Now SWTPC offers complete best-buy computer system with $995

Now SWTPC offers complete best-buy computer system with $995

dual minifloppy, $500 video terminal/monitor, $395 4K computer.

$395 ^4K 6800 Computer

T he SWTPC 6800 comes complete with 4K memory, serial interface, power supply,

$995 MF-68 Dual Minifloppy chassis, famous Motorola MIKBUG®

You need dual drives to get full benefits mini-operating system in read-only

from a minifloppy. So we waited to offer a memory (ROM), and the most complete

floppy until we could give you a dependa- documentation with any computer kit. Our

ble dual system at the right price. growing software library includes 4K and

T he MF-68 is a complete top-quality 8K BASIC (cassettes $4.95 and $9.95;

minifloppy for your SWTPC Computer. T he paper tape $10.00 and $20.00). Extra

kit has controller, chassis, cover, power $500 Terminal/Monitor memory, $100/4K or $250/BK.

supply, cables, assembly instructions, two T he CT-64 terminal kit offers these Other SWTPC peripherals include highly reliable Shugart drives, and a premium features: 54-character lines, $250 PR-40 Alphanumeric Line Printer diskette with the Floppy Disk Operating upper/lower case letters, switchable con- (40 characters/line, 5 x 7 dot matrix, System (FDOS) and disk BASIC. (A floppy trol character printing, word highlighting, 75 line/minute speed, compatible with is no better than its operating system, and full cursor control, 110-1200 Baud serial our 6800 computer and MITS/ IMSAI);

the MF-68 has one of the best available.) interface, and many others. Separately $79.50 AC-30 Cassette Interface System An optional $850 MF-6X kit expands the the CT-64 is $325, the 12 MHz CT-VM (writes/reads Kansas City standard tapes,

system to four dnves. monitor $175. controls two recorders, usable with other

--------� computers); and other peripherals now

Enclosed is: __ $250 for the PR-40 Line Printer : and to come.

__ $1,990 for the full system shown above __ $79.50 for AC-30 Cassette Interface 1

(MF-68 Minifloppy, CT-64 Terminal with __ Additional 4K memory boards at $100 :

I

1 I I 1 ^{.-J.L I .}

CT-VM Monitor). __ Add1t1onai8K memory boards at $250 1

t- 1 r::1

__ $995 tor the Dual Minifloppy __ Or BAC # Exp. Date ___ : Products Corp.

__ $325 for the CT-64 Terminal __ Or MC # Exp. Date ___ 1 219 W. Rhapsody, San Antonio, Texas 78216

__ $175 for the CT-VM Monitor Name Address : London: Southwest Technical Products Co., ltd.

__ $395 for the 4K 6800 Computer City State ___ Zip __ 1 Tokyo: Southwest Techmcal Products Corp./ Japan I I Ci rcle 136 on i n q u i ry card.

You can now have the industry's finest microcomputer

with that all-important disk drive

YOU CAN GET THAT ALL-IMPORT ANT SOFTWARE,

TOO

Loading your programs and files will take you only a few seconds with the new Cromemco Z-2D computer.

You can load fast because the Z-2D comes equipped with a 5"

floppy disk drive ahd controller. Each diskette will store up to 92 kilobytes.

Diskettes will also store your pro­

grams inexpensively-much more so than with ROMs. And ever so much more conveniently than with cas­

settes or paper tape.

The Z-2D itself is our fast, rugged, professional-grade Z-2 computer equipped with disk drive and con­

troller. You can get the Z-2D with either single or dual drives (dual shown in photo).

CROMEMCO HAS THE SOFTWARE

You can rely on this: Cromemco is committed to supplying quality software support.

For example, here's what's now available for our Z-2D users:

CROMEMCO FORTRAN IV COM­

PILER: a well-developed and power­

ful FORTRAN that's ideal for scien­

tific use. Produces optimized, relo­

catable Z-80 object code.

CROMEMCO 16K DISK BASIC: a powerful pre-compiling interpreter with 14-digit precision and powerful

1/0 handling capabilities. Particularly suited to business applications.

CROMEMCO Z-80 ASSEMBLER: a macro-assembler that produces relo­

catable object code. Uses standard Z-80 mnemonics.

The professional­

grade microcomputer for professionals

ADVANCED CONTROLLER CARD The new Z-2D is a professional system that gives you professional performance.

In the Z-2D you get our well­

known 4-MHz CPU card, the proven Z-2 chassis with 21-slot motherboard and 30-amp power supply that can handle 21 cards and dual floppy drives with ease.

Then there's our new disk con­

troller card with special features:

• Capability to handle up to 4 disk drives

• A disk bootstrap Monitor in a 1K 2708 PROM

• An RS-232 serial interface for interfacing your CRT terminal or teletype

• LSI disk controller circuitry

Z-2 USERS:

Your Z-2 was designed with the future in mind. It can be easily retrofitted with everything needed to convert to a Z-20. Only $935 ^{kit; or} $1135 ^for

assembled retrofit package.

