MTA 206 DPDT S 1.70

MTA 206 P-DPDT CENTER OFF « i 85

MSD 206 P-DPDT CENTER OFF

LEVER SWITCH $ 1.85

Circle 340 on inquiry card.

BYTEluly]978 207

Feadep Service

To get further information on the products advertised in BYTE, fill out the reader service card with your name and address. Then circle the appropriate numbers for the advertisers you select from the list. Add a 13 cent stamp to the card, then drop it in the mail. Not only do you gain information, but our advertisers are encouraged to use the marketplace provided by BYTE. This helps us bring you a bigger BYTE.

Inquiry No. Page No.

4 Administrative Systems 114 AJA Software 135 Anderson Jacobson 45 Apple Computer 14 Apple Computer 15 AVR Electronics 159 ATV Research 133 Atwood Enterprises 180 Beckian Enterprises 180 Bit Basement 137 BITS82, 83, 87, 110, 133 Buss 112

BYTE Back Issues 146 BYTE Wats Line 103 California Industrial 185 Canada Systems 143 Capitol Equipment Brokers 126 Carterfone 161 Central Data Corp 103 Component Sales 183 Computer Data Directory 110 Computer Enterprises 106 Computer Headware 111 Computerland 33 Computer Mart of MA 1 59 Computer Mart of NJ 144 Computer Mart of PA 144 Computer Resources 159 Creative Software 159 Cromemco 1, 2 T Y Crowell 120 Cybernetic Micro Systems 131 Databyte 123

Digital Equipment Corp 172 Digital Group 19 Digital Research (CA) 143 Digital Research (TX) 187 Digital Research & Engineering 111 Dynabyte 67 ECHOlab Inc 110 Electrolabs 183

Electronic Control Technology 141 Electronic Systems 189 Electronics Warehouse 191 EMM/CMP 118 EMM/Semi Inc 109 Engram Associates Inc 131 Forethought Products 126 Gallaher Research Inc 129 * GFN Industries Inc 79 148 GRT Corporation 22, 23

6 10 14 15 16 17 25 30 31 35 36

39 40 43 84 45 60 61 70 73 75 74 76 76 77 78 80 81 82

90 95 100 101 110 113 115 120 125 130 132 136 137 140 145

Inquiry No. Page No.

149 H & K Computer Corp 140

153 Hamilton Logic Systems 159

155 DC Hayes 119

160 Heath Company CIV, 34

170 Hobby World 1 79

175 IMSAICIII

178 Info 2000 69

73 Information Unlimited 111

179 Integrand 140

180 Integrated Circuits Unlimited 193 183 International Data Sciences 129 185 International Data Systems 104

187 International Technical Systems Inc 159

190 Ithaca Audio 161

193 J & E Electronics 133

195 Jade Company 181

200 Jameco Electronics 194, 195

202 Kel-Amlnc144

207 LMN Electronics 197

215 Logical Services 173

216 Magnemedia 99

217 Manchester Equipment 137 219 McGraw Hill Publishing 75 223 Microcompl59

226 Micro Computer Devices 109

231 Micro Mart 137

235 Micropolis96

236 Micropolis97 240 Microware150 247 Mikos 198

250 Mini Micro Mart 173

251 Mini Micro Mart 199 260 Mountain Hardware 5 265 mpi 127

* MVT Microcomputer Systems 147

273 National Digital Diagnostic 133

275 National Multiplex 73

280 Netronicsl21

283 Newman Computer Exchange 146

285 North Star Computer 7, 21

287 Northwest Microcomputing Sys 169

290 Ohio Scientific Instruments 24, 25, 26, 27 289 OK Machines Tool 113

291 Oliver Advanced Engineering 135

292 Oliver Advanced Engineering 137

293 Osborne & Associates 93

294 Pacific Digital 136

296 Pacific Office Systems 198

297 Page Digital 188

298 PAIA Electronics 108

299 Pentech Inc 137

Inquiry No.

Page No.

301 PerCom Data 29

302 Personal Computing'78 81, 151

* PolyMorphic Systems 13

303 Poly Paks 203

304 Priority I Electronics 201

305 Processor Technology 8, 9, 10

306 Quantum Science Corp 159

307 Quest Electronics 188

308 Rothenberg Information 115

309 Rotundra Cybernetics 137

311 S-100 108

310 ScelbiSO, 31

322 Scelbi/BYTE Primer 95

* Scientific Research 47, 49

312 Scope Data 133

31 5 SD Computer Products 205

313 Seattle Computer Products 105

314 Sherwood Medical 133

316 Michael Shrayer Software 77

317 Siliconix 59

318 Small Systems Services 147

319 Ed Smith's Software 128

320 Smoke Signal Broadcasting 107

321 Smoke Signal Broadcasting 128 330 Software Records 136

335 Solid State Music 11

340 Solid State Sales 207

350 Southwest Technical Products CM

351 Structured Systems Group 17

352 Summagraphics Inc 122

353 Super Surplus Sales 204

355 Synchro Sound 39

356 Synchro Sound 40, 41 360 Tarbell Electronics 43

370 Technical Systems Consultants 37

372 Technico 65

373 Technicon 117

371 Teletek Enterprises 137

374 Terrapin Inc 71

376 Touchstone Associates 137

377 Transition Enterprises 159

378 TransNet Corp 127 381 Tri Tek 204

383 TRS-80 Software Exchange 141

386 US Robotics 137

388 Vandenberg Data Products 142

393 West Coast Computer Faire 51

395 Worldwide Electronics 133

400 Xitexl16

405 Xybek 142

*Correspond directly with company.

mm

BYTE's Cdgcing Moflifon Bex

Article No.

