Circuit.cellar.014.Apr May.1990

8/13/2019 Circuit.cellar.014.Apr May.1990

http://slidepdf.com/reader/full/circuitcellar014apr-may1990 1/79



It Just Gets Better

EDITOR’SINK

turf s Franklin Jr.

I t must have something to do with a year ending in“0.” My desktop has disappeared under a deluge of pressreleases, product announcements, and data sheets for

products that are new, products that have been updated,and, I fear, some products that are no more than gleams inheir maker’s eyes. Many of the announcements have verympressive corporate logos embossed on them, but an en-

couraging number bear the names of small, entrepre-neurial start-up firms. Since we’ve launched into a decade

still young enough to be full of hope and promise, I see thereemergence of the “garage shop” as a most promisingomen for the future.

The 1980s have been simultaneously held up as the

decade of entrepreneurs and the decade of megamergers.For many people, “The Dream” consisted of having a greatdea, starting a small company, and quickly selling out to

a large, multinational conglomerate. During the last sixmonths of 1989, I read a number of articles which trum-peted the notion that the only way for a company tosurvive in the’9Os was for it to have a billion-dollar budget,

a lean, mean staff numbering in the thousands, and a debtoad that would sink most developing nations. Accordingto this line of reasoning, this world has now become so

complex that only massively organized teamwork canwork to solve problems. I agree that it’s important for ourargest corporations to be healthy, dynamic organizations,

but a thriving class of entrepreneurs and small companies

s vital for economic (and social) well-being in this decade,and the next century.

Let’s look at just one facet of the situation. There areseveral corporations that are able to fund R&D effortsnvolving thousands of people and millions of dollars. I

get press releases from some of these programs, usually

touting the latest advancement in the state of basic re-search. I’m in awe of their capabilities, and they seem to be

making serious progress toward solving some mighty bigproblems. The trouble is that they are so much caught up

in big problems, and the mind-set is so oriented toward big

solutions, that they have trouble seeing the small problemsand (hopefully) small solutions that make up much of ourlives. An individual engineer, on the other hand, may wellspend timegetting to know a small problemonanintimatelevel, and find a solution that fits perfectly.

If the engineer then goes on to market the solution, our

economy has gained a company that will support one, orfive, or fifty people for many years. It may never haveprofits of a billion dollars a year, but then most of us don’tfeel weneed quite that much to get by. I’mseeingevidence

of more and more people deciding that the income from asmall company, coupled with the emotional fringe bene-fits of running a small company, are more than enough to

live on. The dynamic nature of these small companies is

crucial to a thriving economy, every bit as important as thestability and power of the huge corporations.

The ’90s promise to be a decade of dramatic change.

Historically, the decades around the turn of a century areilled with social and technical change, and the turn of amillennium is bound to have enormous psychological

effect on most people. The thousands of small companiesand individuals working to solve practical problems willgive us a technological and economic diversity that will be

part of a strong and growing global society. We’re in for an

exciting ride. I’m glad that I’m here to see it.

April/May 1990 1



FOUNDER/EDITORIAL DIRECTORSteve Cia rc ia

PUBLISHERDa niel Rod rigu es

EDITOR-in-CHIEFCurtis Frank lin, Jr.

PUBLISHING

CONSULTANTJohn Ha yes

ENGINEERING STAFFKen Davidson Jef f Bachiochi Edward Nisley

CONTRIBUTINGEDITORS ThomasCar&e//Jac k G a nssle

NEW PRODUCTS

EDITORHarv Weiner

CONSULTINGEDITORSMark DahmkeLa rry Loe b

CIRCULATIONCOORDINATORRose M a nse lla

CIRCULATIONCONSULTANT

Gregory Spi tz faden

ART& PRODUCTIONDIRECTORTric ia D zied zinski

PRODUCTIONARTIST/ILLUSTRATORLisa Fe rry

BUSINESSMANAGERJea nnet te Wal ters

STAFF RESEARCHERS

NortheastEric Alb ert William Cur/e wRichard Sawyer Robert Stek

MidwestJon E/son

Tm McDonoughWest Coast

f rank Kuechmann

Ma rk Voorhees

Cover Illustrationby Robert Tinney

THE COMPUTERAPPLICATIONS

J OURNAL

q2

q8

Computer-GeneratedHolographsby Dale Nassar

Holography is a method of encodingrealistic 3-D images on standard photo-graphic film. Using a computer, you cansimulate holographic interference pat-terns, with results that can be moreimpressive than laser holography!

Digital Signal ProcessingPart 2 DSP Ap p lic a tio ns with the TMS32OC25by Dean McConnell

In Part 1, we looked at theories and general cases. Now, it’s time to get to

work. Programming the DSP for specific functions, and replacing a pile of discrete components with a single processor are what it’s all about.

Editor’s INK It Just Gets Better 1

b y C ur t is runklin Jr.

Reader’s INK-Lefters to the Ed itor 6

NEW Product News 8

Visible INK Letiers to the INK Resea rc h Sta ff 12

Firmware FurnaceBASIC Radioactive RadomsTrue Ra nd om Numb ers from Mothe r Na ture by Ed Nisley

58

From the BenchHoney, I Shrunk the...New Uses Ab ou nd for the Sm a llest AT-Clone Yet by Je f f Bac h ioc h i

70

2 C lRC UlT CELLAR INK





Letters to the Editor

READER’SINK

AN ISSUE OF ACCURACY that there are packages out there, like Autosketch, that can be purchased in this price range.

I don’t want to start a semantic argument, but “Steve’s Perhaps you could provide a program at a discount forOwn INK” in CIRCUT CELLAR INK I13 pulled my chain. subscribers to the magazine. This could very possibly setThe proliferation of high-technology Tinker Toys has, at an electronic software standard. If the package is acceptedtimes, caused a lot of grief. The perception that the display by your readers, and they are used to using it, they will

of many digits means awesome accuracy is a serious probably want to use the same package at their place of problem. work.If I were to calculate the value of IC as 2.94159268, the

result would be reasonably precise, but totally inaccurate.Of what value is this great precision when few devices can be calibrated to an accuracy greater than O.Ol%?

I hope there is one magazine out there that is willing tostep into the computer age, rather than just write about it.

We live in a world of illusion. Please don’t perpetuateour ignorance by confusing precision with accuracy. Mygross error in the calculation of IC is only 6.5%: not verygood, but close enough for some applications. I must agreewith Steve’s plea that common sense must prevail.

Wayne R. AndersonSmyrna, GA

Robert C. WoodmanBay Springs, MS

Letters such as yours help fuel the conflict between what wewould like to provide for our readers, and what reality will allowus to provide. We have been discussing, for some time, a way to

put schematics on the Circuit Cellar BBS. Problems arise when

we ty to takeintoaccount thevarietyofcomputersowned byourreaders, and the work habits of our staff.In order not to slight subsets of our readers, we would need

toprovideprogramsfirMS-DOS, Macinfosh, Amiga, Atari ST,and (heaven help us) some sort of CP/M platjornz. Next, wewould have to takeschematics from Schema, which oureq@eer-ing staff refuses to give up, and porf them to the new format.

MAKE SCHEMATICS MORE USEFUL

I have been reading electronics and computer maga-zines for many years now, both before and after the computer revolution. In the last few years, almost all of these

magazines have established bulletin boards for down-loading data connected with the projects in the magazine, but I don’t think anyone to date has put schematics and printed circuit board layouts from an affordable programon their BBS. All magazines print this information in the pages of their magazine, but due to errors in reprinting,and paper and original printing flaws, this data is some-times less than perfect.

We are constantly searching for new ways to make Cr~curr

C ELLAR INK more valuable to the readers. Increasing theusefulness of the Circuit Cellar BBS is certainly high on our list,but it is unlikely that CZRCUTCELLARINK oranyothercomputermagazine will be able to offer a cheap, full-function EE-CAD

program in the near fu ture.

ABOUT THOSE PARTS...

Why hasn’t one of these magazines taken a giant stepforward and adopted a software package to do schematicsand printed circuit board layouts, from one to four layers?This package would need to be cost effective for most

readers, and be priced in the $50-$60 range. If it cost muchmore, it would be out of reach for many readers. I know

Ever since the advent of the IBM PC there seems tohave been a steady erosion in the quantity and quality of hardware-oriented books, magazines, and articles. Ithought it was all over for serious computer experiment-

ers. One figure carried on and even progressed. I wouldlike to commend Steve Ciarcia and CIRCUIT CELLAR INK.

6 CIRCUIT CELLAR INK



Issue 9 was a gem. Every article was outstandingThe two articles on neural networks (“The Adaline Learn-ng Neuron” by Scott Farley and “A Neural Network Ap-

proach to Artificial Intelligence” by Christopher Ciarcia)are examples. These articles were better than many booksand articles that I have read on the subject.

Lately I have been finding it more difficult to buildsome of the construction articles. The “high-end” chips are

hard to find in small quantities, if at all. One distributoreven told me I was ineligible to buy anything. Am Imissing something?

Alan LandPittsburgh, PA

I am not much on writing “fan mail” but I just wantedto tell you that I think CIRCYLJ~~ CELLAR INK is great. I have

worked on computers since “way before BYTE” and wasvery glad to see, once again, a magazine devoted to theserious hardware folks. I am also a “pro” (whatever thatmeans), and am pleased to tell you that I found more usefuldeas and information in my first issue than in a year’s

worth of several other magazines I get.As far as feedback goes, I like what you’re doing just

he way you are doing it. I would appreciate an on-line or

disk-based cumulative index. An index that I could searchby keyword or combinations would be a great help.

Another interesting service you might consider isprinting data sheets on new and interesting ICs. “SiliconUpdate” addresses much of this need, but it sure would benice to have a tear-out sheet that you could put into astandard three-ring notebook. I would suggest gettingsome of your parts-house advertisers to stock the “chip of

the month.”Finally, you’ve inspired me: Please send an Author’sGuide. I have an idea or two I’d like to submit.

Carl K. ZettnerSan Antonio, TX

Thanks to both of you for your kind words. It’s nice to getan occasional pat on the back.

Nothing is morefrustrating than not being able toget apartyou need. Wearegoing to ty toaddress this byprintingsourcesalong with construction articles. There will be some exceptions,

but it should generally be possible for individuals to purchase parts for all of our projects in single quantities. Anyone can get a CIRCUIT C E L L A R I N K Author’s Guide by

writing and requesting one. The address is:

Circuit Cellar INK Author’s Guide4 Park StreetVernon, CT 06066

A Division of MING E&P Inc.

1. EXCLUSIVE ITEMS,GOOD PRICE.

2. UNIQUE ITEMS,BETTER PRICE

3. POPULAR ITEMS,BEST PRICE.

DIGITALVOlCERECORDINGMODLILE

l

Long recording up to 2 mins0 10 bit A/D, 32 Kbps. Auto repeat feature0 1MbDRAM (Expandableto4Mb)

0 Applications are unlimitedMING DVM-58 $49.99

PASSIVE INFRARED DETECTOR l Security industry qualityl Very compact reliable0 SMT w/best RF1 immunity

l Cover area 50’ x 50ROKONET RK $49.99

RF REMOTE CONTROL SYSTEM

l 4096 Digital coded number l 2 tiny transmittersl Receiver has dry contact relay

output0 Confirming signal outputZEMCO SA432 $49.99

SYNTAX PROTOTYPING PCBl All types of BUSSl High quality FR-4 material0 Get your job done quickly

Please Call for Free Catalog

l 800) 669-4406977 S. Meridian Ave., Alhambra, CA 91803Tel: (818) 281-4066 Fax: (818) 576-8748

VISA & MASTER CARD ACCEPTED

PC-Based Logic Analyzers

Sophisticated Logic Analysis

a’, Unsophisticated PricesID160 (50 MHz) for $695

*ID161 (100 MHz) for $895*SO MHz or 100 MHz Sampling l 8K Trace Buffer l 32-channelOperation *Multi-Level Triggering *State Pass Counting*Event Timer/Counter l Performance Histograms l HardcopyPutput *Disassembles popular E-bit micros *and much more

30 Day Money Back Guarantee

INNOTEC DESIGN, INC.

6910 Oslo Circle, Suite 207Buena Park, CA 90621Tel: 714-522-1469 FAX:714-527-1812

Reader Sewice 130

April/May 1990 7



NEVVPRODUCTNEWSNE\ NPRODUCTNEWS

DI

FOR PCSystems integrators and

PC users can now add high- performance digital audiofunctions to their systemsand application programswith a new board from AntexElectronics Corporation. TheSeries Z/Model SX-10 digitalaudio processor featuresmultichannel ultra highfidelity, direct-todisk soundsampling and reproductionfor IBM PCs and compatibles.

The unit is designed to

fit into an expansion slot of any IBM AT, F’S/2 Model 30,or any compatible 286/386computer and allows the user to receive both analog and

digital audio signals from a

variety of sources includingnatural voice, CDs, DAT players, and other digitaldevices. The SX-10 candigitize two audio channels,converting the stereo soundinto digital input that can bestored on a hard disk or CDROM. Once stored, the user can manipulate the audiodata and perform mixingediting, and archiving tasks.The SX-10 can record and

playback simultaneously, so“overdubbing” using a PC becomes a simple process.

The Series 2/SX-10 is afull-length board designed

around the Texas

InstrumentsTMS32OClO digitalsignal processingchip running at 25

MHz. Sampling rates aresoftware programmable, andcan range from 6.25 kHz to 50

kHz in lOO-Hz steps. Resolu-tion is 16 bits, and audio

bandwidth is 20 Hz to 20kHz. The board also allowsfor 4:l ADPCM (AdaptiveDifferential Pulse CodeModulation) data compres-sion for decreased disk storage requirements.

An on-board digitalinput interface allows the SX-

10 to be connected directly toCDs, DATs and other digitalsources. Programmers canachieve direct-to-disk recording and playback byusing an optional Series 2driver to call the SX-10 from a

high-level programminglanguage such as QuickBasic,Pascal, Turbo Pascal, and C.An editing program,PCMEDIT, is also available toallow viewing and manipu-lating up to three audio fileson-screen.

The SX-10 requires anIBM AT or higher with a l-to-1 interleave factor disk controller, a hard disk with amaximum 28millisecond

access time, and DOS 2.0 or greater. A special daughter- board is also available toallow PCM digital output tooptical disk drives, DATmachines, and other digitalrecording devices.

The price of the SX-10 is$1995.00 and the optionaldaughterboard is $450.00. Aone-time fee for the softwaredriver is $750.

Antex Electronics Corp.16100 South Flgueroa Street

Gardena CA 90248(213) 532-3092

Reader Service 44190

FOUR-PORT MULTIPLEXER

Combining the signaland handshaking lines fromfour different RS-232 cablesand sending them up to 4000feet on a single cable is possible with the four-portmultiplexer, Model 252FPM,from B & B Electronics. Atthe far end, another 232FPM

separates them into the four different cables. Each port of the 232FPM supports twodata lines CTXD and RXD)

and four handshaking linesCRTS, CTS, DTR, and DSR)and is wired as a DCE port.