Cromemeo

Shown with optional bench cabinet

We're able to put all of this in­

cluding a UART for the CRT interface on just one card because we've taken the forward step of using LSI con­

troller circuitry.

STORE/FACTORY

Contact your computer store or Cromemco factory now about the Z-2D. It's a real workhorse that you can put to professional or OEM use now.

Kit: Z-20 with 1 disk drive

(Model Z20-K) .. . . ..^{. . . .}.^. $1495.

Assembled: Z-20 fully assembled and tested (Model Z20-W) .^{. . .} $2095.

Additional disk drive

(Model Z20-FDO) . . . .... ... $495.

SOFTWARE (On standard IBM-format soft-sectored mini diskettes) 16K BASIC (Model FDB-5) .. . . $95

FORTRAN IV (Model FDF-5) . . ..^..^.. $95

Z-80 Assembler (Model FDA-5) .... $95

2400 CHARLESTON RD., MOUNTAIN VIEW, CA ^{94043 •} (415) 964-7400 Circle 40 on inqu iry card.

TV DAZZLER

To make

your computer more useful-

w ..J 0 "' z 0 () �

() � _{"' >-}

I

5! ·�-:�---=:r-'

a wide choice of memory, 1/0, CPU

Your computer's usefulness de­

pends on the capability of its CPU, memories, and 110 interfaces, right?

So here's a broad line of truly useful computer products that lets you do interesting things with your Cromemco Z-1 and Z-2 computers.

And with your S-100-compatible Al­

tairs and IMSAis, too.

CPU

• Z-80 MICROPROCESSOR CARD.

The most advanced ,uP card avail­

able. Forms the heart of our Z-1 and Z-2 systems. Also a direct re­

placement for Altair I IMSAI CPUs.

Has 4-MHz clock rate and the power of the Z-80 ,uP chip. Kit (Model ZPU­

K): $295. Assembled (Model ZPU­

W): $395.

MEMORIES

• 16K RAM. The fastest available.

Also has bank-select feature. Kit (Model 16KZ-K): $495. Assembled (Modei16KZ-W): $795.

• 4K RAM. Bank-select allows ex­

pansion to 8 banks of 64K bytes each. Kit (Model 4KZ-K): $195. As­

sembled (Model 4KZ-W): $295.

• THE BYTESAVER - an 8K capa­

city PROM card with integral pro-

grammer. Uses high-speed 2708 eras­

able PROMs. A must for all com­

puters. Will load 8K BASIC into RAM in less than a second. Kit (Model BSK-0): $145. Assembled (Model BSW-0): $245.

• 16K CAPACITY PROM CARD. Ca­

pacity for up to 16K of high-speed 2708 erasable PROM. Kit (Model 16KPR-K): $145. Assembled (Model 16KPR-W): $245.

1/0 INTERFACES

• F A S T 7-CHANNEL DIGI TAL ­ ANALOG 110. Extremely useful board with 7 AID channels and 7 Dl A channels. Also one 8-bit par­

allel 110 channel. Kit (Model D + 7A-K): $145. Assembled (Model D

+ 7A-W): $245.

• TV DAZZLER. Color graphics in­

terface. Lets you use color TV as full­

color graphics terminal. Kit (Model CGI-K): $215. Assembled (Model CGI-W): $350.

• DIGITAL INTERFACE (OUR NEW TU-ART). Interfaces with teletype, CRT terminals, line printers, etc. Has not one but two serial I I 0 ports and two 8-bit parallel I I 0 ports as well as 10 on-board interval timers. Kit

Cromemeo

Specialists in computers and peripherals

(Model TRT-K): $195. Assembled (Model TRT-W): $295.

• JOYSTICK. A console that lets you input physical position data with above Model D + 7 AID card. For games, process control, etc. Con­

tains speaker for sound effects. Kit (Model JS-1-K): $65. Assembled (Model JS-1-W): $95.

PROFESSIONAL QUALITY You get first-class quality with Cromemco.

Here are actual quotes from ar­

ticles by independent experts: "The Cromemco boards are absolutely beautiful" ... "The BYTESAVER is tremendous" ... "Construction of Cromemco 110 and joystick are out­

standing" ... "Cromemco periph­

erals ran with no trouble whatso­

ever."

Everyone agrees. Cromemco is tops.

STORES/MAIL

So count on Cromemco. Look into these Cromemco products at your store. Or order by mail from the factory.

We wish you pleasure and suc­

cess with your computer.

2432 CHARLESTON RD., MOUNTAIN VIEW, CA 94043 • (415) 964-7400 Circle 40 on inquiry card.

-0

r

1 0 50 68 72 76 80 94 1 46 1 50 1 66

1 8 26 54 1 72

4 6 30 37 38 46

60, 1 97, 2 1 8 66

1 4 5 1 60 1 62 1 70, 1 98 1 90, 220 206 21 1 226 228 256 256

In l:he Queue

Foreground

M E M O R Y MAPP E D 10 Hardware-Ciarcia

USI N G I NTE R R UPTS F O R R E A L T I M E CLOCKS Real Time Techniques-M F Smith DOES A N Y BODY KNOW WHAT T I M E IT I S?

