AUDIO & HI -Fl COMPUTERS & MICROPROCESSORS ......AUDIO & HI -Fl COMPUTERS & MICROPROCESSORS DESIGN IDEAS RADIO, TELEVISION & COMMUNICATIONS SCIENCE & TECHNOLOGY TEST & MEASUREMENT

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-INN CONTENTSJanuary 1994Volume 20Number 218ISSN 0268/4519ELECTRON/CAS

I . z .1..1 s In next month's issue

Bidirectional RS232- 8 PROJECT: SIM: an 8051 simulator

Centronics converter* By David Mockridge24 cm ATV transmitter 54 PROJECT: Monochrome VGA adaptorLiquid crystal displays* Design by T. SchererMini preamplifierBuilding your own toroid

core inductors and r.f.. ,

transformers 33 PROJECT: Digital dial SAP

DAT copybit eliminator Design by David McBright

and others for your 42 COURSE: Figuring it out - Part 12: Modelling I2C tester - p. 14continued interest By Owen Bishop

58 PROJECT: Telephone -controlled switch

*We regret that these articles,

owing to circumstancesbeyond our control, could not

Design by F. Zapf

be placed in the present issue.' 1 II a : a il 4

24 PROJECT: Radio Data System (RDS) decoder ',,By Peter Topping

68 DX TelevisionBy Keith Hamer and Garry Smith

, I 1 I

24 Coding for GSM Digital dial - p. 33

By Brian P. McArdle

Front coverThe Radio Data System

: t

14 PROJECT: I2C tester

, ,

, * ,,\ ' ,

:%

(RDS) decoder shown in the Design by W. Foede ,

photograph and described 20 Views of the Bridge - Part 2 - --on pages 24-31 is based ontwo powerful, yet affordable,ICs: the Philips Components

By Bryan Hart

. a

SAA6579T RDSdemodulator and the Buyers' guide 74

Motorola MC68HCO5E0microprocessor.

Electronics scene 5

Index of advertisers 74Monochrome VGA adaptor - p. 54

Readers' services 70-71.-

Terms of Business 72

1- :

" II©1994 Elektuur By.

i I

:. 1 V

CONSUMER PRESS

, , , 1...,. .,Telephone -controlled switch - p. 58

Elektor Electronics is published monthly, except in August, by Elektor Electronics (Publishing), P.O. Box 1414, Dorchester, Dorset DT2 SYH, England. The magazine isavailable from newsagents, bookshops, and electronics retail outlets, or on subscription at an annual (1994) post paid price of £27.00 in the United Kingdom; airspeeded: £3400in Europe; £4300 in Africa, the Middle East and South America; £45.00 in Australia, New Zealand and the Far East; and $57.00 in the USAand Canada. Second Class Postage

paid at Rahway N.J. Postmaster: please send address corrections to Elektor Electronics, c/o Mercury Airfreight International Ltd Inc., 2323 Randolph Avenue, Avenel, NewJersey, N.J. 07001.

ELEKTOR ELECTRONICS JANUARY 1994

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ELECTRONICS SCENEBRITISH COMPUTER SKILLSANIMATE FILM DINOSAURS

By Nigel HawkesThe successful film Jurassic Park, madeby the Hollywood director, Mr StevenSpielberg, owes a surprising debt to a smallBritish company tucked away in a Londonside street. With the help of computer soft-ware written by Parallax, launched justthree years ago, the animators who workedon Jurassic Park have achieved a moviebreakthrough weaving seamlessly togethersequences filmed in the conventional waywith animations created entirely on thecomputer screen.The result sets new stan-dards in film special effects and opens aPandorra's box full of tricks for film-mak-ers to exploit.

Traditionally, monster movies sinceThe Lost World of 1925 have relied on mod-els to achieve their effects. In King Kong,the 1933 classic, in which a giant ape seizesFay Wray in a hairy embrace and shakesher over the Empire State Building, ani-mator Willis O'Brien painted his sceneryon glass sheets mounted on a table, andmanipulated a model King Kong frame byframe, creating an illusion of depth andmovement. The results, exciting as theywere, would not satisfy a modern audi-ence.Animated models. For Jurassic Park,Spielberg started out in the traditionalway, commissioning some magnificent di-nosaur models from Hollywood special-ists. For longer shots, he intended to useanimated models in the King Kong style,but his mind was changed by Steve Williamsof Industrial Light and Magic, an anima-tion company set up in California in 1975by George Lucas to make special effectsfor Star Wars. Williams buried himself inhis subterranean office and in two weekscreated on a computer an animated 10seconds sequence of a Tyrarmosaurus Rexthundering across the screen. Spielbergwas hooked.

What has made realistic computer an-imation possible is the development ofhigh -power workstations with crisp, full -colour graphics, and the software to runthem. The terminals are the products ofSilicon Graphics, an American company,and cost around £20 000 each. The soft-ware, which retails at the same figure, iscalled Matador and was written in London'sSoho by a group of young British pro-grammers working for Parallax.Sophisticated chips. Parallax is just oneof a number of British companies makinga success of computer -based entertain-ment. Argonaut Software, established 10years ago in North London to produce com-puter games, now employs 60 people. Ithopes to double the 1993 turnover of £4million in 1994. As well as writing the soft-ware for a range of games, the company

has developed hardware in the form of so-phisticated chips for computer games.

Another London company making asuccess in the computer game businessis BITS, based in Cricklewood, which hasso far developed 24 different games forNintendo and Sega. The firm, started byFoo Katan, employs 35 animators, artistsand programmers full-time, plus another15 who work from home, developing gamesthat are named mostly after current films.Valuable skills. Gary Shinewald, devel-opment director of BITS, believes he knowswhy British programmers are so good."Most of us started as schoolchildren inthe days of the first home computers, whichwere not very powerful. So, we had to workhard to get anything worthwhile out ofthem. Then, when the more powerful Segaand Nintendo machines came along, thoseskills turned out to be very valueable".

Parallax is a relative newcomer, but inan industry like computing what mattersis not age or experience, but what you candeliver. Film companies are convinced thatMatador is the right software for them.More than 400 clients, including televi-sion companies and leading film studios,now use the program.

The program has already been used inmore than 10 major feature films, includingthe Oscar -winning special effects in DeathBecomes Her, where Meryl Streep's headwas rotated on her body in one stomach -turning sequence, Cliffhanger and TheInstAction Hero. But, by general consent,Jurassic Park sets new standards in unit-ing animation and film.Wire -mesh image. The animators whoworked on the film used 15 separate com-puter terminals, and each was responsi-ble for a short sequence which were thenmarried together. The process begins withthe animator creating on screen the out-line of a dinosaur in the form of an openwire -mesh image.

The work is done by drawing with apencil -like tool on a sloping 'tablet', like adesk -top, which picks up the movementsof the pencil and transfers them into thecomputer as digital signals. At the sametime, they appear on a screen. Matadorprovides the animator with a palette of16.7 million different hues and a range ofspecial 'brushes' for creating life -like ef-fects such as a smear of mud on a dinosaur'sback.

The system also allows an animatedsequence to be prepared with much lesslabour than traditional methods. Filmsrun at 24 frames a second, so the first car-toons were created by drawing a sequenceof images of a cartoon character like Felixthe cat, each successive image moving onfractionally.Fewer drawings. Filmed frame -by -frameand then assembled as a sequence, the

eye sees the result as a smooth movement.Matador simplifies the process by inter-polating between the cartoonist's images,so that he no longer has to draw them all.This reduces the number of drawings hemust do by a factor of 10, but against thathe must set the fact that the dinosaurs inJurassic Park are realistic creatures, notcartoon characters.

The system then allows the computer -created sequences to be integrated withearlier filmed shots in which the actorsperformed in empty space, imagining thedinosaurs. Images are digitized and fedinto the computer, where they can be com-bined electronically with the animated se-quences. Finally, the combined imagesare turned back into film.

The results impressed both the ani-mators at Industrial Light and Magic andSteven Spielberg himself. With the skin ofthe dinosaurs moving and their belliesswaying, there is not much danger of mod-ern youngsters complaining they are notreal enough.Powerful techniques. There is a danger,however, Steve Williams believes, that thenew techniques are so powerful that theymay one day be used to manipulate his-tory. Old archive films have a peculiarpower because we know they tell the truth:the camera, as the saying goes, can notlie. But soon, it will be posible to remodelthese images in the computer, creating,say, bogus films. The power of computergraphics will eventually allow the use ofcomputer -generated presidents who havebeen dead for some time giving a speech.When you are looking at the television,you won't know what is real and what isnot.

DEVELOPERS' KIT FOR PHILIPS87C750 MICROCONTROLLER

Developers working with the Philips 87C750microcontroller can now get a low-cost,feature -packed tool set in a new softwaredevelopment kit available from Micro AMPS.

Included with the 87C750 -SDK kit isMICRO/ EDITOR, a full -featured, multi -window text editor, MICRO /ASM-750, arobust Macro Assembler, and MICRO/SLD-750, a simulator/Source LanguageDebugger. This DOS -based developmentpackage has been configured especiallyto support an 87C750 Target ProcessorEnvironment, including memory spacesand peripheral ports and timers. Also sup-ported is a Source Debug Environmentincluding instruction single step, break-points, watch windows and over 17 addi-tional tools.

Applications for the 87C750 includeconsumer and industrial products thatcan benefit from its 80051 architecture,small package size and low cost.


6 ELECTRONICS SCENE

The87C750-SDK is available at an in-troductory price of X49.95 until April thisyear. The regular list price is £125. Formore information, contact Micro AMPSLtd, 66 Smithbrook Kilns, Cranleigh,Surrey GU6 8JJ. Telephone +44 (0)483268 999; Fax +44 (0)483 268 397.

TV MEASUREMENT RECEIVERS FORCABLE AND SATELLITE MARKETS

Two new models in the ITT InstrumentsVX600 Series ofTV measurement receiversincorporate a number of features thatmake them particularly suited to the needsof satellite dish/aerial installers and thecable distribution market.

The new VX600S covers an extendedsatellite frequency band up to 2050 MHzand a satellite sound capability that isfully tuneable from 5.5 to 8 MHz to coverthe multiple sound carriers used on sat-ellite channels.

Also included is a power supply thatproduces a 10-20 V output switcheablein 2 V steps, as well as a variable 0-10 Vsupply, thus meeting the needs of all low -noise converters (LNCs) now in use.

The VX600SD has a similar specifica-tion, but with the addition of built-inD2Mac facilities.

All models in the VX600 Series com-bine the functions of field -strength mea-surement, TV picture/ sound monitor-ing and spectrum analysis in a compact,easily portable package weighing lessthan 9 kg with batteries. The instrumentsmeet IEC 348 Class I safety standardsand the relevant VDE and IEC EMC spec-ifications.ITT Instruments, 346 Edinburgh Avenue,Slough, Berkshire SL1 4TU. Telephone+44 (0)799 520 022.

Produced and published by ELEKTORELECTRONICS (Publishing)

Editor/publisher Len SeymourTechnical Editor J. Butting

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2ND INTERNATIONAL CONFERENCEON ADVANCED A -D AND D -A TECH-NIQUES AND THEIR APPLICATIONS

Papers are invited for the 2nd InternationalConference on advanced A -D and D -Aconversion techniques and their appli-cations, which will be held at RobinsonCollege, Cambridge, UK, on 6-8 July 1994.

The aim of the conference is to pro-vide a forum for the dissemination ofknowledge and experience among a broadrange of people with an interest in thetheory and practice of interfacing 'realworld' analogue signals to the digital do-main.

Papers should be submitted by 7January, 1994, to the ADDA 94 Secretariat,IEE Conference Services, Savoy Place,London WC2R OBL. Telephone 071 3445478/5477, fax 071 497 3633, fromwhom details are available.

HOW TO PROGRAM TOSHIBA MICROSLloyd Research has produced a practicalsolution to an old problem: how to programlow-cost micros such as the ToshibaTMP47PC242VN. After a design is com-plete, it is usually necessary to use OTPparts until the desighn is finally proved andmask parts are available. In addition, withthe lowering of costs of OTP parts, manycompanies are not using mask parts at all.

A simple solution is to buy a number ofsingle socket adaptors and to use a stan-dard EPROM programmer. Such adaptorsare usually wider than a single socket onthe programmer, so it is rarely possible tofit more than four sockets on an eight -gangprogrammer. In addition, the programmermay need to be set up each time for a dif-ferent address range. As if this is not enough,there is always the problem of the mechanicalfit of a delicate adaptor in a production en -

Unit 4, Gibbs Reed FarmPashley RoadTICEHURST TN5 7HETelephone (0580) 200 657 (National )or +44 580 200 657 (hiteniationalFax. (0580) 200 616 (National)or +44 580 200 616 (I nternatronal)

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HUNGARYElektor Elektrondai foly6rat1015 BudapestBatthyany u 13Editor Lakatos Andras

vironment.Lloyd Research has overcome this prob-

lem by designing a special module for theirL9000 programmer. The PL242 module isfited with four sockets for shrink dip de-vices. A second identical or different mod-ule can be fitted to double the capacity orto program other devices such as EPROMsor other microcontrollers.

To cater for short-term requirement,programming systems can be rented fromLloyd Research.

The L9000 is made and supported inthe UK by Lloyd Research who have beenmaking programmer for ten years. Productionmanagers can also take comfort from ap-provals the company has received fromIntel, Texas Instruments and Signetics.Lloyd Research, 7/7ABrook Lane, Warsash,Southampton S03 9FH. Telephone0489574040/885515; fax 0489885853.

ENCLOSURES, TOOLS AND SERVICEFROM OK INDUSTRIES

A range of enclosures, tools and equipment,including that for Surface Mount Technology,is available from OK Industries. The widerange of instrument enclosures include allthose produced by the well-known Canadiancompany PacTec.

OK Industries have been supplying high -quality and competitive products for over30 years. Since 1980, the company hasalso had in-house workshops manned byfully trained engineers who specialize inOK Industries' products.

A catalogue of all OK Industries' prod-ucts is available by phoning or writing toOK Industries Ltd, Unit 1, Barton FarmIndustrial Estate, Chickenhall Lane,Eastleigh, Hants SO5 5RR. Telephone(0703) 619 841; fax (0703) 643 279.

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SWEDENElectronic Press ABBox 550514105 HUDDINGEEditor Bill Cedrum


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Proteus software is for PC 386 compatibles and runs under MS-DOS. Prices start from £475 ex VAT; full system costs £1495.Call for information about our budget, educational & Windows products. All manufacturers' trademarks acknowledged.

8

SIM AN 8051 SIMULATORThis article describes how to use SIM, a power -packedprogram that simulates an 8051 microcontroller on an IBM PC,providing a perfect complement to the 8051/8032 assemblercourse which so many of you have followed with great interest.The reasons for using a simulator are given, followed by a briefdescription of SIM's facilities. A short program is used todemonstrate how to use the simulator, with commentary onhow each feature is used for program development anddebugging. Finally, a typical program bug is demonstrated.

By David Mockridge

EN programming a microcon-troller like the 8051, the develop-

ment environment is Spartan.Development tools are often command -line oriented or run only with dedi-cated ICE (In -Circuit -Emulator)hardware. Although an ICE is an ex-cellent solution for embedded systemdevelopers, it is expensive.

On the other hand, those who pro-gram in high-level languages work incomparative luxury. When things gowrong in Basic, C or Pascal, all theyneed do is single-step through thecode with a fly -swatter at the ready. Ahost of powerful features are available,such as setting watches on variables,editing data and breakpoints.

The microcontroller programmerwith a smaller budget has access tonone of these facilities. After the pro-gram has been written, assembled andburnt to EPROM (or downloaded to anemulator), the programmer is often leftstaring in frustration at a smug lumpof silicon, wishing the lid could betaken off with a screwdriver to seewhat is happening inside. (A heavyblunt object will open the chip quite ef-fectively, but re -assembly is tricky.)

When confronted with this problem,the embedded -system designer mayturn to the fifteen or so vendors of8051 development software. This routeis still expensive, even if the often com-pulsory additional hardware isavoided. SIM provides a solution.

SIM in a nutshell

SIM is a program that simulates an8051 microcontroller. It runs on anIBM or IBM-compatible PC withoutany dedicated hardware. SIM will runyour program either continuously orby single stepping one instruction at atime. Like high-level language environ-ments, you can set watches to see thecontents of any register, port or on -chip RAM location while the program

is executing. If the system being devel-oped uses an external RAM, its datacan be watched, too. All registers andboth of the RAM areas may be edited atany time. Breakpoints can be set tohalt the simulator at selected ad-dresses, so that the state of the ma-chine can be examined. Breakpointsand watches are dynamically manipu-lated with a window -based menuingsystem. Context -sensitive on-line helpis provided for all simulator functions,as well as help for all 8051 instruc-tions. The disassembled mnemonicsdisplayed by the simulator are Intel -

*L114 Tag /PLOT

compatible. SIM comes with a com-mand -line disassembler and assem-bler.

Start, Reset and Run

The short program in Fig. 1 will beused to demonstrate how SIM works.

SNAIL Tiny Assembler, at 22:40:19 on 09-06-1993. Source: "EX_1.ASM"

1 ; SIM DEMONSTRATION PROGRAM EX_12 ; FLASHES AN LED ON PORT 1 BIT 03

4 ; EQUATES5 LED _1 EQU 90H6

0000 7 START:0000 74FF 8 MOV A,#FFH LOAD ACCUM. WITH DELAY CONSTANT

9

0002 10 CONTINUE:0002 14 11 DEC A SUBTRACT 1 FROM THE ACCUMULATOR0003 FD 12 MOV R5,A ; MOVE ACCUMULATOR TO REGISTER 50004 00 13 NOP NO OPERATION, DO NOTHING0005 70FB 14 JNZ CONTINUE ; DOWN TO ZERO YET?0007 110B 15 ACALL TOGGLE _LED ; CALL FLIP LED ROUTINE0009 80F5 16 SJMP START

17000B 18 TOGGLE_LED:000B B290 19 CPL LED_1 ; COMPLEMENT (= INVERT) LED BIT000D 22 20 RET ; RETURN FROM SUBROUTINE

2122

Statistics after assembly (22:40:20 09-06-1993)

Found 1 equate:1: "LED_i" equates to "90H"

Found 3 labels:1: "START" was at address OH2: "CONTINUE" was at address 2H3: "TOGGLE_LED" was at address BH

14 Bytes of object code were written. (OH..DH)

Source file: EX_1.ASM List file: EX_1.LST1561 Bytes of listing file were generated.

Object file: EX_1.OBJ

Fig. 1. LST (list) file produced by asembling EX_1.ASM.


SIM - AN 8051 SIMULATOR 9

While symbolic names are shown inthe assembly listing, SIM disassemblesthe raw object file, and will not displaythese. Start the simulator by typing`SIM' at the DOS command line. Selectthe menu bar 'File' option by typing 'F',followed by the filename 'EX_ 1. OBJ'.As SIM loads this file, it will display ascreen of disassembled instructions,with a highlight bar over the next in-struction to be executed, which will be`CLR A' (clear accumulator).

Once the file is loaded, single-stepthrough the code one instruction at atime by pressing 'S' repeatedly, or runcontinuously by pressing 'N' for themenu 'Run' option. Once you havetried both methods out (use the spacebar to stop running), type 'R' to reset.This option performs a CPU reset ofthe simulator (not the PC!). When yourprogram jumps into uncharted ad-dress space (outside your programarea), the simulator will not budgeuntil it is reset in this way. After yourCPU reset, notice that the highlightbar has returned to address 00.

Now type 'B' to select theBreakpoints option. Menu options inwindows like these are selected bymoving the highlight bar over yourchoice with the arrow keys, followed bythe enter key. Select 'Add breakpoint',then enter '5' to set a breakpoint at thisaddress. Now that a breakpoint hasbeen set, when you set SIM running, itwill only go as far as address 5, whereit will wait for you to single-step or runfurther onwards. Breakpoints have noeffect when single -stepping, since youstop on every instruction anyway.Breakpoints are invaluable when youwant to debug portions of programcode that can only be properly testedby running through initial processing.When initial processing is unnecessaryfor testing, then the `Goto' option maybe used. The 'Clear all' option on thebreakpoints menu will remove allbreakpoints, irrespective of how manyare set. If you want to set a breakpointat your current location (wherever thehighlight bar is located), you can usethe 'Set Brkpt here' menu option.Breakpoints (like edit quantities andgoto addresses) are always entered inhexadecimal. Use 'List breakpoints' toreview the breakpoints that have beenset, and 'Delete breakpoints' to removethem individually.

Adding a watchNext we will add a watch so we can seewhat is happening inside the accumu-lator. Choose the 'Watch' menu fromthe menu bar with 'W'. Select 'Addwatch' followed by `SFRs / CPU'. Allthe SFR (Special Function Registers) inthe 8051 are displayed in this window(see Fig. 2). The cursor will be parked

on the accumulator (À') register by de-fault. When you move over other regis-ters (use the arrow keys), you will seethe direct address of each one dis-played at the upper right of the win-dow. Return your selection to theaccumulator, and press Enter. Selectthe first binary format (`Binary 1') towatch the accumulator in binary. Youcan set several watches on the samepiece of data using different formatsfor each one. For example, if you wantto watch the accumulator in hexadeci-mal as well as in binary, all you needto do is repeat the previous actions,only selecting the format 'Watch ashex' instead of 'Binary F.

SIM SYSTEM REQUIREMENTS

IBM or IBM compatible PC, 640 KRAM, monochrome or EGA or better

screen adaptor. DOS 3.2 or later.

Choose the 'Default name' option fornow. When you hit Enter, the accumu-lator will appear in the watch window.

If you single-step or run throughthe program at this stage, you will beable to see inside the accumulator as itis changed by the program.The 'New name' option in the addwatch menu allows you to enter yourown names for watched data. For in-stance, if you had a DIP -switch at-tached to a port, you might prefer toname the port 'DIP switch' instead ofusing the default watch name of 'P1'.

4.

It

In a timer program, you may want toname an on -chip RAM location or reg-ister as 'Seconds count' instead ofusing an address. Another add watchoption 'Join with prey' allows you tostring watched pieces of data togetherby omitting the text descriptor adja-cent to the watch data. Since watchesare byte -oriented, this allows you towatch a set of (not necessarily contigu-ous) bytes as if they were a string.

Now that you have added a watchon the accumulator, try adding awatch on R5 (register 5), which is at di-rect address 5. Select 'Add watch',then the 'Direct RAM' option. Specifyaddress 5 for register five in addressbank zero, and type in `R5' for the 'Newname' option. If you add the stackpointer too (SFR/CPU window registerSP), you can now watch the accumula-tor, stack pointer and register 5.Notice how the stack pointer goes upby two as the source address ispushed on to the stack, every time thesubroutine call at address 7 is made. Itfalls correspondingly by two wheneverthe return address is popped off by thesubroutine return instruction.

Default watchesThere is a special watch option to adda convenient default set of watches atonce. These consist of the accumula-tor, registers 0 to 7 (from register bank0), the data pointer (DPTR), port 1, theprogram status word (PSW) and thestack pointer. To do this, select theÀdd default' watch menu option. The

Fig. 2. The Watch menu enables you to peek inside the 8051, and see what is happening tothe SFRs and the CPU.