A typical application would

be to connect a small cluster of terminals and printerslocated up to 4000 feet awayfrom their host computer.

The 232FPM alsofeatures a built-in loopbackmode to test for installation problems. It automatically

falls into the loopback mode

_if the two-pair interconnec-tion wiring is broken, or if the power is off at the far end.The interconnecting wireshould be a two-pair twistedtelephone cable for bestresults.

The 232FPM can handle

baud rates up to 9600 bps

with any combination of bits, parity, and so on. Convertersare available to change theDCE port configuration toDTE. These DCE-to-DTEconverters cross RS-232connector pins 2 to 3‘4 to 5,and 20 to 6 and 8.

The Model 232FPM sellsfor $149.95 including power supply. The Model 232DTEDCE-to-DTE convertor sellsfor $15.95.

B & B Electronics4000 Baker Road

P.O. Box 1040

Ottawa, IL 61350

(815) 434-0846

Reader Service 45191

a C lRCUlT CElLA/? INK





NEWPRODUCTNEWSNEVVPRODUCTNEWSIN-CIRCUIT DIAGNOSTIC SYSTEMFOR PC

r

A diagnostic system designed to facilitate the trou- bleshooting and repair of IBM PC/XT, AT, 80286,80386, andcompatible system boards has been announced by Total

Power International Inc. The LOGIMER system consists of ahardware/firmware add-on board that contains diagnosticcodes. It comes with three ROM chips and plugs into anyexpansion slot. The ROM chips, which are installed in placeof the existing ROM BIOS chips, conrain a program thatmakes more than a thousand tests in less than one minute,and displays setup instructions and error messages on-screen.

In the event of a computer screen malfunction, a two-digit alphanumeric display on the card will display hexadeci-mal error codes. The user’s manual and supplementary disk-ette provide additional diagnostic information.

LOGIMER has the capability for detecting intermittent breakdowns. It will still initialize both displays, perform itsdiagnostic tests, and relay useful information about thesystem under test with many intermittent controller, timer,

and memory chips. It also can carry out loop tests to allowtesting during burn-in, and its results may be output to a printer or screen.

The LOGIMER card can locate the exact number of adefective chip, and shows defective RAM chips on a screenerror map to allow easy replacement. It performs complete Total Power International, Inc.

memory diagnostics including EMS memory up to 16 mega- 418 Bridge Street

bytes, and locates up to 70% of real breakdowns on the moth- Lowell, MA 01850

erboard. (508) 453-7272

The LOGIMER card is priced at $399.00. Reader Service 195

ROM-BASED CPUCARD

A controller card fromKila Systems makes disklessstand-alone or embedded ap-

plications easy to design. TheKS-5 is a ROM-based CPUcard that is configured for anIBM PC/AT bus. Using a passive backplane and off-

the-shelf PC/AT-compatiblecards, a user can run existingapplications and MSDOSdirectly from EPROM. MSDOS takes up 83K of the256K total ROM space,leaving 173K available for application programs.

The card features the NEC 70216 (V50) CMOS CPUrunning at 8 or 10 MHz withzero wait states. From 512K to 1 megabyte of dynamicRAM is available, but usableRAM excludes the ROMspace, which can be up to

Correction:

InCCINK Issue 13“New Product News.”the telephone numberfor MacrochipResearch Inc. wusIncorrect.

The correct number is(214) 242-0450.

We are sorry for any

inconvenience this mayhave caused.

256K. Five RS232 serial ports are available at pro-grammable baud rates up to38.4 kilobaud. The card’s 98- pin edge fingers are designedfor insertion into a passive backplane. A 98-pin I/Oexpansion connector with thesame pinout as the PC/AT

bus is available for piggyback cards to interface printers,

floppy drives, SCSI, and keyboard.

The card is 4.5” wide and6.9” long and draws 400 mAat 5 volts. An on-boardconverter provides f12 volts.The V50 also features a power-down mode, and anall-CMOS version, whichdraws only 200 mA, can runoff of a battery or solar cell.

The base price of the KS-5 is $299.00 and significantquantity discounts are avail-able.

Klla Systems655 Hawthorne AvenueBoulder, CO 80304(303) 444-7737

Reader Service 196

10 ClRCUlT CELLAR INK













the target gets off the bus by deas-serting BSY\. We won’t get into ex-actly what the target does once it hasthe bus, because that’s the part of thespec we’re going to ignore.

THE HARDWARE

Now let’s look at the problems ofdesigning a device that only partiallyconforms to the SCSI spec. The firstproblem is that we want our interfaceto be invisible to the initiator when itis running its normal SCSI drivers.This is important because the hostcomputer often initializes the bus byselecting every device ID to see what’sout there. If it selects a device thatrequires a special driver, the initiatorwill probably hang. Our solution is to

modify the selection protocol so thatour interface will respond to selectiononly if the initiator asserts SEL\ andthe target’s ID, but not the initiator’sID. In order to simplify the hardware,we assume that the bus has only oneinitiator, and that it is located at ID 7.

Once our target has gained con-trol of the bus by asserting BSY\, weare free to play with the SCSI signalsany way we want, with the followingexceptions: BSY\ must remain as-

serted, and SEL\ and RST\ mustremain deasserted. As long as theserules are followed, there is nothing

the initiator or target can do on the busthat will affect the other targets. Thatgives us a pretty free rein with the re-maining six control signals.

Before we go hog-wild, we shouldconsider any constraints imposed bythe initiator’s hardware. On the Macin-

tosh, and in many other small com-

puters, the SCSI interface is handledby a single-chip SCSI controller, theNCR 5380. While it can assert all sixcontrol lines, it can’t assert them all atthe same time. When configured as aninitiator, it can only assert ATN\ andACK\. When configured as a target, itcan only assert MSG\, C/D\, I/O\,and REQ\. Because target mode givesus twice as many lines to play with,we will reconfigure the initiator as atarget when talking to our interface.

The 5380 uses the I/O\ line tocontrol the direction of its transceiv-ers, so I/O\ is forced into service as awrite/read line. The initiator is pre-tending to be a target, so “in” nowmeans towards our interface. Assert-ing I/O\, therefore, indicates a com-mand which writes to the interface.The phase lines MSG\ and C/D\ arenatural candidates for the addresses,and REQ\ is used as the strobe line.This leaves ATN\ free as an interface-

driven interrupt line. ACK\ can beused asaninterface-drivendata readyor wait line.

I NT F RF A CE DATA“ 2

Figure 2 illustrates these tech-niques with an interface to a genericbus with eight data lines and eight ad-dress lines (expandable to 16). Theselection process is implemented byone-of-eight selector U3, along withU6b and U7. When the initiator wantsto select the interface, it asserts SEL\

along with the interface ID, but not itsown ID (7), and then deasserts BSY\.When this occurs, U7c will go high,setting the S-R flip-flop formed byU7a and U7b. This sets BUSY high,which causes open-collector NANDbuffer U8 to assert BSY\ on the SCSIbus. Note that U8 must be a 74S-seriespart in order to properly drive the bus.TheinitiatorthendeassertsSEL\,com-pleting the selection.

US decodes the REQ\ line into

eight strobe signals according to thestates of MSG\, C/D\, and I/O\. Allof the even-numbered strobes (I/O\asserted low) are writes, and all of theodd strobes are reads. Strobes 7 and 6are the primary read and write strobes.Strobe 4 writes the address into octalflip-flop U4. Strobes 3 and 2 can beused as high-byte strobes in %-bitsystems. Strobe 0 can be used to latcheight additional address lines.

Strobe 5 ORed with RST\ resets

the BUSY flip-flop, removing the in-terface from the SCSI bus. The capaci-tor on the RST\ line prevents glitches

Figure 2 This circuit

Interfaces SC .9 to a ge neric bus with eight da ta l ines and e ight address l ines (expand- ab le to 16). The d esign trad es simp le hard- wa re and c ustom soft- wa re for the more n te i -

l ige nt hardw are and ‘standard’ software of trad itiona l SCSI.

)SCS I CONTROL

18 ClRClJ/ T CELLAR INK









Computer-GeneratedHolographic Images

Using a PC to G e ne ra te A ffo rd a b le Ho lo g ra m s

[Editor’s Note: This article is a practical tutorialonmethods togenerateahologram using an MS-DOS computer with a VGA screen, a 35mm camera, anda HeNe laser (for viezuing the hologram).

Dale Nassar has written a large

manuscript covering laser basics, lighttheo y, and the fundamentals of generalholography. This article, while a practicaltutorial, is an excerpt from the larger work.

If you would like to purchase Dale’scomplete work, send $7.50 to: Computersand Holography, 4 Park St., Vernon, CT 06066.1

Holographyisaphotographicprocess which, unlike ordinary pho-

tography, does not record an image ofthe scene photographed, but encodesthe emanating light rays themselves.The resulting optical record is called ahologram and can instantly recon-struct the recorded light rays. Holo-grams produce an illusion of the origi-nal scene in three-dimensional spacethat is remarkably life-like.

The beautiful images created by

this unique recording process aremade possible by the coherent light ofthe laser. However, because a holo-gram can be considered an array ofmany bits of information, I decided toinvestigate the practicality of compu-terized hologram synthesis. In thisarticle I will demonstrate, withoutcomplex analysis, how holographicsynthesis can be accomplished in thecomputer room with no special opti-cal materials or holographic lab. The

laser’s role in conventional hologramformation is completely emulated by

22 CfRCfJlT CELLMR INK



com’puter, and in some very crucialsituations the computer outperformsthe laser.

The synthesizing method I use isstraightforward and is designed to

be easily understood and inexpen-

sively applied with standard photo-graphic and computer equipment. Ona more advanced level, a parallel processing environment also lendsitself to the application as the holo-graphic bits are mutually independ-ent..

THESINUSOIDAL GRATING

A thorough understanding of the process of optical interference can

easily be had by assuming light to bemade up of sinusoidal waves of en-ergy (hence the expression “lightwaves”). Figure 1 illustrates a sinu-soidal waveform and the key ele-ments of its structure as defined in physical optics.

It is important to be aware of thefact that light waves are travelingwaves; that is, the contour of thewaveform of Figure 1 should be con-sidered asmoving toward the right at

the speed of light. To get a mental picture of what this means, consider a particle on the time axis in Figure 1that is allowed to move only verti-cally in response to the amplitude of the passing light wave. Then theeffect the wave has on the particle isa very rapid sinusoidal vertical mo-tion (vibration) about a fixed point onthe horizontal axis. It is obvious thatthe frequency of a light wave is ex-tremely high, visible light has a fre-

quency of the order of lOi* Hz (100,000GHz).

FEATUREARTICLE

Dale Nassar

These important quantities arcrelated by the very simple (and obvi-ous) expression f=c/h, where f is thefrequency in Hz, c is the velocity of thewave in m/s (3 x 108m/s for light) andA is the wavelength in meters. The

period of the wave, T, is the reciprocalof the frequency. T represents thetime required for one wavelength to pass a given point. Mathematically,the energy of a wave is a measure of i tsintensity, which is proportional to thesquare of itsamplitude. Thisencrgy iswhat does the work responsible for exposing photosensitive film.

When two plane waves meet atthe surface of a film, as shown in across-sectional view in Figure 2a, the

interference pattern recorded consistsof a series of parallel line fringes (inthe diagram the lines are perpcndicu-lar to the page). This is called a photo-graphic grating and appears as inPhoto 1. Figure 2b depicts the samesituation but with a larger angle be-tween theinterferingbeams. As illus-

trated, the effect of increasing the angle between the two beams causes thefringe spacing to become finer. Figure3 isa graphof theamplitude transmis-

sion across the surface of the gratingof Photo 1. There are no abruptchanges in the transmission-thevariation is sinusoidal with the fre-quency of the waveform representingthe spatial frequency of the grating.

In Fourier analysis it is shownthat a wave with very sharply chang-ing shape such as a square wave can

be broken down into many sinusoidalcomponents, while a sinusoidal waveis the purest formpossible. In the case

of the abruptly changing amplitudetransmission of the grating, the result

April/May 1990 23



(a) Amplitude

ON

In

Figure 1 -Parf (al shows a basic waveformoflight, while (b1 showsrelofive wavelengthsof the extremes of the visible spec trum.

is many orders of diffracted beams.Each diffraction order consists of two beamsdeflected at equal angles meas-ured above and below the zero-order (straight through) beam. The angle of deflection 8 of the diffracted beam iscalculated from the standard gratingequation:

D=hsinf f3

where D is the fringe spacing and ilis

the wavelengthinvolved. On theother

hand, the sinusoidal grating producesonly one diffraction order.

THE ZONE PLATE:HOLOGRAM OF A POINT

From a holographic point of view,an object consists of many tiny surface

points or resolution elements. Whenlight is reflected from such an objectonto the film, each resolution elementof the object canbe treated as if it were

a point source of light generating acoherent spherical wavefront. Figure4a is is a hologram of a basic entity-a resolution element (smallest resolv-able point) of the object. Let’s definethe axis of the system as the line pass-ing through the object point and cen-ter of the film. Symmetry exists aroundthis axis, and the microscopic patternrecorded on the film will have theform of concentric circles as shown inPhoto 2. Notice that the fringe spacing

is relatively coarse at the center of the

Figure Oa--When two p lane wa ves me e t ,an inter ferenc e p atte rn c onsist ing of a series ofp a rallel l ine fringe s is rec orde d .

system, but becomes finer, approach-ing one wavelength, as the wavesmove radially outward from the cen-ter of the film. This pattern of alter-nately light and dark circular fringesis called a zone plate and is the generalappearance of a hologram of a single point.

Figure 4b shows what happenswhen theprocessed filmisilluminated.The fringes diffract the light waves asif they were coming from the locationof the point source, forming a virtualimage of the point. A set of converg-ing waves forming a real image of the

point on the opposite side of the holo-gram is also formed. If this were theactual object wave used in the record-ing process in place of the diverging point source, exactly the same inter-ference pattern would have resulted.The certain amount of error present inthe system is desired to give the mathe-matical points physical dimension.

The first holograms were made in1948 (12 years before the invention of the laser) by Dr. Dennis Gabor of theImperial College of London with thelight from a mercury arc lamp whichhad a coherence length of only about

0.1 mmand a bandwidth of about 1 A,which is low coherence by the stan-dards of the laser. Because of the poor sources of coherent light available atthe time, these were on-axis type holo-grams and the object was restricted totwo-dimensional transparencies withopaque lettering. These conditionsgreatly reduced the coherence require-ment. The light was shined directlythrough the transparency onto thefilm. The light passing through the

clear areas served as the reference

Figure2b A large r a ngle beiween the Interfering be am s ca uses the fr inge spa c- ing to b e i me r

Photo 1 -When rec orded on f i lm. the inter - ferenc e p attern show n ab ove is ca l led a pho tog raph ic gra t ing .

beam and the light diffracted by theedges of the lettering served as theobject beam. At this time the conceptof off-axis holography was unknown.Around 1961 Emmett Leith and JurisUpatneiks of the University of Michi-gan, in an attempt to separate the realand virtual images of Gabor’s holo-gram, made off-axis holograms withthe gas laser. The discovery of holog-raphy, or wavefront reconstruction asthe technique was called at the time,earned Gabor theNobel prize in phys-ics in 1971-he died in 1979.