Peripherals-Grappel

A D D I N G AN I NT E R R U PT DRIV EN R E A L T I M E C LOCK Real Time Systems-Sneed

F LOAT I N G P O I N T A R I T H M ET I C Software-Hashizume

B U I L D I N G A COMPUTER F ROM SCRATC H Hardware-Jones

A 6502 P E RSONA L SYSTE M DES I G N : KOMPUUTAR Hardware-Brader

I MP LE M E NTI N G AN LS I F R E QU E NCY COUNTER Hardware-L ynne

SWE ET1 6: T H E 6502 D R EAM MAC H I N E Software-Wozniak

DO YOU N E E D T H E R E A L T I M E ? Real Time Systems- Troll ope

Background

S I M U LAT I ON OF MOT I ON : An I mproved Lunar Lander Algorithm Mode/ling-S P Smith

A M I N I COMPUTER F A I R : T I N Y A N D P E R SONAL Computer Fairs-Piele

SPI KES: Pesky Voltage Transients and How to Minimize Their Effects Hardware-McCain

N I M B L E : HiE U LT I MATE N I M?

Software-Doliner

Nucleus

I n This BYTE

The Compleat Robotics Experimenter Letters

BYT E 's B ugs BOMB Lands on APL

The TRS-80 : Radio S hac k's New Entry Programming Quic kies

My Experiences with the 2650 Ask BYTE

Switching R OMs in the Fairchild F8 Evaluation Kit BYTE's Bits

Tech nical Forum Languages Forum Book Reviews Clubs and Newsletters Classified Ads What's N ew?

B O M B Reader Service

Cover by Bruce Holl oway

BYTE is published monthly by B YTE Publications Inc, 70 Main St, Peterborough NH 03458. Address all mail except sub­

scriptions to above address; phone (603) 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 manu­

scripts or photos. Opinions expressed by the authors are not necessarily those of BYTE. Address all subscriptions, change of address, Form 3579, and fulfillment complaints to BYTE Subscriptions, P O Box 361, Arlington MA 02174; phone (617) 646-4329. Second class postage paid at Peterborough NH 03458 and at additional mailing offices-USPS Publication No.

102410. Subscriptions are $12 for one year, $22 for two years, and $32 for three years in the USA and its possessions. Add

$5.50 per year for subscriptions to Canada and Mexico. $25 f�r a one year subscription by surface mail worldwide. Air deli­

very to selected areas at additional rates available upon request-$25 for a one year subscription by air delivery to E u rope.

Single copy price is $2.00 in the USA and its possessions, $2.40 in Canada and Mexico, and $3.50 in Europe, and $4.00 elsewhere. Foreign subscripti ons and sates should be remilled in United States funds. Pri nted in United States of America.

Entire contents copyright ©1977 by BYTE Publications I nc. All rights reserved.

����

PUBLISHERS Virginia Peschke Manfred Peschke EDITOR IN CHIEF Carl T Helmers I _r PRODUCTION MANAGER Judith Havey

CIRCULATION MANAGER Gregory Spitzfaden ASSISTANT PUBLISHER Debra Boudrieau EDITOR

Christopher P Morgan CO-OP EDITOR Scott Morrow PRODUCTION EDITORS Karen Gregory Nancy Salmon ADVERTISING Debra Boudrieau, Director Noreen Bardsley Virginia Peschke EDITORIAL ASSISTANT Ingrid Nyland

PRODUCTION ASSISTANT Cheryl Hurd

Cl RCULATION ASSISTANT Pamela R Heaslip

CONVENTION SUPERVISOR Elizabeth Alpaugh DEALER SALES Ginnie F Boudricau CLUBS AND NEWSLETTERS David WoLmak

TRAFFIC MANAGER Edmond D Kelly I _r ART

\Vai Chiu Li Ellen ShJmonsky Dorothy Shamonsky SPECIAL PRODUCTS Floyd W Rehl i ng Medellin Stephens EXECUTIVE SECRETARIES Jill Callihan

PatriciJ Clark BOOKS Christopher E Smith RECEPTIONIST jacqueline Earnshaw DRAFTING Douglas Glen Stephen Kruse

Lynn Malo Bill Morello Dorothy Shamonsky TYPOGRAPHY

Custom Marketing Resources Inc Goodway Graphics

PHOTOGRAPHY Ed Crabtree PRINTING Rumford Press

NEW PRODUCTS EDITOR Daniel Fylstra

ASSOCIATES Walter Banks Steve Ciarcia David Fylstra Portia Isaacson

ADVERTISING SALES Southern California:

Buckley/Boris Associates Inc 9¹2 South Barrington Suite 202

Los Angeles CA 90049 (213)826-4621 Northern California:

Jules E Thompson 1 nc Hearst Building Suite 1 1 1 1

San Francisco CA 9 4 1 03 (415)362-8547

BYTE November 1 977 3

In This

I n th is issue, author Steve Ciarcia begins what we expect to become a regular feature in BYTE: Ciarcia's Circuit Cellar. Steve, a senior engin­

eering consul tant to the aerospace industry by profession, is a rare com­

bination of writer and tinkerer. The conceptual model he brings to his interactive column format is that of the late C L Stong's stewardship of

"The Amateur Scientist" in Scientific American, but with an emphasis on hardware and software combina­

tions to accompl ish interesting appli­

cations of personal computing systems. Steve welcomes feedback from readers . . . CH

Games and models wh ich employ moving objects require some attention to details of motion as simulated by a computer program. Beginning a series of articles on the subject of moving objects, Stephen P Smith's Simulation of Motion : An I mproved Lunar Lander Algorithm shows how a real time game can i ncorporate models of motion in more than one d imension.