10 COMPUTERS AND MICROPROCESSORS


1 SIM DEMONSTRATION PROGRAM EX_22 FLASHES AN LED ON PORT 1 BIT 03 BUT USE A NESTED LOOP TO MAKE FLASHING4 SLOW ENOUGH TO BE VISIBLE.5

6 ; EQUATES7 LED_1 EQU 90H8 TIMEDLY1 EQU #FFH9 TIMEDLY2 EQU #FAH10

0000 11 CARRYON:0000 1109 12 ACALL DELAY LONG DELAY SUBROUTINE0002 1106 13 ACALL TOGGLE_LED FLIP LED SUBROUTINE0004 SOFA 14 SJMP CARRYON DO THIS ENDLESSLY

1516 ; SUBROUTINE TO TOGGLE THE STATE OF LED BIT

0006 17 TOGGLE_LED:0006 B290 18 CPL LED_1 ; COMPLEMENT (= INVERT) LED BIT0008 22 19 RET ; RETURN FROM SUBROUTINE

2021 ; SUBROUTINE FOR LONG DELAY

0009 22 DELAY:0009 78FF 23 MOV RO,TIMEDLY1 ; PRIME OUTER LOOP

24

000B 25 FINISHEDYET?:000B E8 26 MOV A,RO CHECK IF OUTER LOOP DELAY DONE000C 600C 27 JZ DONEDELAYING GET OUT IF IT IS000E 74FA 28 MOV A,TIMEDLY2 ELSE START ANOTHER INNER LOOP

290010 30 INNERLOOP:0010 00 31 NOP ; DO NOTHING TO INCREASE DELAY0011 00 32 NOP0012 00 33 NOP0013 00 34 NOP0014 D5EOF9 35 DJNZ EOH,INNERLOOP ; EOH IS ACCUMULATOR DIRECT

360017 18 37 DEC RO0018 80F1 38 SJMP FINISHEDYET?

39001A 40 DONEDELAYING:001A 22 41 RET

4243


Found 3 equates:1: "LED_1" equates to "90H"2: "TIMEDLY1" equates to "#FFH"3: "TIMEDLY2" equates to "#FAH"

Found 6 labels:1: "CARRYON" was at address OH2: "TOGGLE_LED" was at address 6H3: "DELAY" was at address 9H4: "FINISHEDYET?" was at address BH5: "INNERLOOP" was at address 10H6: "DONEDELAYING" was at address lAH

27 Bytes of object code were written. (OH..1AH)


Object file: EX_2.OBJ

Fig. 3. LST (listing) file of EX_2, an example program that flashes a LED at a visible rate.

results of this action are shown inFig. 2. Since maintaining a large num-ber of watches can slow the simulatordown, you may wish to delete somewatches. Do this by selecting the`Delete' option from the watches menu.Page up and down through the list ifnecessary, until you have placed thehighlight bar over the watch to bedeleted. Press Enter to delete the se-lected watch, and use the Escape keyto quit out when you have finisheddeleting. Use the 'List' watches optionto review the watches set withoutdeleting any. The list, delete and addfunctions of the breakpoints menu are

operated in exactly the same way.

Goto, Help and Escape

The `Goto' option will allow you to startexecuting from any address in yourprogram. If you go to a data address,the simulator will interpret the data asan instruction, with unwanted results.Use the Goto option with care, al-though if you do get lost by branchinginto a data area by mistake, you canalways reset and start over. To practicea Goto command, do a reset, selectmenu option `Goto' and enter ad-dress 7, the address of the subroutine

call. The highlight bar will jump to ad-dress 7, from where you can now sin-gle-step (or run). `Goto' is useful forskipping past portions of code that youknow are working, and for testing sub-routines in isolation.

Wherever you go in the menu sys-tem, context -sensitive help is at hand.Select the watch menu again, andmake a few random choices. Press F1to pop up the help window, followed byEnter again to get context -sensitivehelp for the watch sub -menu you areat. When you have finished reading,use the Escape key to quit out of help.Pressing Escape repeatedly will backyou up through the sub -menu win-dows chosen up to this point. Anotheroption in the help window provideshelp for each op code in the 8051's in-struction set. The help descriptionsare no substitute for trying the in-structions out with the simulator,which is more fun than merely readingabout them.

A bit at a time

The 8051 has a dedicated Boolean bitprocessor and accompanying bit -ori-ented instructions. SIM allows you toset watches on bits and edit them indi-vidually. Add a watch as before, butselect the 'SI-Rs/CPU bits' option tosee a window with all bit -addressableregisters and their bits (also shown inFig. 2). When the bits have specialnames, for example CPU flags, theseare shown. The bits covered with as-terisks which the cursor skips are notbit addressable. Besides the SFR bits,all the directly addressable bits in thechip are individually selectable in aspecial window for single -bit editingand watching. Watches may be set onindividual bits of ordinary direct RAM,but these may only be edited at a bytelevel. Try setting a watch on port 1

bit 0, and then use 'Edit' to change itsvalue before the program does. Thewatch window is updated immediatelyas you complete the edit. Editing canbe used to simulate external eventslike switch depressions or A/D (ana-logue -to -digital) inputs, by setting dataat ports.

Another use for editing is escapingfrom a loop (or nested loops) that relyon a counter reaching a particularvalue before moving on. In the testprogram, we have to wait for the simu-lator to count down from 255 (FFH).Once the loop has been entered, thislongish wait can easily be cut short byediting the accumulator down to a fewcycles away from completion.

Interrupts

The interrupt menu lets you choose ahardware interrupt to trigger. Like the


SIM - AN 8051 SIMULATOR

; Stack -destructing demonstrationStart:

ACALL SubroutineOneSubroutineOne:

SJMP Start


1 ; STACK -DESTRUCTING DEMONSTRATION0000 2 START:0000 1102 3 ACALL SUBROUTINEONE0002 4 SUBROUTINEONE:0002 80FC 5 SJMP START

6


No EQU(ate) statements were found in this source

Found 2 labels:1: "START" was at address OH2: .... "SUBROUTINEONE" was at address 2H

4 Bytes of object code were written. (OH..3H)


file.

Object file: EX_3.013J

Fig. 4. Assembler (ASM) and listing (LST) file of a stack -destructing program, EX_3.

physical 8051, interrupts are ignoredunless they are properly enabled withthe interrupt priority register. SIM alsotraps attempts to vector to an inter-rupt past the end of your program, anddisplays a warning. Try a serial portinterrupt (interrupts menu, option `121& T1') to do this intentionally. Do notforget that whenever you are con-fronted with a warning message boxlike this, you can always use help toget more details on the condition thatcaused it.

The tiny demonstration programwas chosen for size and simplicity.With a 16 -MHz clock the flash rate isinvisibly fast. See the programÈX_2.LST' in Fig. 3 for a nested -loopflasher that is slower, and whichflashes visibly. While each exampleprogram fits on one screen, SIM han-dles programs that span severalscreens, displaying only the currentscreen. When a jump is made off thescreen, a new screen is disassembledfrom the destination address onwards.

Catching a bug

The program in Fig. 4 demonstratesan interesting bug. A subroutine call ismade repeatedly without ever execut-ing a return. One would expect thestack pointer to wrap around (SIM willtrap this event and issue a warning),but it does not. The stack pointer itselfis located at address 81H, above thetop of the stack. This means it pointsto itself when it grows too high, writingpushed address data over the pointerbefore it grows higher still. The fault isobvious in such a tiny program, but a

larger program might well have thesame problem, only buried in hun-dreds or thousands of lines of code.

Try loading and running program'EX_3.013,1', to see it self-destruct. Theresults make it clear how important itis to return from subroutines.

External RAM consists of RAM chipsphysically external to the CPU. Sinceexternal RAM can take up 64 KBytesmemory, SIM only allocates storage forexternal memory if it is referenced.When any action (edit, watch or move)is performed on an external memorylocation, that location is created andmaintained by SIM. This approachsaves memory space but imposes anincreasing processing time overhead ifmany external memory locations areused. SIM is not recommended for pro-grams needing large amounts of exter-nal memory.

Object file edit facilitySIM incorporates a file edit function.This facility allows changes to bemade to the file you are running in thesimulator, without exitting SIM.Instead of quitting, changing your as-sembler source code, reassembling itand then starting the simulator again(assuming you had no assembly er-rors), the file edit facility allows you tochange values in the object file you arerunning, while you are running it. Ifyou change an instruction displayedon -screen, the screen will be re -disas-sembled to reflect your change.Changes may be made to any instruc-tion or data, including the highlighted(next to be executed) instruction. This

does mean that your assembly sourcecode is no longer in step, but freshsource code can be generated by run-ning your changed object file throughthe disassembler. The disassembledcode will not, of course have any com-ments or labels in it, so changing yourassembler source will usually be a bet-ter option.

SNAIL, DISASS and SIM

All example programs referred to inthis article are provided with SIM, insource and compiled form. A tiny butfully -functional 8051 assembler calledSNAIL is provided with SIM for thosewho have not yet got one. SNAIL andDISASS are limited to small (around15 KBytes maximum) source files.DISASS is a full 8051 disassembler,useful for picking up bugs. DISASScomes with SIM. Brief documentationand sample programs for the disas-sembler, assembler and simulator areprovided on the diskette. Add yourfavourite editor or word processor, andyou have all the tools required to de-velop 8051 programs.

The example programs used herewere the simplest possible demonstra-tions. SIM is capable of much more,including responding to software inter-rupts, register bank switching, power -down modes, relative addressdecoding, running object files of up to65 K and use of the full instructionset.

Finally I would like to mention thelittle-known software design phaseknown as bugging. This occurs some-where between the design and codingstages, and is inversely proportional tothe time required for the better knownphase of debugging. Cutting down onbugging time is difficult, but by usingSIM I hope you will lessen debuggingtime considerably.

For further reading:8051/8032 assembler course (8 instal-ments), Elektor Electronics Februarythrough November 1992.

Program ordering informationThe programs SIM, SNAIL, DISASS,explanatory text files, and the threeexample files discussed here are con-tained on a single 31/2 -inch MSDOS for-matted diskette which may be orderedthrough the Elektor ElectronicsReaders Services. The order code is1931. Price and ordering details maybe found on page 70.

The courseware diskette and the sys-tem monitor EPROM for the8051/8032 Assembler Course are alsoavailable through the ReadersServices. The order code is 1661.



;1;7%1..M L A 91 V

9338 VICOM G FAX 081-552 0946

7440574 0.647400589 1,647400590 a947440592 1.197400593 1.667400595 0927400597 ass7400620 1,627440623 1.627400633 1,62

746C1243 07674407244 0.5774407245 05274007251 0.8674007253 0.5174407257 a5474401258 0.7274407259 07874407273 0.6874401280 098

74F14 04174F20 02874027 a2874030 0.2874F32 OP874137 04174F38 0.4474040 0.6674051 0.4474F64 012

7440251 ass7440253 0807440258 0807440273 1.107440283 1.407440299 2067440373 0947440374 0.927440377 098744C540 198

78512 ao78515 0.55790579054 0.32

7909

0.28

7905E4 0.600.55

7912 0.307912A 0.367912FA 0.787915 0.30

0.9A/200VDIL 0383.04/200V 0100.5764/100V SIL 1,60134/200V SIL 1.96354/1000 Sqr 2.98KBPC1002 1.64KBPC3502 2.98W005- 14/51300.32W020- 1.5A 0.40

Freq.= MHz3.6864,4,8,10,12.16,20,24,32A0 8 50Price: £4/0 each

TTL Output14pin DIL Layout

Sealed Metal4pin Pkg

Freq.= MHz

KM44C2564Z-10 6 95'M5M4464P-15 4.6C

MK41164-54 2 8CMK45644-15 120NMC37644-15 100UPD414640-12 4.20UPD41464C-15 4.20UPD416C-2 340UP241611-3 1600024460.1 2.60

TEL 081-471 TLX 929709

DIGITAL INTEGRATED CIRCUIT SPECIALIST 74006407400643 1,32

74401283 ass741901297 0.82

0.3074F85 1.46

7440541 0.987440573 1.38

79187924

0.300.30

2W02 6460

2KBB1OR/SIL 00..1MHz E8.90 ea.

7400645 1.40 74401299 1.64 74E86 0.41 7440574 1.38 790124 0.35 2K882012/510 am 4,4.9152,6.89.8304,STATIC RAM

7400646 1.77 74001354 1 28 740109 0.56 7440646 POA 790124CP 0.35 88001500/5q 035 10121816. 2114-30 3.404000 SERIES 45130 120

4514B 1.12401613T 0.43401787 0.78

74160 09474161A 0.98

741_0169 0.597475170 POA

7400669 1 077405670 0.78

7440648 1777440651 1.47

74001356 1.28740C-1365 0,54

74F112 0.72740113 1.30

7440648 POA 79M05 0.4279M055 0.42

88001500010 080SKB6008/604 POA

18.432, 19.6608,20, 24. 25 & 30MHz

62640P-10 2.4C

62640P-12 2.4040008 0.16400008 0.18

4515B 1.1245168 044

4018BT 0.78402061 0.95

74163 1.2874164 1.20

7405173 0.39741_0173A 0.44

74LS673 POA7400674 17.60

7440652 1.477440658 449

74001366 ass74401367 0,54

74F114 1.30

74E125 0.6074C SERIES 79M05FA 0.65

79M12 0.50 CRYSTALSPrice) 83.52 MI. 62256LP-12 49.

4001A 0.1640016 0.18400100 0.2240026 0.18HM1-6116-540066 0.39

45178 1.8445180 0.4045196 0.364520B 0.3645218 0.72

4021BT 265402381 0.38402461 0.7640250T 038402787 0.45

74165 1.577416674174 1.5374175 1.2374180 1,29

7400174 0.367405175 0.3474051E11 1.827405182 2.057405183 2,05

7400682 2.627405683 POA7400684 3 857405685 P087400686 POA

7460659 4.497440664 4.497440665 4.497440670 1 10

74001168 0.8074401373 04474007374 ass74401377 0.64

74F126 0.98741132 0.58740138 0.58741139 0.58

74000 0.5674002 0.5674508 0.5674510 0.56

79M124 0.60LM3177 ass081317MP 1.06

LM31712 0.55

_,H.C49( HC18/U)

'- ci'MHzCDM61176631843200 1.602000000 1.66

30, 32, 32.768,33.33. 40 & 50MHz

Price' £4.45 CO.

62256LP-10 4.95CDM6116453 530

5.854.36

hIM3-6116-5 160400708 0.20 45220 0.86 402801 0.56 74184 PO4 7405189 2.60 7405687 PO4

7440677 3.787460678 5.91

74007390 0,6874001393 ass

740148 0.94741151 0.58

74014 0.5674020 0,98

LM338K 4.45L1478GU1C 1.02 1.49

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HM6116LP-2 2.6C40088 0.4040094E 0.23

45266 0.5045278 0.58

4029BT 0.86404001 078

74185 1.7679191 1.41

7403190 0.497405191 0.99

7405688 1 987400693 POA

7440680 3.83 74007394 0,00 74F153 0.62 74030 198 71479GU10 1.02,`,..",,f,To`c/,'

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OscillatorsHM6116LP-3 2.600M6117LP-3 5.77

4009UB 0.29 452813 0 49 404281 0.74 74192 1.41 7405192 0.49 74LS794 POA7440682 4.21 74007423 0.62 740157 0.58 74032 ass 14041954 1.80

3.686400 1,02 HM622561_110 7.9340108 0.29 45298 0.57 404661 1.41 74193 1.65 7405193 0.48 7400795 POA

7460684 5.70 74001533 1.44 74F158 0.70 74C42 288 DIODES 4200000 1.02EXO-3C SERIES HM6264ALP-12 3.95

40116 0.18 7405796 POA7440688 087 740C-1534 0.75 74F160 1.10 74048 2.98 8pin OIL Plastic HM6264ASP-20 3/5

401106 0.18453013 1.9245310 1 14

404787 1.06404913T 1.06

74221 1.2374259 2.92

7405194 02474051946 0 57 7405797 POA

7460690 182 74HCT540 0.64 7461606 1.10 74073 1.28 142986% 18.204.096000 1,104.194304 1.10

Package HM62671,35 5174012AE 0.16 45320 044 405013T 0.48 74265 1.46 74001956 057 7400848 POA

7460691 1.62 74407541 0,64 746161 1.10 74074 0.94 143881 2.54 4.433619 1.10 Peg' z HM6281287P-8040128 0.204013B 0.20

45348 2.824536B 1.22

4051BT 0.78405287 0.84

74273 POA74276 3.56

7405196 0.68741_5197 0.68

7440692 1.737460693 1.73

74401563 0.9874001564 0.78

740162 1.28740163 1.28

74076 1.2674085 1.86

1439974 6.56144001 0.04

4.608000 1.104.915200 1.20

12 14 31818 16- '16 384,19.6608 8

18.50HM662047-12 158C

74HC SERIES

4014B 0.42 45386 0.60 405367 098 74279 1.38 7400221 044 746000 0.19 7460696 1.48 74001573 0.64 740164 1.28 74090 1.29 154002 0.04 5.000000/5 1.02 2°MHz 4.954015B 0.42 45398 0.62 4060EIT 0.84 74283 1.26 7405224 20.24 744002 0.19 7440697 1.24 74001574 0.64 741166 74093 2.10 1114003 0.04 5.068800 1.10

£3.92 COKM62256ALP-10Price: -' 01-151640-101. 2.404016B 0.24 45418 0.52 40668T 0.59 74298 POA 7400240 0.42 740003 0.24 7440698 1.24 74007583 0.00 74F168 4.48 74095 1.60 144006 0.04 5.242880 1.20 P211440-2 3 40

40170 0.38 4543B 0.57 406861 0.38 74365 0.70 7413241 0.42 746004 0.19 7460699 1.24 74401597 1.52 74F169 3.60 740150 5.40 154007 0.04 5.888200 1.8016pin DIL Plastic P2114AL-4 3.40

40186 0.38 45448 2.11 4069UBT 0.38 74367 1.06 7405242 0.42 744CUO4 0.24 74404002 035 74407640 1.34 74F174 0.76 740151 3.94 144148 0.03 6.000000 1.02 P'ee'g,,,e, PCD5101P 3.3040196 0.26 45478 1.88 407067 038 74393 2.94 7405243 0.42 740005 0.20 74604015 107 74007643 1.34 741175 0.76 740154 5.82 154149 0.06 6.144000 1.02 Programmable 'Sr UP043256AGU10040204E 136 45498 POA 40718T 0.38 74403 PO4 7413244 0.42 744008 0.20 74404016 0.44 74001645 1.11 740181 4.48 740157 3.80 1114150 0.08 6.400000 1.64

57 Dig Frequency8 33

40200 0.38 45518 1.62 4075134 038 74423 POA 741_5295 0.42 740010 0.29 74404017 0.42 741901646 2.40 741182 1.80 740184 2.54 154448 0.06 6.552000 1.40 UPD432560-12 5.604021B 0.40 45538 2 37 4077BT 0.38 7405247 0 44 746011 0.20 74604020 0.52

74404022 0.56741-101648 1.90 74E189 4.98 740165 254 154728A 0.24 6.553600 1 21

88,8540-- --- - -AN UPD4364C-15 4.70

40226 0.40 4554B 6.01 4078131 038 74LS SERIES 7405248 0.68 744014 0.25 74001651 1.64 741190 3.40 740221 2.98 1547356 0.24 7.372800 0.780.005 to 600kHz

40236 0.20 45558 0.48 40818T 038 741-10142 0.34 74604024 050 74401652 0.00 741191 3.20 740240 1547366 0.24 8200000 1.00 UVPROMS740000 0.184023UB 0.23 45568 0.49 409381 0.45 7405251 0.32 746020 0.22 74404028 058

74404040 0.5074401670 1,10 740192 3.20 740244 2.041547406 0.24 3867231- 1.34 SPG8640BN402440 0.27145578 1.88 409411 0/5 740001 0.18 7405253 0.44 746021 0.22 74001673 1.64 741193 3.20 740373 N 743A 0.240.00834 9830400 1 20

to 1MHz 270128-25 3.954024B 0.3240258 0.19

4558B 2.1845606 1.51

4508BT 205451087 1.02

740002 0.18740503 0.18

7405256 0.787405257 0.34

746027 0.22746030 0.22

74404046 1.5474404049 00874604050 0.36

74007688 1,10746014002 0.39

740194 1.48740195 2.2474E219 4.38

740374 2.08740901 1.18

1547446 0.241547566 0.24

.10.00000 1.101029500 1.90

580864004270646-15 3.95270256-15 3.95

4026B 0.54 45616 1 74 4511 BT 1.35 740504 0.21 741_52574 0.46 746532 0.22 740074015 1,13 740902 1.18 1552288 0.09 11.0 1.100.064 to 768kHz

40276 0.30 4562B 5.15 4512BT 0.68 740005 0.21 7405258 0.44 74HC42 0.48 74404051 0.64 7400-14016 0.52 74F224 POA 740903 1.52 1452326 0.09 12.0 0.92 D27256 5.4040288 0.38 45668 1.10 4514BT 220 740006 0.51 741_5258A 0.48 744051 0.29 74404052 068 741-1014017 ass 74E240 0.62 740906 1.10 1552346 0.09 13.87500 2 40

sp,86.502-20 27C512D-12 6 4E

40296 0.35 45686 5.17 451681 102 740507 0.51 7405259 0.48 746058 0.42 74604053 0.68 740014020 074 740241 0.62 740907 1.10 1553376 0.48 14.000001..64222- 4,84No2

- ----- - ..'"' 27010000-12 8 924030B 0.21 45690 304 451887 1.18 740008 0.18 7405260 0.22 748073 0.34 7440405341 10 740074024 0.68 740244 0.82 740908 2.20 1553496 0.48 14 31818/0 0 2704096-12 POP40316 1.04 4572U8 0.70 452061 1.18 740509 0.18 7405266 0.32 744074 3.25 74604060 0.47 740C-14040 am 74E245 0.72 740911 14.42 1553520 0.48 14.74560M 1.8150

Price: ,. 4 , p- ---- -0' HM270101G-20 9.80

403213 0.70 4573P POA 4521131 107 740510 0.18 7405273 0.42 744075 0.40 74404061 252 740074046 2.10 74E251 0.82 740912 14.42 1453578 0.48 14.74560 1.10DC to DC 4527010244010

40336 0.58 45806 8.84 4522BT 1 22 740511 0.18 7405275 POA 744076 0.40 74404066 0.46 740074051 0.96 7402514 0.66 740914 1.16 14536513 0.481 00000/5 1.10

5

Converters 11624034B 1.10 4581B 3.85 4528BT 0.88 740512 0.18 7405279 0.33 744077 0.51 7440406640.54

744104067 472746014052 ass 740253 0.62

740257 0.62740E115 2.74 1953660 0.48

1 6.000001.02 44270640P -20T 140

40356 0.39 4582B 3.0.5 740513 0.19 7405280 0.86 744085 740074053 0.84 740922 6.80 1553706 0.48 16.00000/S 1.201DIC 0E-0344 5.60 46270640-15 4.20

40366 2.57 45838 0.86 453867 1.05 740014 0.24 7405283 0.45 744086 0.28 74404072 0.45 746014059 224 74E2574 0.66 740923 6.80 11453800 0.48 18.43200/5 1.1030054 15-15 2750 64270640-20 4.20

4037E1 1.27 4584B 0.57 454187 1.05 740015 0.38 7405290 0.48 744093 0.44 74404075 032 740014060 0.84 740258 0.82 740925 9.30 145401 0.11 1066080/5 1.20IPL S.010 23.40 44462532P 4.5C

40366 078 45858 0.49 4543BT 1.02 740520 0.16 7405292 16.86 7440107 039 741904078 0 46 740074066 0.66 740259 PO4 740926 9.30 145402 0.11 20.00000/5 1.604548271280-25 4554039B 3.22 4597CP 6.90 4555BT POA 74L021 0.18 74LS293 0.38 7440109 0.35 74404094 0.64 744014067 4.93 74E260 0.78 740929 9.30 1462874 1.55 22 1184 168

PIN

1 Watt DC/DC 454827640 3.8040406 042 45986 6,90 4556B7 1.05 741322 0.18 7405294 17.62 74110112 0.40 74404316 0 68 740074075 0.36 740269 7.48 79S SERIES 15825 2400000/5 1.82 5V input --Output