1

2

3

4

5

6

7

8

9 10 11 12 13

ARTICLE

Baker: KIMER: A KIM-1 Timer

Bosen: The Axiom EX800 Printer: A User's Report

Hearn: Top-Down Modular Programming

Hauck: Who's Afraid of Dynamic Memories?

Williams: Antique Mechanical Computers: Early Automata

Loewer: The Z-80 in Parallel

Libes: The First Ten Years of Amateur Computing

Walton: Controlling DC Motors

Reid-Green: A Short History of Computing

Ciarcia: Build a Keyboard Function Decoder

Frenzel: How to Choose a Microprocessor

Williams-Conley: A High Level Language for 8 Bit Machines

Weinstein: How to Get Your Tarbell Going

PAGE

12

28

32

42

48

60

64

72

84

98

124

152

162

Readers Tune In to Ciarcia

The winner of the April BOMB is Steve Ciarcia's "Tune In and Turn On: A Computerized Wireless AC Control System, Part 1," page 114. Second prize goes to Ernest W Kent's "The Brains of Men and Machines, Part 4: The Machinery of Emotion and Choice," page 66. The authors will receive prizes of $100 and $50, respectively.

The BOMB (BYTE's Ongoing Monitor Box) is your way of telling us what you think about the articles in BYTE each month. To cast your votes, see the card on the opposite page."

208 luly 1978 © BYTE Publications Inc

icrocomputer System Solution.

Announcing thelMSAI VDP'40.

Fully integrated video data processor in a single cabinet.

T\vin floppies, professional keyboard, S-100 expansion slots. 24 line by 80 char. CRT, insert/delete, programmable font, protected fields, inverse video.

Handsome flip-top cabinet for easy access. Serial and parallel I/O ports included. FORTRAN IV, Extended and Commercial BASIC.

IMDOS (enhanced CP/M*). r rj

ISAM. . "f r fft:

-ffrr

You've decided you want a microcomputer system—but what to buy? The component system? A computer lx)x here, a CRT lx)x there, a keyboard box here, a floppy disk box there... Messy! The $695 system? But ... no disk; no way to add enough memory ... and, if you could, it's not so cheap anymore, and you still wind up with an expensive box collection anyway. Messy!

The IMSAI VDP-40, a fully integrated Video Data Processing system that, in one handsome package, combines a professional keyboard, heavy-duty power supply, twin mini-floppies, multi-slotted motherboard and 9-inch CRT at a new low price.

System Expansion? The IMSAI VDP-40 was built for you. The extra slots in our

S-100 bus motherboard and heavy-duty power supply allow almost unlimited expansion. Need more RAM? Add up to V2 MByte with our Intelligent Memory Manager and 64K RAM boards. Need more disk storage? A controller option of the VDP-40 will allow you to expand to nearly 5 megabytes! Add a line printer, an IBM-compatible tape drive, a MODEM! IMSAI has them all, with the interfaces and software to make it work for you. The standard of excellence IMSAI places at your disposal at a price/ performance no one else has put together allows you to achieve the full potential of your imagination.

Check us out. IMSAI has what you want and what you need. Visit your dealer or write us directly. Ask about the IMSAI VDP-40 and the entire IMSAI line.

Features and prices subject to change without notice. * CP/M is a trademark of Digital Research Corporation.

The Standard of Excellence in Microcomputer Systems

IMSAI Manufacturing Corporation, Dept. EWN, 14860 Wicks Boulevard, San Leandro, CA 94577 (415) 483-2093

IMSAI EUROPE Europa Terrassen 8 Rue Jean Engling Dommeldange, Luxembourg 43-67-46 Telex: 1428

See us at the NCC Show, booth 2860

Price/Performance no one else has put together.

Circle 175 on inquiry card.

This 8-bit machine,

by itself, is as versatile

as a lot of systems

that include peripherals

orientation allows you an almost unlimited opportunity for growth.

Memory is fully expandable, the 8080A CPU extremely versatile, and with the addition of high speed serial and parallel interfacing you gain the added flexibility of I/O operation with tape, CKT consoles, paper tape reader/punches, and now our new floppy disk systems!

The H8 offers superior documentation including complete step-bystep assembly and operation manuals, is backed by 54 years of Heath reliability, and comes complete with BASIC, assembler, editor, and debug software others charge over $60 for!

H8, simplicity for the beginner, sophistilation for the expert nd at $375* just rigt r you.

the H8 is the only machine in its price class that offers full system integration yet, with just 4K of optional memory and using

I/O Port Display

System Engineered for Personal Computing

Be sure to use coupon on

page 34 of this magazine

to order your FREE

Heathkit Catalog!

only its "intelligent"

front panel for I/O, may be operate

completely without peripherals!

In addition, by using the features of its built-in Pam-8 ROM panel control program, the H8 actually allows you to dig in and examine machine level circuitry.

Responding to simple instructions the "intelligent" panel displays memory and register contents, lets you inspect and alter them even during operation. And for greater understanding, the front panel permits you to execute programs a single instruction at a time. The result is a powerful, flexible learning tool that actually lets you "see" and confirm each detail of H8's inner workings.

If you need further evidence, consider the fact that H8's system

U

Circle 160 on inquiry card.