Donald T Piele shows that a com­

puter fair doesn't have to be big to be good . A Minicomputer Fair: Tiny and Personal descri bes the U niversity of Wisconsin's efforts to produce their own micro extravaganza, which drew over 700 attendees. Readers may get some ideas about putting on shows of their own based on Professor Piele's experiences.

What might not be appreciated by the neophyte is the fact that an interrupt d riven clock suggests other uses besides keeping time. In M F Smith's article on Using Interrupts for Real Time Clocks you 'll find a simple timekeeping algorithm, and a s.ketch of how it can be extended to share processor time between two different processes.

4 ^BYTE November 1 977

Do you occasional ly find incorrect data in you r computer when you know you entered the correct informa­

tion and processed it with <;� rel iable program? Does your computer do strange things every time the washing machine or furnace turns on? Perhaps your problem is vol tage transients.

j ohn McCain writes abou t Spikes:

Pesky Voltage Transients and How to Minimize Their Effects.

If you want to post a calendar of events in your computer's memory with a resolution of 1 second, a mere th ree integrated circu its added to an existing LSI digital clock can turn it into a source of time information for your computer. Use Robert Grappel 's article in this issue to find an answer to the metaphorical question: " Does Anybody Know What Time I t I s?"

Any regular source of interrupts can be used as the key element in a simple real time clock for the typical personal computer. j ames R Sneed shows how to create such an interrupt source, then program a 6502 to gen­

erate internal variables for hours, min­

utes, seconds and 1 /1 5th seconds of the day in his article on Addi ng an Interrupt Driven Real Time Clock.

If you do a lot of mathematical cal culations on your microcomputer, you'll enjoy reading Floating Point 'Arithmetic by Burt Hash izume. Find out how to add an economical floating point package to you r system and improve your number cru nch ing facil ities.

An excellent way to learn about computers is to build one yourself.

Hi lary D j ones shows that this is not such a terrifying task. Read Building a Computer From Scratch and find out h ow to construct a working (a I be it limited) com puter for under $70 (plus the price of a power supply).

Occasionally readers ask for detail plans of computer systems. David Brader, a BYTE reader from Electric City WA, has implemented an excellent piece of h omebrew craftsmansh ip in his Kompuutar system based on the MOS Tech nology 6502 processor. In this issue, we provide David 's com plete design for the central processor, control panel interface, and serial term inal interface of a general purpose computer.

Frequency cou nters are usefu l tools for a variety of appl ications. Perry Lynne shows you how to add one to your microcomputer in I mp lementing an LSI Frequency Counter. His design takes advantage of the Intel 8253 programmable interval ti mer (as wel l as the power o f the microprocessor) to produce a design that is both accurate and economical.

How do you m ake an 8 bit mach ine emulate a more com prehensive d esign?

In his article, SWEET16: The 6502 Dream Machine, Stephen Wozn iak de­

tai ls the design and functions of a low level interpreter for 1 6 bit operations which extend the fu nctions of the more lim ited 8 bit 6502 processor.

Continuing the theme of real time and how to keep track of it, G A R Trol l ope provides an example of the interrupt driven app roach, imple­

mented through the IRQ i nterrupt line of a 6800 processor with a PIA port. Do You Need Real Time? If so, turn to th is article.

The game of N I M is wel l-known in the annals of compu ter lore, but many people have had no contact with it. I rwin Dol iner presents us with a version of the game and supplies us with the design theory behind it in his article, N I MB LE:

The U ltimate N I M?

-� . ' . . .

E�iiuPi�l ^The

By Carl Helmers

6 BYTE November 1 97 7

Compleat Robotics Experimenter

On August 1 6 1 977 I received one of those refresh ing and intox icating articles (or rather group of articles) which makes the combined intel lectual and emotional joys of creating a magazine once a month rise to new h eights. This group of articles is a basic bac kground tu torial on biological inputs to the field of robotics and artificial intell igence, written for the personal com­

puting experi menter by Ernest W Kent, a professor i n the department of psychology of the University of I l l inois at Chicago Circle. I t is one of those articles, l i ke Ralph Holl is' article on N EWT in the June 1 977 BYTE, wh ich gets instant high priority due to the subject matter and style of presenta­

tion. (Readers sh ould see the beginning of the series in early 1 978.)