= M2716-101 3.5040410 0.41 45998 5.50 458581 0 95 740524 0.58 7400295 1.11 7440113 0.40 74804351 0.89

74404511 0.55740074094 0.84 740273 0.84

74E280 0.68148254 1 27.64800/S 1.20

DIL & SIL by M5L2732K 44074500 a4474502 0.4440426

404106 0.324042B 0.32

47208 POA4720V POA

40106BT 0.5340244BT 1.35

740526 0.18741327 0.18

74052954 1.157400298 0.98

7440123 0.407440125 0.40 74404514 1.38

744014316 0.66740074351 1.04 740283 a92

14827155252

3a00000f5 8.9932 00000/5 1 40

NewportNMA050565V

M5027648 V30MI3M27C64-20/21V

40436 .0.36 47238 POA 40373BT 2 34 741328 0.24 740S299 1.53 7440126 0.47 74004515 1.42 74001-4510 1.54 74E299 POA 74503 ,5-, 50822800 0.66 '48.00000/5 1.68NMA0509s9V 4.50

40446 016 47248 1.90 740530 0.18 7405321 3.82 7440131 0.52 74004518 0 80 7419074511 094 74F323 POA 74004 0.42 5082-2810 1.40 s = Series NMA0512s12V MBM270128-30 4.2074 SERIES4045B 094 4731VP 9.80 741331 1.58 7405322 POA 7440132 0.32 74404520 0.72 744074514 1.64 740350 1.50 74008 0.42 5082-2835 0.441 4 MA0515815V MBM270256-30 5.10

40460 0.42 473,18.25 740532 0.20 74L03224 POA 741-1C133 0.32 74004534 0.00 744014515 2.50 74E352 0.64 74309 0.48 44119 ark H033/1.1 Price:87.90es. MI02702560-2540476 0.38 4738VP 18.50 7400 ass 740533 0.20 7405323 3.24 7440137 0.76 74404538 0.68 744074516 1.61 74E353 1.14 74$10 0.98 4.6144 0.72 4.9540480 0 82 475000 28.50 7401 ass 740537 0.18 7405347 2.86 7440138 034 74004543 0.81 744074520 ass 740365 1.28 74511 0.48 44Z15 0.58 0204800 8 23 DC/DC Converters rymc27c846).25 313640496 0.24 4752VP 29.25 7402 0.34 74 0.18 7400348 1.98 74140139 0.31 741907001 1.01 744014538 102 740366 120 74020 0.48 4.6217 0.58 0.307200 6.99 by Computer TM52516JL-45 4.5E40497113 0.28 4753VP POA 7403 0.34 741340 0.18 7400352 1.88 7440191 0.61 74407002 1,01 7419017007 a39 740367 1.48 74532 0.78 0.48 1.000000 3.95 Products TMS27128JL-25 4.6040508 0.22 4754VP POA 7404 0.40 74LS42 0.32 7400353 1.68 7440147 0.61 74607032 1.01 744017046 230 740368 1.30 74540 0.25 AV10 1.843200 371 PM623 24.60 11452716a-45 4.6040516 0.34 40085 1.98 7405 0.40 74 2.11 7400363 2.10 7440148 055 74007266 0.84 7460140102 243 74E373 0.62 74351 0.36 AV45 2.000000 465. PM671 26.70 UPD27256(1521V 5.6C4052B 0.33 40097 0.62 7406 0.68 741347 0.56 7405364 POP 7400151 0.40 74007074 1.99 7440140103 1.48 74E374 0.62 74364 0.36 40062 0.06 2 097152 3.71 PM672 26.70 UPD27324/21V 4.9540538 034 40098 0.62 7406A 0.72 74LS48 0.54 7405365 0.30 7400153 0.40 74007292 1.10 7440140104 2/1 740377 0.92 74074 018 P1(18 0.06 2.457600 1 92 PM903 44.00 UPD27C256D-15 58040548 0 68 40100 2.48 7407 0.63 741349 1.38 74003654 0.34 7440154 0.98 74007294 1.10

74004010274190140105 132 74E378 1.56 74586 1.12 6204 0.32 2.500000 1 92 PM951 46.50 0PD270512D-15 6184055B 0.6274311240101 POA 7407A 0.65 741351 0.19 7400366 0.36 7440155 0.09 1.10

74HC SERIES 74S381 3.68 128 6212 2.48 3.0"°' 225 RESISTORS 0PD27064D-25 495405613 048 40102 1.207408 0.37 740554 0.19 741_0366A 0.42 7400157 0.42 740040103 1.10

SURFACE 740385 PO4 745124 2.42 134058 0.2240596 29840103 0.88METAL7409 0.67 740555 0.32 7405367 0.29 7440158 0.47 740040105 1.40

MOUNT 740395 PO4 745132 098 0809 0.60H049/U44

FILM EEPROMS4060B ass40638

40105 1.82741040106 0.30

0.357412 0.64

741373 0.40741373A 0.48

74003674 0.34741_0368 0.36

74F10160 0347440161 142 741-1COOM 0 32

740002M 032

740399 09874E412 PO474F413 POA

740133 073740134 1.95

179 0.42260-200 3.58

2 276880 5--- 1 63 57,45 .58

0.25W 1%E24 Series 28064-25 9.80

74HCT SERIES40668 0.2740678 1.85

40107 0.4240108

7413 0.767414 0.72

741374 0.227413746 0.24

74053684 1.7274L5373 0.38

7440162 1647440163 0.42 7440100 0.22 741-1CO3M 0.32 740432 POA

745138 0.88740139 0.88

261-200 318YV28-100 0.99

5.068800 225 100 to 1M 3p eachN.B Min Sty. Order

28064-15 10.95280255-20 228440688 0.20Min.40109 1.24 7418 0.53 740575 023 7400374 0.44 7440164 142 7440102 0.22 7411004M 0.32 74F521 1.20 740140 0.78 sO/32-50 1.60

7864320 1 495pcs per value 280258 15 27.50

4069UB 0.2140706 0.21

40110 1.0440114 2.62

7417 0.487420 0.37

74L.S76 0.68741376A 0.72

7405375 0.427405377 0.66

7440165 0.657440166 0.88

7440103 02674H0104 0.22

740CUO4 0.3274HC08M 0.32

74E524 POA74F533 1.20

745183 1.26745157 1.72

8805 0.600180 0.40

8.000000 1.141000000 2.25

METAL FILM280256-15DC 28.505281640 5.10

40718 0.2040728 0.204073B 0.20

40756 0'19

40116 12.4840117 1.8040147 1.23

74257428 0.

7427 0.59

741377 0.42741378 0.32740683 0.39

7405378 0.98741_5379 0.9974753814 4.96

7440173 0.767440174 0.4274H0175 0.367440181 1.94

7440108 0227400710 1227440111 0227480114 0.26

7441010M 0.32740014M 0.36740C20M 0.367411030M 0.36

74E534 1.2074F537 1.8074F538 1.6074E539 1.60

748163 2.8,0

740174 0.92740175 1.35740182 3.29

V1404 15.90V209 1.206200 0.10

11.05920 240

12 000001.14

160000C) 2.2516.00000 1 14.

PRECISION0.25 WATT 01%

696 Series

X2816AP-25 5.1002864AP-35 122024001 1.624076B 0.422440160 0.54

40161 0.5474307432

7405836 0.39740585 0.38

741_5385 3.487405386 0.98 7460182 0.59 7400120 026 74HC32M 036

7400744 0.36740540 1.98 745189 2.14

0.20447

1 52soma* .

00000 1.00100R to 2556Price: £0.94 each

24002 2.1024004 2 96

40778 020 40162 7437 0. 741386 0.27 7405390 0.46 741-10190 0.67 741-1C121 0.267411075M a34

74E541 1.98 745195 2.40 490 0.14 ' 24016 5.4040788 22140816 0.18

4016340174

7438 0.497440 0.77

740590 0.40741391 POA

7405393 0.407400395 0.66

7440191 0.52741-10192 0.77

7440127 0.267400430 026 740085WM 065

7400136M 136

74E543 3.98741544 POA

745240 1.00745241 1.12

KE366 0.886KE47A 0.88

UM -1 HIGH PRECISIONNON -INDUCTIVE

280046-20 44059011 1.44

4082B 0.20 42175 0.47 7442 0.55 741-592 POA 74053954 0.94 7460193 0.54 7440132 0.22 74F545 POA 745244 1.77 EC53A 0.40 6.000000 225 WIRE WOUND 93006 1,1240858 0.38 40181 A 7445 1.20 741.593 0.44 7400396 POA 744C194 0.67 7400742 0.46 74001234M 0.46 74E547 POA 745257 1.22 P2270 006 8.1920013 212 0.15 WATT 0.1% 93046 1.26408613 018 40192 .82 7446 1.53 741.595 0.48 7405398 POA 74510195 0.47 741-1C-173 0.36 7400125M 0.46 740573 2.92 740258 1.22 10 00000 2 2540898 0/8 40193 0.74 7447 0.98 741398 0.82 7400399 0.81 7440221 0.44 7400174 ass 7440132M 0.42 74F574 2.92 745260 070 ENER DIODES 1120000.2.25 Temp.Coeff.3ppm MISC, MEMORIES40936 0.24 40194 1.82 7447A 1.67 7405107 0.28 74LS423 0.98 79HC237 0.73 74FICT75 0.36 7400138M 138 740579 7.98 740273 2A4 MISC. 12.28800 2.66 109,509,1009,2508,40948 0.38 40195 2.24 7451 0.57 741_5107A 0.38 7400445 POA 7440238 0.64 7440185 a60 7400139M 0.38

7400154WM 0.6474E604 4.84 74S274 242 1500000 2.25 104 100K 6341-1,1 4.5E

4095B 0.7040968 1.10

40240 2.6240244 1.36

7454 0.727470

7413109 0.2874051094 0.32

7400450 10.687413461A 7.16

7440240 0.447440241 0.44

7400186 ass7400193 0.58 7440157M 038

7440161M 0.48

74E620 POA740621 604

740280 0.96740283 1.90

BZI93C7V5 2.66BZY93015 2.66

17 .73447 23018.00000 250

Price: 8325 each A142148-4500 5.49AM270281P0 3.9E

40978 2.75 40245136 7472 0.387405112 0.28 741_0465 3.82 7440242 0.80 741907107 040 74F623 POA 745374 2.18 13ZY93C1842.66 20.00000 2.25 HIGH PRECISION IDT7130LA-100840988 040 40257 0.54 7473 0.59 74051126 0.34 7400467 7.78 7440243 0.88 74007109 0.42

74001112 0 427440164M 0.487440165M 0 57

74E646 5.15740676 POA

745284 2.10 82093020 P66 21.00000 2.25 NON -INDUCTIVE POP40996 0424104P 1.01

40373 1.1040374 1.10

7474 0.537475 0.67

7413113 0.327413113A 0.38

7400468 7.787405469 6.10

740C244 0.43745E245 044

-

74001123 0.64 7440173M 0.48 740821 398740412 2.10745436 2.62

13ZY93024V 2,66BZY93C331 2.66

24 00000 280 WIRE WOUND0.33 WATT 0.1%

101713204-1006POP

41608 085 45026 4.42 7476 7405114 0.32 74004694 6.70 74110251 035 741107125 0.56 7440174M 0.38 740823 POA 745437 2.62 BZ1030120 ao CRYSTALS MISC. MB8414E 4.9541610 0 85 45027 5.99 7460 1.28 74051146 0.36 7400490 2.85 740C253 0.52 74007126 056 7440221AM 0.65 740825 POA 740472 232 82X610902 0.09 Temp.Coett3ppm MCM40276C3 2.8041740 1.27 45028 4.49 7483 1.10 7400122 0.39 74004914 12.82 74510257 0.47 74001132 0.50 74HC240WM ass 74E827 79S734 2.62 137061024V aos 0043/7 1R,5R,10R,201,5011 48201264N 2.4641758 1.14 45040 POA 7485 0.58 7405123 0.36 7400502 POA 74110258 073 74401137 0.52 744C244WM 0,55 74F841 4.48 ZENER DIODES 1.000000 6.99 Price: f3.60 each N8251534 5.80VOLTAGE4194B 1 43 45041 PO4 7486 0.53 7405125 0.28 7405540 020 7400259 0.65 74407138 132 74402454W 162 74F843 4.93

400mW N82518144 6.0004409P 11.05 45100 POA 7490 0.78 741_0125A 0.32 741_5541 0.80 7400266 a36 74401139 0.45

74401147 0.687440251M 04274HC259M ass

74E845 POA74F1244 375

REGULATORS2.9V to 750 MINI CYLINDER

1004,12011 2501,'

NMC6504J-9 3.404410P 16.45 45106 7.98 74906 1.34 7405126 0.32 7400569 POA 7400273 0.54

744011151 152 7440273WM 0.55 7800848 1.15Price' 6p each

'

0.032768 ass5004,1K, 2K, 5IL NMC93064 1.45

44118 21 584412FP POA441200 POA4412VP PO4

45109 POA45138 POA45145 10.0445146 POA

/491 2.567492 0.6774924 1.127493 0.68

74051264 0.367405122 0.297405133 0.187405136 0.38

7405573 1.347405574 1.34741_5590 4.85741_5592 5.28

74HC279 0.517400280 0897400283 0.587400298 0.73

74401153 0.4474401154 1.24741901157 0.44

7440367WM 0.5374HC373WM 0.55741-1C374WM a55

74AC SERIES 7805 0.2878054 0.32780506 0.45

ZENER DIODES500mW

2.4V to 2000

WATCH0132768 ass

10K 20K

price: 0)10 esch051010-1 3 9CTBP 1800304 1.74788245104 290TBP2454104 310

744000 0.38744002

CRYSTALOSC. MODULES

MEMORIES4416P POA 45151 19.50 74936 0.70 7405137 0.98 7475593 6.79 7400299 1.09 741901158 0.48 7440390M 0.57 0.49 7806 0.28

'''' 4 e.",.. 7055016 3.504419P

DYNAMIC RAMPO4 45152 21.45 7495A 1.10 7400138 0.31 74L5595 4.85 74H0323 1.58 74001160 0.56 74HC393M 0.53 744009 0.40 7808 0.281055044P-2 1404429PB POA7411C116145156 15.80 7497 5.23 7400139 0.34 741_5597 4.95 7400354 0.55 056 74HC540WM 0.76 744006 0.40 7809 0.32

ZENER DIODESapin DIL 105516FL-15 4.20

44336 PO4 45157 14.38 74104 0.67 7400145 0.66 7405621 POA 7440356 0.65 74007162 0.84 74HC541WM 0.76 744010 0.40 7812 0.281.3 WATT

Plastic Pkg 416410 140 TC55174P-2 4.2C4443P POA 45158 11.94 74107 0.60 7405147 2.86 7405622 POA 7400365 0.41 74001163 0.56 74HC573WM 1.09 744011 0.40 78124 0.32

2.70 to 200VTTL Output 4164-12 120 70556580-15 3.6C

4447P POA4468P POA

45159 POA45406 2.73

74110 POA74116 3.10

7400148 0.837405151 0.32

7405623 2.987405624 2.10

7400366 0.527400367 0.47corners74401164 0.52741907165 0.52

74HC574WM 0.8474HC688WM 0.84

746014 0.40744020 0.40

7812070 0127815 0.26 Price10p each

4 Pins spaced atof 8pinDIL

4164-15 1.2041256-8 2.40

7M54014JDL 3.40

4469P PO4

4489P PO445407 6.4745411 POA

74118 POA74119 POA

7405153 0.327405154 1.12

741_5625 5.377405626 POA

7440368 05274190373 a 44

74004166 0.5274007173 0.52

74004017M 0.4874004020M 0.48

744032 0.407818744074 0.48

ass7824 0,28 ZENER DIODES Freq.= MHz

41256-10 2.4041256-12 140 CAPACITORS

4490P 120 7440374 0.94 74001174 052 74004040M 044 7440109 as4 78005 024 3.0 WATT 4, 4.9152 8, 10, 41264-15 2.24 SURFACE MOUNT44956 6.27

45414 15.6045428 POA

7912174123 0.94

741.5155 0.34741.5156 0.38

7405627 POA7405628 1.78 7440375 0.76 74007175 052 74404046M 138 7440112 0.81 780054 0.28 7.5V to 2700 12, 16 820 41464-12 4.45

4497P 13513 45433 POA 74125 0.67 7405157 0.38 7400629 138 7440377 0.51 74007181 3.24 74004060M 148 7440138 0.65 781154CLP 0.40 Price:40p each Price: 02.98 ea. 41464-10 4 45 Multilsyer Ceramic4499P 624 45440 POA 74126 0.98 7412158 0.34 7400631 POA 74190386 0.29 74007182 0.96 74HC4066W 0.84 7440139 0.65 781_0540Z 0.28 ZENER DIODES 4484-10 2.80 63 VOLT4500B 19.45450113 012

45441 POA 74128 1.1974132 0.86

7408160 0.4874001604 0.54

7400639 POA7405640 0.98

7440390 0.387400393 0.41

74001190 0.6474401191 0 64

74004538M 078 7440151 0.687440153 035

78012 0.28781.124 ass

5.0 WATT130 to 2000PriCe:42

24. 32 40 &50MHz

4142566-70 3.9044025642-10 6.95

Case Size: 12061-21/W1.25P'.74F SERIES

45026 0.384503B 038450413 1 124505B 4.42

74145 1.1674150 1.8674151 0.80741514 0.80

74L0161 0.467406161A 0.497400162 04874051624 1.07

7400641 ss7400641-1 1.2874L5642 0.997400642-1 POP,

7400423 0.647440521 0157440533 1957400534 0.89

74h101192 0.9474401193 0.6474401194 1.1374401195 1.16

7440157 0817440158 0.657440163 0.807440169 1.98

78712A0Z 0.3078015 028781_24 0.2878756 1.10

each

ZENER DIODESSTUD MOUNT

20 WATT

Price 03.40 ea

13pM DILSealed Metal

940256-8 5.00511000-85 8.45HM48418AP-15

4.60

10pF 22pF 33pF

47,F100pF 220pF 33090470pF 1000pF 2200pf

4000 SERIESapSURFACE

MOUNT40018T 0 32

74000 02874,02 02874,04 0.28

45068 1.14 400201 0.32 74153 0.90 7405163 0.42 7400643 POA 7440540 ass 74407221 0.98 74008 0.747440174 085 78M05 0.32

7.5V 75VPackage HM48416AP-204.25 33000F 4700pF

45060 1 14 401187 0.32 74154 2.10 74001634 D.47 74L0644 PO4 7400541 060 74h101237 0.94 0.747440175 180 78M054 0.36 to

Price: 04.94HCMOS Output HY530256L5-80 10000,

45086 1.14 40110670 32 74165 0.81 7405164 0.34 7400645 1.12 7400563 088 74407238 0.51 74,08 0.287440191 118 78M12 032 ea. 1.60 22000p0 33000pF

451013 05445118 0.44

401267 0.32401381 0,45

74157 0.7474158 1.57

7400165 0.597400166 159

7400645-1 1.287475646 5.85

7400564 0887440573 0.64

74h101240 0.5574401241 0.55

74,10 02874, 0.28

7440240 0/27440241 0.92

78M124 0.3678M134 0.65 BRIDGE

RECTIFIERS

13.2mm sq .Pins spaced at

HY530464L5-803.95

Price: 159 peach

45128 0.38 4015BT 0.84 74159 3.98 7400168 0.75 7475652 POA 74410573A 0 72 74401242 0.76 74113 0.627440244 0927440245 1,10

78M15 0.3278005 0.48

corners of 8pinDIL 41 E1511000-85 845 4700000 10000000Price: 18p each


Please mention ELEKTOR ELECTRONICS when contacting advertisers1.98 CL7611DCPA 1 32 LM340T5 0.30 NE536H 4.90 AL071CP 0.64 IMMOMIE BC182 0.08 BFWI 0 1.20

MICROPROCESSOR H01-0165-5& SUPPORT ICs

10 96HDI 468113AP 420HD3-6402-9 6.168016440-9 8.89HD3-6495-9 8.89HD44883 9.52HD46505SP 9.85HD46802P 5.50HD6321P 4.20H063485PS32 32.50HD63903XP 11.95

8068000-8 11.59HD6845SP 6.92HD68A52P 5.60HD68821P 4.29H1171591 20.98913.7159A-5 23.40HM10422 14.300820869 17.06M6402AIPL 10.20M64021PL 775M6403IPL 10.80

SAB8155-P 382 TIL1005888259AP 3.59 TIL11109882054-2-P 4.12 TIL113SA682C559-2-P 4.80 TI

SC80C45100n6413.60 TILI0GN2661 561 128 315 TIL31150N2661o0n28 3.35 TLP504APALI 6R4-1505 2.98TL16C552FN 1218TMP7002NL-2 4.97TMP8085AP-2 5.981MS3477NL 6.68TMS3700NSB 8.78TMS3702ANS 8.78TMS3835ANS 7.55AMS77COINL 10.74TMS9900NL 24.40T1159901NL 14.16TMS9902ANL 15.94TM59914ANL 23.10TMS9928ANL 7.40TMS9995JDL 69.85

0.600.60

L117 0.851 9

9.651.58

TLP521-4GB 4.2010RX173 4.96TOTXI 73 496

CL7621DCPA 1 98

L7622 POACL7650CPD 468CL76500CPD 6.270L7652BCPD 8.24CL7652CPD 824CL7660CPA 1.40

CL76600CPA 3.80CL7662CPA 4.40CL7663BCJA 6.78CL7663BCPA 5.10CL7664CPA 7.95CL7665ACPA 498CL7673CPA 1.38

CL8052ACPD 8.73

CL8068AJD 11.38L8069C050 3.75

CL8069DCSO 2.88L806900ZR 268L8211GPA 156L8212CPA 148

LM343H 8.80LM346N 396LM3480P 0.40LM348N 0.40LM3504 6.85LM351N 2.60LM358N 0.32LM3595 4.68LM360H 172LM361M/SMD 6.40LM363H-100 16.50LM369DN 3.82LM369DRC 3.70LM380N 120LM381AN 7.88LM385Z-I.2 2.20LM3852-2.5 2.20LM386M-1/SMD 1.65LM3865-1 140LM3865.3 1.80LM3868-4 2.60

NE5530N 3.82NE5532AN 158NE5532N 0606E5534AN 1.80

NE555N 0.20NE556/550 0.70NE556N 0.38NE5585 2.28NE564N 342NE5655 294NE5675 0 65NE568N POANE5705 4.60NE571N 140NE5895 4.25NE592/SMD 1.80NE592N 1.40NE592N14 a92NE602AN 198NE6025 240NE604AN 8.24

TL072ACP 1 48 78167TL072CN 0.50 70107AAL072CP 0.50 75100TL074ACN 2.85 751088TL074CN 0.84 751088TL081CP 0.48 75109ATL0132CP 0.48 75110A-1-1_084CN 0.48 75113TL27L2CD/SMO 1.98 75114TL497ACN 3.44 28118TL507CP 4.03 75116TL7702ACP 75121TL7705ACPTL7705CP 2.04TL77O9ACP 2.04TL7770-SC 3.82TL783CKC 5.10TLC2201CP 3.74

TLC2274CN 2.85TLC251CP 2.54TL02652CP 4.92

1021021.80

1.842.08

2461383022.04 130184B

1.603.302 60

75122 POA75136 3.1075138 4.4075140 2.6575150 1.6028188m 2.6575152 6.362818, 1.7528184M 1.75

80182A 0.08B01 62B 0.08BC182L 008BC182LB a0860183 0.08B0183C 008BC183L 0.08BC184 0.013

0080.08

BC184LC 00800212-18 0.08802121 0.08B021213 068BC212L 008BC2 1 2LB 0080C213 068BC2I3L 608150214 00880214L 0.11

8C237 0.08

BFX48 0.49BFX85 a59BFX88 0.308FX89 1 5989550 0.34EIFY52 0.34BFY90 0.92135107 0.28BS170 01800250 0.52B0060 0 48BSX20 0.3800021 0.48BSX61 185131131600 110BUW46 414BUZ11 1.60BUZ1IA 162BUZ47A a90IFIFZ14 1.14

IRFZ20 1.77

100114DEC 7

100141DC .409806303XP 6.766321P4.206 3485CP32/sm 19.9563803X9 10.076502 3.986502A80184L6520P 4.406522 9406522A

6 ,6

6551 T 4.43T-

6551AAAA

65CO2P2- -

5 846500293

6'86---

65010292 7.00650229265051E-165051E-2 438

.LINEAR & M1SCS

363013M 3.4049623BB POA555 -TIMER 0.206341-1J POA741.0PAMP 0.18ADOPO7CN 214

AD52224 POA

30524 21.52AD534.1H POA

68000P-10 6.98680009-16 1620 M52600P-15 4.40

NS8250N 7.80UA9636ACP 1.983196371 1.98

AD537JH POAAD548.15 1.80

M7170IPG 6.42M7207A1P0 642

LM387AN 590LM3885-1 4.25

NE605NNE612AN 2.87

TLC2654CP 4.84TLC271CP 0.84

75155 1 2028152 4.40

I3C238 0.12

130307 0.08J113 0.39J175 0.68

680009.8 6.50A0578JN680089-8 7 '85

NS8250N-B 7.80M5M82051AP 4.20

UA9638CP 198UA9639CP 1.98

POAAD581JH 8.92

M7207190 542M72091PA 3.75

LM3895 3.40LM3900N 1.60

NJM4556DNJM4558DX 1.20

TLC272CP 1.30TLC274CN 2.40

75159 5452,1801 595

6C327 0.0880328 0.08

J270 a92JA101 048

680109-12 POAM5M82C54P-6 5.40 UM6845B 4.95 AD581KCSA/SPA09.97 M7211 AMIPL 468 LM3909N 0907CJ 3.60 TLC339CN 1.98 75161A 6.47 0C337 0.08 M80501 1.10

68029 3.406803AP

pc:, MAB80318912P 4.56 UM9151 p0A, 9058530 908AD592CN POA

M7211MIPL 4.68M7212AMIPL 3.88

LM3914N 4.