THE FASCINATING FRESNEL

A Fresnel zone plate hasa strikingsimilarity to the interference patternof the hologram of a single point. Weuse the properties associated with theFresnel zone plate in many of the cal-culating procedures required to pro-ducecomputer-generated holograms.In deriving the structure of a Fresnelzone plate we make use of Huygen’s principle which simply states (and can be proven) that each point on awavefront may be regarded as a new

source of secondary wavelets (of the

24 C lRC Ui7 CELL/AR INK



Figure J The freq uen c y of the a m p litud e transmission a c ross the surfac e of the grat ing in Photo rep resents the spa t ia l f req uenc y of the grat ing.

Photo 2-A ho log ra m o f a p oint co nsists of c onc ent r ic c irc les on the f ilm .

Figure 4-_(a) A ho log ram of a sing le p oint c onsists of a l terna tely ligh t a nd da rk c ircular fring es and

is c al led a zone p late . (b l When the p roc essed ho log ra m is i llum i- na t ed , a v i r tual image o f t he o rig i- na l point is formed .

REFE-RENCE BEAM

ILLUMINATING /\ y /’ / ,‘.

BEAM

same wavelength) and the interactionof these wavelets is responsible forinterference effects observed. Figure5a illustrates the principle. Here aplane wave illuminates an opaquescreen with a pinhole in it. The pin-hole acts as a new source of spherical

waves as shown by the segments ofcircular arcs. The small circle repre-sents a secondary wavelet of thespherical wavefront. The amplitudeof this secondary wavelet is not thesame in all directions but varies ac-cording to:

A=i l +cos a) (2)

where A is amplitude and a is theangle at which the radiating ampli-

tude is to be calculated. This equationis known as the obliquity factor. Theobliquity factor has a maximum valueof 1 which occurs when a = 0, corre-sponding to the direction of travel ofthe source. At 90 degrees the obliq-uity factor gives a value of l/2 and at180 degrees the obliquity factor is zeroindicating that, as shown in Figure 5b ,there is no wave in the backward di-rection. Figure 5c is a polar graph ofthe amplitude and intensity distribu-

tion as predicted by the obliquity fac-tor. It follows from Equation 2 that theintensity of the secondary wavelets isgiven by

In this respect we can ignore thelight source once the coherentwavefront isdefined at the diffractingaperture(s). The Fresnel zone plate isa patternof concentric transparent andopaqueringsdesigned tofocusabeamof plane wavefronts incident upon it

Ap ril/ Ma y 1990 25







illustrate respectively the amplitudetransmission of a Gabor zone plateand a Fresnel zone plate. A sinusoidalzone plate is also called a Gabor zoneplate. It should be interesting tocompute the concentrations of lightproduced by a Gabor zone plate byusing as parameters the secondary

wavelets, obliquity factor, and sinu-soidal transmission of the film.To make a distinction between

diffraction and interference, diffrac-tion refers to the situation whena verylarge number of tiny wavelets of awavefront, such as the Huygen secon-dary wavelets, are summed (inte-grated) to produce a the pattern while,interference refers to the interaction(simple addition) of a smaller numberof beams. Briefly, the hologram inter-

ference pattern will be calculated bysumming all of the sinusoidal wavesemitted from each point of the objectand calculating the resultant phaseand amplitude at the hologram sur-face and then assigning either trans-parency or opacity at that point. Thissummation is done for each point.

PRELIMINARY CONSIDERATIONS

The procedure used to produce

the computer-generated hologramswillconsistofthefollowingthreesteps:1) An optical interference pattern

of a mathematically represented sceneis computer calculated by digital ap-proximation. This interference pat-tern is of the type produced by an off-axis holographic recording process.

3) The pattern is then reducedphotographically thus becoming atransmission hologram designed tobe viewed with laser light.

2) This pattern is then drawn on a

screen or plotter producing a mono-chromatic output.

Consideration of the standardrecording process of an off-axis trans-mission hologram reveals some diffi-culties that will be encountered inreproducing the process by artificialmeans. We have seen that this proce-dure produces an extremely fine in-terference pattern. Specifically, Equa-

tion 1 implies that, when the anglebetween the two recording beams

approaches 60”, the fringe spacingapproaches that of the wavelength ofthe light involved, which for a He-Nelaser corresponds to about 1600 line-pairs/mm. Such large angles arerequired because it is desirable for theoff-axis scene to be near the film, thuspermitting a large angular viewing

range. This necessitates an extremelyhigh resolution film such as the Kodak649F Spectroscopic emulsion which iscapable of resolving a maximum of7000 line-pairs/mm. A 4- x 5-inchhologram with a maximumdeflectionangle of 60” will be required to recordabout 132 billion dots.

The hologram also records a grayscale. If 64 levels of gray are assumed,the effective data content exceeds 8trillion (8,000,000,000,0001. (These

calculationsareveryconservative. Toprevent aliasing errors, the resolutionin each direction should be at leastdoubled, and preferably quadrupled.)The size of the hologram is significantbecause the observer moves his headduring viewing to exploit parallax.The dimensions of the hologramshould thus be considerably largerthan the separation of one’s eyes.

The calculation time of the com-puter-generated holograms will bedecreased by reduction of the follow-ing four parameters:

Now consider the time requiredto numerically calculate the data con-

tent for a hologram of a typical (small)object consisting of 1 million resolu-tion elements. This means that therewould be l,OOO,OOO calculations re-quired foreachof the 132billionpointsof the hologram. Although the laserwould produce this data instantly ona photographic emulsion (the highestinformation storage material known),the process would take a computer,working at a rate of one million calcu-lations per second, over 4000 years!

Z&&gram size-The hologramswill be no larger than the standardframe size of the popular 35mm film(36 mm x 24 mm).

Quantify of resolution elements of subject-The subject will be a simplegeometrical shape such as a circle con-sisting of only a few pixels.

Angles between object and referencebeam-The maximum angle here will

SAVE Developmentand Debugging Time

of EmbeddedMicroprocessor Systems!

l INTROL-C Cross-Compilersl INTROL-Modula-2 Cross-

Cross-Assemblers-

COMPILER PACKAGES INCLUDE:Compiler l Assembler l Linkerl Runtime library, includinga multi-tasking executive l

Support utilities l Full year’smaintenance

TARGETS SUPPORTED:6301/03 l 6801 J O3 l 6809 l

68HCll l 68000/08/10/12 l

68020/030/881/851 .32GOOJ32181182

AVAILABLE K>R FOLLOWINGHOSTS: VAX and MicroVAXApollo; SUN; Hewlett-Packard;

Macintosh; Gould Power-Node; IBM-PC, XT, AT, andcompatibles

INTROL CROSS-DEVELOPMENTSYSTEMS are proven, acceptedand will save you time, money,and effort with your develop-ment. All INTROL products are

technical support. IwI

for facts NOW!

CORPORATiON

9220 W. Howard Avenue

Milwaukee, WI 53228

4141327-7171 FAX: 4141327-7734^

Ap r i l /Ma y 1990 29



be minimized for a given fringe spac-ing of the hologram.

Gray scale-There will be no grayscale. The hologram will consist ofonly transparent or opaque areas.There is a very mysterious and littleknown property of holograms that isof great significance in this applica-

tion: The gray scale of the subject is in-dependent of the gray scale of thehologram. One may deduce that if thehologram is of binary form, then thereconstructed image must also bebinary in nature. This is not the case.The reconstructed image may have acontinuous gray scale regardless ofthe binary nature of the film. Anylevel of brightness that is assigned toany pixel in the recording process isstored in its relative proportion in the

wave summation over the entire holo-gram area.

HARDWARE CONSIDERATIONS

Holographic patterns will bedrawn using the following three typesof output devices:

A standard VGA display of 640 x480 dot resolution and hologram reso-lution (640 x 427).

A pen plotter with an effectiveplot area of 864 mm x 546 mm and O.l-mm resolution with a 0.3-mm tip di-ameter pen giving a hologram resolu-tionof2880x1820(819mmx546mm).

A multihead laser plotter with aneffective plot area of 24”~ 18”and 0.5-mil(O.0005”) resolution giving a holo-gram resolution of 48000 x 32000 (24”

x 16”).The effective plot area of each

device is shown in parentheses inorderto obtain a width-to-height ratio ofthat equal to the standard 35mm filmframe (3:2). This clipping represents asignificant time savings when thereduced pattern is to be of maximum

size (36 mm x 24 mm).I used technical pan film to photo-graph the holographic interferencepatterns since this filmis readilyavail-able and can resolve up to 400 line-pairs/mm at various contrast levels.This film is also ideal for applicationsinvolving a He-Ne laser as it has a

high sensitivity to light in the redportion of the spectrum. EktagraphicHC slide film might also be used be-cause of its 750 line-pair/mm resolu-tion.

REDUCTION METHOD

Because we are creating a holo-gram artificially by imitation of theactual process on a large scale andthen reducing it for illumination withthe light from a He-Ne laser, we mustconsider what effect reduction of thepattern as well as reduction of the re-cording wavelength has on the finalimage. Keeping in mind that in theplotting process, a large wavelength(imaginary, of course) can be associ-ated with the recording pattern, we

will look at the effect, on the recon-structed image, of reducing the holo-gram pattern as well as the recon-structing wavelength.

To simplify matters for illustra-tion, suppose that the object consistsof a single point A as illustrated inFigure 7. We know the values of the

EXPRESS CIRCUITS

MANUFACTURERS OF PROTOTYPE PRINTED CIRCUITS FROM YOUR CAD DESIGNS

TURN AROUND TIMES AVAILABLE FROM 24 HRS 2 WEEKS

Special Support For:

l TANGO.PCB

l TANGO SERIES II

l TANGO PLUS

l PROTEL AUTOTRAX

l PROTEL EASYTRAX

l smARTWORK

l HiWIRE-Plus

l EE DESIGNER I

l EE DESIGNER III

l PADS - PCB

l OTHER PACKAGES ARENOW BEING ADDED

l FULL TIME MODEM

l GERBER PHOTO PLOTTING

Express

Circuits314 Cothren St., PO. Box 58

Wilkesboro, NC 28697

Quotes:l-800-426-5396

Phone: (919) 667-2100

Fax: (919) 667-0487

30 C lRC UlT CELLLAR INK





the edges of the plot. Notice how the jagged edges arrange themselves toproduce several families of secondaryzone plates. When this pattern is illu-minated with laser light, each of thesesecondary zone plates has a focusingeffect, and the error emerges as amatrix of concentrations of light (sec-ondary foci) about the primary centerfocal point as shown in Photo 4b.Photos 4c4e illustrate zone plate for-mation on a VGA screen with antiali-asing factors of 1,2, and 3. As can beseen, the aliasing error decreases (less

Figure 8 / f a hologram is to b e formed without e x c e e d i n g t he m a x i m um s p a t ia l

secondary zone plate contrast) as thef req uenc y , then a l l ob jec t points m ust be c onf ined to the shad ed reg ion. Any points l oca ted outside th i s area such that l a rge r ang les are produc ed between the interfer ing

antialiasing factor increases. From beams wil l prod uc e e rrors in the pa - i t m .

GET TO WORK!

A New ProjectOur line of macro Cross-assemblers are easy to use and full featured,including conditional assembly and unlimited include files.

Get It To Market--FASTDon’t wait until the hardware is finished to debug your software. Our Simulators can test your program logic before the hardware is built.

No Source! A minor glitch has shown up in the firmware, and you can’t find theoriginal source program. Our line of disassemblers can help youre-create the original assembly language source.

Set To GoBuy our developer package and the next time your boss says “get towork”, you’ll be ready for anything.

Quality SolutionsPseudoCorp has been providing quality solutions for microprocessor problems since 1985.

BROAD RANGE OF SUPPORT. Currently we support the following microprocessor families (with more in

development):

Intel 8048 RCA 1802,05 Intel 8051 Intel 8096Motorola 6800 Motorola 6801 Motorola 68HCll Motorola 6805Hitachi 6301 Motorola 6809 MOS Tech 6502 WDC 65CO2Rockwell 65CO2 Intel 8080,85 Zilog 280 NSC 800Hitachi HD64180 Motorola 68000,8 Motorola 68010

0 All products require an IBM PC or compatible.Cross-Assemblers as l ow as 50 00

Simulators asl owas 100. 00

Cross-Disassemblers as l ow as $100. 00

Developer Packages as l ow as 200.00

(a $50. 00 Savi ngs)

So What Are : Waiting For?

PseudoCorpProfessional Development Products Group

716 Thimble Shoals Blvd, Suite E

Newport News, VA 23606(804) 873-1947

this data, I decided to use an antiali-asing factor of 2 for the computer-generated holograms.

SYNTHESIZING A HOLOGRAM

Let’s start our example by calcu-lating the interference pattern for ahologram of a computer-generatedcurve (a three-leaved polar rose). Here,the situation for the VGA display (640dots horizontally by 480 dots verti-cally) is used. These displays areusually about 10” x 7.5”. Because thewidth/height ratio is lightly different

than that of a 35mm camera, whenphotographing with a 36-mm x 24-mm viewfinder, simply fill the areavertically. Ideally there will be a smallvertical strip along one edge of a full-scale (36 mm x 24 mm) hologram, butall pixels will be used. The spatial fre-quency of a VGA display is about 1.26line-pairs/mm. We will divide thisvalue by 2.5 to prevent error: 1.26/2.5= 0.504 line-pairs/mm. I will conser-vatively round this value to 0.5 in

actual calculations.The hologram plane is defined in

a three-dimensional Cartesian coor-dinate system as illustrated in Figure9. The origin of the system has coordi-nates (x,y,z)=(O,O,O), with the coordi-nate signs assigned as implied by thedrawing. The hologram plane coin-cides with the xy plane with its topedge on the +x axis and upper-leftcorner at the origin. Note that +x is totheright and +y isdownward to matchthe native coordinate system of thecomputer display. The +z direction is

32 ClRCUlT CELLLAR INK

Reader Savice P 155



a)

b)

d)

Photo 4-_(a) A typ ic al zone plate. (b l The

ma xtrix of d ots are errors c aused by sec on- d ary zone plate s. ( c ) - ( e ) Zone plate s with ant ial iasing fac tors of I, 2, and 3 .

toward the rear looking through thehologram plane. The coordinates ofthe lower right corner of the hologramextent have VGA coordinates(639,479). The screen size photo-graphed will be 10” (0.254 m) by 7.5”(0.192 m). The position, in three-di-mensional space, of the lower-right

corner of the hologram is located at(0.284,0.192,0). Let’s give the rose aradius of 0.1 m and let it consist ofabout 41 (I incremented the full polarrotation of pi by0.075) equally spacedpixels of equal intensity (more on in-tensity assignments shortly).