I cal l the twin su bjects of robotics and artificial intelligence "hot" ideas for BYTE based on reader interest as exp ressed in the BOM B pol l 's responses to Ralph Holl is' article on N EWT and M i ke Wimble's articles (among others) on various artificial intelli­

gence concepts. I nspired by rece ipt of Dr Kent's articles, the theme of th is editorial is the concept of smart machi nes and related robotic mechan isms as a fertile field for . experimentation with design and imple­

mentation. What are the categories and classes of experimentation which are rele­

vant to artificial intell igence and robot design? Why are we (experimenters all) so fascinated by the simulation of life? What are the topics of stu dy needed to become

"the complete robotics experime nter?"

What will we see over the course of the next decade or so, as personal computers become the refined personal software development systems needed to su ppor·t private mbotics research?

I t often helps to draw inspiration from fiction, an element of our· culture wh ich has been present from its . beginnings in the allegorical tales of primitive rel igions to the soph isticated and future oriented tech no­

logical fiction tales of contemporary fi lm, television and printed med ia. Fictional

representations of p lots, scenarios and tales are a sort of logical game practiced by creators, logical games with very real emo­

tional and value orientations wh ich stimulate thought about real problems while providing an interesting and enjoyable diversion for users of the art. Technological fiction, of wh ich science fiction is a proper su bset, is the appropriate contemporary place to turn for inspiration regarding the very comtem­

porary possi bil ity of ingenious and usefu l automatons gu ided by artificial i ntell igence.

A particular science fiction tale wh ich has been one of my greatest emotional inputs regarding the positive values of tech nology in human culture is a tale entitled Door Into Summer, by Robert Heinlein. First publ ished in the 1 950s, th is now outdated tale of the near futu re (1 970 is the year when the action commences with fl ashbacks to th e fictional 1 960s) is perhaps the one science fiction story wh ich maps most closely to the current tech nological milieu of the smart m ach ines made possible by microprocessor tech nology. Anyone who is seriously interested in practical use of robo­

tic technology and smart mach ines should read this boo k as a sou rce of backgmund information and ideas about what is or might be possi ble. (The actual plot is a wel l constructed romantic tale in sp ite o f its use of th at logical trap which is the time travel deus ex machina.)

The inspiration to be drawn from the story of Door Into Summer is that of an exciting ti me when technology has advanced to the threshold of intell igent 'robotic mech­

anisms mass-produced for use in mu ndane tasks. It is the era of Drafting Dan (auto­

mated intelligent drafting machine), H ired G i rl (automated housekeeping robot), and nu merous similar special ized devices. Some of these fictional concepts have already been implemented in practice, especial ly i n the area o f au tomated aids t o th e p roduction of capital goods. The idea of Drafting Dan, the intell igent drafting device, is actually i n use on a small scale today bu t with ,a far h igher degree of refinement and intel l igence : I refer to the various computer aided design tech niques utilizing graphic displays and computational support in fields as diverse as airp l ane design, computer design, and archi tectu r·e. Others among the concepts in Robert Heinlein's story h ave yet to be implemented with any degree of perfection or wi despread use.

The parallels between Door Into Summer and the current era are many. I n the fic­

tional accou nt, technology has developed

Continued on page 1 38

$. Tlte fOIIip\ete

655 hoe pnnter.

Its ready to plug in, has an 80-column format, a remarkable MTBF and is

14 times faster than a teletype!_

Breaking the hardcopy barrier It's fin�lly hq.ppened! The Axiom.

EX-800 provides full performance hardcopy <:J.t a price compatible with today's low cost micros. This little 80-column machine zir>s along at 160 characters per second (14 times faster than a teletype) -at a breakthrough single quai'ltity priee of $655 for a complete printer.

When we say complete we mean it

The EX-800 is a stand-alone uJ;�it wiili case, power supply, 96 charaoter ASCII generator and iTilterface, paper roll holder, infra-red )ow paper detec­

tor, bell, and rnulti-line asynchronous inp1:1t buffer, You won't find these standard features on any other printer, regardless of pric.e!

Our only option

Our printer is so complete, that we offer only one option. A serial inter­

face (RS 232C or current loop) good for 16 baud Fates from 50 to 19;200 and thoughtfully provided with a switch for either Centronics pr Tally compatibility. Might we call it a 'ifally­

whacker? At $85.00 it certainly ·

should be! ⁰

Built-in LSI microprocessor The heart

of tJ1ie EX-800 is a printed

•t>.uoa )Us

17UJ ^AlnCII circuit card,

. T

containing a ^t I ^{f ' 1} 1 1 1

liO>/iw"_IQf ________ - -

custom LSI chip made by Intel to Axiom specification;;, whi<I:h contrqls all printer functions. Microprocessor power means flexibility. Such as the built-in self test routine and variable

character size . It also means reliability.

Several industliy surveys have shown LSI to be many times more reliable than equivalent con\1entional circuitry.