LM393NOPO7CN 0.95OPO7CP 0.95

TLC372CP 1.40TLC551CP 3.68

26182A 7.59 90337.25 0.08BC489 0.24

MJE13070 110MJE340 168

6805638 1a98MAB8035HL-6P 5.98MC10103P 1.98

UM91511 POA

UPB8238 904 AD594AD 12.64 M72131P0 458 LM393P 0.30 OPO7EP 3.10 TLC555CP 0.6575172NG 3.6875173 3.68 BC490 a30 MJE350 1.10

6810P POAMC 10115L 3.21 UPBB282C 4.98 1059510 10.20 M7216AIJI 22.44 LM394CN 5.98 OP11GP 5.85 TLC556CN 1.58 75174 3.20 BC516 022 MJE520 080

6821P 1.52MC10115P 1.98 UPB8284AD 4.98 AD648J5 3.40 M7217AIPI 9 20 LM3999Z 2.76 OP177FP 3.71 TL07524CN 5.24 75174NG 3.68 BC517 0.20 MPS3638 0.18

68407 3.40MCI 46805E2P 9.18 L19682860 4.98 AD707JN 3.40 M7217B1J1 1042 LM399H 7.85 092709 2.89 TLE2061CP 2.20 26128 260 BC546 065 MPSACI6 012

68449 17.20

6845P 4.86MC68000P12/16 POAMC68010P10/12 POA

UPD70108C-10 9.10390701080-8 6.95

AD711,15 2'34AD7I 2JN 3.72

CM7217IJI 10 42

CM7218AIJI 6 85LM4250J 11.82

LM555CN 0.28OP42FZ 7.44OP77GP 2 07

TLE2062CP 3.90TLE2064CN

28,281

75176B 2 28

805461 0.058054613 0 05

MPSAI3 0.12MPSA63 0.32

6845SP 5.40MC6802P 2.47 390701160-1012.90 AD7245JN/KN POA 0M7218A1P1 665 LM565CN 7.48 OPO7CN 0.95 TLE2161CP 2.42 7517613T 4.98 00547 0.08 MPSA92 0.24

881009 906M061309P 6.78 UPD70116C-8 9.20 AD741KN 3.69 CM7218DIJI 185 LM710CH 2.80 PM7548HP 18.20 TMS3477NL 596 75177 2.60 BC547A 0.08 MP5005 221

1381099 4.30M06821P 1.80 UPD71055C 4.38 AD7523KN 9.80 CM7218EIJL 14.76 LM723CH 2.80 IRC473681 0.98 TPIC2406NE 7.14 75178 260 BC547B 0.08 MTP8P08 2.80

68821P 1.98M06840P 5.05 UPD7201AC 11.68 AD252224 32.98 CM7224IPL 898 LM723CN R041935 909 17102802KV 75182 260 90547C 0. 00147 1.80

68A40P 2.58M06844P 18.40 39072010 6.80 AD7537LN POA C57226AILL 26 12 LM733CN 2.65 0041945 2.85 TP1062595 3.28 75183 260 BC548 0.08 0019 1.85

68A50P 2.98MC6845P 7.38 UPD785AC 5.42 AD7542K5 POA 0972261518. 2154 LM741CJ-14 2.20 RC4207GN 1.92 19IC62735 3.28 75188 0. 805488 0.08 0025 0.65

688099 3.98 M06850P 3.35 UPD765AC 5.42 AD7543JCWE POA CM724910M POA LM74ICN 0.45 904558 0.90 TPIC65955 3.28 75189 085 90549 0072 06068621P 1.98

MC6870593P 25.35 0707800-1 4.76 AD7578KN 46 15. CM7555189 240 LM747CH 2.40 RC4558P 0.60 TSC426CPA POA 75189A 0.85 905496 0078 0.80613640P

MC68AOOP 7.02 UPD80C39HC 8.42 AD844AN 8.75 CM7555IPA 084 LM747CN 0.90 REFOICP 3.33 TSC500CPE 75361 2.84 BC550 0.08 OC81M 0.806080A

a Qg-- M068809P 7.62 UP08155HD 5.84 ADC0804LCN 4.20 CM7556IPD 1.85 LM78GCP 2.40 REF01HP 3.33 TSC7106CPL 6.81 75365 2.72 8055013 0.08 00812 0928085AHA 5.98

MC8314P UPD8251AFG 4.08 ADC082000N 22.40 M6403IPL 10.80 LM79GCP 2 40 REFO2CP 3. TSC7116CPL 5.25 75437A 3.28 130550C 0.08 PN3643 0.185086 3.40

MCM6810P 3.00 UPD8253C-2 3.32L272ADC08340CN 10.80 2.10 LM833N 2.82 REF0309 3.89 TSC7128CPL 5.35 75450B 0.64 BC556 0E8 TIC1 06M 0.7880E52 3.90

MCM68A10P 5.35 UPD8253C-5 3.32L272MADC804LCWM 12.10 2.10 LS285AB 2.40 REF25Z 1.12 TSG7660CPA 1.40 75451 0.28 008561 008 710720613 0.6180028612/094 48.50

MM53200N 3.40 09582860 POA - .10 12400846G66 L293E 3.90 LS28138 3.60 52560A POA U1095B 9.92 754518 0.48 805566 038 1ICV106D 024800286-8/9100 24.40

MM581678N 10.54 390874110 12.52 ADC908HP 18.42 0297A 4.69 LS7210 4.40 0111027 651 0206613 2.64 75452 0.28 60557 0.08 TIP115 0.55800858 4'95

MM58174AN 14.80 07D8749HC 13.98 ADDAGBON POA L41305CV 2.20 LT10060NB 2.72 5491043P 7.99 024006 5.50 754528 805578 008 TIPI 21 06880085A-2 5.94

MM58274CN 9.18 112110MHz 9.10 ADG201AKN 4.86 L487 315 LT1010CT SAA3049P 9.92 U664B 185 75453 0.64 50558 0.08 119145 1378111 509 7.60

MSM5832R5 3.39 V21 8MHz 6.95315ADOPO7CN 2.32 L4960 L41028CN8 7.32 SAA5025D 7.65 UA2240PC 1.40 754538 0.64 605581 018 1192955 0.8893L34DC 7.08

MSM8003505 4.90 1130.10MHz 12.90 AHOO i 5CD 17.20 L7028 214 LT1032CN 4.70 01160021 10.80 UA709CP 0.85 284, 0.64 8C5586 018 TI 730 048AM25LS2568P 2.68

MSM80C391SMO6.45 1130-8MHz 9.20POAAY31270--3.60L86250 LT1070CT 9.14 0455609 3.40 UA709PC 0.85 754548 098 130559A a08 1193055 0.88AM25LS2569P A68

MSM80C85A 3.95 V6I COOPPOA7.80 A7-5-1013 3.20 LA83,8 LT1083CP 8.82 SED2000FVA 9.60 UA715HC 4.50 28482 098 805596 008 TIP31A 038AM2602PC 2.30

MSM80085A-2 5.98 V00106N6 8.60 AY -5-1013A 5.24 ,A86,0 POA LT1086CT 2.90 0002301ADC 6.76 UA723CP 0.70 75463 110 805608 0.08 TIP32A 040AM26LS31DC 2.30

MSM80086 7.60 20800110PSC 16.90POAAT1-1015D 3.60 L46520 L1C1052 7.97 5FC27410C 0.18 3973302 2.98 26488 3.60 BC560C 0.08 T1947 0.80AM26LS3I PC 1.26

MSM81C55 4.60 Z0868112PSC 3.20 AY -5-1250 POA LC7132 POA LTC485CN8 2.16 SG35245 4.60 UA741MP 0.60 75469 1 30 801840 0.08 V2750A10 092AM275191ADC 1020

MSM82C51A 3.58 Z180MPU POA 95 -5 -3600 -PRO 9.96 007522 POA LTC490 51766002 1.92 UA741TC 0.28 75470 POA 90071 0.22 VN0104N3 092AM275281PC 6.25

MSM82C53-2 3.98 Z800113.CPU 11.98 BA6109 116 LC7555 POA M52I BAL POA SL1452 6.75 3A748CP 0.36 75471 1.68 80131 VN66AFD 1A0AM29640DC 12.36

MSM82C53-5 3.58 Z8018008VSC 8.25 BA6208 1.40 LD111ACJ POA M5220 POA SL2364C 3.97 UA748TC 0.52 75472 148 80135 0.44 VN9OA8 2.96AM2965DC 8.36

MSM82C54-2 4.20 Z80A-CPU 1.25 CA3046 2'51 LF13508D 1120 55238L POA SL3117B POA UA77000UIC POA 25423 1.48 130241A 0.98 VP0104-N3 0.92AM2966PC 3.98

MSM82C59A-2 3.98 Z804-CTC 1.98 CA3046(SMD) 0 89 LF311H 10.80 M5298P POA 5148609 2.98 UA798TC 3.80 75474 2.25 802420 0.52 VP010452 0.98AM29826DC 3.34

MSME12084A 3.30 2804 -DART 3.15 CA3054 0.94 LF347N 2.40 M70681 1.25 SL4900P 2.80 UCN5800A 2.40 75477 2 10 BD243 0.50 790104N3 0 92AM685DL

MSM82084A-2 3.80 3.,280A.DMA0.98CA3059 1.20 LF351N MAXI 232CNG POA SL560CDP 3.00 UCN5801A 2.60 75491 0 68 BD516 0.78 ZTX212 0.18AM8238PC 5.60

MSMEI2C88 12.60 Z80A-P10 1.28 CA3078AT 2.42 LF3531,1 0.86 MAXI 232GPA 3.57 SL6270CDP 130 UDN298IA 75AL5176 2.88 50675 0.52 210237 a26AM9050CDC 495AM90500PC 4.60

N80C286-10/p1 24.50N80C286-12/5 29.54

280A-010/0 3.40Z80B-CPU 1.52

CA3079 D 88'

CA3080E 0.70LF3555 1.82

LF356N 1 82MAX1259CPE POAMAX162ACNG POA

5L670000P 547SN5281CN POA

UDN2982A 2.00UDN6118A 1.65

75ALS192 2 8875ALS193J 3.22

80676 0.52BD679 0.54

776300 0.18ZTX313L 0 28

AM9102CPC 2.82N80L286-8C2M136.20 2801CTC 3.00 CA3081 0.96 LF357EIN 4.98 MAX232ACPE 4 84 SN5545IBJG POA UGN3501M POA 7501184 288 813680 0.56 ZTX320 0.38

AM9114BDM 9.96 882355 3.68 2800 -DART 5.80 CA3089E 1.22 L0357M/SMD 418 MAX232CPE 2.80 SOGI 2 0.20 ULN2001AN 0.44 7501406 2.73 50743C 1 90 ZTX510 118AM9551PC 9.66AM96L02PC 3.35

N82645N825126AN

Z808 -DMA POAZ8013 -P10 2.20

CA3094AECA3096AEICLF357N 1.20LF398NI 198

MAX232EWE 3.80MAX2321a 2.80

59164800 5 53SP4534 POA

ULN2002.8 0 44ULN2003AN 0.44

76C1, 3.98750188 1.20

B0115 1.12006713 2.78 SOCKETS

AT -5-8136 6.45NI825181F 10.04 Z1301010 4.5, CA3096CE 1 82 LF411CN 1 48 MAX280CPA 6.94 SP47401313 4.46 ULN2004AN 140

180196 3.60 LOW PROFILE

AT -5-8136-006 6.455516450N 468 280000486 218 CA3097E 2.60 LF412CN 1.98 MAX452CPA 5.38 09862909 3.44 ULN2024A 1.40

7501896 32

1.32 BF195-C 0.08No. Pin Gold TIn Goldof spacTurn sldr sldr

C1164/SMD 4.98C823I A 59.00

NS16550AFN 12 60NSC800N-1 10.80

CA3120E75C189AD90901313067 1920

LF441CN 075LF442CN a99

MAX6270PA 2.98MAX660CPA 5.72

SP8660DP 4.96TA7215P 7.20

ULN2032A 1 40ULN2B03AN 0.84

75LBC176 2.60 90199 0.22BF200 0.16TELECOM & SPEC1A

C8253 3.60P8032AH 4 29

FUNCTION Co! CA3130E 1.10TRANSISTORSLF444C5 2.71 MAX690ACPA 6.58 TA7256P 2.60 UM5100 POA BF2566 ER Pins-ing Pin Tali TailCA80C85B 5.98

P8051A9 11.206220891U18 370 CA3140AE 1.34 LH0002CN 1E80 MAX694CPA POA 1973689 POA UM5101 180 THYRISTORS

130256C E38 6 0.3 18p 6p 18p0082085 9.62 9805218/Basic 23.45

707W02020 5 25 CA3140E 0 44 18003200 33 60 MAX697CPE POA 7176589 POA X82211CP POA 8 TRIACS BF259 0.40 8 0.3 18p Bp 18pCD82C881-1-5 674

P8080A 3.90733W00124 5.25 093146E

0-22 LM101AH 5.65 MAX7219CNG 7.15 TA78005AP POA XT11110K9 9.95 BF324 028 14 0.3 31p tip 31p40406 1 60CG80C286-12 48.50

P8085A-2 5.98AMA1503GX6 4.68 CA3160E 1.22 LMIOGN 9.24 MAX8211CPA 2 28 TA8200AH POA Y1112/TI 4 60 BE421 0.12 16 0.3 33p 10p 33p

00800296-16 65E0P8085AH-2 5.98

8111505 1.80 CA3240E 098 LM1119 6.74 MAX90113CPE POA 198410K 2.80 2151445 po A 40673 2.4080450 020 18 0.3 39p 11p 39p

C0M8136 8.45P8088 4.80

CLA25106/PLCC 5.95 CA3240E1 216 LM13600N 3.40 MC1377P 413 TA8449P POA 25414Z 104 801078/161 0 17BF451 022 20 E3 45p 12p 45p

COM81C17 8.15980031BH 4.54

09050010013 3.20 09801324E22LM13700N 140 MCI 413P 0 74 TA8659AN POA ZN415E 1 84 130108NB/C 0 17 80494 0.3 54p 14pCP82054 6.42

980086AL-2 12.60KS-49258/91CC 5.92 013260E 1.68 LM I 3915 3.40 MC14411P 11 38 TAA861A POA ZN423 2 20 BC109B/C t 18 BF759 o.

24 0.3 54p 14pCP4.8004-001 9.85008205 8.92 P81 85H/2 5.98

P8185 18.10

MJ145468 7.65MK51755 310

0132801E 5.94342013280E80146/01LM139J 6.60

LM14585 0.82MC 1 4416L 17 60MC 14495P 4.82

T1391205 060TBA240B POA

ZN425E-8 59725426E-867981BC140-16 0.48a58

BF961 0.660.90

24 06 54p 14p28 0.6 600 165

03232 5.60P8205 2.00

00.147.7 2.40 015550E 020 LM1496N 2.95 MCI 45406P 2.10 TBA570 POA ZN428E-8 5.95 50149 0.40BF982 A88 32 0.6 65p 22p

08086 5.48P8212 2.40

78C/352303 4.35 017410E 319 LM1801N 7.92 MC1455P 0 40 T59820MT POA 25429E-8 2.54 80187 0.34BFG65 1.79 40 0.6 70p 22p

28086-2 8.8098226 2.40

99340108 6.80 CS5503-KD POA LM1881N 4.80 MC1455P1 060 TB/1920 POA ZN449E 476 76 130158 0 54 BFR53-20Hz 048 48 0.6 85p08202A POA

P8251A 3.9004704 3.60 00792513 POA LM1889N 740 MC1458P 0.32 TBA990 POA 801690 014

BF1991.5GFId 0.90 64 075 260p06254-2082841

P8253 2.8098255A-5 3.90

C/MV16BP5 7.98OMV113C 6.95

DI 69CJ 909DAC0800LCN 410

LMI 8945 4.16LM218H 15.75

MC 1488L488LMCI 488P 0.38

TC9106BP POATCA335A POA

90179 124BFR91A-6GHz 1.20 64 0.9 2600

PERSONAL COMPUTER - HARDWARE& SOFTWARED8288 6.480820284-12 9.60

98259 2.85P8259A 3 20

OMV18CN1 7.85QMV1BCW1 7.85

DAC0832LCN 10.670ACO8CP

LM239N 3.90LM290I N 1.25

M014991 0.80MC1489AL 2.25

701965 909TCM1520AP POA MOTHERBOARDS- VESA LOCAL BUS (Wthout CPU & DRAM)

D820284-8 7.85P8274 9.98

OMV25C 8.42 DAC08EP LM2903N 1.25 M01489AN 0.80 TCM1531P POA Processor Chip BIOS Cache Max Expansion BoardSize Pirce0820288-10 10.96

P8279-5OMV62AW1 6.90 DAC1008LCN 10.73LM2904N 1.25 MC1489L TCM1705AN POA Intel Set RAM Memory Slots in mm 0 p

082028612 11.85P8282 2.64

54534-AMI 4.20 0101222105 2040 LM2917N-14 6.10 MC1489P TCM3105N 9.42D82C288-8 a36

P8286 3.60SA336931 2.95 DG201ABK LM29175-8 5.80 MC14965 2.20 TCM5087N 2.40 80486SX0X/DX2 SIS AMI 1286 32MB 7.16(ATJ242(VESAi 260 x 220 120.00

087488P82C54 4.10

SAA502513 5.40 00211 LM29400T15 2.95 MC1558L 3.32 TCM5089N 2.40 80486040KCX2 SIS AMI 256K 32MB 781801).242(VESN 260 x 220 129.00DM960I N .4

P82C54-2 4.80SCM66115P 3.40 D0508ACJ LM2940CT5 2.50 MCI 648P 12.40 TDA1083 2.60

DP82285098238N E36DP8304BN 2.34CLAIRPALI 04.13CNPALI 2H6CN 1.90LM301AN

PAL16R4BCN 117

50579050 4.5509145013 5.76

8029E1 6.80

005080..1

DS1488N 0.36DS14C88M/SMD 1 65

LM2984CT 7.500.36

LM3075

MC1658P 1278MC1709CPI 1.20MC1723CP 1.20

70110851 2.98TDAI085C 80TDA1151 1.10

MICROPROCESSORS CO -PROCESSORS8028516MHz INTEL C55.00 802875 INTEL £40.0080386DX-40MHz AMD 075.00 80287-10 INTEL £48.00

D983115 6.54PAL20L1OCNS 4.35

UL9209K008E159.72 DS14C885 165 LM3081,1 1 MC1741CP 045 TDA1170S 2.8080486S0-25MHz INTEL £115.00 130287-00 INTEL £62.00

001221 6.44001231-20 4.44 PAL20X8CNS 3.32

PALC16L80-25C0

014-15683 3.60ZNA2L029J-130 310

DS14C89AN 1.659912017 1 44

-

LM3105LM311N

MC3242AP 7 54MC3301P a88

TIDA1515A 498TDA152IA 4.37

8048600-33MHz INTEL £245.00 8038700-33MHz INTEL £82.008048608-50MHz INTEL £350.00 MEMORIES

051232 3.28 A10ZNPCM14130 8.95 HA13426 11 96 LM311N-14 2.15 MG3302P 0.60 TDA1578 3.90

804136DX2.66MHz INTEL £390.00 SIMM 1Mx9x9 CHIP 70ns P.O.A.00348614 3.200534875 120 PALC20L8Z-45COS

5 17OPTO

ELECTRONICS811 7723 1.1090791897 POA

LM312H 8.95LM317AT 2.60

MC3340P 1.60MC3357P 3 20

TDA1576A 3.607012595 3.32

SIMM 1Mx9x3 CHIP 7Ons P.O.A.CONNER HARD DISK DRIVESSIMM 4Mx9x9 CHIP 7Ons P.O.A

55340866 480PALC22V10H-350S HEF4754V 22.20 Lm3.7, 0.52 MC3403P 1.40 TDA30485 1.85

.DP 30174 170MB 19mseo 3 5 LP £15500SIMM 4Mx9x3 CHIP 7Ons P.O.A.

DS3.4C87N 4.80053631N 3.3345268.34 4625 0 60

0.60011.0201-5 1 60HI15088-5 11.21

LM317T-SGS 0.52 MC3446AP 6.75 T043505443505 POACP 302 2 OMB 1 " £212 00

5 5 5"'see I' LP ' SIMM 2561ity9 CHIP 8Ons P.O.A.C910344 340MB 13insec 3.5' LP £290.00DS36325 2.81

PCD13584P 8.2890085669 8.28 4933 040 HI1549-5 POA

LM3I 8NLM3I 9N

MC3479P 7/2MC3523U 510

TD13810 POATDA440 PO4

SOFTWAREDS3633N 3.330.56

PCF8566T 8.28 4N32 1-111-574AKD-5 42 50 LM320L2-12 0.34 MC4024P 12.78 TDA4510 138FLOPPY DISK DRIVES MICROSOFT ORIGINAL

0S36345 2.81

DS3691N 4.960538625 7.38

PCF8570P 7.85PCF8573P 6.72

65139 1.60CNX36 0.38CNY17-3 0.64

813.0201-5 3.20913a509A-5 7.15H13-201-5 32°

LM324AN 3.68Lm, 147MCT2 a84MCT61 1 18

TDA4563 138TDA4660 POA

A L. I'S IA1423E214 1.44119 3.4 83060TEAC FD -23580 1.44MB 3.5" £30.00TEAC FD-55GFR 1.2MB 5.25'

WINDOWS 3.1 565.00

3500 IMPORTANT

DS5000-32-12 4750CNY21NP0F8574P 5.90POA HIIL1MITSUBISHIPOA

LM324N 064 MFIOCCN 895 70170101 POA MF3550258MG 1.44MB 3.5' U9.00 All prices quoted are

DS86405 1.20PCF8574T 5.90

DF°8 0.40 06574 -AK 11.20MITSUBISHILM325N 9.40 ML924 4.90 1047052 2.52 MF5040118MP 1.2MB 5.25' £35.013 Excluding V.A.T.