We will now consider how closethe reconstructed image can form fromthe hologram plane. If the entire screenof 0.254 m x 0.192 m is to be reduced asto just fill a 36-mmx 24-mm film frame

then the reduction factor is 8, as shownin Figure 10a. This will result in the0.500 line-pairs/mm of the plot to be-come about 4 line-pairs/mm in thefinal hologram. We also know that thesynthetic wavelength should be eighttimes that of the reconstruction (he-lium-neon laser) wavelength, or 5.0624x 1OA m. Equation 4 tells us that themaximum angle that the hologramcan deflect the reconstruction beam isabout 0.146”. This corresponds to a

minimum object distance (on the plotscale) of about 63 m if the maximumhologram radius is, using the diago-nal, 6.25”. Notice that an additional39.52 m must be added to the mini-mum object distance if the entire O.l-

m rose is to be recorded. Since itwould be desirable for the image to besomewhat closer to the hologram, let’slook at a reduction twice as great.

+X

CENTER (0.284.0.,92.0) 0.284.O.l ?. 0)

f+Y

Figure 9-7he holog ram p la ne is de l i ned in

a three-dime nsiona l Ca rtesian co ordinate system a nd is show n a s the shad ed region.

P Lab ard

I/O Cards:l A/D, D/Al Digital I/O & Counter l IEEE-488 Interfacel RS-422/485 Comm.l Stepping Motor Controll Prototypingl MicroChannel Digital I/Ol MicroChannel GPIB Interface

Daughter Boards:l Amplifier/Multiplexer l Wiring Terminall Opto-Isolated D/Il Relay Outputl SSR Output

Industrial Computer:l Industrial Computer Chassisl Computer Card Cagel Slot Extension Kitl CPU Cardl RAM/ROM Disk Card

Software Support:l AMS (Strip Chart Recorder)’ ASYSTANT+

’ ASYSTANT GPIBl DADiSP

l LABTECH NOTEBOOK l PC-LabDAS

l UnkelScope

CALL FOR FREE CATALOGS!

(408) 293-6786

American Advantech Corp.

A1460 ‘Ittlly Road, Suite 602

Ad,,antee,, San Jose, CA 95122-9967 Fax: (408) 293-4697

Dealer and OEM Inquiry Welcome

Ap r i l /May 1990 33







Photo 6-Plot t ing a sma l l offset o f

the interferenc e p at tern show n in

Photo 5b el iminates any hint of the

rose shap pe d out l ine. When i/ / u-

minuted, the p ro jec ted rea l im-ag e is identica l to that in Photo 5c .

Photo 7 1

shapped

the peta l s

b l an ce to

expec t ed





FEATURE

Modulating Laser DiodesARTICLE

Steve Ciurciu

TheSearch

for th e Perfect Driveway Sensor

I t all started when I bought one of those Radio

Shack infrared doorway detectors and tried to use

i t a c r o s s m y d r i v e w a y t o t e l l w h e n s o

proaches the house. It’s not that I don’t like sur-prises, it’s just that any good home control system

should be aware of its perimeter property as well. At

least, that’s what I tell people who see the array of

sensors and devices lining the driveway. In actual-

ity, most of it is now an electronic graveyard con-

taining the remnants of many attempts to make a

no-fault organic/inorganic driveway sensor. Let me

explain.

The C irc uit Ce lla r driveway sensor farm inc lud es i? mot ion , modula ted and unmodulatedin terrupte d b ea m. and pneuma t i c sensors.


Unlike the average colonial orsaltbox house you’d expect in NewEngland, I live in one of those strangelyshaped California contemporariesmore befitting a reclusive personality.It affords spacious living and I don’t

have to see any neighbors. Unfortu-nately, I can’t see my BOO-foot drive-way either. When I go down in theCircuit Cellar and turn on the stereo Imight as well be on another planet asfar as anybody pounding on the frontdoor is concerned.

A half dozen years ago circum-stancesmademe reevaluate ignoranceof above ground events. One timewhile I was buried (figuratively) in aproject in The Cellar, a large truck

pulled into the driveway and dumped14,000 lbs of crushed stone. Later,another truck dumped 8 cubic yardsof top soil. I just happened to goupstairs in time to see a third truckbacking in with a load of landscapingtimbers.

I practically had to throw my bodyacross the hood of this truck to stop itfrom being dumped next to the otherpiles. Believe me, it was a real fight.From the driver’s perspective I was in

the wrong, of course; after all, therewere two piles of stuff already on thedriveway. This had to be the rightplace.

Shortly after that I decided theonly way to avoid similar situations inthe future was to apply the typical Ci-arcia response: massive interventionof electronic countermeasures. Tokeep a closer eye on ground level andperimeter events, I installed a closedcircuit video systemand put monitors

in strategic locations. If I heard some-thing or wanted to check on outside



conditions without leaving my desk, Imerely looked at a monitor andswitched to an appropriate camera.

As a refinement to the system, Iinstalled devices in the driveway andaround the perimeter that triggeredcontrol events when they sensedpeopleorcarscomingdownthedrive-

way.Without resorting to esoteric“military budget” solutions involv-ing strain gauges under the pavementand hidden microphones with DSP“signature-detection” electronics inthe bushes, or low-light-level CCDcameras with video pattern recogni-tion, I decided to attempt a more eco-nomical perimeter intrusion detector(I am working on a video digitizer/DSP analyzer “seeing” detector as the

ultimate solution to this problem butthat is a future project).A relatively simple combination

ofinfraredmotionorbeamsensoranda magnetic coil sensor mounted in thesame physical location seemed to of-fer a quick solution. A large steelvehicle (inorganic) passing the sensepoint would trigger both the infraredand magnetic sensors (the magneticsensor is a coil of wire under the drive-way with the electronics of a classic

metal detector; simple but effective).A person (organic) passing the sensepoint would trigger only the infraredsensor. Simple binary logic and youhave both a people sensor and a ve-hicle sensor.

Being a pessimist, I expected tohave a real problem building theunderground metal detector. Fortu-nately, I found a off-the-shelf mag-netic field “vehicle” sensor in aSporty’s catalog (Clermont Ave., Ba-

tivia, Ohio 45103, 800-543-8633) for$159 whichIpromptlyinstalled. Sinceit worked like a charm with littlemodification (provided you don’tdrive in on a lawn mower), I focusedmy attention on the easy chore ofmaking an infrared driveway sensor.After all, how difficult could it be? Godown to your local Radio Shack andbuy one of those infrared door entrysensors and mount it across the drive-way? Or, how about a motion detec-

tor like the ones that trigger outsidelights?

TRUTH IN ADVERTISING

The first thing you should knowabout practically all low-cost commer-cial infrared sensors is that they’re ba-sically good for nothing when usedoutdoors. Spend a little time watch-ing one of those IR motion detectors

when it is raining and see how manytimes it triggers falsely. Or, drive a carthat has been sitting at ambient tem-perature a few hours past a sensorwhile the engine is still cold (what

enclosure (heated and cooled) andperfectly aimed at an appropriate re-flector across a driveway. Unfortu-nately, in my experience, they lack thesignal-to-noise discrimination to dealadequately with the dynamics ofbright daylight and seasonal changes.Adding black tubular sun shields in

front of the lens extended the usefuloperatingperiod,but there were timeswhen the ambient light completelyswamped the reflected signal and therewas no output (false-negative error>.

The Circuif Cellar la ser d rivew a y sen sor consists of a n R laser transmitter on the g a r a g e (righ t ) and a rec eiver on a po st ICO feet aw ay (left).

car?). Of course, if the only repercus-sion is that the porch lights are left onfor a couple extra minutes, we hardlynotice. Even when the light stays oncontinuously we frequently don’t care.

(While I had some success with nar-rowly aimed IR motion detectors, Iwas never satisfied with the numberof false-positive errors).

In a world of real control applica-tions, however, if such a detector trig-gered several lighting control actionsin the house or opened/closed thegarage door, you’d notice false trig-gering and errors immediately.

Indoor-use interrupted-beamsensors hold a little more promise.

Withalittleworktheycanbemountedin an environmentally conditioned

Instead of more efficient mirrors,and so on, the solution to increasingsignal-to-noise ratio is to eliminate thepassive reflector and actively trans-mit a bright modulated beam from the

opposite side of the road. This is, infact, the design basis of most indus-trial IR beam sensors. Unlike theindoor-use units that have 20-30-footranges using a reflector at the oppo-site sense point, industrial interruptedbeam sensors generally use separateIR transmitters and receivers and canhave ranges of hundreds of feet.

A CHALLENGE IN THE MAKING

CreatingbothasufficientlybrightIR source (signal) and a discriminat-

Apr i l /May 1990 39









LED operation

L a s e r th’reshold

Drive current

Figure J The laser diod e’ s drive c urrent m ust be c arefu l ly regulate d nea r the laser threshold so it is

high e noug h to be ab ove the threshold, but low enoug h to a vo id burn ing o ut t he d i ode .

using a visible laser was impossible.

What seemed barely visible in day-light was now quite spectacular indarkness. Certainly no semiintelli-gent door-to-door salesman wouldallow himself to be detected by a sys-tem that he could merely step over oraround. Should hebe closely followedby some eco-phreak protesting laserirradiation of the neighborhood andinnocent children, I could also have abunch of crazy radicals on my hand. Ihad to be more clandestine about such

activities. Invisibility was the onlyanswer.

INFRARED LASER DIODES

I had had more experience withthem. Laser diodes have beenaround for years for use in fiber-optic communications, but theyhave been extraordinarily ex-pensive and complicated tomodulate. Theones I had previ-ously used were pulse-mode-

only devices that were hardlyapplicable. Fortunately, im-proved manufacturing tech-niques and higher productionvolumes have changed the situ-ation entirely. With millions oflasers in CD players and print-ers, it’s possible to find continu-ous-output devices for aslow as$5 apiece from surplus houses.

The more cost-effective invisiblelasers emit in the infrared range. Themost common types of these are car-bon dioxide gas <CO,> and LED solid-state lasers. CO, lasers tend to be a bitlarge and on the powerful side. Ofcourse, if one’s intention is deterrence

as well as detection, setting fireto a salesman’s sample case ashe passes through the beam willcertainly do that. All humoraside, however, CO, lasers aremuch too costly and dangerousfor anything less than high-heatapplications or starwars. IRlaserdiodes are really the better wayto go.

Laser diodes are similar in struc-ture to standard LEDs. The laser di-ode is a block of semiconductingmaterial containing a p-n junction justlike an LED (Figure 2). When currentpasses through the junction, energy isreleased as light and heat. The color oftheemitted light dependson theband-gap energies of the materials used,and the amount of waste heat dependson the conversion efficiency. Con-

tinuousoutputdouble-heterojunctionlaser diodes, typically used in CDplayers, are made from GaAs orGaAlAs. They radiate at 720 to 900nm. New InGaAsP and InP lasersemit in the range of 1150 to 1600 nm.

From a structural standpoint,LEDs and laser diodes are very simi-lar. The only important difference isthat in a laser diode two of the edgefaces (or facets) are cleaved and coatedso that they reflect part of the gener-

CONNECTION

This was not a new revela-

DIODE DYNAMICS

tion, unfortunately. I would

have used a laser diode instead

Figure4 Wh ile the a c t u u l ase r d iod e is q u ite

of an IR LED in the first place if sma ll, the he a t sink an d co l l omato r a ssem b ly are nec essary for prop er ope rat ion.

LIGHT EXI T

ated light back into the semiconduc-tor. The reflected light stimulates theemission of other photons. The stimu-lated emission also tends to producethe strongest amplification at narrowwavelengths rather than across a broadrange like an LED.

Of course, there is a price to be

paid for all this. Laser diodes operateat much higher drive currents thanLEDs. At low currents, LEDs andlaser diodes behave the same. Atslightly higher currents, the laser di-ode becomes a superluminescent di-ode but does not have sufficient gainto produce laser oscillation. Onlywhen the operating current is equal toor greater than the laser diode’s“threshold current” will the diodeoperate as a laser. Figure 3 shows a

typical threshold curve.This threshold curve is very im-portant to laser diode operation andfigures prominently in driver circuitdesigns. The threshold point of a laserdiode is a dynamic value which de-pends greatly on case temperature.Special care should especially be takenat low temperatures. A laser diodethat takes 80 mA to operate when thetemperature is 60°C might only take50 mA at 0°C for the same light out-

put. Unless the current is reduced asthe temperature decreases, excessivedrive current will burn up the diode.

The lifetime of a laser diode de-creases sharply with higher operatingtemperature and output power. In-creasing the operating temperaturecauses threshold current to rise andefficiency to drop. The lost efficiencycreates more heat again. Left un-checked, such a condition can causethermal runaway of the laser diode.

To facilitate proper operation,laser diodes incorporate an integralphotodiode (usually mounted on therear facet) which directly monitorsthe light output. Using this photodi-ode in a closed-loop controller allowsa system to set a specific light inten-sity regardless of ambient tempera-ture. In combination with a simpleheat sink to remove excess heat dur-ing operation, virtually all worry ofthermal runaway is eliminated.

Once you’ve got the diode run-ning you might think that a tight beam

44 C IRC UITC ElLAR INK



of light is automatically emitted fromthe laser’s quartz window and youcan project a spot on the wall, right?Guess again. Like an LED, the beamspreads out in an elliptical patternfrom the diode. For the typical IRlaserdiode, the beam spreads out at a 35”angle perpendicular to the junctionand 10” in the plane of the junction.

Just like regular LEDs, laser di-odes rely on external optics and hous-ings to redirect the light. Laser diodesgenerally use stacked lenses called acollimator to tighten the beam intocircular form and concentrate theenergy. In my experience, trying touse a laser diode without a collimatoris like running a car without gas: it hasa lot of potential but goes nowhere.When you purchasea laserdiodemake

sure it has a collimator if your inten-tion is to have a laser “beam.” Like thelaser diode used in my prototypedemonstrates (Figure 4), this collima-tor and diode combination need notbe particularly large.

MODULATING LASER DIODES

Diode lasers require no warm upand can be modulated directly byvarying the drive current. However,

whatever the modulation technique,the laser’s specified operating enve-lope must be maintained below itsmaximum operating limits.

Figure 5 is the schematic of theclosed-loop laser diode modulatorpictured in Photo 2. The laser diode isa 780-nm5-mW Sharp LT022MC laserdiode with attached collimator whichI bought from Meredith Instrumentsfor $15. Its threshold current is nomi-nally 50 mA at 25°C. The IR3C02A

chip is a special closed-loop laser diodecontroller chip made by Sharp. Itincludes all the current averaging,driver, and comparator circui ts neededto operate and protect a laser diode.

The IR3C02A chip operates on +5V and -5 V. Because my particularcontrol system uses a common 12-Vbus to power remote peripherals, Iadded power supply circuitry to themodulator that allows it to operatefrom a single 9-24-V supply input.

This supply voltage is regulated downto +5 V with a 7805 three-terminal reg-

ulator and inverted with an ICL7660DC-to-DC converter to produce -5 V.

The IR3C02A providesbothmoni-toring and feedback control to the laserdiode and provides up to 170 mA ofdrive current. The laser diode is con-nected between pins 1 and 2 with aseries current-limiting resistor. The

laser’s photodiode monitor is con-nected between pins 2 and 3.When current is turned on, the

controller chip ramps the power to thelaser diode. As power is applied, thelaser’s output is compared to a presetmaximum power level determined bythe settingof Rl. If theoutputexceedsthe setting, the chip automaticallylowers the current to compensate.