The advantages of electrosensitive printing

The EX-800 can print 80, 40, or 20 characters across the flve inch wide electmsensitive paper. Under software control, stngle characters or wmds may be printed larger for

�mphasis. The permanence of the harcl.copy· is archival, because once the aluminum coatililg has been re­

moved, there is no way to put it back.

It's unaffected by sunlight, moisture or heat . Althol!lgh the printer doesn't provide multiple copies, excellent quality photocopies can be made from the high contrast printout. Also,

�D©[M]

5932 San Femalilde Rd., Glendale, CA 912p2 ^• (213) 245-9244 ^{_ • TWX} 910-497-2283

Circle 8 on inqu iry card.

the paper is inexpensive and reaclily available, costing about 1¢ for an 8Vz x 11" equivalent.

Light, small, quiet, reliable, ..

and versatile ^{· 0} Our EX-800 weighs in at 12 pounds, is just 9Yz inches wide, 4 inches high, and 11 inches deeg, and

· is delightfully quiet whien makes it ideal for office and other low noise environments. The simple print . mechanism is virtually maintenance free. In fact, tests show an incredible MTBF, many times greater than impact printers. 'fhis versatile printer is the ideal mate for mieros, minis, CRTs, instruments amcl systems.

- -

:;: t z e s ^=-. u p p e t-

Just unbox and plug it in That's all you have to d0 ,fo the Axiom EX.-800 - apart from pa)l for if, and at $655 that's almost a pleasure.

r•••••ll!l••••w

Send to:�� ^·

I 5932 San Fernando Rd., I

I ^Glendale, CA 91202 ^· 1

I D Urgent Please ph�ne me at e·xt _ I

D Have rep contact me

I D I'd like tp have a demonstration I I LJ Send lit including sample of printout I

I ^�m I

I ^Company 1

I ^Dep ·I

I ^Address I

City State __

I I

B¥TE November 1 977 'Z'

Check out TIS

neW" 4K static RAMs.

They've got everything

you ever liked about the 2102.

SIMPLE TO USE ,

NO CLOCKS. NO TIMING STROBES.

8 BYTE November 1 977

And more.

2102 1K Static RAM

Like the p o pular 2102, Tl's new 4K stati c RAMs are easy to use. Minimize system overhead; no refresh; simple add ress­

i n g . It's easy!

No c l o c k i n g needed for Tl's fully static 4K RAMs. N o edges. Just present an ad­

d ress to the selected device and data can be read at access ti me. That's i t.

Circle 1 52 on inquiry card.

FULLY STATIC. ACCESS TIME= CY CLE TIME.

DATA VALID­

NO TIME LIMIT.

AODRESSE

t?

\;l gt

c.

Oe:.

r=-ACCESSTIME

�

...-----.-�� .-,-:;:H:m D

DATAOUT

'0\JOQO

^-(�)'

SINGLE +5 V SUPPLY.

FULLY TTL COMPATIBLE.

±1 0% TOLERANCE SUPPLY.

HIGH SPEED.

2102

TI4K STATICS

1000 900 BOO 700 600 500 400 300 200 100 ACCESS/CYCLE TIME (ns)

Max.

4K ^X 1 1Kx4

Access

150 ns TMS 4044-15 TMS 4045-1 5

200 ns TMS 4044-20 TMS 4045-20

250 ns TMS 4044-25 TMS 4045-25

300 ns TMS 4044-30 TMS 4045-30

450 ns TMS 4044-45 TMS 4045-45

LOW POWER.

Parameter Four Low Power 1 K One TI4K Sialic Static RAMs (2102AL-2) RAM (TMS 4044-25)

Max. Access 250 ns 250 ns

Min. Cycle

Operating 1368 mW 500mW

Power (Max.)

Package(s) 4 x 16 pin 1 x 18 pin

Board Area 3.7 1 .0

Ratio

HIGH DENSITY 18-PIN PACKAGE.

2102 1 K Static RAM

Fully stat i c RAMs are total ly asynchro­

n ous. Requi re n o precharge or recovery t i me. Access and cycle t i mes are always the same.

Ful l y stat i c RAMs offer output data t h at are v a l i d as long as the add ress is valid.

Makes design i ng straightfo rward. No l i m i t on output valid t i me. No extra circuitry_

Just one +5 V supply needed. Ful l TTL compati b i l ity on all i n puts and outputs with ful l 400 mV guaranteed de noise immunity.

I mproved power supply tolerance means l ess str i ngent regulation. Less cost.

Tl's new 4K stat i c HAMs take up where the 2102 left off. Offering a wide choice of speeds from 1 50 ns to 450 ns maxi­

mum access/mini m um cycle. P lenty of performance to match today's and to­

m o r row's CPUs.

Compare the power savings of the new 4K statics to the low power 21 L02. For e quivalent speed, the new TMS 4044 uses 63% less power.

For super l ow stan dby-power/battery­

backup operation, use the pi n-compati ­ b l e 20-p i n TMS 4046/47 Series. Data i s retained d o w n t o 1 0 mW.

The new 4K stati cs come i n i n d ustry­

standard, 1 8-pi n packages, plast i c o r ceramic. A de nsity i mprove ment of al­

most four-to-o ne over 2102s.