DS8820ANPCF8591P 9.35

HGPL.2200 5.98 L7104-16CPL26.08LM3301N 2.60 MM5309N 576 7018702 522

DS88325 2.6BHCPL-2231058836N 2.44DS883781 2.40

R6502AP 5.70R65209 4.40LM335ZR6522 4.40LM3362.2.55.98

HCPL-2602 5.68HCPL-2630 3.68

CL7107COH/PLCC5.20

CL7109GPL 9.85

LM334Z 2 202.48148

MM53105N 4.98MM80C95N 1.44MP7570JD POA

TEA1045 POATEA1060 4.204E85620 POA

GRAPHIC CARDS1 I RP CS 5,12n GV81111 VI:BUS Window And. W I MB (0530TRIDENT TVGA 8900CL New Trident 1MB SvGA640.00

Postage & PackingCharge of 63.00 is

applicable to all goods

DS883881R6522AP 5.,

HCPL-2730 3.45 CL7116CPL 6.74LM3313Z-5.0 1.48 MUX24E0 B60 TIPC280110./ 8.40 ASENG LAB ET -4000 I MB SVGA C60.00 under the heading of

EF6803A-113 o865002P2 5.84

HCPL-2731 3.20 CL7117CPL 6.744,433, 1.15 MUX24FP 9.60 7L026CP 1.84

KEYBOARD & MICE 'Personal Computer

EF6803P 3 8'

R65CO2P3 5.905165CO2P4 8.95 HCPL-4200 5.98 CL7I26CPL 6.74

LM339AN 2.98LM339N 0.60

MV500DP 3.05MV601DP 3 36

TL062CN 0.52TL062CP 0 52 BTC 7849R 102 UK KeyBoard, Regular Siza24.00 Hardware & Software'.

EF682I 9 1.30EF68809P 3.18

R65C102P2 8.85 ILD74 1.44801 1.80

0L7135CPI 8.98CL7135CPL 594

LM34OAT12 1 98 MV8870DP 5.52 TL06400 0 98 IMSI SYSTEM MOUSE 3 Button Serial £10.00MOUSE MS

Postage & Packing will

EF68B21P 1.44EP610PC-35 709

86502192 5 94R65022P2 4

8074 2.80 .25

15074 2.25CL7137CPL 694CL7606C2N 12.24

LM340T-5 0.48LM340TI 2 0.48

NE50205 10.84NE527N 3.71

TL064CN 0.88TL0641DISMO 2 10

/II, 3 801700 COMPATIBLE 111.181

I/0 CARDSbe charged at cost for

all destinations outsideSAB80C32P 5.95 LM340T15 0.30 NE532N 160 TL071ACP 1.84 IDE 2802FD/25/1P/1G with cables 615.00 the United Kingdom.

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14

I2C TESTERThere can be no doubt that the 12C bus has become the defacto standard for communication between ICs in audio andvideo equipment. The three wire bus, invented by Philips,provides an intelligent way of exchanging data between theincreasingly complex ICs in such equipment. Normally, anoscilloscope or a logic analyser is used to test the functions inan I2C system. Since an oscilloscope is sometimes inadequate,and a logic analyser costly or not available, a good, low-costalternative to these instruments is described in this article.

Design by W. Foede

THE I2C system has been with us forseveral years now, and has been

the subject of a number of articles inElektor Electronics. Following the de-scription of an interface circuit thatenables a PC to take control of an I2Cbus, a number of extension circuitswere published for various applica-tions (see the I2C publicationsoverview at the end of this article).

Nowadays, there exists an I2C com-patible IC for almost any application inconsumer electronics equipment. If afault occurs in a piece of equipmentfitted with I2C ICs, it is often necessaryto test the bus and the componentsconnected to it. In most cases, it ispossible to use an oscilloscope for a

basic test. Unfortunately, the scopewill only tell you if there are signals onthe SDA and SCL lines (high level: busis free; alternating voltage: dataand/or clock present), no more, noless. For a more extensive test youneed a special tester, and that is de-scribed here.

The present I2C bus tester has anumber of LEDs and DIP switches thattell you exactly what is happening onthe I2C bus. The instrument allows anIC address to be set, and can beàrmed' to see if this address appearson the bus. Further, it allows the gen-eral data traffic to be monitored. Thereare six LEDs which provide the follow-ing indications:

SDA/SCL: data present on SDA orSCL;START: valid start condition is beingtransmitted;ACK: hexadecimal address set on thetester is confirmed by the relevantslave IC (with an ACK pulse);ADDRESS: hexadecimal address setwith the aid of the DIP switches is pre-sent on the bus;LOGIC: static logic level on a line; in-dependent of the I2C bus.

In principle, such test data could bemade visible on a logic analyser, butthat soon becomes problematic if thereare several slave ICs on a bus.Moreover, the logic analyser is a costlyinstrument which is rarely seen in ahobbyist's workshop. None the less, ifyou are the fortunate owner of a logicanalyser, the I2C tester offers an addi-tional output supplying the ADDRESSsignal, which enables the logicanalyser to be triggered on certain ad-dresses. Since only two relatively slowdata streams are to be visualized, analternative would be to use a digitaloscilloscope (whose external synchro-nization input is connected to the AD-DRESS output on the I2C tester).

Heart of the circuit: a GALAt the heart of the circuit is a GAL(generic array logic) Type 6001. It con-tains a large number of logic functionsneeded for the I2C tester, and thuskeeps the component count in the cir-cuit to a minimum. Although the 6001looks similar to the 20V8 which hasbeen used before in Elektor Electronicsprojects, its internal structure is farmore intricate, offering more possibili-ties. The most important extra featuresare:- 10 instead of 8 In/Out macro cells

IOLMC (pins 14 through 23). Eight`hidden' macro cells BLMC (notbonded out to pins).

- The number of product terms allowedon one output is only restricted bythe total number of 74.

- Each macro cell can be clocked indi-vidually with a product term (asyn-chronous clocking).

- All macro cells can be reset simulta-neously (asynchronous reset).

- Eight IN macro cells ILMC (pins 2through 11) (not used here).

The above additional features are fullyexploited in the present design, hencethe choice of the 6001 in favour of the20V8.

Defining the desired GAL functions


I2C TESTER

K1

vA1 20 0

0 3 0 4

R1 R3

SDA

05 o$loo.69 0 0

6

8

C10

IC2 gm100n

100n

R2

SCL

S2 si

°I0

IC2a

>3I1

R4

01

5

IC2b

>5l 1

D1 D2

5V6 5V6

4

10

9

11

5

4

14

6 8

0

7 9

777

2 4 3 58

SDA RS

AO

Al

A2

A3

A4

A5

A6

A7

ACK

A

'ClSDA 0

SCL 0

GALCO

Cl

C2

SCL C3

R12

Cl

5

16

R6

22k

IC2c

D3R5

5V6

6

IlOnIC2d

D4

+4 R7

3900

LOGIC

D7

44 R910

22n D5 1N4148 START

D8

1N4148 I -17n-

11

IC2e

7

D9

4412

1N4148 ACK

18

2

21

22

2

D12

1N4148

D10

1N4148

O 5VD13

5 C6

3:SCL-41

10nT1

10n

er.

14

O

I110nIC2f

13

5VD15

.. 5VSDA®T2

3900

R10

3900

D11

44 R11

39052

ADDRESS

7805$ IC3

BC550014x BC550 C8

1N4148 100n

9...15V250mA

0QC7

100n16V

930128-11

Fig. 1. Not much of a circuit diagram, really, this one of the I2C tester, but bear in mind the complexity of the circuitry contained in the GAL,

circuit IC1.

with 'bare hands' is a pretty arduoustask. Fortunately, a number of afford-able computer programs are availablethese days that come to your rescue.In this case, the author made use ofthe program 'easy ABEL'. This programallows you to describe the design ingeneral terms with the aid of aHardware Description Language,whereupon the program compiles theoptimized functions, and in additionsuggests ICs for that purpose. Afterthe IC selection, pins are automaticallyassigned to the different functions.The result is a JEDEC programmingfile which can be read by most GALprogrammers to burn the design into aGAL. Not to worry if you do not have aGAL programmer, because the GALused in the present circuit comesready -programmed through ourReaders Services (see p. 70).

Two ICs and a powersupplyLooking at the circuit diagram of theI2C tester, Fig. 1, you may feel a littledisappointed because it is so simple.Well, that is because so many func-tions are implemented in the GAL.Apart from the 6001, only a few buffersare required to complete the circuit.The buffers being contained in a single

CD4050, the total number of logic ICs grammed GAL used in the present cir-in the circuit is ... two! cuit is given in Fig. 2. Obviously, the

The internal diagram of the pro- circuit would have been a lot more

17

8

14

SDA

SCL

SDA VSCL

BUFFER

GAL6001

BUFFER

LOGIC

EDGE

A

8 - BIT

AR

CLK CLK

SHIFTREGISTER -4-SIN

B7 B6 B5 B4 B3 B2 B1

IVVV VVV1

8 - BITCOMPARATOR

BO

4 - BITCOUNTER

C3 C2 Cl CO

SR -FLIPFLOP

NC

NC

NC

24

12

2

7

13

15

23

22

21

20

V V

A=BLOGIC

1A31A21A11A0tACK

6 4 5 3 11 9 10 8 16

LEO B

930128-12

19

Fig. 2. Block schematic representation of the functions contained in GAL Type 6001.


16 GENERAL INTEREST

complex and difficult to build if all thefunctions shown were realized usingstandard logic ICs.

The operation of the circuit will beexplained with reference to the circuitdiagram (Fig. 1) and the timing dia-gram shown in Fig. 3. Signals SDA(serial data) and SCL (serial clock) ar-rive on connector K1. Zener diodes D)and D2 reduce any excessive inputvoltage levels to about 5.6 V (the nor-mal supply voltage in an I2C system is5 V). Next, the signals are 'cleaned' bybuffers IC2 and IC2b, whereupon theyare taken to pins 1 and 14 of the GAL.Inside the GAL, the SDA and SCL sig-nals are buffered again, and then sentto two LED drivers, T1 and T2, viapins 17 and 18. Capacitors C5 and C6ensure that the LEDs light on the pos-itive SDA and SCL signal edges only.

A start condition on the I2C bus isrecognized by a small logic circuitshown at the right in Fig. 2. This sub -circuit supplies the signal called 'edge',which is generated the moment SDAgoes low when SCL is high. The 'edge'signal starts the read cycle of an 8 -bitshift register, and resets a 4 -bitcounter. It is also used to reset an S -Rbistable. Clocked by the SCL signal,the shift register turns the serial ad-dress transmitted via the SDA line (7 -bit address + R/W bit) into an 8 -bitparallel word. In the block diagram,the most significant bit (MSB) is at thefar left on the shift register outputs.The first seven received bits form theaddress, while the eighth bit indicatesthe data direction. A '0' means: master

SCL

SDA

SDA

START

A7 A6 A5 A4 A3

42h (WRITE)

A2 Al AO

R/W 1 ACK

1 x tp = 25ns

EDGE 11 EDGE = SDA & SDA 0 & SCL

CLK - SCL

CO

CLK = CO

Cl

AR = EDGE

C2

C3

R = EDGERS 0 -START -I

A EQ BADDRESS

ACK

CO&Cl&C2&C3 = S

L__

930128-13

STOP

Fig. 3. This timing diagram shows what happens to the signals that enter the GAL

ready to send data (write). A'1' means:master ready to receive data (read).The shift register outputs are con-nected to an 8 -bit comparator circuitwhich also reads the bit combinationset on two 4 -way DIP switches, S 1 andS2. When the received addressmatches that set on the DIP switches,the comparator supplies a 'match' sig-nal to the logic section shown in the

lower right-hand corner of the blockdiagram.

The bistable and the 4 -bit counterare added to ascertain that the bytedetected by the comparator is actuallythe address byte. This double check isnecessary because the same bit pat-tern may be conveyed while data isbeing written. The bistable and thecounter are reset by the 'edge' signal(which appears after the start condi-tion), whereupon the 4 -bit counter isclocked by the SCL signal. The bistableis set again by the logic during thenine pulses following the start condi-tion. The three outputs 15, 16 and 19are connected to three buffers (IC2d,IC2e and IC2f) which are 'shunted' bycapacitors to make them function asmonostable multivibrators. This isnecessary because pins 16 and 19supply 'short' pulses. In this way, theLEDs connected to the circuit outputslight long enough to ensure a clear in-dication. On output 15, C) and D5 en-sure that rising (positive) pulse edgesare made visible.

Correct reception of a byte ad-dressed to a particular IC is acknowl-edged by that IC returning an ACKpulse. The transmitter (in this case themaster IC) pulls the SDA line high, andwaits for the slave IC to pull it lowagain. If that does not happen, thecommunication between the two ICs isstopped. The ACK LED lights if the ad-dress byte is acknowledged by theslave IC. In that case, you may safelyassume that the slave IC is functional(that is, the I2C communication sec-tion in the IC).

ELEK'I'OR ELECTRONICS JANUARY 1994

Resistors:R1;R3;R5 = 100k0R2;R4;R6;R12 = 2242R7;R9,R10,R11 = 3900R8 = 8 -way resistor array 10141

Capacitors:= 22nF

C2 -C6 = 10nFC7 = 10011F/16VC8;C9;C10 = 100nF

Semiconductors:D1,D2;D3 = 5V6/400mW zener diodeD4;D9;D11 = LED red, 3mmD5;D6;D8;D10;D12;D14 = 1N4148D7 = LED green, 3mmD13;D15 = LED yellow, 3mmT1;T2 = BC550IC1 = GAL6001 (order code 6341; seepage 70)IC2 = 4050IC3 = 7805

Miscellaneous:K1 = 10 -way straight boxheader.51;52 = 4 -way DIP switch.Printed circuit board and programmedGAL. Set code: 930128 (see page 70).1 off Mains adaptor 9-15V/250 mA.

The remaining buffer, IC2,., is usedto make a simple logic tester that al-lows logic levels to be made visible. Ason the SDA and SCL inputs, a protec-tion is provided that limits the inputvoltage to about 5.6 V.

The power supply is conventional,consisting of a 7805 three -pin fixedvoltage regulator and the usual decou-pling capacitors for noise suppression.The mains transformer is connectedexternally. In fact, it is contained in amains adaptor with an output voltageof 9-15V a.c. This is a safe as well aseconomical solution to the mainstransformer problem.

I2C TESTER

Fig. 4. Artwork for the printed circuit board designed for the I2C tester.

ConstructionThe tester is simple to build on theprinted circuit board shown in Fig. 4.This board is available ready-madethrough our Readers Services. Construction is straightforward usingthe component overlay printed on theboard. The GAL is best fitted last, sothat it can not be damaged when theother components are soldered.

The front panel (Fig. 5) is designedsuch that the function of the LEDs andthe switches are clearly indicated. Payattention to the depth of the enclosureyou are using when mounting theLEDs, the DIP switches and the 10 -pinheader, K1. Obviously, the LEDs must Fig. 5. Suggested front panel layout of the I2C tester.

'

.a

930128-F


18 GENERAL INTEREST

be fitted just behind the front panel,while the DIP switches and the headershould be accessible, which meansthat they are mounted at least levelwith the top side of the front panel.Fortunately, that is easy to achieve bymounting the printed circuit board be-hind the front panel, using PCB spac-ers (stand-offs) of the right length.

The power supply socket is fittedinto a side panel of the enclosure. Thetype of socket depends on the mainsadaptor used.

Finally, make a 'test cable'. Thisconsists of a piece of 10 -way flatcable(about 50 cm long), fitted with a 10 -way IDC (press -on) socket at one side,and miniature test clips at the other.The test clips should be labelled toavoid confusion about their connectionin the circuit under test.

The tester is then ready for mea-surements on I2C circuits of almostany complexity. One problem you maybe faced with during such measure-ments is that the addresses of the ICson the bus are not known. Althoughthe base addresses of most I2C ICs arefixed by the manufacturer, the de-signer of the circuit still has the free-dom to determine part of the actualaddress with the aid of certain IC pins.It is, therefore, desirable to have handyas much data on the ICs as possible,and, preferably, also a circuit diagramof the equipment under examination.To help you on the way, the addressesof a wide range of I2C ICs from PhilipsSemiconductors are shown in Table 1.Unfortunately, when you encounterICs whose address is not clearly recog-nizable, there is no other alternativethan to try a couple of different deviceaddresses using the DIP switches, tosee if the IC responds at all to masterread/write operations.

Previous I2C projects in this maga-zine:Inter -IC communications, September1990Video digitizer, July/August 1991.I2C interface for PCs, February 1992.I2C LED display,June 1992.Speech/sound memory, December1992.I2C alphanumerical display,July/August 1993.I2C bus fuse, July/August 1993.I2C opto/relay card, February 1993,I2C power switch, December 1993.

Type

n.a.

n.a.

PCD3311/12PCF8200

PCF8566

PCF8570/71

PCF8570CPCF8572

PCF8573

PCF8574

PCF8574APCF8576

PCF8577

PCF8577APCF8578PCF8579

PCF8582APCF8583

PCF8591

SAA1064SAA1136SAA1300SAA3028SAA4700SAA5243/45SAA9020SAA9050/51SAA9055P/8ASAA9055P/8ESAA9062/63/64SAA9068SAB3035/36/37SAF1135TDA8370TDA8400TDA8405TDA8420/8421TDA8425TDA8440TDA8442TDA8443ATDA8444TDA8461TDA8440TEA6000/6100

Function

'general call' addressreserved addresses

DTMF/modem/tone generatorspeech synthesizeruniversal LCD driverstatic RAM (256x8/128x8)static RAM (256x8)EEPROM (128x8)realtime clock/calendarremote 8 -bit I/O -expanderremote 8 -bit I/O -expanderuniversal LCD driverLCD direct/duplex driverLCD direct/duplex driverLCD -driver for dot matrixLCD -driver for dot matrixEEPROM (256x8)clock/calendar w. static RAM8 -bit A/D and D/A converter4 -digit LED driverPCM audio interfacetuner switching circuitIR transcoder (RC -5)VPS dataline processorcomp. controlled teletext circuitmemory controllerdig. multistandard TV -decoderdig. SECAM decoderdig. SECAM decoderdig. deflection controllerpicture -in -picture controllercomp. tuning interfacedata line decoderTV sync processorcomp. interface prescaler synth.stereo TV sound processorstereo audio processorstereo audio processorvideo/audio switchcolour decoder interfaceYUV/RGB interface8 -fold 6 -bit DACPAL/NTSC decoderswitch for TV receiversFM/IF system and µF) tuner

TEA6300(T)/10T sound fader circuitTEA6330T control amplifierTEA6360 equalizerTSA5510(T) 1.3-GHz frequency synthesizerTSA6057(T) radio PLL frequency synthesizerUMA1000T data processor for cordless tel.UMA1010T un. synthesizer for radio comm.

A3, A2 or Al = user -programmable address bit.X = RAN bit (1 = read; 0 = write).Y = don't care.

Address

0000 0 0 0 X

0000 Y Y Y X

1 1 11Y Y Y X

1

0

1

A3

A3

A3

0

A3

A3

0

0

1

1

A3

0

A3

0

1

0

1

0

0

1

1

1

1

1

0

0

0

1

0

0

0

0

A3

1

A3

A3

1

A3

0

0

0

0

0

0

1

0

0 Al0 0

1 AlA2 AlA2 AlA2 AlA2 AlA2 AlA2 Al

0 Al1 0

1 1

0 Al0 Al

A2 Al0 Al

A2 AlA2 Al

1 0

A2 Al1 0

0 Al0 1

A2 Al0 1

0 1

1 1

1 0

1 AlA2 AlA2 Al

1 0

A2 Al100 Al0 1

A2 Al0 0

A2 AlA2 Al

0 AlA2 Al

0 1

0 0

0 0

1 AlA2 Al

1 AlA2 Al

0 Al

Table 1. Overview of I2C integrated circuits and their bus addresses (courtesy PhilipsSemiconductors).


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20

VIEWS OF THE BRIDGEPart 2: Instrumentation applications

By Bryan Hart

Instrument rectifiers

The diode bridge, in conjunction with a mov-ing -coil meter, enables us to measure thepeak value, Up, of a sinusoidal signal volt-age, or alternatively its root -mean -square(r.m.s.) value, Up N2.

Consider Fig. 13. The arrowed full -linesections show the path of current flow for pos-itive -going half cycles (i>0 ), and the arroweddotted -lines that for negative -going half cy-cles (i<0). For ideal diodes, the rectified cur-rent waveform is shown in Fig. 14. Themeter movement can not follow rapid vari-ations in current because of mechanical in-ertia. The net result is that the pointer in-dicates a mean value I. This corresponds tothat constant level of i for which the area ofthe hatched region above it is equal to thatof the hatched region below.

I is related to Up by the relationship

7= 2UpITER = 0.636 ( Up/R ).

Making the design choiceR= 6.361(.0, for easycurrent -scaling, gives I =1 mA for Up =10 VAlternatively, for R = 63.6 k51, I = 100 ILIA forUp= 10 V.

R can be range -switched to suit the sig-nal amplitude being measured.

Connected across the secondary of an iso-lation transformer having a turns ratio 1:1,the circuit of Fig. 13 is capable of giving anaccurate indication of mains voltage ampli-tude ( Up = 340 V). However, the circuit is clearlylimited in the measurement of small am-plitude signals because of the finite voltagedrop of real diodes.

A solution to the problem of measuring volt-ages in the millivolt range is provided bythe use of the circuit in Fig. 15. In this, R ismade the input arm of an opamp inverter con-figuration that has the diode quad as thefeedback network. Note that the drawing ofthe bridge is rotated anti -clockwise througha right angle compared with that shown inFig. 13, for ease in explaining circuit oper-ation, but the load is still connected betweenterminals X and Y.

The action of negative feedback forces Ato be a 'virtual -earth' point. Hence, the wholeof U, appears across R and the conductingdiodes and meter (M) are forced to pass a cur-rent, U0IR, that is independent of the mag-nitude of the diode drops. Figure 14 againapplies to i and Fig. 16 shows circuit volt-age waveforms. When Us goes positive,Aat-tempts to rise but the amplifier output switchessufficiently negative (approx. -1.4 V) for D2,D4 to conduct the current i (= UsIR) neces-sary to keep Aat earth potential. Similarly,

U0 switches to 1.4 V when U, goes negative.An upper limit to signal frequency is set bythe slew rate of the operational amplifier, be-cause it determines the time taken for U0 to

S

930118 -II- 11

Fig. 13. Basic instrument recti-fier. Arrowed full lines are for

> 0; dashed lines for i< 0.

ditional gating diodes, makes a versatileswitch for generating and processing wave-forms.

Figure 18 shows a basic arrangement. Inthis application, the bridge of Fig. 13 is ro-tated clockwise through a right angle. Also,the input is now at B and the output at A.Control waveforms for switching the bridgeon and off are applied to terminalsY and Xvia gating diodes D5, D6.

The constant -bias currents,/,, can be theoutputs of current -mirrors or grounded -basestages. The operational amplifier, strappedas a unity -gain voltage -follower, provides abuffered output so that impedance Z is not

T/2

4-

930118 -11- 16

Fig. 14. Idealized current waveform for Fig. 13.

930118 -II- 13

Fig. 15. Precision instrument rectifier.

switch from -1.4 V to +1.4 V and vice versa.The popular 741 operational amplifier isacceptable for signals in the low kilohertz range.

The input resistance of the circuit ofFig. 15is R. To minimize loading of a circuit beingmonitored, the alternative high input -im-pedance circuit of Fig. 17 can be used. Theopamp now operates in the non -invertingmode. By 'follower' action UA = Us so the cur-rent forced through M is U9 /R. Once again,Fig. 14 shows the time variation of this cur-rent and its mean value.

The diode -bridge gateThe diode bridge, usually with a pair of ad-

+ 1.4 V

UPI

0

-1.4 V

930118 -11- 14

Fig. 16. Voltage waveforms for Fig. 15.

930118 -11- 12

Fig. 17. Instrument rectifier with highinput impedance.


VIEWS OF THE BRIDGE -2

a

930118-H-15

Fig. 18. Diode bridge gate.

it

0

/

ugt

a

LIloR

c-loR

M1

930118-11-20

Fig. 21. Transfer characteristics of analogue gate.

Ugt

At

b 0a

0.1 V

M

(Us -U.)

930118-11-18

Fig. 19. An idealized i vs (us- U0) plot, with lettered conductionstates, for Fig. 18. Dashed line shows actual characteristic d.