External modulation is appliedthrough a separate transistor which

provides additional drive current tothe laser. The collector resistor limitsthis additional drive current to bewithin protectable limits. The base ofthe transistor connects to any TTL-level modulation source. You can usethe 16.8-kHz/40-kHzoscillatorcircuitfrom Figure 1 to make an interrupted-beam sensor or you can send any formof digital data.

SEEING IS BELIEVING

The good news about using amodulated infrared laser as an inter-rupted beam sensor is that you canuse it for hundreds of feet. The badnews is that it is impossible to aimwithout considerable effort.

Twenty-foot reflected-beam sen-sors project a very large irradiationpattern. A little trial and error holdingthe reflector until you happen uponthe right “spot” to trigger the beam isa relatively easy task. At 20 feet, simpleeyeballalignment techniquesarequiteadequate.

Using an infrared laser at a dis-tance of 200 feet is quite another mat-ter. Commercial units usually incor-porate sighting scopes for direct line-

of-sight alignment. Like sighting ahunting rifle, one simply sets the re-ceiver in the crosshairs of the trans-mitter’sscopeand tumson the switch.Unfortunately, once we add any kindof an angled reflector into the laserbeam’s path, visible alignment is com-plicated by an order of magnitude.

Still, like the visible He-Ne laser,there is no real substitute for seeing

COMMUNICATIONS

508-485-1144FAX508-481-7222BBS508-460-9203

LOWBUDGETSPECIALS19” COLOR SUPER VGA MONITORLIKE NEW 6 MONTH WARRANTY . . . . . . . . . . . . . . . . . . $800.66

USED 3 MONTH WARRANTY . . . . . . . . . . . . . . . . . . . . . . . . . . .

USED WITHOUT CASE . . . . . . . . . . . . . . . . . . . . . . $300 To $660.06

19” COLOR SONY 1280 X 1024 . . . lSOO OO

THESE SONY TRI NI TRONS HAVE A FU LL 6 MONTH

WARRANTY PARTS AND LABOR.LIMITED QUANITY16” IKEGAMI KHZ 1280X1024 NEW . . . . . . . . $899.00

16” PANISONIC 64KHZ USED . $599.00

” IKJZGAMI Tm VGA CHASIS . . . . . . . . . . . . $249.00

NEW WITH 1 YEAR WARRANTY

19” PHILLIPS 1024X800 48 KHZ GRAY SCALE . . . . . . . . . . . . . . . . . . $350.00NEW 1 YEAR WARRANTY MAY BE ORDERED FOR VGA AT NO EXTRA CHARGE.WHEN USED IN VGA MODE THE MONITOR WIL L RUN 800 X 600 X 256 GRAY SCALE ?R 24X768x 6 GRAY SCALE ONLY

CALL US ABOUT OUR LARGE VARIETY OF GRAPHIC CARDS

194 Main ST. Marlboro,MA 01752

April/May 1990 45



7 9

Power

Modulated

where the beam is actually going. Arewe receiving the true incident beam ora secondary reflection? Is the receiverset in the center of the projected spotor at the edge? Just how bright of a

signal is this after bouncing off tworeflectors anyway? How do I know Idon’thavesomedangerousreflectionspointed directly at my eyes while I’mworking on this? Questions like thiscan only be answered if we actually“see” the infrared laser beam.

While infrared radiation is invis-ible to the humaneye,itisquitevisibleto “electronic eyes.” A video cameraor camcorder which incorporates aCCD (charge-coupled-device) video

sensing element “sees” infrared lightthe same as visible light. If you aim aCCD camera at a blank wall and pointthe average hand-held IR remotecontrol at it, it will appear like youhave a flashlight aimed at the wall. Infact, these invisible sources of lightlook surprisingly bright once you cansee them!

The correct and safe way to ex-periment with and align an IR laserdevice is to do it entirely with a CCD

camera. While wearing IR safetyglasses, view the operating laser on avideo monitor. That way you can seeexactly where it’s going and measurerelative intensity as well.

Of course, this can all appear a bitRube Goldberg to the neighbors. Inthe dark of night I loaded the videomonitor, camera, tools, and assortedtest gear into a wheel barrow with a200-foot extension cord. I attached thetransmitter to the side of the garage

and pointed it toward a piece of white


Figure 5-The c l o s e c ~ o o p la -

ser o d e m o la t o r c i r c u i t

uses a Sa rp c h ip des igned

spe c i f ica l ly for the purpo se.

Photo 2--The LRl22MC laser

d iode c an be seen on the le f t

side of the prototype of thec ircuit in Figure 5. The L M7805

is at tac hed to the hea t sink.

posterboard about 100 feet away.Using the CCD camera, I easily cen-tered the three-inch spot on the mir-ror. Using the cardboard again al-lowed me to find and position the

beam at a convenient location on theside of a post. I centered the receiverin the beam pattern and the relay in-stantly pulled in. Success!

OUT OF ISOLATION

Unfortunately, a good designtends to multiply. One little laser onthecomerofthegaragehasbeenjoinedby one across the front deck and onebetween the house and small garage.

Next, I suppose1 have to add one fromthe small garage to the big garage, oneacross the rear deck and, I suppose,across the other driveway entrance(What? I failed to mention that one?).Monitoring the perimeter could get alittle out of hand. Eventually I couldhave this giant web of infrared sens-ing energy encircling the wholeplace.. .

Enough! See what happens whenyou make a little LED flasher that

works!

Inactuality, thisinterrupted-beamsensor design is only part of an inte-grated network of environmentalmonitoring and control. I view thesesensors as positive verification that

other more esoteric devices are actu-ally working correctly. It is quite truethat a web of IR beams is a total solu-tion in itself but this involves a lot ofhardwiring and physical placementof sensors. Considering that the latteris done primarily with a postholedigger, I continue to look for lessstrenuous sensing alternatives.

being down in the Circuit Cellaris no longer like being in a hole (actu-ally, this cellar is better than most

people’slivingrooms). Icanseewhat’sgoingonoutinthedrivewaybyglanc-ing at a video monitor with automaticcamera switching (see CIRCUIT CELLAR

INK issues 1 and 2 for the design ofthis video multiplexer). My next de-sign objective is to totally dispensewith the perimeter sensors and use aprocessor with the cameras to directlydo motion sensing and pattern recog-nition.

Yes, I know that such systems

supposedly exist. I already have a

















DIAL.ASMThis program generates a dial tone (350 Hz + 440 Hz).It is an adaptation of: "Precision Digital Sine-WaveGeneration with the TMS32010 by Domingo Garcia, TexasInstruments found in "Digital Signal ProcessingApplications with the TMS320 Family, Volume 1.

This program also demonstrates the use of the timerinterrupt. We want a timer interrupt to occur every125 microseconds (an 8-kHz rate). The PRD, periodregister, determines the number of clock cycles which

are counted down prior to a timer interrupt.For a 40-MHz TMS320C25, PRD 1250,For a 36-MHz TMS320C25, PRD > 1125,For a ZO-MHz TMS32OC25, PRD 625,to yield an 8,000-Hz timeout rate.

The tone variables, Ton350 and Ton440, determine thefrequency of the resulting sine waves by theformula: tone = desired frequency/O.25For example: Ton350 = 35O~z/O.25 = 1400

and, Ton440 = 44OHz/O.25 = 1760

;CONSTANTSPRDVAL EQU 1125TON350 EQU 1400TON440 EQU 1760:PAGE 0 VARIABLES

; value for 350 Hz; value for 440 Hz

DEL350 EQUALP350 EQUSIN350 EQUTEMP EQUMASK EQUOFSET EQUALP480 EQUDEL480 EQUSIN480 EQUTMPO EQUSTRT: LDPK

LALKSACLLALKSACLZACSACLSACL

LALKSACLLALKSACLLALKSACLLSTLALKSACLLSTlZACSACLLACKSACLLALKSACLLACKSACL

EINTLOOP: BTMRINT: LAC

SACHLACADDTBLRLACADDANDSACLLACSACHLACADD

96

;li991001011021031041050

~~FFFHMASKSINEOFSET

ALP350ALP480

TON350DEL350TON440DEL480OEOOHTMPOTMPO03FOHTMPOTMPO

TEMP1

TMPOPRDVALPRD008HIMR

LOOPALP350,8TEMPTEMPOFSETSIN350ALP350DEL350MASKALP350ALP480,8TEMPTEMPOFSET

;SET STATUS 0 REG

;SET STATUS 1 REG

;SET PRD REGISTER;FOR A 8KHZ TIMEOUT;INTERRUPT MASK FOR;TIMER INTR ONLY

RATE

COI?iinued)

generation of the 350-Hz sine wavewhile ALP 4 4 0 and DEL4 4 0 are usedin the generation of the 440-Hz sinewave. TONE1 and TONE2 are con-stants to which the Delta variables areinitially set, respectively. At an 8-kHzsampling rate, the constant equals thedesired frequency multiplied by four.For example, the constant for 350Hzis350*4 or 1400. Just prior to sending theoutput to the D/A converter via theSac1 DXR instruction, the two sinewaves are scaled and added together.Connecting the DAC output to an os-cilloscope would show how the twosignals add together to form an envel-oped waveform. Or, you could con-nect theoutput to an audio amplifier/speaker (such as the Radio Shack 277-1008) to hear the dial tone.

GOING FURTHER

We could continue with the sinewave table look-up theme to includeDTMF generation, busy tone, ringback tone, error tone, and many oth-ers. All it takes is a few calculations of the Delta table index constants andtiming loops. For instance, a busytone is the sum of 480-and 620-Hz sinewaves pulsed on/off at a half-secondrate. Ringback is the sum of 440 Hz

and 480 Hz waves turned on for onesecond and turned off for three sec-onds.

With constants having been cal-culated for mark/space frequenciesalong with the proper bit period tim-ing, one could develop a simple FSK modulator. At each bit boundary, amark or space frequency would beselected depending on the next bit’svalue. Inherent in the look-up tablescheme, a transition from a mark to a

space (or vice versa) results in a changeof the table step size, providing a phase-continuous waveform at bit boundaries. Phase-continuous FSK switchingallowsforbettersignalproc-

essing on the opposite end of themodulation process (demodulation).An analog FSK modulator whichswitches between two free-runningoscillators (one for space, one for mark)doesn’tprovidephasecontinuitysincethe two oscillators are asynchronous

with each other.listing 2 D IA L A SM ge nerates a stand ard te lepho ne d ia l tone, which is the sum o f 350

Hz an d 440-Hz sinu so id s.







BASIC RadioactiveRandoms

FIRMWAREFURNACE

Ed Nisley

\J enerating random num-bers is a perennial-computer maga-zine topic, but the articles always seemto discuss the linear congruential orsoftware shift register implementa-tions. While pseudo-random (pro-nounced “fake random”) numbersmay be OK for computer science types,Real Engineers get Real RandomNumbers by timing nuclear disinte-grations with a Geiger-Miiller detec-tor. When you want random num-bers, why settle for less than the best?

The problem has always been thatyou had to build a radiation detectorfrom scratch, adapt one from the sur-plus market, or pay far too much for aheavy-duty chunk of electronics withfar more features than you need. Afew monthsagoIsaw theRM-6OMicroRoentgen Radiation Monitor fromAware Electronics. It is a Geiger-Miller tube that connects to a PC’sparallel or serial port, with the cir-cuitry drawing power from a singleinterface pin.

The RM-60 costs under $100 inonesies and comes with some reasona-bly well-done software that turns your

PC into a Geiger counter, strip-chartrecorder, and data logger. All that iswell and good, but as soon as I saw thegadget I realized that Real RandomNumbers were now within reach! AllI needed was an RTC52 and a littlefirmware.. .after all, who wants to tieup a PC to count fissions? [Editou’sNote: See “From the Bench” in issue 8 ofC IRCUIT C E L L A R N for the design of theRTC52 single-board controller.1

Although the RM-60 is interest-ing, I thought this would provide a

good excuse to explore grafting as- make sure that the bits are actuallysembly language programs onto the arriving at the right ports. Figure 1BASIC-52 interpreter. Measuring time shows the interface between the RM-intervals is a common industrial prob- 60 and an RTC52 board; while you canlem and I have never met anyone who certainly usedifferent computer hard-wrote a BASIC program that ran fast ware, it’s hard to mess up three color-enough. coded wires.

I’ll start with a pure BASIC im-plementation and wind up with aBASIC language extensiondevoted toreturning random numbers. Alongthe way you’ll learn more about theinnards of the BASIC interpreter thanever showed up in the manuals.

The RM-60 produces a down-going 75-90-ps pulse each time it de-tects a radioactive decay particle. It issensitive to alpha, beta, and gammaparticles, but the output pulse is iden-tical for all three because the detectortube operates in Geiger mode. Themaximum count rate is thus over10,000 counts per second...at whichpoint you have more than just a radonproblem in your basement.

BASICALLY RANDOM

Regardlessof how trivial the hard-ware interface appears, you shouldalways write a simple test program to

The background radiation in myoffice provides about 10-15 counts per

SCREW

TERMINAL

CONNECTORS

MODULAR

PHONE

CONNECTOR

SERIAL

CONTROLLER

Figure 1 --Inte rfa c ing the RM-60 Micro Roe ntge n Rad iat ion Moni tor to a m icroc om pute r

Is a s ea sy a s three w ires.

58 ClRCUlT CELL/AR NK









because the simulator doesn’t dependon the actual 8052 hardware, yourprogram can’t crash the system bydoing something really stupid.

Simulatingyourcodeisone thing,but how can yoube sure that you haveall the interfaces between it and theBASIC interpreter correct? The an-

swer is easy, but not obvious: simu-late the whole BASIC interpreter alongwith your (teeny) program!

The key is to get the interpretercode as a hex file that you can feedinto the simulator. To do so, you canactually extract the code directly fromwhatever processor chip you’ve got.Without going into the grim details,this program fragment will dump theentire contents of the internal ROMon the console:

FOR i=O to lfffh :

PHO.CBY(i) : NEXT i

Of course, you must wrap a bit ofcode around that core to output thedata in standard Intel hex format, then

capture the console output to a PCdisk file, but the process is not particu-larly difficult and serves as a goodlearning experience. Hint: you needto write a routine that converts a vari-able into two or four hex digits anddisplays the results on the console. Asyou’ll find out, the PH 0 statement pre-

pends a blank and appends an “H”character, making it useless for pre-cisely formatted output.

And a caveat: the interpreter isboth copyrighted and mask registered,so you need to be careful about mak-ing duplicates.

Anyhow, once you have loadedboth BASIC-52 and your code into thesimulator and fired it up, you can, nokidding, type BASIC code directly intothe (simulated) serial port! It runs

rather slower than real time, but worksprecisely like the real system. You canset code breakpoints and single-stepright through the interface. After youhave done this a few times, you can bequite sure that your code will workthe first time in real hardware.