FOR DATA SHEETS, application reports, price and delivery, call your nearest authorized Tl distributor or Tl field sales office.

€)1977Texaslnstrumentslncorporated Circle 1 52 on inq u i ry card.

TEXAS INSTRUMENTS

INCORPORATED ""'

BYTE November 1 977 9

Steve Ciarcia Box 582

Glastonbury CT 06033

Power Wiring Table

Number Type +5 VDC Pin

IC1 7420 14

IC2 74154 24

IC3 7407 14

IC4 7407 14

IC5 74100 24

OUTPUT ST ROBE

l..J

Memory Mapped 10

I don't want to get into a figh t over which microprocessor chip is better. They al l have their favorabl e and u nfavorable fea­

tures. But, if you look a l ittle closer, you may find that some of these extra features can be added with very l ittle expense.

I was speaking with a fellow. computer nut recently, and he was arguing about the merits of the 6800 versus the 8080. I really didn't care to continue the conversation nor to justify why I had an 8080 and Z-80. But, when he said that one reason was that the 6800 had memory mapped 10 and the 8080 didn't, I knew he didn't know what it was.

This of course made me curious, and ^I approached a number of 8080 users to ask if they knew what m�mory mapped ¹⁰ was.

They assured me that they did, and that it was in fact one of the main features of the 6800. But such a feature is hardly exclusive to the 6800!

First of al l, memory mapped ¹⁰ means simply that a portion of memory address space has been reserved for interfacing with external devices. A byte of data is stored into a memory l ocation, as always, but this storage u nit, rather than being made up of 1024 bit programmable memory chips, is an

OUT P U T DATA BUS {FROM C P U)

Gnd Pin

7 12 7 7 7

+ 5V D C

(TYPICAL FOR 8)

8 10 12 4

D7 ' D6'

X �---�19 ^{G2 D5'}

A7 A6 A5 A4

A3 s I A2 R I AI

I 0 ADDRESS BUS

(10 CARD CON N E CTOR-22 P I N )

18 _Gl

20 D 21 c 2 2 B

23 A I C 2 74154

12

2 3 22 21 I I 10 15 16

Dl D2 D3 D4 D5 D6 D7 DB

8 B I T LAT CHED PARALLEL OUT PUT

LS B

D4' BU F FE R E D OUT PUT D3' BUS D2 ' D I ' D O'

Figure 7: A schematic diagram for a direct addressed output port decoding circuit. The port assignments as diagrammed are from octal codes 360 to 377. The bus pin assignments are for the Digital Group bus system, but the Altair (5-7 00) bus is logically equivalent.

1 0 BYTE November 1 977

Intel delivers ^50�85. It's the quickest

way to sink your ^teeth into ⁸⁰⁸⁵ design.

Intel wants you to prove to yourself why the 8085 has become the new industry stan�

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sign Kit for the 8085 is available now for only $250.

SDK�85 is the best way we know for you to evaluate MCS�85T"

and develop proto�

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And to simplify your evalu�

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T he 8085 family of components provides you with unprecedented design flexibility. T he basic three�chip, high level integration MCS�85 system is included in SDK�85. It includes the 8085 CPU, 8155 256�byte RAM with I/0 and timer and 8355 2K�byte ROM with I/0. And there's an on� board single�chip keyboard/display interface, the 82 79. Sockets are provided for easy RAM and ROM/EPROM expansion.

And there's ample free space layed out for easy wire wrap expansion using Intel's

Circle 71 on inqu i ry card.

complete family of programmable peripheral controllers and

your own prototype logic and special

circuitry. _

SDK�85 makes an excellent teaching aid for both microprocessor design and program�

ming courses, for microcomputer design seminars and as a project for the progressive

hobbyist. Because the 8085 is the most advanced micro�

computer, SDK�85 is the key to state�orthe�art knowledge.

SDK�85 can be assembled in just a few hours with a solder�

ing iron and a few basic tools.

Hook it up to your 5V power supply and it's operational the same day you receive it. You can get your SDK�85 from any of Intel's distributors for $250 in single unit quantities.

To order SDK�85 or any of the MCS�85 components, contact:

Almac/Stroum, Components Special�

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Or, for more information, use the reader service card or write: Intel Corporation, 3065 Bowers Avenue,

"' 'f:·_•r�.

Santa Clara, CA 95051.

Telephone: (408) 246�7501.

inter ^delivers. - �---

-,

- �

,

-;._ _ ;

ⁱ

BYTE November 1 977 1 1

Photo 7: A realization of the hardware circuit shown in figure 7 with the addition of eight lights connected to the outputs of ICS. The connector attaches to bus lines for the author's other front end projects.

Photo 2: A prototype for the circuit shown in figure 2.

1 2 BYTE November 1 9 77

8 bit storage register such as a 741 00. This type of procedure provides access to the data by te through the "back door," or output l ines of the 741 00. If you have followed me to this point, you can see that the concept of memory mapped 10 is applicable to any microprocessor that directly addresses memory! I don't know of too many processors which operate without this ability, so we 'll just have to concl ude that any microprocessor can be wired to provide memory mapped 10, including the

8080.