Ust

ug,

Ugz

P1 P2 P3

t-*

930118-H-19

930118-H-21

Fig. 22. Operation of sample -and -hold (S/H) gate.

01

03

04

( top view )

-Ucc

V

930118-H.22

Fig. 23. Bridge with matched 'diodes' using IC array Type 3046.

Fig. 20. Analogue gate waveforms.


930118 - - 23

Fig. 24. Symmetrical triangle voltage generator using a bridge.Note that D5 and D6 are not necessary here.

T/2

930118 .11- 24

Fig. 25. Waveforms for Fig. 23 with lettered diode conduction states.The 'start-up' phase is not observed on an oscilloscope trace.

Diode Condition

Mode D1 D2 D3 D4 05 D6

b

d

Dot indicates diode on

930118 - - 17

Table 1. Operating mode and diodeconduction states for Fig. 18.

loaded.Possible operating modes a, b, c, d, that

are related to the conducting states ofthe diodes,are shown in Table 1. The characteristic re-lating the current i in Z to the differentialvoltage (Us - U0) is shown, correspondinglylabelled, in Fig. 19.

For a, the 'off' state, UG1 and UG2 ofFig. 15 have the polarity and amplitude re-quired to hold the bridge diodes reverse -biased for the maximum Us, so U0 = O. Hence,the characteristic is the axis of (Us - U0).

In the 'on' state, the idealized character-istic of Fig. 19 comprises the three straightline sections. Departure from the ideal, whenreal diodes are used, is indicated by the dot-ted line.

There are two basic gate applications ofthe bridge: the 'linear', 'analogue' or 'trans-mission' gate for which Z, in Fig. 18, is a re-sistor, R, and a sample -and -hold (S/H) gatein which case Z is a capacitor, Cs.

Consider, first, the linear gate. The wave-forms of Fig. 20 illustrate a typical applica-tion in the field of nuclear instrumentation.A pulse, P1, from a particle detector is time -selected from a series of such pulses so thatits shape and amplitude can be examined indetail.

The relevant transfer characteristic(Fig. 21) is derived from Fig. 19; thus, pointsLi, Mi of Fig. 21 correspond, respectively, toL, M, of Fig. 19. For the output to be an ac-ceptable copy of the input when the gate ison, it is necessary to operate on section d

(Fig. 21) only. Furthermore, if the magnitudeof the maximum output voltage required isUom, then, to minimize distortion, it is desirablethat

IoR> 10 Um.

Thus, for Uom =1 V, /of? 10 V. This does notfix the individual values of /0 and R and itmight seem that the choice /0 = 2 mA,R = 5 ki-1, would be as good as an alternativesuch as /0 = 10 mA, R =1 k12.

However, the second choice would oftenbe preferable because it offers faster opera-tion. More current is available to charge un-avoidable circuit stray capacitances (notshown) when the gate switches from the offto the on state and vice versa. A greaterspeed potentiality is what makes the diodebridge superior to currently available CMOStransmission gates (e.g., 4016 range).

Consider, next, an S/H gate. One of itsmany uses is with an analogue -to -digitalconverter (ADC) when a speech signal is tobe transmitted digitally over a link.

Figure 22 shows what happens whenthe bridge is switched on at t1 by a samplingpulse of duration T. Z is now a capacitor, Cs,which charges up to U1. This is stored untila further sample is taken because there is(ideally) no discharge path when the gate isswitched off. During the 'hold' phase thereis adequate time for an ADC to digitize U1.In the worst case, Cs may be required tocharge from its maximum permitted nega-tive value -U0n, to its maximum allowablepositive value Uom, and this requires a charge2CsUom. As the charge available in the intervalr is /0t, this leads to the condition

lot?_2CsUom

A second condition involves the ampli-fier slew rate, S (V lis-1). If /0 is expressed inmA and Cs in nF, then we require S>/0/C, sothat the amplifier output can follow thecharge and discharge of Cs. Suppose, for ex-ample, that Io = 10 mA and Cs = 1 nF. Then,S>(10 VI.ts-1). This means the use of an FEToperational amplifier such as the 351. FETopamps also have a very low input currentso capacitor discharge in the 'hold' state isminimized.

For optimum circuit performance, thelinear gate and the S/H gate should bothemploy bridges in which the diodes arematched in their respective static and dynamicparameters. Matching by selection is a tediousand costly procedure. Fortunately, there isa way of avoiding it that may be applicablein some cases. It entails using a matched ICtransistor array with the transistors strappedas diodes. Figure 23 shows the connectionpattern for the popular, low-cost CA3046array.

As a final instrumentation application ofthe bridge, consider the waveform genera-tor outlined in Fig. 24. The bridge, a bufferamplifier and a Schmitt trigger are con-nected together in a loop. Diodes D5 and D6are not required in this circuit.

The Schmitt has trigger levels of UT andit swings between the limits ± Um. Circuit wave-


forms, lettered according to the diode con-duction state of Table 1, are shown inFig.25. The capacitor charges and is dischargedat a constant rate, set by /0, during a timeinterval T/2. The change in charge is 2CSUTand this must be equal to /J/2. If we write4 (pulse repetition frequency) = 1/T, then

fp = /0/4CsUT.

Regarding/o as a variable, under the controlof an external input signal, leads to the ideaof a current -controlled oscillator. Using avoltage -to -current converter, we obtain avoltage -controlled oscillator, which is im-portant in signal transmission and phase -locked loops. END

Increase your electron-ics know-how and skills

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24

RADIO DATA SYSTEM (RDS) DECODERWITH CLOCK/ALARM FUNCTION

This article describes a compact radio data system (RDS)decoder based on two extremely powerful, yet affordable, ICs,the Philips Components SAA6579T RDS demodulator and theMotorola MC68HCO5E0 microprocessor.

By Peter Topping

MHE Radio Data System (RDS) adds1 digital data capability to the VHFFM broadcasts on band III (87.5 to108 MHz), and is in use in most ofWestern Europe. The specification isdefined in EBU technical documentnumber 3244 (see Ref. 1). A descrip-tion of the capabilities of RDS can befound in previous Elektor Electronicsarticles (Refs. 2 and 3), but a briefrecap is given here.

To transmit the data, a subcarrier isadded at 57 kHz, three times thestereo pilot tone. This subcarrier isamplitude -modulated with a bi-phasecoded signal. The subcarrier itself issuppressed to avoid data -modulatedcross -talk in phase -locked loop stereodecoders, and to maintain compatibil-ity with the German ARI (AutofahrerRundfunk Information) system, whichuses the same subcarrier frequency.Information is sent in groups of four26 -bit blocks. Each group of 104 bitsis one of several types containing dif-ferent information. It is up to thebroadcaster which features are trans-mitted as long as the specified format

is adhered to, and PI, PTY and TP areincluded. Each group contains a differ-ent sub -set of the RDS features. A listof all currently defined RDS features isshown in Table 1.

The retrieval of data is carried outby demodulation hardware which gen-erates clock and data signals that canbe used by a microprocessor. Suitabledevices that can perform this functioninclude the SAF7579T, SAA6579,TDA7330 and LA2231. The Elektor

Electronics RDS demodulator board(Ref. 2) is based on the SAF7579T. TheSAA6579 used in the present decoderis a similar device that integrates thefiltering, and thus requires fewer ex-ternal components (Ref. 4). Those ofyou who have already built theSAF7579T-based demodulator will bepleased to know that this unit may belinked to the present decoder via con-nector K1.

The block diagram of the RDS de-coder is shown in Fig. 1. The MPX(multiplex) signal needed to drive theRDS decoder is 'tapped' from the FMtuner. In most cases, it can be foundstraight after the FM demodulator, i.e.,ahead of the stereo decoder and/orany low-pass filter(s) that may be fit-ted.

The microprocessor, in this case aMotorola MC68HCO5E0, decodes theRDS data using the clock and data sig-nals from the demodulator, and sendsselected data to a dot-matrix module,which can be an LCD or a vacuum flu-orescence type.

The decoder incorporates an alarmclock which, if permanently powered,can be used to switch on the radiosupplying the RDS data at the re-quired alarm time.This is achievedwith the aid of a relay contact on con-nector K4. The relay contact could con-trol the power supply of the radio, oronly the audio stage. If an audio muteis used, RDS data can be updated evenwhen the radio is 'off. The radio isthen always switched on at the righttime, even when a change from sum-mer to winter time (or vice versa) hasoccurred. Alternatively, the decodercan be used to simply display RDSdata with its power being suppliedfrom the radio, and manually switchedon and off.

There is a second output intended

MAIN SPECIFICATIONS Permanent display of PS name and time or date and time (depending on

mode). Optional display of PI code and secondary RDS features (RT, PTY, PIN, MS, DI,

TA, TP, MJD and EON) on demand, including the principalfrequencies of up to 11 other networks.

Full use of CT providing auto -setting, accurate clock with au-tomatic date and summertime adjustment.

Implemented as an alarm clock which can control the powerto the radio and/or sound an alarm.

Sleep timer. TA=TP=1 (traffic announcement taking place) output

R'DISRADIO DATA SYSTEM


RADIO DATA SYSTEM (RDS) DECODER

Feature Information

FMTUNER

MPX RDSDEMODULATOR

DATA

CLOCK

AUDIOAMPLIFIER

DISPLAY(S)

MICROPROCESSOR

KEYBOARD ANDCONTROL SWITCHES

930049 - 11

Fig. 1. Block diagram of the RDS decoder.

to sound a beeper. This output is can-celled when any key is pressed, leavingthe control output active.

RDS features supportedThe present decoder supports PI, PTY,PS, RT, CT, TP, TA, MS, DI, PIN andEON. It facilitates permanent displayof the 8 -digit station name (PS) andtime (CT) and, on request, can displayprogram type (PTY). radiotext data (RT)and the status of the other RDS fea-tures. EON data can be displayed, butthe retuning features associated withAF and EON are not supported asthere is no capability to control thetuned frequency. In a car radio, EONdata is used to switch the radio to astation which is broadcasting localtraffic information, while AF data isused to tune the radio to the strongestsignal carrying the selected device.

Program identification (PI) is a two -byte number which identifies thecountry, coverage area and service. Itcan be used by the control micro-processor, but is normally intended fordisplay. A change in PI code causes theinitialization of all RDS data as it indi-cates that the radio has been detuned.This decoder facilitates the display ofthe current PI code on request.

Program type (PTY) is a 5 -bit numberwhich indicates the type of programbeing broadcast. At present, 16 ofthese types are defined. Examples in-clude 'no programme type', 'current af-fairs' and 'pop music', although theactual syntax which is displayed is de-termined by the software of the con-trolling microprocessor. In thisexample, PTY can be displayed on re-quest - Table 2 shows the display

used for each PTY code.

Program Service Name (PS) is theeight character name of the station.and is permanently displayed (exceptin standby mode).

Radiotext (RT) constitutes a string ofup to 64 characters which give addi-tional information regarding the ser-vice or programme being transmitted.In this application, RT is displayed onrequest on the 16 -digit dot matrixusing scrolling. The data often con-tains extra spaces to centre the text ona 2x32 character display. As these arenot appropriate for a 16 -characterscrolling display, the software reducesall sequences of two or more spaces toa single space.

Clock Time (CT) data is transmittedevery minute on the minute. and pro-vides a very accurate clock, traceableto national standards. The (modifiedJulian) date and local time variation isalso transmitted. Time is permanentlydisplayed. In standby mode (seebelow), the date is displayed instead ofthe PS name. The MJD number, whichis the form in which the date is trans-mitted, can also be displayed. The mi-croprocessor converts this numberinto day -of -week, day -of -month,month -of -year.

Alternative Frequencies (AF) wouldbe used by a car radio to retune to thestrongest signal carrying the selectedservice. AF data, along with TDC andINH, is not used in this application.

Traffic Announcement (TA) andTraffic program (TP) are flags. TP is setif the transmitter normally carries traf-fic information, and TA is set if a traffic

PI

PTYPSRTCTAFTATPMSDI

PINEONTDCINH

Program identificationProgram typeProgram service nameRadiotextClock time and dateAlternative frequenciesTraffic announcementTraffic programMusic/speech switchDecoder identificationProgramme item numberEnhanced other networksTransparent data channelIn-house data

Table 1. RDS features.

PTY Display

0

1

2

3

4

5

6

7

8

9

10

11

12

13

1415

16-31

no programme typeNewsCurrent affairsInformationSportEducationDramaCultureScienceVariedPop musicRock musicEasy listeningLight classicsSerious classicsOther musicNo programme type

Table 2. PTY types.

announcement is in progress. Thecombination TA=I and TP=O is used toindicate that EON data is being usedto supply information to other net-works, including traffic announce-ments. The status of these flags can bedisplayed, and the combinationTA=TP=1 is brought out to microcon-troller pin 68, and is used to control anLED or external hardware, whichcould demute the radio, or switch fromcassette when a traffic announcementis taking place.

Music -Speech (MS) is a single bit indi-cating either music or speech, and isintended to be used to make a tone orvolume adjustment to a radio's audiostage. The MS bit is displayed on re-quest.

Decoder Information (DI) constitutesfour bits indicating the type of trans-mission (mono, stereo, binaural, etc.).It is not essentially in use in the UK,but can be displayed as a number be-

ELEKTOR ELECTRONICS ,IANUARY 1994

26 RADIO AND TELEVISION

RDS

10

S

6

O

5V

100p H

C6 ICS

22716V710 n

10

RDS

[-)5=5-11 MUX

330p

VREF

CII VSSA OSC I OSC 0

VDD.,

TEST O

16

2 -7i6,H4,

C7

47p

IC3

SAA6579T

0.332MHz

DUAL

KEYSNFD

G 5V

vsc-..°T

T57

1

MODE

VSSD

MAI

2

:00n

Tseop

12V70mA

RI

K5

5V

BC557

5V

Ok

0

5V

LCDJP1

R2

RDCL

5V

+12V

1 N4001

IC2

5V117

3 19 154

TS ePAO 00

DI

06

PA2

PA3

PA4

PAS

PA6

PA7

PC2

PC3

PC4

3

PO4

P05

P06

PD7

OSC2 OSC1

F.C34 ...4MHz

47p 50p

00n

PEO

PE1

PE2

PE3

RESET

TEST

3 DO

2 DI

02

0 03

VP

AO

Al

A2

A3

AO

A5

A6 EPROMA7

A8 27C64

A9

Cl

1:160

0 PGMNC

DO/12 01/

3 02/15 03/16 DO/17 05/18 06/19 07/

1N4148

SI: SLEEP AT ALARM52: ALARM ENABLE

- HT

C VFD ti

Module v

ON/OFF

12V

OR 2 K2'

BC547

BC547

14

SLEEP(-1

SOS

LCD Module

O

OOOOOOO

O

OO

OO 1

13 13

12 12

10 10

9 9

8

7

6 6

5 5

4 4

3 3

2 2

00? 4005

930121 - 11

07

D6

D5

DO

D3

D2

DI

DO

E

R/44

RS

Vo

VDD

VSS

Fig. 2. Circuit diagram of the RDS decoder.

tween 0 and 15.

Programme Item Number (PIN) isused to identify the programme cur-rently being broadcast. The format is a2 -byte number which includes thescheduled time and date (day -of -month) of the start of the programme.It can be displayed as four hexadeci-mal digits, or fully decoded to day -of -month and time. Once it is fullyimplemented, PIN information will beable to facilitate automatic switch -onor recording of a pre -selected pro-gramme when it actually starts, even ifthis is not at the scheduled time.

Enhanced Other Networks (EON) re-places the older Other Network (ON)format. If type -14 groups are used toprovide EON data, then type -3 groups(ON) will not be used (Table 5 showsthe currently defined group types).Type -14A groups are used to send in-formation about other networks. ThePS name and principal frequency of upto 11 other networks can be displayedon request. Type -14B groups are used

to switch to traffic announcements onother stations in a radio in which themicroprocessor can control the tunedfrequency.

Circuit descriptionFigure 2 shows the circuit diagram.An external RDS demodulator, if used,may be connected to K1, when the cir-cuit around IC3 is, obviously, omitted.Here, it is assumed that you use theSAA6579T from Philips Compo-nents,which is accommodated on the board.Only a handful of passive parts, in-cluding a 4.332 MHz quartz crystal,are needed to get going with theSAA6579T, of which the block diagramis shown in Fig. 3. The demodulated,but unfiltered, MPX signal is applied tothe demodulator via the MUX inputpin. This signal has a bandwidth ofabout 60 kHz, and is supplied by theFM radio. As regards the bandwidth, itis essential that the MPX signal arrivesunfiltered, i.e., it must contain the 57 -kHz component which carries the RDSinformation. No filtering of any kind is

allowed on this signal, so be sure tofind the right point to 'tap' in your FMradio.

A remarkable feature of theSAA6579T is that it has an on -chipeighth -order 57 -kHz bandpass filterwith a bandwidth of only 3 kHz. The ICautomatically regenerates the 57 -kHzsubcarrier, and extracts the RDS datawith the aid of a synchronous modula-tor. After some more processing, thedata and clock signals that belong withthe RDS signal are output via pinsRDDA and RDCL respectively. The mi-croprocessor uses these two signals todecode the actual information con-veyed via the radio. A thirs signal,QUAL, is used to mark good(QUAL=high) or bad (QUAL=low) recep-tion of RDS data. The processor doesnot use this signal. However, a LED(D1) lights when reception is too poorto warrant valid RDS data.

The circuit of the decoder is verysimple as the MC68HCO5E0 uses anon -multiplexed bus, and includes itsown chip selects. The only other chiprequired is an 8-KByte 27C64 EPROM



MAX

330pF

47pF

4.332/8.664MH2

0501

82pF

922611

OSLO

+5V

10088

vOOD

SCOUT

ANTI.ALASNG

FILTER

57 kHzBANDPASS(8th ORDER)

A

H RECONSTRUCTIONFILTER

160pF

VDDA

TOOnF

5

ZpF2

CLOCKEDCOMPARATOR

[ REFERENCEVOLTAGE

14

OSCILLATORAND

FILTER

1COSTAS LOOPVARIABLE ANDFIXED DIVIDER

SAA6579T

BIPHASESYMBOLDECODER

12

V

QUALITY BITGENERATOR

48-10.

DIFFERENTIALDECODER

DUAL

2

RDCL

CLOCKREGENERATION

AND SYNC

TEST LOGIC AND OUTPUTSELECTOR SWITCH

9 10

T57

VSSA MODE TEST VSSD930121.12

Fig. 3. Internal diagram and typical external parts connection of SAA6579T (courtesy PhilipsComponents).

MODEKEY

On/Off Sleep Alarm RDS

Standby (Off) mode normal (On)

mode sleep (On)

mode alarm

-

Normal (On)

mode stndby (Off)

RT

PTY

PI

TIVTPPIN(h)

PIN(d)

MJDMS/DIEON 1

EON 11

Alarm OFF mode alarm ON

Alarm ON mode alarm set-up

mode alarm OFF

Alarm SET UP toggle hr/min dec. hr/min inc. hr/min

Table 3. Key functions.

of which about 4V, K is used. TheEPROM is available ready -pro-grammed through our ReadersServices (see p. 70).

In order to facilitate a choice of dis-play technology, the decoder is capableof driving both a parallel LCD module(based on a HD44780 controller, withor without an HD44100 driver) and aserial VFD module (based on anMSC7128 driver). The displays showthe same data (within the limitationsof their character ROMs). Either orboth modules can be connected - thechoice is up to you.

LCD modules using only theHD44780 use divide -by -16 multiplex-ing. The software is written for thistype of display, and will also work with

modules incorporating the additionalHD44100. Modules with both chipsare capable of higher contrast, by em-ploying divide -by -8 multiplexing. Touse this capability, fit jumper JP1 asrequired: position 'A' for ÷8 multiplex-ing, for which a HD44100 must be pre-sent in the LCD module; or position 'B'for 1=16 multiplexing (no HD44100 fit-ted).

It is also possible to connect a seri-ally driven VFD module, which showsthe same data as the LCD module. Thedisplay driver used has a differentcharacter set from the standard ASCIIset used by the LCD module, and atable is used to convert ASCII data intothe required characters on the VFDmodule. If a VFD module is connected,

Display mode Format

Standby

(Off)

Alarm offAlarm off, no CTAlarm on

Thu 30 Apr 18:05Mon 0 inv 0:000659 ALARM 18:05

Normal(On)

With RDS PS nameWithout RDS

BBC R9 18:05- 18:05

Alarm Alarm offAlarm on

Alarm - OFF

Alarm - 6:59

Sleep Sleep 60 min.

RDS RT

RP(

PI

TA&TPPINIhex)

PIN(decod)MJDMS & DIEON 1

2

3

4

5

6

7

8

9

10

11

BBC Radio 9 ....News

PI code - C209TP - 0 TA - 1PIN no. - F98030th at 16:00

M.3 day - 98742m/s M DI 15BBC R3 92.10

BBC R.SC 103.60

BBC Nwc1 96.00

BBC Scot 94.30

BBC Mtme 92.50

BBC Ned 93.50.BBC R5 909kH2

BBC Eng. 100.00

BBC 01 99.50

BBC R2 89.90

Table 4. Display formats.

R7 should be connected to bit 7 of portC. This bit is read by the microproces-sor to check that the controller in themodule is ready to receive a command,and may cause the software to hangup if it is left open -circuit.

The only other components requiredare a crystal, the 4 -key keyboard, twoswitches, and a few passive components.Correct operation of the clock in the ab-sence of an RDS signal requires that a4.000 -MHz crystal be used (trimmer C3on pin 6 should be adjusted for accuratetimekeeping).

Principle of operationOn power -up, the software initializesthe display modules (the display shows

00:00' until a valid group 4Ais received) and an idle loop regularlychecks the local keyboard for a keypress, compares the current time withthe alarm time, and performs othertime -dependent functions related tothe display modules and the sleeptimer.

The keyboard software scans the 4 -key matrix for a key press every 16 ms.If the same key is pressed on threesuccessive scans, it acts on this keyfunction by calling the relevant sub-routine. These routines also controlthe repeat rate of the SLEEP and RDSkeys. This rate is set at 6 Hz (after aninitial 750 -ms delay) when the keysare used to change the alarm time, and1 Hz for their normal function. Theother keys do not repeat if held down.Table 3 shows the various functionsavailable in each mode.

The On/Off key toggles between ONand standby modes. A port pin (3, PortE) can be used to control the power tothe VHF radio and/or other externalhardware. It is active high (low in



RADIO DATA SYSTEM GROUP FEATURES

Groups handledIf a complete group has been received, the datacan be processed. The PI code is checked to see if ithas changed. If it has, the displays are initialized. Inan application using the AF capability of RDS,more use would be made of the PI code. All RDSdata, except date and time, is cleared if no validRDS data is detected for a period of 10 -seconds.

Next, PTY and TP are updated, and the grouptype identified. Group types OA, OB, 1A, 1B, 2A, 4A,14A and 15B are handled. Table 6 shows the typeof information contained in each group, andTable 7 shows the detailed structure of thesegroups.

Groups 0 and 15BAs AF data is not handled, there is no difference inthe treatment of groups OA and OB. PS data is ex-tracted and placed in RAM according to the ad-dress bits in block 2 (see Table 6). TA, DI and MSdata are then read, DI is sent a single bit at a timeand uses the same address bits as the PS name todetermine which of the four bits is being updated.Groups of type 15B also contain all this switchinginformation. They are used to increase the repeti-tion rate of this data, but contain no PS or AF infor-mation.

Group 1Group types 1A and 1B are again treated identi-cally as they contain the same data except for therepetition of the PI code in type 1B. The PIN data isrecovered and saved in RAM.

At present the decoder simply allows the dis-play of PIN data both in its raw hexadecimal form,and fully decoded to day -of -month and time. Fulluse of PIN data would require continuously com-paring the PIN day -of -month and time with the cur-rent day -of -month and time, and switching onexternal hardware (radio and/or cassette recorder)when there is a match.