Al though you can bum your hexfile into an EPROM, you may want touse an EPROM emulator instead. I’vebeen using the Parallax 2764 EPROMemulator for a few months and find itto be an invaluable tool. You’ve seenthe picture in ads, but the real charmof the device is that it uses surface-

mount components on a circuit boardthat is only slightly larger than the2764 EPROM it replaces.

The board connects to the parallelport on your PC through a modularphone cable. The EM64 program trans-fers a hex file through the cable to theemulator hardwareand-poof!-yourprogram is available to the 8052 as ifyou had burned an EPROM. EM64has several other useful tricks up itssleeve, but the hex file loader gets the

most use. The gadget is an example ofclean, simple, dedicated design thatdoes one job and does it well.

It would be nice to have a full in-circuit emulator to provide hardwarebreakpoints, true single-stepping,andsuchlike when the program is run-

249 TERMINAL

Featuring l Standard RS-232 Serial Asynchronous ASCII Communicationsl 48 Character LCD Display (2 Lines of 24 each)l 24 Key Membrane Keyboard with embossed graphics.l Ten key numeric array plus 8 programmable function keys.l Four-wire multidrop protocol mode.l Keyboard selectable SET-UP features-baud rates, parity, etc.0 Size (5.625” W x 6.9” D x 1.75” H). Weight 1.25 Ibs.l 5x 7 Dot Matrix font with underline cursor l Displays 96 Character ASCII Set (upper and lower case)Options-backlighting for alsplay, RS-422 I/O, 20 Ma current loop I O

tumpuTf~mhf INC.302 N. Winchester l Dlathe, KS 66062 l 913.829.0600’* 800-255-3739

A rugged CABGGE CASE? lined withplenty of foam for your equipment canTAKE A LOAD OFF YOUR MIND

when you’ve got to travel.

TAKE A LOAD OFF YOUR BACK

with our exclusive tilt-wheelsand extension handle option.

UNLOAD ON US!Call or write to tell us about your

shipping or carrying problemsWE HAVE SOLUTIONS!

CABBAGE CASES, INC.1166-C STEE LWCOD ROADCOLUNBUS,

OHIO43212-1356

(614) 486-2495 FAX (614) 486-2788(800) 888-2495

A p r i l / M a y I990 63 eader service Xl 14



Listing Ja- EXTRAND.BAS. A c leane r wa y to a d d func t ions to BASIC-52 uses the b uilt - in la ng ua ge extension feature, as inLine x0 Th is examp le a d d s a sing le key-word, but more com -

p lex cod e ca n have

add i t i ona iarguments t ha t m ay inc lude comp l e t e BASiC e x- p ression s.

100110200

210220230240300310320330400410

rem - setupso=5

rem get the next interval, spin if notavailable

randomPOP t0if t0 < 0 got0 210t0=t0/1000 : rem convert to millisecondsrem - print a chart lineprint using( . ),tO,Hl',sl=tO*sO : if s1>70 then sl=70print spc(~l),'**@~rem - back to the topgot0 200

ning on the real hardware, but I findthat the combination of a softwaresimulator, an EPROM emulator, andsome careful coding work nearly aswell for the problems I need to solve.

KEY WORDS

But, for all of that, CALLRANDcan still miss an occasional pulse whileit’s pushing values on the A-stackbecause two pulses may occur fasterthan the code can absorb them. Thesolution is to put all of the pulse tim-ing into an assembly routine and leavethe console output to the BASIC pro-

gram, which is just whatEXTRAND . BAS in Listing 3a does.

If you take a close look at Line 210in EXTRAND.BAS you’ll see thekeyword RANDOM , which you won’tfind in your BASIC-52 manual. RAN-DOM , as you might guess, puts the next

random time interval from the assem-bly language routine on the A-stack,ready for the POP in Line 220.

Admittedly, the CALL interfacefrom CALLRAND. BAS would work aswell for this code, but I find that theslight extra effort required to integratenew functions right into the languagepays off handsomely. RANDOM makes

TM

The DA/MThe Lowest Cost Data Acquisition System

Our DA/M can solve more of your data acquisition problems at a lower price than any other product on themarket. DA/M’s are used for:

l Military meteorological stations.

. Building management.

l Automated hydroponic farming.

l Industrial process control.

0 Your application

In fact, DA/M’s can be used whenever you can’t affordto use any one else’s product.

Made in North America, DA/MS are available NOW!

Phone l - 403-486-3534

Fax l - 403-486-3535

much more sense thananopaque C ALL

2, particularly after a few months on adifferent project.

Although the BASIC keywordinterface is somewhat more complex,the bulk of the code in EXTRAND . ASM

is due to its improved capabilities.EXTRAND records times to the nearest

millisecond, can’t missaninput pulse,and blinks the LED automatically...what more can you ask?

TIME FOR A BUFFER

Unfortunately, the full listing forEXTRAND . ASM won’t fit in the pagesCurt gives me, but you can downloadit from the BBS. [Editor’s Note: The

software for this article is available for downloadingfrom theCircuitCellarBBS,

or on Software on Disk 14. See page 84 for information on downloading and or-dering all the software from this issue.]For our purposes here, there are twosections of interest: the interrupt rou-tine that captures the pulse timingand the BASIC keyword interface.

Before that code can do anythinguseful, though, the code must repro-gram some of the 8052’s hardware.BASIC-52 passes control to a “userreset” after a power-on reset, soEXTRAND ASM can set the serial bitrate, set Timer 0 to count l-millisec-ond ticks, define a handler for Exter-nal Interrupt 1 that gets control ondown-going edges, and performotherhousekeeping functions with notrouble at all.

Because Timer 0 runs at five timesthe normal rate, EXTRAND . ASM alsoincludes an interrupt handler to incre-ment the variables BASIC uses for theTIME

andCLOCKX

functions, but onlyevery five ticks. In effect, the BASICprogram behaves as though CLOCK1

were always in effect, so you can’tturn off the clock without disturbingthe EXTRAND interrupt handler. Inaddition, EXTRAND incrementsElapsed, a separate 16-bit counter,every millisecond.

The code shown in Listing 3b getscontrol whenever the RM-60 detectorp ro du ce s a n o utp ut pul se .

Ext 1Handle r doesonly three things:copy thecurrent contentsof Elapsedinto a ring buffer, clear Elapsed to

Readerservice 119

I CiRCUlT CEL LLA R NK











Honey, I Shrunk the...

New Uses Ab o und f o ; t h e Sm a lle st A T-C lo ne Ye t

CL eaon’t you dare bring another

piece of equipment into this house!” I

knew those were the words I would

hear. I wouldn’t even chance it

Unless, I could somehow.. . ‘Naw, that

couldn’t possibly work, or could it?” I

mumbled to myself. It certainly was

worth a try. Let’s see, I’ll start with this

old Model I, The covering of dust

which had settled like a blanket on myold friend was an indication of the last

time I’d seen the TRSDOS sign-on mes-

sage. “Look at all these single-sided

diskettes,” I thought. “I could put ten

of these on one high-density floppy

now.”

I called to one of my sons for help,“Dan, help me carry this stuff out of

here, OK?” I instructed him to use the

front door and load the car. After

complaining that the car was much

closer to the back door, I explained

there was a method to my madness.

‘If you use the front door Mom will seeyou.” ‘So what?” Dan argued. “She’s

FRObTHI

BEN0Jeff Bachiochi

70 ClRClJll CELLAR INK



sure to wonder what we’re doing,” I answered back. ‘Yousee,” I continued, “I don’t think she’s ever seen any equip-ment going out! It’s sure to spark her curiosity.”

I returned to the scene of the yet-to-be-committedcrime and viewed the now-empty void, nestled rightbetween the XT and the oscilloscope. This was practicallythe only free space left in the house. You see, we are aboutto add on to this crackerbox, since space is at such a pre-

mium.

ing system which is compact yet powerful enough to allowsoftware development and program maintenance. Rum-maging through my flea market leftovers was easy; notmuch was left. It seems it’s getting tougher and tougher tofind good junk, er, equipment nowadays. I did find a 6-inch monitor in the heap, but it’s not even composite video.“It’ll need horizontal and vertical syncs,” I thought.“Humph, no enclosures. Wait, the TRS-80 I just removed

“This old vacuumshould do the trick,” Ithought to myself. As Iswitched it on, a puff ofsomething blew out theback, like starting a carthat was badly in need ofa ring job. The roar wasdeafening. I went rightto work cleaning up whatwas left behind. You

know the kind of stuffI’m talking about: bits ‘npieces of the cosmos.Even God couldn’t ex-plain how it got there.

It didn’t take long forthe curiosity to build to alevel of investigation.“Wh...on... hmmf,” Iheard as my wife pokedher head around the cor-ner. I powered down the

01’ sucker and asked“What?” as a final puffblew out of the vacuum,like a dying gasp. ‘Youkilled it,” she gleamed,

The Hom e M onitoring System is ma de up of a Mitsum i 286 Microe ngine, ATI EGA Wond er, Seagate ST-02 flop py / hard d isk c ontroller, 3.5’ flopp y drive, 3.5’ hard drive, Metraby fe Rs485 serial interfac e. and an Aud iotronic s 5-inch m onitor. all in an lntegrand enc losure.

certifying the need for a new one.I knew this was it, time for that costly phrase. “Yeah,

I guess you can start shopping around for a new one.” Herface paled, as if hypnotized. “By the way,” I added, “Thisis where I’m going to install our new Home MonitoringSystem.” “That’s nice,” I heard her say, but I knew shemeant, “Where’s the checkbook?” We were both happynow.

ONE FOR ALL AND ALL IN ONE

The Home Monitoring System will take years tocomplete. In fact, it is one of those projects that just keepson growing. Adding the extra wiring necessary for homemonitoring is much easier to accomplish during the fram-ing stage of building. Now is the time to prepare, beforeconstruction of the addition actually begins. Did I sayaddition? This is more like adding a house to an alreadyexisting garage.

Cramming things into small spaces has become thenorm at our house. So naturally I’d like a home monitor-

had two full-sized floppy drives mounted in an external ox ”

I carefully smuggled the appropriate equipment backinto the house. Upon ripping out the old drives, I smiledas I noticed its built-in power supply. “Look at that, themonitor even fits.” Now with a four-slot PC-style passivebackplane, yeah, and 3.5-inch drives, that’s it.

That’s not it. There is no room for any full-length PCboards like the OEM-286. Rats! [Editor’s Note:The OEM-286 (CCAT) was presented in ‘Garcia’s Circuit Cellar” in theSeptember/October 1987 issues of BYTE.1

THE BIG SQUEEZE

Intel entered the miniaturized computer market in1988 with their WILDCARD-88. An 8OC88 PC/XT-com-patible motherboard on a small 2x4-inch form factor. Un-fortunately, DRAM and DRAM drivers were left off, mak-ing it fairly useless without a considerable amount ofadditional system design. The module uses a high-density68-pin SIMM socket as an expansion connector.

Apr i l /May I990 7



Could size reduction of this scale be accomplishedusing today’s technology to produce a complete 80286 en-gine?

ENTER, THE JAPANESE-SPONSORED AMERICANS

Here’s a role reversal for you: A Japanese company,Mitsumi Electric, creating a California-based subsidiary,

Mitsumi Technology Inc. or MTI, to employ Americansexperienced in computers, software, and telecommunica-tions. Their job: to develop new technology and productsfor the U.S. marketplace.

Upon visiting Japan, MTI was enlightened by the parent company’s ability to produce miniaturized elec-tronics. With this information, they set out to shrink thesizeof today’s popular powerful computersinto a packagewhich could be embedded into industrial and consumer devices.

HYBRID SUBSTRATE FALLOUT

Integrated hybrid circuits consist of multiple semi-conductor chips placed on the same substrate. This issimilar to surface mounting chips without all the plasticand leads which normally surround each device. The finalsubstrate, which can contain many individual chips, isthen enclosed as one hybrid circuit. Each individual semi-conductor chip, as it stands prior to bonding, can only be

guaranteed for a 95% reliable yield. That’s a 5% rejectionrate. Not great, but it’s only the beginning. The worst-casescenario would be something like this (assuming a 5%rejection rate): Build 100 substrates. If each substrate hasone device on it you end up with five bad ones. If eachsubstrate has two devices and the 10 possible bad devicesare all on different substrates, you end up with 10 bad sub-strates out of 100. If each substrate has 20 devices on each

and all bad devices are on different substrates, all thesubstrates will be bad. Notice how the problem com-pounds itself. These devices are not like ICs where you cansimply take the bad ones out of their sockets and replace‘em.

In order to achieve a better yield, pretested devices arenecessary. Since pretested devices are also prepackaged,their size is limited by the number of leads and the leadspacing. Fifty-thousandths of an inch lead spacing isstandard on most surface mount components. That’stwenty leads per inch, or 68 leads in a l-inch-square 80286

processor.

To produce products without using the hybrid approach at the substrate level, some special techniques areneeded. In addition to multilayer glass epoxy boardsusing double-sided surface mounting techniques, special packaging to house some of the standard VLSI chips must be developed. This reduces package size but retains pretest and replacement criteria. With the new packagesize, some VLSI chips now require only one quarter of the

LEARN MULTITASKING

COLLEGE KIT $95The smx College Kit allows you to learn and toexperiment with multitasking. It includes demo

source code, a tutorial User’s Gulde, aReference Manual, and help files everythingyou need to try out multitasking! The CK is areduced version of ou r simple mulfitasklngexecutive It runs at full speed and is ROM’able.

Use it with MS-DOS or stand-alone. Works withthe 80x86 family and Microsoft or Turbo C andassembler. The full version of smx is availablefor $1495 with no royalties.

MICRO t

IdPIGITAL

l - 800-366-2491CYPRESS, CA 90630-5630

Cross-16 V2Meta AssemblerTable based absolute cross-assembler using themanufacturer’s assembly mnemonics.

:b/^

Includes manual an assembler disk with tables for @LoA ng processors:

1802 6

GeneratIntel, or MO

Free worldwide airmaFshipping and handling.