Look no further! I t's a bird .. . it's a plane ... no, i t's Superch ip! I t looks like an

8080, acts l ike an 8080 and, wh ile not trying to steal Motorola's thunder, has memory mapped 10! The name of this new ch ip?

Well, it's the plain old 8080 with an intelli­

gent user.

Why should I consider memory mapped 10?

The 8080 directly addresses 64 K ^bytes

of memory and 5 1 2 10 ports (256 in and

256 ^out). The only way data can arrive at an output port is by being passed through the accumulator and routed to a particular port ·

by a 2 byte output instruction. Similarly, a

2 byte instruction directs input data to the accumul ator. Additional programm ing is necessary to store this input byte in memory.

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3. Convert numbers between the decimal, binary, octal arid hexadecimal systems.

4. Follow the execution of a simple program, including arithmetic and logic statements.

1 1 . Explain the operation of bidirectional data bus systems.

1 2 . Describe the operation and use of semiconductory memory systems, i.e.

EROM, ROM, RAM.

The emphasis is on the practical.

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·

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2201 West Howard Street Evanston, Illinois 60202 5. Identify and describe the circuits neces­

sary to interface a microprocessor sys­

tem with the outside world.

,---·

6. Describe the data transfer between the microprocessor, memory and peripheral equipment.

7. Understand the techniques of trou­

bleshooting micro-computer-based sys­

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8. Observe the proper servicing procedures for MOS circuits.

9. Understand the basic operation of a mi­

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Circle 1 0 on inquiry card.

Send to: Bell & Howell Schools, ²²⁰¹ W. Howard, Evanston, Illinois ⁶⁰²⁰² 0 Enclosed is my check or money order for

$89.50. Please send postpaid the Bell & ^Howell

Schools Microprocessing Program. If not com­

pletely satisfied, all materials will be returned within 10 days for prompt refund.

0 Charge to credit card below:

BankAmericard # ________ _

Master Charge # _________ _

For Master Charge card, include 4-digit number

a bove name ^·

Expiration date _________ _

Signature ___________ _

Name

Address

City

State

Zip

�-^----^-----^----�

BYTE November 1 977 13

MEMORY ADDR ESS BUS (MEMORY BOARD CONNECTOR)

I I

ME M WRI TE X STROBE I

A 3 A 2 A I

I I I I I

I s I R I p I A 0 N

Obviously, if the data path went to a memory location instead of an output port, a broader range of instructions would be available. The 8080 (like most computers) has some very powerful instructions when it comes to memory operations. For the 8080 these include M OV, MVI, STAX and STA instructions which, by definition, are added to the output data manipulation repertoire with memory mapped 10.

Ofte n the best way to approach a new subject is to analyze the present method.·

Figure 1 il lustrates the basic design of an

Number

I C 1 IC2 I C3 I C4 I C5 I C6 IC7

Power Wiring Table Type

7420 741 54 7407 7407 741 00 7402 7420

+5 VDC Pin

1 4 24 1 4 1 4 24 1 4 1 4

Gnd Pin

1 2 7 7 7 7 7 7

8080 output "port." To emphasize simpli­

city I 've used 741 00 latches for this examp le rather than the more complex ports such as the M otorola 6820 peripheral interface adapter. This configuration provides 1 6 output strobes, starting with the octal output port address 360 and ending with octal 377. I ntegrated circuits 1 and 2 decode the address bus and, when provided with an output strobe during an output i nstruc­

tion, load the present conte nts of the data bus into an 8 bit storage register (I C5).

ICs 3 and 4 provide buffering and allow more 741 OOs to be attached to the buffered ouput bus lines for multiple ports. The pin desig nations are for the Digital Group bus system, but the Al tair (S-1 00) bus is logically equivalent.

Converting an output system to memory mapped 10 (il lustrated in figure 2) requires the addition of two more integrated circuits, ICs 6 and 7, to decode the additional eight lines associated with memory addressing.

With the decoding arrangement illustrated in figure 2, the 1 6 output (memory) l oca-

MEM ORY DATA BUS ( FROM CPU)

19 G2

18 Gl

20 D 21 c 22 B 23 A

1.f

I C2 74154

+!>V DC

li

220.0.

(TYP I CAL FOR 8)

I STROBE NO. I

N0.2 N0.3 N0.4 N0.5 N0.6 N0.7 N0.8 N0.9 NO.IO N O. I I NO.I2 N0.13 N0.14 NO.I5 N0.16

8 10 12

8 BIT LA TCHED PARALLEL OUTPUT

4

LS B D 7 ' D 6' D 5'

D4' BUF FERED MEM ORY D3' DATA BUS D2'

D I ' DO'

Figure 2: A schematic diagram for a memory addressed output port decoding circuit. The port assignments in this case are from split field octal memory addresses 377/ 360 to 377/377. Here again, the bus pin assignments are for the Digital Group bus.

14 _BYTE November 1977