Group 2ART data from blocks 3 and 4 is written to RAM ac-cording to the address included in block 2. Thereare four address bits and four ASCII encodedbytes, giving the possibility of 64 characters. If theText A/B flag changes state, the RT area in RAM iscleared as this indicates that the message haschanged. Group 2B is not handled as it is rarely ifever used.

Group 4ATwo of the more complex tasks to be performedare required by the CT calculations for group 4A.These are for the local time difference, and the con-

version of the MJD number into a recognizabledate.

The broadcast time is Universal CoordinatedTime (UTC, effectively the same as GMT). Time dif-ferences from UTC, including summer (daylightsaving) time, are sent as an offset of up to±12 hours in half-hour increments.

The software includes 4 -function 9 -digit inte-gral BCD arithmetic which is used to decode thedate from the MJD number using the formulae:

Y' = int [MUD -15078.2) / 365.251M' = int IIMJD-14956.1-int(Y'x365.25)) / 30.6001]Day = MJD-14956-int(Y'x365.25)-

int(M'x30.6001)If M'=14 or M'=15 then K=1; else K=0Year = Y'+KMonth = M' -1-12K

Group 14AThis group contains EON data. A large amount ofinformation can be sent using this group, and itcan take up to two minutes for all the data to arriveafter the radio has been retuned. This applicationsaves the PI code, PS name and principal fre-

Group Features

All PI, PTY, TP0 TA, DI, MS, PS, AF1 PIN

2 RT

3 ON (replaced by EON)4A CT

5 TDC6 INH

14 EON15B TA, DI, MS

Table 5. RDS groups

quency of up to 11 networks, although more net-works, each with many frequencies, and other data(e.g., PTY(ON), PINION), TAION), etc., may be sent.Table 4 shows the format of the EON display. Allthe information shown in Table 4 is real data fromthe Black Hill transmitter in Central Scotland.

Block 1 Block 2 Block 3 Block 4

Croup 0 and155

PI

codechck A

tols1 use

15-12 group no.11 group type10 TP flag

9-5 PTY code

4 TA flag

3 M/S bd2 DI bd

1-0 PS/DI address

chck 0

AF

IPI code In type OB and 15E1

chckC

Of

C'

PS name

las block 2 for 15B1

chckD

Group 1PI

codechck A

15-12 0001

11 group type

10 TP flag

9-5 : PM' code4-0: not used

chck Id

not used

IPI code in type 101

chckC

or

C'

PIN data

15-11 day -of -month

70-6 hour

5-C mown

chck

D

Group 2API

codechck A

15-12 001011:010 TP flag

9-5 PTY code4 text NB flag

3-0: text address

chck Id

R1

2 ASCII characters

chckC

RT

2 ASCII characters

chckD

Group 4API

codechck A

15-12 010011 0

10 TP flag

9-5 PTY code

4-2 not used1-0 MJD 116-151

chck B

CI

15-1 MJD 114-01

0 hour 141

chckC

CT

15-12 hour 13-01

11-6 : minute 15-0/5 offset sense

4-0 offset 14-01

chckD

Group 14AEl

codechck A

15-12 1110

11 0

10 TP flag9-5 PTY code

4 TP 10n1 flag

3-0 usage cede

chck B

EON thlorrnahon

code: 0-3: P54 AF

5-9: AF 1rnapl10-11 not used12-15 not Imp

chckC

PIONchck

D

Table 6. Detailed structure of RDS groups handled.

AN,,'Nkkkk\\

\Nkk

stand-by). In stand-by mode, with thealarm disabled, the time and date aredisplayed. If the alarm is enabled, thealarm time is displayed along with thecurrent RDS PS -name. Table 4 showsthese display formats.

The Alarm key enables the currentalarm status to be displayed. A secondpress changes the alarm armed status.When armed, the alarm time is dis-played. In this mode, the On/Off keycan be used to select either hours orminutes (indicated by flashing), andthe Sleep and RDS keys to increaseand decrease the settings. If the alarmhas triggered, the first press of any keycancels it. The alarm display has oneof the two alarm formats shown inTable 4, according to whether or notthe alarm is armed. As all the keyshave a special function in the alarm


RADIO DATA SYSTEM (RDS) DECODER29

C 0-4)0 1:1

0000000000000o o 00000000p

Fig. 4a. PCB component side and solder side copper layouts (direct reading).

set-up mode, the only way to exit thismode is to wait for a time-out. If nokeys are pressed for five seconds, themode returns to normal.

The Sleep key controls the sleeptimer. If the decoder is in the standbymode, the first press of SLEEPswitches it on, and initializes the sleeptime to 60 minutes. Subsequentpresses of the SLEEP key decrease thetime remaining by 5 minutes. Whenthe sleep timer is running, this is indi-cated by a flashing decimal point inthe right -most character of the displaymodules. When the sleep time haselapsed, the decoder returns to stand-by. In the alarm set-up mode, this keydecreases the alarm time.

The RDS key steps through the var-ious RDS data displays. Holding downthis key steps through the displays at

1 Hz. The displays are RT (scrolling),PTY, PI, TA/TP, PIN (hex), PIN (de-coded), MJD, MS/DI and EON (11 net-

works) as shown in Table 4. In thealarm set-up mode, this key incre-ments the alarm time.

Alarm functionsThe alarm time can be entered as de-scribed above. If the alarm is enabled(alarm time displayed on the first pressof the ALARM key, and permanentlydisplayed in stand-by mode) then, atthe alarm time, the auxiliary controlline, PE3, will go high. This can beused to control external hardware, forexample, to switch on the VHF radiosupplying the RDS data, via Rel. If theauxiliary line is already high (decoderfully on, or on via the sleep timer),then it stays high. The operation of thesleep timer is not affected if bit 0 ofPort E (controlled by switch Si) is high.If this I/O line is low at the alarm time,the sleep timer is actuated for an hour.This takes place whether the decoder

was previously on, off, or running thesleep timer, and has the effect ofswitching the auxiliary line low anhour after the alarm time, regardlessof its condition prior to the alarm.

At the alarm time, the alarm output(PE2) will also be actuated (active high)as long as it is enabled by bit I of port Ebeing held low (switch S2; alarm enable).This output is intended to drive an alarmsounder. When this output is active, apress of any key cancels it until the nextalarm. This cancellation does not affectthe auxiliary output.

Construction andadjustmentThe artwork of the double -sidedthrough -plated printed circuit boarddesigned for the RDS decoder is shownin Fig. 4. All components are accom-modated on this board, with the excep-tion of the switches, the two LEDs and



NK5 + 0

930121

C14

C15

X2 01

IP I

B

P1 0 0

Cif*R

J001 R2 Jo

C4-1001 R5 10

X 01 R7

rekx044041-414 Nit 46/0x601/0-4, 44,44040$0041W er it MOW - XX

K3

f.10 9 10

K1 X1

C2

a. 2.T

,r

C1711

Lire4

K2

\. S2 S1

6 4L9 (L9

T3

Re1

C4

C

D

Fig. 4b. Component mounting plan.

Resistors:R1,R5;R6 = 10kg/R2,R8 = 47001:13;R7;R9;1110 = 100k11R4 = 10MS1R11;R13 = 41627R12 = 100R14 = 2200./350V (e.g., MRS25)R15 = 2k512P1 = 101d/ preset H

Capacitors:Cl =1µF/16V radial02,07 = 47pFC3 = 50pF trimmerC4 = 100nF/400VC5;C12;C13;C14 = 100nF06 = 221.1F/16V radialC8 = 82pFC9 = 330pFC10 = 560pFC11 = 2µF2/16V radialC15 = 10µF/16V radial

016 = 100uF/16V radialC17 = 100nF SMT

Inductors:L1 =100µH

Semiconductors:D1;02 = LED03,D4 = 1N4148D5 = 1N4001T1 = BC557T2,T3 = BC547IC1 = 27064 (order code 6331; see page

70)102 = 7805103 = SAA6579T (Philips Components)1IC4 = 68HCO5EOFN (Motorola)

Miscellaneous:JP1 = 3 -way SIL header with jumper.K1;K3 = 10 -way boxheader, angledK2 = 14 -way boxheader, angled.K4 = 2 -way PCB terminal block, raster

7.5mm.K5 = 2 -way PCB terminal block, raster

5.0mmS1;S2 = on/off switch.X1 = 4.000MHz crystalX2 = 4.332MHz crystal 1.Re1 = PCB mount relay, coil voltage

12V, e.g., Siemens V23127 -A2 -A101.

Bzl = 12V buzzer.1 off 68 -way PLCC socket.4 off Digitast press -key 1.1 off LCD module, 1x16 (LM015A) or2x16 (LM016A) 1 or1 off VFD module.1 off Telet case type LC850(60x200x132mm).1 off printed circuit board and pro-grammed EPROM, set order code930121, see page 70).

1 C -I Electronics, P.O. Box 22089, 6360AB, Nuth, Holland. Fax +31 45 241877.

the display (LCD or VFD).Start the construction by fitting the

SAA6579T, which is an SMT (surfacemount technology) component. Thisjob requires a low -power soldering ironwith a fine tip. Make sure of the orien-tation, because the IC is very difficultto remove once all pins are soldered.Some desoldering braid should be kepthandy in case adjacent pins are acci-dentally connected by excess solder.Next, mount all passive components,such as resistors, capacitors, the relayand the connectors. Fit IC sockets inpositions IC1 and IC4. Do not forget theSMT capacitor, C17, which is fitted atthe solder side of the board, under-neath IC.

Before you proceed with the rest ofthe construction, have a good look atthe HF section of the circuit. To makesure that the operation of the sensitiveHF circuit is not upset by digital sig-nals emanating from the microproces-sor section, the RDS demodulator (IC3and associated components) is com-pletely screened. The screen is madefrom 1.5 to 2 cm wide thin metal sheet,which is bent into shape and then sol-dered onto the PCB, after the HF partshave been fitted. The screen is sol-dered to six solder pins, at a height ofabout 0.5 mm above the board sur-face. The shape of the screen is indi-cated by the dashed lines on thecomponent mounting plan.

Although it makes more sense tomount them behind the front panel ofthe RDS decoder case, LEDs D1 and D2may also be soldered onto the printedcircuit board for testing purposes. Thefour press -keys, ON/OFF, Alarm,RDS(+) and Sleep(-) are mounted on asmall piece of veroboard or stripboard,which is secured to the inside of theenclosure front panel with the keysprotruding at the front side.Alternatively, the switches may beglued into suitably drilled holes in thefront panel. As shown by the circuit di-agram, the wiring of the switches is ex-tremely simple.

If an LCD display is used, this mustbe connected to K2. When the LM015



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or LM016 is used, the link is simplebecause it is 'straight through' for all14 connections (pin 1 to pin 1, etc.).Next, set jumper JP1 as required (seeabove).

Figure 2 also shows how to connecta VF display. Note that this requires aseparate supply to furnish the filamentvoltage and the high voltage.

A suggested front panel layout forthe RDS decoder is given in Fig. 5.Having checked the construction andfitted the board into the case, all thatremains to be done is adjust preset P1and trimmer C3.

After applying power (use a

12V/150mA mains adaptor), the LCDdisplay will show a text, which may bea bit difficult to read owing to poorcontrast. Adjust preset P1 for optimumcontrast. This adjustment is not nec-essary if a VF display is used.

In most cases, trimmer capacitor C3can be set to the centre of its travel.Adjustment is only required if theclock is not accurate when no RDS sig-nal has been received for a relativelylong period. In this way, the clock devi-ation may eventually be eliminated.

Once the MPX signal is connected tothe decoder input, the RDS informa-tion will appear on the display. That is,

if your radio is tuned a station trans-mitting RDS, which is indicated byLED DI going out.

References:1. EBU technical document 3244:Specifications of the Radio DataSystem, RDS, for VHF/FM SoundBroadcasting.2. Radio Data System (RDS) demodu-lator. Elektor Electronics May 1989.3. Radio Data System (RDS) decoder.Elektor Electronics February 1991.4. RDS demodulator with integratedfilter. Elektor Electronics October 1992.

r ED ED

SLEEP AT ALARMRDS DECODER/ALARM CLOCK ALARM ENABLE

CRDS SLEEP ALARM ON/OFF

(+) (-)

930121-F

Fig. 5. Suggested front and rear panel layouts (shown at 78% of true size).



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MAG5P5*FM BUG BUILT AND TESTED superior design to kit, assupplied to detective agencies etc. 9v battery req'd. £14 REF:MAG14TALKING COIN BOX STRIPPER originally made toretail at £79 each, these units are designed to convert and ordinaryphone into a payp hone. The units we have generally have the locksmissing and sometimes broken hinges. Howeverthey can be adaptedfor their original pupose or used for something else?? Price is just £3REF: MAG3P1100 WATT MOSFET PAIR Same spec as 2SK343 and2SJ413(8A,140v,100w) 1 N channel and 1 P channel, £3 apair REF:MAG3P2VELCRO 1 metre length of each side 20mm wide (quick way offixing for temporary jobs etc) £2 REF: MAG2P3MAGNETIC AGITATORS Cosisting of a cased mains motorwith lead. The motor has two magnets fixed to a rotor that spin roundinside. There are also 2 plastic covered magnets supplied. Made forremotely sti ming liquids! you may have a use? £3 each REF: MAG3P32 for £5 REF: MAG5P6TOP QUALITY SPEAKERS Made for HI Fl televisions theseare 10 watt 4RJap made round with large shielded magnets. Goodquality general purpose speaker. E2 each REF: MAG2P4 or 4 for E6REF: MAG6P2TWEETERS 2' diameter good quality tweeter 140R (would begood with the above speaker) 2 for £2 REF: MAG2P5 or 4 for £3REF: MAG3P4AT KEYBOARDS Made by Apncot these quality keyboards needjust a small modification to run on any AT, they work perfectly but youwill have to put up with 1 or 2 foreign keycaps! Price £6 REF.MAG6P3XT KEYBOARDS Mixed types, some retums, some good, someforeign etc but all good for spares! Price is £2 each REF:MAG2P6or 4 for £6 REF: MAG6P4PC CASES Again mixed types so you take a chance next one offthe pileE12 REF: MAG12 or twoidentical onesfor£20 REF: MAG20P4component pack bargain 1,000 resistors r-1,000 capacitors (allsame value) £2.50 a pack. REF:MAG2P7

1994 CATALOGUEOUT NOW

MASSIVEWAREHOUSE CLEARANCE

FANTASTIC £20.00 REDUCTION

REFURBISHED PC BASE UNITSCOMPLETE WITH KEYBOARD

FROM ONLY £29.00

AMSTRAD 1512 BASE UNITSGUARANTEED

PERFECT WORKING ORDER.A LOW COST INTRODUCTION TO THE HOME COMPUTER MARKET.

AMSTRAD 1512SD1512 BASE UNIT, 5.25" FLOPPY DRIVE ANDKEYBOARD. ALL YOU NEED IS A MONITOR AND

POWER SUPPLY. WAS 849.00

NOW ONLY £29.00REF: MA G29

AMSTRAD 1512DD1512 BASE UNIT AND KEYBOARD AND TWO5.25" 360K DRIVES . ALL YOU NEED IS A MONITORAND POWER SUPPLY WAS £59.00

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SOL411 POWER PANELS

3FT X 1FT 10WATT GLASS PANELS14.5v/700mA

NOW AVAILABLE BY MAIL ORDER£33.95

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TOP QUALITY AMORPHOUS SILICON CELLS HAVE ALMOST ATIMELESS LIFESPAN WITH AN INFINITE NUMBER OF POSSIBLEAPPLICATIONS, SOME OF WHICH MAY BE CAR BATTERYCHARGING, FOR USE ON BOATS OR CARAVANS, OR ANY-WHERE A PORTABLE 12V SUPPLY IS REQUIRED. REF: MAG34

ALSO 1FT X 1FT GLASS SOLAR PANELS 12v 200mAONLY £15.00. REF MAG15P3

FREE SOFTWARE!Brand new, UNUSED top quality Famous brandlicensed software discs. Available in 5.25" DSDD or 5.25'HD only. You buy the disk and it comes with free BRANDNEW UNUSED SOFTWARE. We are actually selling you thefloppy disc for your own "M EGA CHEAP" storage facilities,if you happen to get software that you want/need/like aswell you get a "MEGA BARGAIN" 801DSDD PKT10 02.99 REF: MAG3P7 PKT100 £16.00 REF: MAG16HD PKT10 £3.99 REF: MAG4P3 PKT100 025.00 REF: MAG26P1

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Ticks 02'3 303500Va4

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COMMODORE MICRODRIVE SYSTEM mini storagedevice for C64's 4 times faster than disc drives, 10 times fasterthan tapes. Complete unit just £12 REF:MAG12P1SCHOOL STRIPPERS We have quite a few of the aboveunits which are 'returns' as they are quite comprehensive unitsthey could be used for other projects etc. Let us know how many youneed at just 50p a unit (minimum 10).HEADPHONES 16P Theseare ex Virgin Mantic. You can have

8 pairs for E2 REF: MAG2P8PROXIMITY SENSORS These are small PCB's with what looklike a source and sensor LED on one end and lots of components onthe rest of the PCB. Complete with fly leads. Pack of 5 E3 REF: MAG:3P5 or 20 for £8 REF: MAG8P4FIBRE OPTIC CABLE Made for Hewlett Packard so pretty goodstuff! you can have any length you want (min5m) first 5m £7 REF:MAG7 thereafter E1 a metre (ie 20m is E22).REF: MAGI Max length250m.SNOOPERS EAR? Original! made to clip over the earpiece oftelephone to amplify the sound -it also works quite well on the cablerunning along the wall! Noe is E5 REF: MAG5P7DOS PACKS Microsoft version 3.3 or higher complete with allmanuals or price just £5 REF: MAG5PB Worth it just for the verycomprehensive manual! 5.25' only.DOS PACK Microsoft version 50riginal software but no manualshence only £3 REF: MAG3P6 5.25' only.FOREIGN DOS 3.3-German,Frenchitalian etc £2 a pack withmanual. 5.2T only. REF:MAG2P9MONO VGA MONITOR Made by Amstrad, refurbished £49REF: MAG49CTM644 COLOU R MON FOR. Made to work with the CPC464home computer. Standard RGB input so will work with othermachi nes.Refurbished £59.00 REF:MAG59JUST A SMALL SELCTION of whatwe have- to seemoregetour 1994 catalogue (42p stamp) or call in Mon -Sat 9-5.30

HAND HELD TONE DIALLERS Ideal for the control of theResponse 200 and 400 machines. £5 REF:MAG5P9P IR DETECTOR Made by famous UK alarm man ufacturertheseare hi spec, long range intemal units. 12v operation. Slight marks oncase and unboxed (although brand new) £8 REF: MAG8P5

WINDUP SOLAR POWERED RADIO AWFM radio com-plete with hand charger and solar panel! £14 REF: MAG14P1

COMMODORE 64 Customer returns but ok for spares etc £12REF: MAG12P2 Tested and working units are £69.00 REF: MAG69

COMMODORE 64 TAPE DRIVES Customer returns at £4REF: MAG4P9 Fullytested and working units are £12 REF: MAG12P5

COMPUTER TERMINALS complete with screen, keyboardand RS232 input/output. Ex equipment. Price is £27 REF. MAG27

MAINS CABLES These are 2 core standard black 2 metre mainscables fitted with a 13A plug on one end, cable the other. Ideal forprojects, low cost manufacturing etc. Pack of 10 for£3 REF: MAG3P8Pack of 100 £20 REF: MAG20P5SURFACE MOUNT STRIPPER Originally made as someform of high frequency amplifier (main chip is a TSA55117 1.3GHzsynthesiser ) but good stripper value, an excellent way to play withsurface mount components E1.00 REF. MAGI P1.MICROWAVE TIMER Electronictimer with relay output suitableto make enlarger timer etc £4 REF MAG4P4PLUG 420? showing your age? pack of 10 with leads for E2 REF:MAG2P 11

MOBILE CAR PHONE £5.99 Well almost! complete in carphone exduding the box of electronics normally hidden under seat.Can be made to illuminate with 12v also has built in light sensor sodisplay only illuminates when dark. Totally convindng! REF: MAG6P6

ALARM BEACONS Zenon strobe made to mount on an externalbell box but could be used for caravans etc. 12v operation. Justconnect up and it flashes regularly) £5 REF: MAG5P11

FIRE ALARM CONTROL PANEL High qualrty metal casedalarm panel 350x165x80mm. Comes with electronics but no informa-tion. £15 REF: MAG15P4SUPER SIZE HEATSINK Superb quality aluminium heatsink365 x 183 x 61mm, 15 fins enamble high heat dissipation. No hdes!£9.99 REF: MAG10P1PREMOTE CONTROL PCB These are receiver boards forgarage door opening systems. You may have another use? £4 eaREF: MAG4P5LOPTX Line output transformers believed to be for hi res colourmonitors but useful for getting high voltages from low ones! £2 eachREF: MAG2P12 bumper pack of 10 for £12 REF: MAG12P3.

PORTABLE RADIATION DETECTOR

£49.99A Hand held personal Gamma and XRay detector. This unit contains twoGeiger Tubes, has a 4 digit LCD dis-play with a Piezo speaker, giving anaudio visual indication. The unit de-tects high energy electromagneticquanta with an energy from 30K eV toover 1.2M eV and a measuring rangeof 5-9999 UR/h or 10-99990 Nr/h. Sup-plied complete with handbook.

REF: MAGS0

EI,EKTOR ELECTRONICS JANUARY 1994

DIGITAL DIALThere is a vast number ofcommunication receiversaround that have an analogue(needle and dial) tuning scale.Although the RF performanceof many ex -army and othersurplus receivers (whethervalve, transistor, or 'hybrid') isquite acceptable for radioamateur use, their tuningscales and mechanicallyoperated dials are really oldfashioned these days, and infor 'digital' revision.

From a basic design by DavidMcBright

ALTHOUGH their number seems toave decreased considerably since

the nineteen seventies, ex -army com-munication receivers from the SecondWorld War and the Cold War years arestill to be found in electronic surplusstores, and at radio amateur rallies.An example of a very popular surplusreceiver is the BC348, which was onceused in the B17 'flying fortress'bomber. Only a few modifications arerequired to make this receiver suitablefor radio amateur use, in particular,for reception of SSB (single-sideband)and narrow -band FM (frequency mod-ulation). Since the short-wave bandscovered by receivers like the BC348are pretty crowded these days, there isa clear need of an improved (digital)frequency readout. This allows you totune the receiver as accurately as pos-sible, 'dredging' the station you wantto hear from the noise and interferencecaused by other, stronger, stations.

A serious problem with older re-ceivers is the wide variety of first andsecond intermediate frequencies (IFs)used. This means that the digital dialwe are about to describe must be de-signed such that it can be used withmany different local oscillator (LO) fre-quencies and output levels.

The circuit proposed here has every-thing to meet the above requirements,and more: low power consumption, acrystal -controlled timebase, and an IFoffset which can be programmed toany value between 0 and 1.6 MHz insteps of 1 kHz. The offset frequency

4.*

may be subtracted from the LO fre-quency, or added to the LO frequency,depending on whether the LO fre-quency is above ('LO -high') or below(1.0 -low') the frequency of the receivedsignal.

The digital dial has a frequencyrange of up to 39.999 MHz at a resolu-tion of 1 KIlz. The display refresh rateis 4 Hz.

The circuitThe circuit diagram of the digital dialis given in Fig. 1. The circuit is basedon inexpensive and commonly avail-able components only. To make surethat the tuning frequency can be readunder all circumstances, a bright or-ange 41/2 -digit LED display is used.Circuit IC10, an ICM7217AIPI fromIntersil (Harris Semiconductors), con-trols four display segments. The mostsignificant display segment is drivenby IC7, a 4543. In this configuration,the highest counter state is 39,999,which is composed as follows: 0(blanked), 1, 2 or 3 via LD1 and IC7,and 0000 to 9999 via the displays dri-ven by IC10. The five digits form a sep-arate unit, together with IC7, IC10 andconnector K3, to allow the display to bemounted in the best visible positionwhen it is fitted into the receiver.