Check, Money Or or P.O. US 99.00VISA, Mastercard aad Canada CNS119.00

Universal Cross-Assemblers

POB 6158, Saint John, NBC a n a d a E2L 4R6Voice/Fax: (506)847-0681

72 C iRC UlT CELLAR INKRederwvice 141



CIRCUIT CELLAR INK’s

ADVERTISER’S INDEX

Reader ServiceNumber

101102103104105106

107108109110111tt

112113114115116117118119120

121122123124125126127128129130131132133134135136137138139140141142143

144145146147148149150151

152153154155156157158159

160161162l

163164165166

167168169

AdvertiserPage

Number

Alligator Technologies 50 Alpha Products 11 American Advantech 33 Andratech 77 Ariel Corp. Avocet g

Berry Computers 41Big Bang Software 80Binary Technologies 35Cabbage Cases 63Catenary Systems 40Ciarcia Design Works 86Ciarcia’s Circuit Cellar 68Circuit Cellar 67Circuit Cellar 65Computerwise 63Cottage Resources 31Covox Inc. 77Dalanco Spry 47Davis Instruments (DIGITAR) 14Dycor Industrial (DA/M) 64Emerald Microware 57

Engineers Collaborative 37Express Circuits 30F&W Communications 45Gott Electronics 27Grammar Engine 80GTEK c 4Hazelwood 43High Resolution Technologies 37Information Modes 87lnnotec 7Intro1 Corp 29Komputerwerk 87Laboratory Microsystems 84Link Computer Graphics 47Logical Systems 35LS Electronics 83LS Electronics 87Magnum Opus 87Meredith Instruments 13

Micro Dialects, Inc. 74Micro Digital 72Micro Resources 84Micromint 17

Micromint 61Micromint 69Ming Engineering (Electronic 1 2 3) 7Needham Electronics 81

Nisley Micro Engineering 87NOHAU Corp 81

Paradigm Systems 75Parallax, Inc. 51

Parks Associates21

PC Boards 43Peripheral Technology 74PseudoCorp 32R & D Electronics 75Real Time Devices 19Ryle DesignSierra Systems :‘3

Silicon Alley 26SIMAR, Inc. 68Timeline 415Tinney 69Traxel Laboratories Inc. 14Universal Cross Assemblers 72University of Pittsburgh 87Unkel Software 53

URDA, Inc. 87Witts Associates 87Wytec 69

HAJAR ASSOCIATES

NATIONAL ADVERTISING SALES

REPRESENTATIVES

NORTHEASTLisa D’Ambrosia

Tel: (617) 769-8950Fax: (617) 769-8982

MID-ATLANTICBarbara Best

Tel: (202) 741-7744Fax: (201) 741-6823

SOUTHEASTChrista Collins

Tel: (305) 966-3939Fax: (305) 985-8457

MIDWESTNanette TraetowTel: (708) 789-3080Fax: (708) 789-3082

WEST COASTBarbara Jones & Shelley Rainey

Tel: (714) 540-3554Fax: (724) 540-7103

SUBSCRIPTION

PROBLEMS?

Ifyou have problems with yoursubscription (delayed or miss-ing issues, change of address,or questions on renewals), callthe Circuit Cellar INK Sub-scriber Service Line at (914)628-0885 or write:

Circuit Cellar INKSubscriber Service Dept.

P.O. Box 2099Mahopac, NY 10541

IRSINK Rating ServiceHow useful is this article?

At the end of each article and somefeatures there are 3-digit numbers bywhich you can rate the article or fea-ture.

Please take the time to let us, at Circuit

Cellar INK, know how you feel1 our ma-terial rates with you. Just circle the

numbers on the attatched card.

A p r i l / M a y 1990 73



previous board space. Addi-tional space is gained by us-ing gate arrays.

Within three years of theinitial investigations ofmanufacturing techniques,MT1 released the “286 Micro-engine” shown in Photos laand lb. The Microenginecontains all the major com-ponents of an 80286 mother-board, including 512K ofDRAM, compressed into a 4x 2.6-inch module. What’smost interesting is that it istotally manufactured in theU.S. using a ZyMOS ATchipset and Award’s ATBIOS. Although another

Photo 1 a-The top side o f the 286 Mic roeng lne show s the 80286

p roc essor, half of the ROM BIOS, DRAM pa r / t - y bits, an d a ssorted

glue logic.

BIOS and chipset may be used in the future, the end prod-

uct will always be electrically compatible with the originalmodule.Photo la shows the top surface of the 286 Microengine.

The 80286 CPU is mounted on the top side of the module.It is the largest chip because it is used in its standard J-leadpackage. To the right of the processor is the only othercomponent used in its original package: the digital delayline. Above the delay line, in the upper right corner of the

board, is a custom VLSIchip holding the odds andends logic of the system,such as RAS and CASgeneration. It uses 0.040”lead spacing. To the left ofthis VLSI and above theCPU is a standard surface

mount 512x8 PROM.Three standard TTL sur-face mount packages andthe 32.76-kHz crystal forthe real-time clock func-tion reside to the upper leftof the CPU. To the imme-diate left of the CPU is oneof the BIOS ROMsmounted in special pack-aging with 0.033” lead

spacing. On the extreme left of the module are two 256Kxl

surface-mount DRAM memory devices. These are used asthe parity bits for the system’s two 256K-byte banks ofDRAM.

Photo lb shows the bottom surface of the Micro-engine. The two banksof DRAM are located on the far left.Four 256Kx4 surface mount DRAMS comprise the 512Kbytes of system memory. The second BIOS ROM is theupper chip located next to the DRAM S. The Award BIOS

16 MHZ

68000SINGLE BOARD COMPUTER

The new PT68K4computer board has all the features of the K2series plus extra benefits. It is available in 2 speeds- 12MHZand a super fast 16MHZ -with increased memory capacity toa maximum of 12MB

’ 4 RS232 p o rk l Floppy disk controller

l 7 XT expansion slot

l Real-time clo ckl 1 Memory expansion slotl 2 Parallel ports

l Optional operating systems

BASIC KIT 12MHZ - 4 layer board, processor, Humbug monitor,4K SHAM, 2 serial ports $220

K4 COMPLETE KIT 16MHZ) -with 512K of DRAM $545

ASSEMBLED BOARD 16MHZ) with 1 MBDRAM $649

PROFESSIONAL OS9 with compiler:only valid if purchased with board

$299

SK’DOS OPERATING SYSTEM: s 60COMPLETE INFORMATIONAVAIlABLE UPON REQUEST

PERIPHERAL TECHNOLOGY1710 CUMBERLAND POINT DR. 8

MARIETTA, GA300674041984-0742 l FAX 4041984-8248CODIMASTERCARDNISAICHECK

SK’DCS IS A TRADEMARK FOR STAR-K SOFTWARE SYSTEMSOS9 Is A TRADEMARK OF MICROWARE AND MOTOROLA

*TEXT EDITOR, CROSS ASSEMBLER, ANDCOMMUNICATIONS FACILITY IN A COMPLETEINTEGRATED DEVELOPMENT ENVIRONMENT

l MACROSl CONDITiONAL ASSYl LOCAUAUTO LABELS us$149.95l SYMBOL TABLE CROSS REF EACH

l S OR HEX FILE OUTPUT DOWNLOADS pLus S/H*TO MOST EPROM PROGRAMMERS

AVAILABLE FOR MOST 8-BIT MICROPROCES-SORS. CALL OR WRITE FOR TECHNICALBULLETIN. 30 DAY MONEY BACK GUARANTEE.MCIVIAE.

PER SHIPMENT:

$4 CONTIGUOUS USA$8.50 CANADA AK. HI

Micro Dialects, Inc.DEPT. C, PO BOX 30014CINCINNATI, OH 45230

$15 INTERNATIONAL (513) 271-9100

CIRCUIT CELLAR INK





. DFW.4 REFRESH LocItiC

sary to run MC-Net. As it stands now,until CEBus becomes a bit more estab-lished, the plan is to use MC-Net for theHome Monitoring System.

One of the smallest implementationsof a combination floppy/hard disk con-troller card is the Seagate ST-02. This willsupport two SCSI hard drives and two

floppies (360K/720K/1.2M/1.4M), al-

thoughnothinglargerthan3.5-inchdrivesfit here. The floppy drive is mounted tothe opposite side of the monitor’s “L”bracket, which allows the monitor andfloppy to be installed as one unit. Thebracket is made out of sheet aluminumwhich makes a good electrical and me-chanical connection with the enclosure,eliminating interference between the twodevices.

SPEAKER KEYBOARD

Figure 1 -A block cf fagram of the Microeng ine 286 shows that the mod ule co ntains a ll the nec essary co m po nents to put Q complete AT m otherbo ard on a ha lf-size expansion card. .

The MT1 Evaluation card completes the hardwarenecessary for this transportable AT. Although it probablywon’t be moved, it will establish a firm base for the Home

Any serial port card would do as an

interface to an RS-485 adapter for MC-Net. However, MetraByte Corp. comesin with one of the smallest serial portcards that has RS-485 output.

BUS 80287 BUS

within a metal container to contain EMI and offer someheatsinking to the 80286 processor. Figure 1 shows a blockdiagram of the 286 Microengine.

To help engineers feel comfortable with the 286 Micro-engine, the MT1 engineering team has a half-size Evalu-ation Card. This card contains AT-bus edge connectorsand the necessary jumpers and clocks to simulate a com-plete IO-MHz 512K l-wait-state AT motherboard. The

half-size card can drive an AT passive backplane just likethe full size OEM-286 processor board.Applications for the 286 Microengine such as PC-

based workstations, laboratory control, and data acquisi-tion equipment will be springing up left and right. Mod-ules containing other functions such as video, serial, andparallel I/O are already under development. The 286Microengine is competitively priced at $500 in singlequantities. The evaluation card adds an extra $100. The286 Microengine consumes less than 5 watts at 5 volts andits lower-power sibling uses less than 3 watts.

JUST THE RIGHT SIZE

As you can probably guess by now, I had an immedi-ate application for the 286 Microengine. My choice of en-closures and desire to include an internal monitor capableof displaying EGA (for use with MC-Net; see Photo 2) de-termined the need. The enclosure is similar to the 2905WAfrom Integrand Research Corp. The display is an Audi-otronics 90094641, a 5-inch 12-volt monitor. The moni-tor is attached to an “L” bracket which bolts to the enclo-sure where a disk drive would normally go. A standardmonochrome display card would drive the monitor fine,

but I had to use an EGA Wonder card because it can drivea TT’L monochrome monitor with the EGA video neces-


Photo 2-Unt i l CEBus becomes a b it mo re established, the plan is to use MC-Net for the Home Monitoring System .





SILICON

Whither Zilog?UPDATE

Tom unfr ll

A Ro lle r C o a ster on the Ba c k of the 280

The heroes and villains of Silicon

Valley sometimes seem to be drawn

from the pages of a fairy tale.. .o r a

soap opera. The only difference is the

source of the wealth that drives the

intrigue: Instead of the Golden Goose

or oil wells, it all starts with sand.

Zilog is just one story in the “Valley of

the Heart’s Delight.” But, over the

course of the company’s history we

get to see all the ups and downs that,

like earthquakes, make life aroundhere interesting.

IN THE BEGINNING

Zilog was founded in the mid-70s by a couple of Intelguys (Federico Faggin and Ralph Ungermann) with abetter idea. They scratched together some venture capital,made a foundry deal with Mostek and voila -the Z80 wasborn.

The chip was an instant hit. It combined the softwarepopularity of Intel’s 8080 with the 5V-only, single-chip (noclock generator, bus controller, or interrupt controller ICsrequired) advantages of Motorola’s 6800.

The company quickly followed on with the necessaryperipheral ICs: SIO, PIO,CTC, and so on. These chips werequick winners too. In fact, many who weren’t convincedof the merits of theZilog CPU were often swayed by the ca-pabilities of these peripheral ICs with which it worked. Itwas a high-tech version of the proverbial tail wagging thedog.

By the end of the 197Os, Zilog had become, along with

the much bigger Intel and Motorola, a powerhouse in themicroprocessor world.


TROUBLE IN PARADISE

In retrospect, what befell Zilog in the early 1980s wasas much bad luck as a bad business decision. At the time,despite the ongoing shipment of millions of 8-bit CPUs,Intel, Motorola, and Zilog all adopted the conventional

wisdom that the 8-bit world was dead, and that all existingcustomers would quickly move to the new 16-bit chips (theZilogZ8000, Motorola 68000 and Intel 8086). So began the16-bit wars, a bitterly fought campaignbetween the giants.

Arguably, the 28000 was a good chip. Some say it lostbecause it was a little late. Others point to the competitors’marketing strength. I think the main problem was thepremise that everyone needed a 16-bit chip. In fact, untilthe emergence of the PC and Mac, there was little X-bitbusiness for anybody.

Meanwhile, Zilog, under the tutelage of former inves-tor and then owner Exxon, continued to lose focus (and

money) dabbling in everything from RAMS to UNIX boxes.Too late, the company tried to retrench in the 8-bitworld with the infamous 2800. The chip was intended tooffer a high-performance alternative for existing 280 cus-tomers. Unfortunately, management and personnel tum-over had reached the point that completing the designbecame impossible. New engineers would leave evenbefore they got up to speed on what the previous engineerhad done. The final straw was the conclusion late in thegame that the 2800 should be a CMOS, not NMOS part.Back to the drawing board again.. .

The mid-80s were not a happy time at Zilog, with

semiconductor market slow-downs, little28000 business,management turmoil, and the 2800 faux pas. If the storystopped here, the title of this article might be “RememberZilog?”

Z86CO9

Z86C19Z86C30Z86C40

Z86C90

Package I/O Lines RAM ROM

18 pins 14 lines 124 bytes 2K bytes18 pins 14 lines 124 bytes 4K bytes28 pins 24 lines 236 bytes 4K bytes40 8 44 pins 32 lines 236 bytes 4K bytes

40 8 44 pins 32 lines 236 bytes OK bytes

Figure 1 -2ilog’s new CC P c hips cf f fermost ly in p in co unt , numb er o f / O lines. and am ount of on-boa rd m em ory.









ICONNEC-

TIME

Exc e rp ts from fhe Ci r cu i f Ce l l a r BBS

The Circuit Cellar BBS300/ 1200/2400 bps24 hours/7 days a week

203 8 7 1 - 1988Four Incoming Lines

Vernon, Connecticut

Conduc t ed by

We have just one message thread this issue, so we’ll makeit a good one. Telephone circuits always seem to be popular, and detecting call-progress tones is somethingmany applications require. There are numerous methodsthat can be used to accomplish the goal, some better than

others.Msg :23806

From: DAWN R. BANKS To: ALL USERS

I’ve been trying to put together a circuit to do telephone callprogress monitoring. So far, I’ve bought a DTMFdecoder chip atthe local Radio Shack, and that gives me digits. Next, I wired upfour 567s to give me dial tone, ringback, and busy. After this, Istart running down a rathole. First, I see that if I want to detectthat loud “you left the phone off hook” noise, I’m going to haveto detect four simultaneous frequencies, which don’t seem tooverlap anywhere with those that I’m already looking for. After

that, I also find that if I want to listen for that “bodo-weep” foran out-of-service phone number, I’m running into still morefrequencies to detect.

Before I get done with this, I can see having a whole room full ofPLLs, each detecting one of the frequencies, and each incorrectlydetecting two or three of the others. The question that this leadsup to is: Is there really any better way of doing this? Is there someoff-the-shelf DSPchip that Icould easily adapt to myneeds,oramI completely out of luck here? I would happily accept any otherconstructive suggestions, including those that indicate that I’mwasting my time completely. Keep it simple, because I’m notreally a hardware type, and this project is just me pretending that

I am. Thanks.

Msg :23821

From: NATHAN ENGLE To: DAWN R. BANKS

Call progress is one of those sorts of things that gets harder to doas your requirements get closer to never giving you an error.

Part of the problem if you’re trying to design a product that isgoing to be sold all over the place (I know you’re not, but just bearwith me) you find that telco central offices tend to use a very widevariety of cadences, and so on for different call progress tones. So

trying to squeeze that last 5 -of-the-time error condition out ofyour design can be really hard.


One tactic that you might want to consider is to backoff from theidea of trying to detect the “phone left off hook” tone, and just usea timer to hang up the phone after a given wait. I have to admitthat it isn’t a lot of good if you’re doing something like anautomated telemarketing box that has to know when the dis-

gusted party at the other end of the line has cut your sales pitch.

Msg :23828From: DAVE EWEN To: DAWN R. BANKS

If this system is based on a PC or something with computationalability, you might consider an ADC to sample the tones and thentake the data and perform an FFT to convert to the frequencydomain.

MsgW:23854

From: DAWN R. BANKS To: NATHAN ENGLE

Thanks for the ideas. Yes, it will be connected to something withsome computing power (a Z8), so the ADC is a point worthconsidering.

Question: Am I going to get into some kind of hairy FFTs whenI’m detecting something that’s more than one tone (such asDTMF, dial tone, etc.)? The next question I have concerns callcompletion; that is, what do I listen for? Do I get a “wink” on thephone line, or is there something more involved? As a relatedquestion, how do I differentiate this “call disconnection” signalfrom the “call waiting” signal? (I ask this because other devices,

such as phone answering machines and other RS boxes, seem tohave difficulty with this distinction.)

From this, I guess I’ll just stick with the basic four-tone decodethat gives me dial tone, ringback, and busy. I should probably seea dial tone before I see the “phone off hook” noise anyway.Thanks again (suggestions still happily accepted).

MS@:23889

From: KEN DAVIDSON To: DAWN R. BANKS

Or you could just use a call-progress-tone detector chip. Teltone

makes a few (M-980, M-981, M-982, and M-984). Silicon Systemssecond sources most of them as the SSI 980, SSI 981, and SSI 982.



Contact the companies and get data for the chips. I think it’llpmbablybeeasierthanusingaDSPtodoFFTsorwhateveronthe

incoming signal...

Teltone Corp.P.O. Box 65710801120th Ave. N.E.Kirkland, WA 98033-0657(206) 827-9626

Silicon Systems, Inc.14351 Myford Rd.Tustin, CA 92680(714) 731-7110

Msg :23899From: BOB PADDOCK To: DAWN R. BANKS

Mite1 also makes call progress parts. Try (619) 2763421, (408)249-2111, or (312) 574-3930, whichever is closer.

If you’re trying to find out if the other end of a long-distance callhas hung up, maybe you can detect the short ‘beep“ you hear atthe end of the call. It is a 2600-Hz tone, called “line idle.” Problemwould be to not have voice detected as this tone.

Msg :23919From: DAWN R. BANKS To: KEN DAVIDSON

Thanks. This is exactly what I was hoping someone wouldsuggest (just didn’t know what to ask for).

Since my sources here in New England for electronic parts seemto be a bit limited, any suggestions as to where I could obtain acouple of these (assuming that I’ve successfully laid hands on thedocumentation)? Mail order sources?

Msg :23930From: KEN DAVIDSON To: DAWN R. BANKS

It’s not likely you’ll find either Teltone, SSI, or Mite1 at anysurplus mail order place. About the only way to proceed is tocontact each company directly and find out where the nearestdistributor is, then ask them about getting some.

Msg :24@42From: ERIC BOHLMAN To: DAWN R. BANKS

Teltone is pretty good about giving out engineering samples; in

fact, I was able to get an M-982, which is a pretty good call-progress detector chip. I think they run about $12 in smallquantities.

Signals to indicate 1) when a call has been connected and 2) whenthe party on the other end has hung up are far from standard.Folk wisdom says that the polarity of your line reverses brieflywhen the other party answers; my experience has been that that’strue only if you’re on a step-by-step exchange. You also can’tcount on getting a burst of 2600-Hz at the end of a connection,since that’s an artifact of using trunks with SF signalling, and notall connections are routed over such trunks.

One further note: if you’re just interested in detecting dial tone,try using a DTMF detector like the SSI 202, but use a 1.3-MHz

crystal instead of the usual 3.58. Dial tone should then show upas the “*” output from the detector.

Msg :24057

From: DAWN R. BANKS To: ERIC BOHLMAN

Thanks for the input. I was just looking at an “IC Master,” whichseems to be the only reference source I can find for any of thisstuff. Obviously, I can get this information from the manufac-turer, but I was hoping to find the differences between the 980/

981/982/984. From the sound of things, the 982 does prettymuch what my set of four 567s does, albeit in a much smallerpackage, and probably better. (That is, the IC Master said itdetected 350,440,480 and 620.) The short description for the 984said it also detected other frequencies, although there wasn’t anydescription of which.

I thinkI’mgoingtotrytogetacoupleof984s. Anotherintriguing-looking chip is the SSI 2OC90, which purports to be a DTMFtransceiver with call progress indication. Again, this is all I knowabout the chip.

The most recent reason I’m so hot on using one of these chips isthat although I can detect most of what’s advertised with my littlebreadboard of a DTMF decoder and those four 567s, I can hearone of the chip’s oscillators on the phone line it’s plugged into. Ididn’t start hearing it until I started adding the 567s, so I suspectit’s just shoddy design on my part, and not the SSI 202 DTMFdecoder chip. I have the phone line isolated with a 600/600-ohmtransformer (with DC-blocking capacitor on input, and the 567s

8031 BASEDPROGRAMMABLE CONTROLLER

l Board size 4.5 x 5.5l Requires 5 V dc supply 20 inputs, 16 outputs. 24 virtual bits.24hour RealTme Clock

with 8 timersl 8 set/reset flip ltops 4 timing pulses. 8 one-shot timersl stack architecture 2 file spaces up to 256

Instructions each

. Uses PC for operatorinterface

. Program storageon disk

. English like commands

. Easy to programl Ideal for testing, moni-

toring and automationapplications.

E’E xz f Board and Manual. Kit, all parts and manual

“UJ ; ;

April/Ma y 1990 83





CEBus Comes One StepCloser to Reality

DOMESTICAUTOMATION

Ken Da vidson

Anyone following the home automation in-ustry has no doubt heard of CEBus. Well, after over ve years of work, we’re finally about to see some-

hing official come down the line. I recently gotack from the November EIA/CEG CEBus Com-

mittee meeting in Sunnyvale and have somenteresting events to report.

First of all, we should dispense with allhistalkabout “CEBus.” The’EIAHome

utomation Standard” (as it willways correctly be referred to)ill be known to the public atrge as 5ynq” (assuming itets through the trade-ark search; the backup

“Harmonet”). After

xtensive research byoth EIA and an out-de consultant pro-ucedalistofadozenr so potent ialames for the stan-ard, EIA settledn this one. No, itoesn’t stand for

physical layer details. Similar groupsexist for the other physical media plus conformance, publicity, and so

In charge of all the working

groups is the Technical SteeringCommittee (TSC). The TSC over-sees the entire specification-mak-ing process, sets policy guidelines,and has the final say in any mat-ter regarding the spec.

Once a working group has a portion of the specification that

nything. It’s easy to say, conveys an aura of high techith the “Q” at the end, and should be just what the

marketing boys are looking for. Please forgive me if I

ontinue to refer to the standard as CEBus for the timeeing.

they feel is ready for public comment, they present it to theTSC for approval. Once approved, the proposed spec is published and goes out for a comment period. During the

comment period, anybody who would like to review the proposed spec and make comments on it is free to do so.The intention is to get the spec into the hands of engineerswho work for companies that are members of the commit-tee, but haven’t necessarily been able to attend meetings.

However, anybody who takes the initiative to obtain acopy of the spec may comment. Positive comments arealways welcome, but don’t affect any final decisions.

Negative comments must be accompanied by supportingarguments, and may also include altema tive ideas. Nega-tivecommentswithoutsupportingargumentsareignored.Each comment is acknowl-edged by the TX, thoughthey are under no obligationto take action on the com-ment.

The long-anticipated event, though, was the officialelease of several portions of the CEBus specification for omment. Before getting into exactly what was released,et me explain EIA’s procedure for releasing a specifica-on,

EIA STANDARDS MAKING

When the committee was first put together, several

working groups were established to hammer out the de-ails of individual portions of the spec. For example, theanguage Working Group (LWG) is responsible for theupper network layers including CAL. The Power LineWorking Group (PLWG) is responsible for the power line

Once all comments have been received and acknowl-edged , any s igni fi cantchanges that the TX makesto the spec as a result of thecomments are sent out for comment (rather than the

whole spec). This cycle con-tinues until everyone ishappy with thespecification.At that point, the document

becomes a interim EIA speci-

April/May



fication that companies can be comfortable in using to puttogether product.

At the November committee meeting, the LWG andPLWG hammered out several last minute details andsubmitted the power line physical layer (PLBus), the datalink layer (which is made up of the node medium accesscontrol sublayer [MAC] and the node logical link controlsublayer [LLC]), the node network layer, the node applica-tion layer, and CAL to the TSC for approval. The T X gavesuch approval, so the power line physical layer and all theother network layers have gone out for comment.

The current schedule calls for the initial commentpen’+ to close at the end of April, at which time thecommittee will take a careful look at all the comments andmake any necessary changes.

Once the CEBus spec has graduated from being a proposed spec to an interim spec, it will be known as I %O.

Once adopted as an official specification, it will be EIA600.

To get your own copy of the proposed CEBus specifi-

cation and have the opportunity to influence the future of homeautomation, see theinformationboxat theend of thecolumn. EIA is encouraging engineers to scrutinize the proposed spec and make constructive comments. I’m surethey’d love to hear from you.

MORE CEBUS HARDWARE \ \ lll/

Inissue lOof~curr~~INK,I described in my CEBus overview ar-ticle two hardware implementationsof CEBus that are available for engi-

neersinterested in embedding CEBusin an upcoming product. Texas In-struments has developed a pair of chips that make implementing aCEBus interface much easier and have a new-generationevaluation board available that uses those chips. TheSEM300 (I talked about the SEM200 in the overview ar-ticle) uses TI’s new SN75C080 CEBus controller chip andthe SN75081 powerline modem chip to implement acomplete PLBus CEBus interface that can be attached toswitches, lights, or a processor for smarter control. Theyalso have software available that allowsmonitoringof net-

work traffic, and sending and receiving of packets. Con-tact TI for more information.

OVERSEAS

In developments overseas, the Eu-ropean community is about to officiallyannounce IYB to the world. DZB is aninternational standard for control andcommunication for audio/video devices.Expect to see stereos and VCRs startingto show up in the trade shows in the

months ahead sporting D2B interfaces.

WRAP UP

IalsojustgothomefromLasVegas

whereIattendedtheWinterConsumer

Electronics Show (WCES). Though Ididn’t see as much as I’d hoped aimedat the home control market, there wasenough to be interesting. In the com-ing months, I’ll be going into moredetail about what I saw and where the

market seems to be headed. And, of course, as soon as weget our hands on some hardware, especially actual chips,we’ll be putting it through its paces and showing it to.youin these pages. Stay tuned...+

sources

EIA CEBus ProDosed SDecification ( 351EIA Standards Sales Dept.

1722 Eye St. NWWashington, DC 20006

SEM300Texas Instruments, Inc.P-0. Box 809066Dallas, TX 753804957 ~- ,,.-.

:

Ken Davidsonis themanagingeditoranda memberoftheCircuit CellarIAKengineeringstaff. HeholdsaB.S.inwmputerengineeringandan

M.S. in computer science from Rensselaer Polytechnic Institute.

IRS228 Very Useful229 Moderately Useful230 Not Useful

’ Steve Garcia has assembled a team of engineers,designers, and programmers to produce the productsthat have made Circuit Cellar famous. Now you can put

the Ciarcia team to work for you.Steve Ciarcia and his staff have designed products

ranging from communications and networking compo-nents to multiprocessing computers. Current capabili-ties include every phase of design and production, frominitialconcept through packaging of the finished product.

Whether you need an on-time solution for a uniqueproblem, complete support for a startup venture, or experienced design consulting for a Fortune 500 com-pany, the Ciarcia Design Works stand ready to workwithyou.

Remember.. .a Ciarcia design works!

8 CNCXJlT CEllAR INK



The Home ComputerRevolution is Over

STEVENO W N

INK

I remember the early days of The Revolution. Thereweren’t many small computer systems, there were evenfewer magazines about them, but there was an almostevangelical fervor about how these “toy” computers weregoing to change our lives. Of course, in the years sincethen, the computers have changed, and our expectations

have changed along with them. I’m not going to go intowhat computers have done for our business lives, but Ithink it’s time for a quick peek at the corpse-littered trail ofthe home computer market.

In the late ’70s and early ‘BOs, you couldn’t read atechnology-oriented magazine or newspaper article with-out seeing several paragraphs about how every homewould soon have a personal computer occupying a posi-tion of honor and importance. Dad would bring homework from the office and keep the family checkbook inorder, Mom would search a voluminous recipe databaseand work budgeting miracles to rival the Pentagon’s, and

little Buffy would churn out Ph.D.-level term papers andlearn with joy, havingreplaced stemMs. Grumpit with thefriendly warm glow of her CRT.

Now, we know that, with the possible exception ofboth Mom and Dad bringing home work from the office,very little of that scenario has come to pass. Most peopledon’t want to complicate their lives with a new system. Afour-function calculator provides as much computinghorsepower as most folks can cope with, and costs aboutthe same as a box of Twinkies. Generally, the media andgeneral population have written off the home computeralong with the home autogyro and personal hovercraft.

It’s not that the bestof American industry didn’t try tomake the home computer as much a part of the residentiallandscape as the television Apple IBM TI Sinclair

they were embracing microwave ovens like long-lost rela-tives. Nearly all of the microwave ovens carried microcon-trollers or microprocessors into the homes of the heart-land. Meanwhile, the energy crisis was making morepeople think about improving their home climate controlsystem. In most cases, better control meant a microproces-

sor of some flavor. The tide swept onward, with VCRs,televisions, stereos, telephones, coffee makers, and othercommon household items flooding American homes withlittle computers. Ever hear of Nintendo? Yes, it’s arhetorical question. Every time a wild-eyed adolescentplugs into the Super Mario Brothers, he or she is bootinga computer.

Now that most people are more comfortable withdigital electronic technology, marketers are starting to-oh, so cautiously-introduce computer-like appliances. In Japan, there are keyboards and storage devices that pluginto Nintendo systems. Several digital televisions would

need a minimum of add-ons to start functioning as high-quality data terminals. (If you have trouble with thatconcept, just remind yourself that Sears owns a largechunk of Prodigy.) More than all of that, however, thetrend-watchers are telling us that “home offices,” com-plete with computer, fax machine, photocopier, and shred-der, are going to be all the rage in the 1990s.

Thesimpletruthis that, while weal1 hadourhandsfullof microwave popcorn, the “home computer revolution”was fought and won by microprocessors and embeddedmicrocontrollers. The home office, stuffed to the gills withcomputing and communications gear, wouldn’t be pos-sible if millions of people had not become comfortablewith the idea of computers through microwaves, videogames and VCRs The barricades are down: It’s time to

Date post:	04-Jun-2018
Category:	Documents
Upload:	sarah-kaya
View:	219 times
Download:	0 times

Circuit.cellar.014.Apr May.1990

Documents