The performance of the circuit is de-termined to a large extent by the sensi-tivity and the frequency range of theinput amplifier. Here, the input ampli-fier consists of three low-cost transis-

tors type BSX20. These fast switchingtransistors can be used without prob-lems in the frequency range of the pre-sent circuit because their cut-offfrequency is specified at 500 MHz. Analternative to the BSX20 is the ZetexE -line ZTX313. The input amplifierhas a relatively high input impedance,so that it has virtually no effect if acharacteristic impedance of 75 L2 isused to couple the LO signal to the dig-ital dial. The highest input level thatmay be applied without the transistorsgoing into saturation is about 4 Vpp Inprinciple, it is possible to increase thesensitivity of the input amplifier, sothat signals with a level smaller than100 mVpp or even lower can be mea-sured. Unfortunately, increasing thesensitivity will result in a narrowerinput bandwidth.

According to the datasheets, theHCMOS digital circuits used here op-erate at the highest possible speed at asupply voltage of about 6 V. For HCTICs, this specification is about 5.5 V.Hence, the supply voltage in the pre-sent circuit is raised a little above theusual 5 V, to 5.6 V. Arguably, this is areasonable compromise between a longIC life expectancy and high speed. As amatter of interest, both HC and HCTICs are beginning to have a hard timeat supply voltages above 7 V.

The timebaseThe central part in the timebase is aninexpensive, yet highly accurate,



32.768 kHz digital watch crystal, X1.The oscillator signal generated withthe aid of this crystal is scaled downby a 4060 to give the required clocksignals. Dividing 32.768 kHz by 213yields a signal with a frequency of4 Hz. The half period time of this sig-nal is 125 ms, which can be found onpin 2 (Q12), and is used to enable thecounter. The second half of the periodtime, when the signal is low, ensuresthat the result of the counter operationis stored in the display.

It is readily seen that dividing theinput signal by 125, and using a time -base gate of 125 ms, yields the inputfrequency in kilohertz (kHz). In thistiming arrangement, the counter stateis updated four times a second, whichis ample for the present application.

Apart from the 4 Hz gate signal, IC9also supplies 8 -Hz and 16 -Hz signals.The 4 -Hz and 8 -Hz signals are com-bined in gate IC2, which consequentlysupplies a short pulse (62.5 ms) with arepeat rate of 4 Hz. A differentiatingnetwork, C15 -R1, turns this signal intoa needle -shaped pulse (LD) which isused to latch the information into IC7.The short 4 -Hz signal is also used togenerate a store pulse for IC10. This isachieved with the aid of a buffer, IC3,and a second differentiating network,R2 -C16. Gate ICsd combines the 16 -Hzsignal with the output signal of IC2, togive an even shorter pulse (31.25 ms)with a frequency of 4 Hz. This signal isused to reset IC5, IC6 and IC7 fourtimes a second. IC4 is reset directly byIC2,.

The display circuit is contained inthe dashed box in the circuit diagram.IC7 drives the first of the four displaydigits, which shows 1, 2, 3 or nothing.The zero that would normally appearwhen IC7 receives a 0 is ingeniouslysuppressed by a purposely incorrectsegment connection order. The num-ber that appears on the display is de-termined by drive lines LI and L2. Thelogic levels on these lines are, in turn,determined by the number ofcarry/borrow (C/B) pulses generatedby integrated counter IC10. Thesepulses also arrive at IC5 via counterIC6. Both binary scalers supply theiroutput signal to IC7. Next, the arrivalof the LD pulse causes the bit combi-nation to be stored into IC7, and thedesired segments of LD1, a HD11070,to light.

Most of the counting work is doneby IC10, a complex integrated counterType ICM7217 from Intersil (HarrisSemiconductor). This IC is capable ofcounting from 0000 to 9999. The C/Boutput of the ICM7217 signals anoverflow in the counter. The storepulse applied to pin 9 determineswhen the counter state is transferredto the display. The multiplexing of the

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four segments is also done by the elec-tronics contained in the ICM7217. Areset pulse at pin 14 clears the inputof the counters, and resets the displayto zero. Unfortunately, IC7 can not bereset to zero with the aid of a resetpulse, so that a different way of doingthis has to be devised. The contents ofIC7 are cleared by supplying the ICwith an LD pulse, after the counters towhich it is connected are reset.Consequently, a value of nought isstored in the driver, and the LED dis-play goes dark again.

Three dual decade counters Type74HCT390 are used to divide the RFsignal, and implement the offset com-pensation. The counters may be di-

vided into two sections which divide by2 and 5 respectively. Further, theyshare a reset input.

As already mentioned, a total scalefactor of 125 is required. This is fairlysimple to achieve by cascading threedivide -by -five scalers. The LO -highand LO -low correction is realized byvarying the gate time. When LO -highuse is required, the gate time is length-ened with an extra measurement pe-riod which is deduced from the desiredoffset. Similarly, the gate time is short-ened when LO -low use is in order.Switch Si is used to select betweenLO -low and LO -high. The gate time canvary by ±62.5 kHz. On the display, thismeans that a margin of 0000 kHz to


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1,999 kHz is available to compensatethe frequency offset of the local oscilla-tor.

The counting operationSince four measurements are takenevery second, a period of 250 ms isavailable for each complete measure-ment cycle. The first half period(125 ms) is reserved for counting,while the second half period is avail-able for updating the display. As al-ready mentioned, the input signalneeds to be divided by 125 to obtainthe correct measured value in kHzwithin the gate time of 125 ms.

Further, the counter has to take

care of the IF offset. This is achievedby adding or subtracting a certainnumber of pulses to or from the mea-sured value. The counter circuit con-sists of IC4, IC5 and IC6. These ICs areconnected in a fairly complex way be-cause they have two functions.Consequently, the operation of thecounter may not be obvious straightaway.

The Type 74HC390 IC (of whichthere are three in the counter circuit)consists of two identical blocks whichwill be designated ICxp, and ICXB for thesake of convenience. One block usesthe high pin numbers, the other, thelow pin numbers. Each block consistsof a divide -by -two and a divide -by -five

counter, which form a (BCD) decadecounter when cascaded. The two coun-ters are linked by connecting outputQa (pin 3 or 13) of the divide -by -twosection to the clock input (pin 4 or 12)of the divide -by -five counter.

The input signal reaches the inputof the divide -by -five counter in IC4a viainverter IC3f. This counter is connectedin series with, successively, the divide -by -five counters in IC5a and IC6a. Thisgives a total scale factor of 125.Depending on the two control signalsat the other inputs of IC2h, the outputsignal is fed to the integratedcounter/display driver, IC10. This sig-nal is also fed to the offset counter viaIC2a. The offset counter consists ofthree series connected BCD counters,IC4b, IC5b and IC6h. To realize an extradigit, these counters are followed bythe divide -by -two section in IC4a. Inthis setup, the 13 outputs of the offsetcounter allow any desired IF frequency(offset) to be set in steps of 1 kHz.

The output of NAND gate ICI goeslow as soon as the desired offset isreached. This means that pin 13 ofIC2a is first high, and that the passingor blocking of the clock pulses de-pends on the level at pin 2 of this gateonly. The offset counter is disabled assoon as the programmed offset value isreached.

LO -low use (LO frequency belowthat of the received signal) is selectedby closing switch S1. The output ofIC80 is then always high, while IC8bcontrols the flow or interruption ofclock pulses to IC10. The output of IC8bis high as long as the offset counterhas not reached its end value.However, the offset counter is disabledvia IC8,, and not enabled again untilpin 2 of IC9 goes logic high.Consequently, IC 10 continues to re-ceive pulses after the measurementcycle. The result is that the offset isadded to the measurement value.

When switch S1 is opened, the digi-tal dial is programmed for LO frequen-cies above those of the received RFsignals. The opened switch causes thepulses for IC10 to be blocked by IC80 atthe start of a measurement cycle.During this time, the offset counter isenabled. This counter stops as soon asthe programmed offset value isreached, whereupon clock pulses arefed to IC10. Effectively, the offset valueis subtracted from the measuredvalue.

The binary counters in IC5a andIC6a are used to drive display LD1. Thisfairly unusual approach allows theleading zero to be suppressed. Theleading zero suppression on IC io isswitched off since there is no connec-tion with the highest digit of the dis-play.


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Resistors:R1;R2;R3;R6 = 101d2R4 = 1000R5 = 10R7 = SkinR8;R10 = 2200R9 = 56t-2R11 = 39052R12 = 4427R13 = 5416R14 = 6k128R15 = 11(12

R16 = 68052R17 = 10Mt2R18 = 8 -way SIL array 10kt2R19;R20;R21 = 3300

Capacitors:C1;C2;C3;C5-C11;C14;C15;C17 = 100nFC4 = 220pFC12 = 330nFC13 = 65pF trimmerC16.1nFC18 = 10011F/25V radialC19 . 100gF/16V radialC20 = 100pF

Inductor:L1 = 1gH

Semiconductors:01;02 = 1N4148T1;T2;T3 = BSX20IC1 = 74HC30IC2 = 74HC11IC3 = 74HC141C4;1C5;IC6 = 74HCT3901C7 = 4543IC8 = 74HC1321C9 = 4060IC10 = ICM7217AIPIIC11 = 78051_131-LD5 = H011070

Miscellaneous:K1 = 13 -way pinheader.K2 = 8 -way pinheader.K3/K4 = 10 -way pinheader.S1 = on/off switch.X1 = 32.768kHz crystal.Printed circuit board 920161 (see page70).

ConstructionThe digital dial is best built on theprinted circuit board shown in Fig. 2.In view of the complexity of the tracklayout, and the high track density, wedo not recommend etching this boardyourself.

Separate the main board from thedisplay section before you start fittingcomponents. The display is a separateunit to enable it to be fitted at the mostconvenient position in the receiver, or

IF -Offset(kHz) MSD LSD

455 II

460

465 0

470 0

560

915

1600

1 8 4 2 1 8 4 2 1 8 4 2 1

2 3 4 5 6 7 8 9 10 11 12 13

o o q 000ppp o ,J) 0 .0N / ,,\ / / // / / z/ // / / /

0 0 b icf I e cr" K28 7 6 5 4 3 2 920161 - 13

K1

Fig. 3. Examples showing how to program the IF offset compensation.

at right angles on to the main board.The use of IC sockets is recom-

mended only to those of you who feelnot so certain about their solderingskills. Although the circuit operates atfairly high frequencies, the construc-tion is not critical. The passive partsare fitted first, then the active parts.

The resistors next to LD I are fittedupright to keep the display section ascompact as possible. Make sure thatthe resistors do not protrude above thedisplays. If they do, the completed dis-play board can not be fitted properlybehind the front panel of the receiver.If the resistors are too large, either fitthem at the track side of the board, orfit IC sockets for the displays.

Connector K3 is fitted at the trackside of the display board. K1 and K2are two single -row pin headers.Alternatively, use small PCB solderterminals.

Once all components are accommo-dated on the boards, and the boardshave been interconnected, the oscilla-tor around X1 may be adjusted, andthe receiver IF offset programmed. Theexamples in Fig. 3 provide informationon programming the offset compensa-tion. Obviously, you have to know thereceiver's IF offset to be able to do theprogramming. In most cases, this iseasy to find out from the documenta-tion, or by looking for the print on theIF filter contained in the receiver. Ifyou are still unable to ascertain the IF,simply tune to a station with a knownfrequency, and measure the local os-cillator frequency. This will also tellyou if the LO frequency is above orbelow the input signal frequency.

All that remains to be done at thispoint is fit the wire links between K1and K2. The setting for a number of

commonly used IFs is already given.The wiring example is based on the as-sumption that the IF frequency is475 kHz. If you are faced with an un-usual IF, you have to 'assemble' thefour digits yourself. Look at the475 kHz example; the last digit (LSD)is composed of 4+1, the second digit of4+2+1, and the third of 4 only. Afourth digit is not necessary because itis 0. Hence, the 1 is not used. Havingfitted the appropriate wires, you needto set S i for LO -low or LO -high. Thisselection should also be based on tech-nical information you have availableon the communications receiver, or ona measurement as mentioned above.Obviously, if the digital dial is alwaysused in the same receiver, switch Smay be omitted or replaced by a wirelink.

The finishing touch is, of course, fit-ting the digital dial into the communi-cations receiver. Alternatively, some ofyou may wish to build the dial as aself-contained unit, i.e., in a separateenclosure. If this is done, the circuit isbest powered by a mains adaptor withan output voltage of 8-15 V, and a cur-rent rating of 250 mA. The input of thecircuit is connected to the local oscilla-tor via a short length of coax cable.Some experimenting may be requiredto locate a 'tapping' point that does notcause oscillator detuning. If possible,go for light inductive coupling, sincethat is electrically safer than capaci-tive coupling (however light) in valvereceivers.

Switch on the receiver, and tune toa known station. If necessary, correctthe frequency readout on the digitaldial by carefully adjusting trimmer C1.From then on, the digital dial is readyfor use.



ESR ELECTRONIC COMPONENTSStation Road, Cullercoats, DEPT. EETyne & Wear NE30 4PQTel. 091 251 4363 Fax. 091 252 2296

74LS-Series74LS0074LS0174LS0274LS0374LSO474LS0574LS0874LS0974LS1074LS10774LS10974LS1174LS11274LS11374LS11474LS1274LS12274LS12374LS12574LS12674LS1374LS13274LS13374LS13674LS13874LS13974LS1474LS14574LS14774LS14874LS1574LS15174LS15374LS15474LS15574LS15674LS15774LS15874LS16074LS16174LS16274LS16374LS16474LS16574LS17074LS17374LS17474LS17574LS19074LS19174LS19274LS19374LS19574LS19674LS19774LS2074LS2174LS2274LS22174LS24074LS24174LS24274LS24374LS24474LS24574LS24774LS25174LS25774LS25874LS2674LS26674LS2774LS27374LS27974LS3074LS3274LS36574LS36774L536874LS3774LS37374LS37474LS37574LS37774LS37874LS3874LS39074LS39374LS39574LS39974LS4074LS4274LS4774LS5174LS67074LS7374LS7474LS7574LS7674LS8374LS8574LS8674LS9074LS9274LS93

£0.14£0.14£0.14£0.14£0.14£0.14£0.14£0.14£0.14£0.23£0.21£0.17£0.21£0.21£0.21£0.14£0.31£0.31£0.21£0.21£0.14£0.21£0.18£0.16£0.24£0.25£0.18£0.56£1.26£0.70£0.14£0.25£0.25£0.70£0.25£0.25£0.25£0.25£0.32£0.32£0.32£0.32£0.26£0.48£0.30£0.24£0.24£0.24£0.25£0.24£0.24£0.24£0.24£0.24£0.24£0.16£0.14£0.14£0.36£0.32£0.32£0.32£0.32£0.32£0.33£0.32£0.24£0.24£0.24£0.14£0.14£0.14£0.32£0.25£0.14£0.14£0.21£0.21£0.21£0.14£0.32£0.32£0.34£0.32£0.62£0.14£0.25£0.24£0.26£0.62£0.14£0.25£0.42£0.14£0.69£0.17£0.19£0.19£0.25£0.31£0.35£0.20£0.23£0.35£0.25

ENAMELLEDCOPPER

WIRE

Alt 2oz Reels14 SWG16 SWG18 SWG20 SWG22 SWG24 SWG26 SWG28 SWG30 SWG32 SWG34 SWG36 SWG38 SWG40 SWG

£0.63£0.67£0.67£0.72£0.76£0.80£0.89£0.91£0.93£0.93£0.99£1.04£1.10£1.22

4000 Series40004001400240064007400840094010401140124013401440154016401740184019402040214022402340244025402640274028402940304031403340344035404040414042404340444046404740484049405040514052405340544055406040634066406740684069407040714072407340754076407740814082408540864089409340944095409740984099450245034508451045114512451445154516451845204521452645274528452945324534453645384541454345554556456045664572458445854724401064010940163401744017540193

£0.17£0.17£0.17£0.32£0.17£0.31£0.19£0.23£0.16£0.16£0.17£0.30£0.31£0.18L0.27£0.27£0.19£0.31£0.31£0.32£0.16£0.21£0.15L0.59£0.18£0.22£0.27£0.17£0.70£0.56£1.24£0.31£0.29£0.31£0.22£0.28L0.35£0.31£0.25£0.31£0.20£0.20£0.25£0.25£0.25£0.56L0.34£0.31£0.29all 8£1.91£0.16£0.20£0.17£0.20£0.17£0.17£0.17£0.30£0.17£0.14£0.17£0.28£0.26£0.5540.18£0.31£0.56£1.20£0.31£0.38£0.38£0.31£0.90£0.26L0.32L0.32£0.73L0.98£0.31£0.27£0.26£0.62£0.40£0.39£0.40£0.44£0.32£2.24£1.00£0.37L0.33£0.46£0.34£0.34£1 1 8£1.96£0.25£0.24£0.32£0.70£0.31£0.50£0.46£0.34£0.36£0.60

TRANSISTORS2N16132N17112N18932N2218A2N2219A2N2222A2N26462N2904A2N2905A2N29072N29262N30532N30542N30552N34402N37022N37032N37042N37052N37062N37712N37722N37732N38192N38202N39042N39052N39062N40362N52962N53212N6107AC126AC127AC1213AC187AC188ACY17AD149AD161AD162BC107BC107BBC108BC108ABC108CBC109BC109CBC114BC115BC116BC118BC132BC134BC135BC140BC141BC142BC143BC149BC154BC157BC159BC160BC170BC170BBC171BC171B5C172BC172BBC177BC178BC179B C182BC182LBC182LBOCt83BC183LBC183LBBC184BC184L

£0.31£0.26£0.29£0.28£0.25£0.16£0.80£0.25£0.23£0.20£0.16£0.27£0.90£0.62£0.50£0.09£0.10£0.10£0.10£0.10£1.44£1.51£1.79£0.40£0.58£0.10£0.10£0.10£0.31£0.57£0.57£0.60£0.30£0.30£0.28L0.45£0.37£3.84f1.67£0.92£0.92£0.14£0.15L0.13£131 4£0.14£0.14£0.15£0.41£0.41£0.41£0.41£0.36£0.36£0.36£0.25£0.27£0.31£0.34£0.12£0.36£0.12£0.12£0.28£0.16£0.16£0.11£0.16£0.13£0.13L0.18LO.18£0.17£0.08£0.08£0.08£0.08£0.08£0.08£0.08£0.08

TRIACSZ0105DA £0.42TIC206D £0.65TIC226D £0.73BTA08-600B £0.84TIC236D £0.96DIAC £0.20

VOLTAGEREGULATORS78L0578L1278L1579L0579L1 279L15780578127815790579127915LM3177LM723L200CVLM323KLM338K

£0.24£0.24£0.24£0.28£0.28£0.28£0.28£0.28£0.28£0.38£0.38£0.38£0.44£0.29£1.16£2.70£5.52

OPTO DEVICES5mm Red LED5mm Green LED5mm Yellow LED5mm Orange LED3mm Red LED3mm Green LED3mm Yellow LED3mm Orange LED5mm Flashing Red5mm Flashing Green5mm Br Colour5mm Tri Colour5mm Plastic Bezel3mm Plastic Bezel0 3" 7 Segment Display Redcommon anodecommon cathode

£0.09£0.10£0.10£0.10£0.08£0.12£0.13£0.13£0.50£0.54£0.36£0.48£0.04£0.05

£1.14

BC186BC204CBC206BBC207CBC208BC209ABC212BC212LBC212LBBC213BC213LCBC214BC214LBC237BBC238CBC239CBC251BC252BC2618BC262BBC267BBC307BC306BC327BC328BC337BC338BC414CBC441BC461BC463BC478BC479BC490BC516BC517BC527BC528BC537BC546CBC547CBC548CBC549CBC550CBC556ABC557CBC558CBC559CBC560BBC637BC638BC639BC640BCY70BC071BCY72BD135BD136BD137BD138BD139BD140BD150CBD165BD166BD187BD201BD202BD203BD204BD222BD225BD232BD237BD238BD240BBD243BBD244ABD246BD441BD442

£0.33£0.72£0.72£0.72£0.72£0.72£0.08£0.08£0.08£0.08£0.08£0.08£0.08£0.09£0.09£0.10£0.13£0.13£0.24£0.24£0.30£0.10£0.10£0.10£0.10£0.10£0.10£0.13£0.40£0.40£0.29£0.32£0.32£0.24£0.22£0.20£0.20£0.20£0.20£0.08£0.09£0.08£0.10£0.08£0.08£0.08£0.08£0.08£0.09£0.21£0.21£0.21£0.21£0.21£0.20£0.20£0.20L0.21£0.22£0.22£0.23£0.24£0,82£0.42£0.35£0.39£0.40£0.40£040£0.40£0.40£0.42£0.38£0.32£0.32£0.37£0.50£0.53£1.06£0.41£0.41

BD534BD535BD536BD646BD648BD650BD707BD807BDX32BDX33CBDX34CBDX53CBDX54C8E180B F182BF185BF1946E195BF244BF2576E2598E337B F355B F4238E451B F459BF469BF029BFX84BEX85B FY50B FY51B FY52BS107BS170BSW66BL1126BU205BU208ABU326ABU500BU508ABU526BU806BUX84I RF540I RF740MJ11015MJ11016MJ2501MJ3001MJE340MJE350MPSA13MPSA42MRF475TI P121TIP122TIP125TIP127TIP132TIP137TI P142TIP147TIP2955TIP29CTI P3055TIP30CTIP31CTIP32CTI P33CTIP41ATI P42CTI P47TI P48TI P50VN1OKMVN66AFZTX300ZTX500

THYRISTORSP0102AATIC106DTIC116DTIC126D

£0.30£0.40£0.66£0.77

£0.47£0.48£0.65£0.52£0.52£0.53£0.42£0.80£1.78£0.46£0.50£0.47£0.50£0.31£0.31£0.31£0.19£0.19£0.35£0.33£0.33£0.36£0.38£0.13£0.19£0.29£0.36£0.29£0.31£0.31£0.29£0.26£0.28£0.21£0.21£1.35£1 .70£1.82£1.73£1.80£2.32£1 .76£2.24£1.36£0.77£1.60£1.63£2.11£2.11£1.60£1.52L0.40£0.42£0.12£0.17£6.21£0.35£0.37£0.37£0.37£0.46£0.46£1.06£1.12£0.63£0.31£0.63£0.31£0.32£0.32£0.72£0.36£0.38£0.48£0.62£0.53£0.44£1.50£0.16£0.16

HARDWARE12 Box 75 x 56 x 25mm £0.82T3 Box 75 x 51 x 25mm £0.82T4 Box 111 x57 x 22mm £0.98MB1 Box 79 x61 x 4Ornm £1.44MB2 Box 100 x 76 x 41mrn £1.56MB3 Box 118 x 98 x 45rnm £1.82MB5 Box 150 x 100 x 60mm £2.50

LINEAR ICsCA311ECA324CA555CA741 CECA747CECA3046CA3080CA3130CA3130ECA3140CA3240ICL7621IC M7555ICM7556LM301ALM348NLF351 NLF353LM358NLM377LM380NLM381LM386LM387LM392NLM393NLM748CNLM1458LM3900LM3914LM3915MC3340MC4558NE531NE556NN E567NN E5532NE5534TBA120STBA8105TBA820MTDA2030TL061TL062TL064TL071 CPTL072CPTL074CNTL081TL082CPTL084CNUA733ULN2004ZN414ZZN425EZN426EZN427EZN428EZN435EZN448E

£0.28£0.23£0.22£0.18£0.39£0.37£0.72£0.98£0.98£0.56£1.22£1.70£0.43£0.96£0.25£0.31£0.36£0.41£0.27£2.57£1.12£2.70£0.48£1.60£0.79£0.28£0.31£0.26£0.72£2.70£2.70£1.60£0.36£1.56£0.36£0.36£0.80£0.66£0.77£0.68£0.39£1.35£0.35£0.42£0.46£0.32£0.34£0.48£0.33£0.34£0.46£0.64£0.48£1.04£4.68£2.61£8.82£6.12£5.31£7.92

EPROMS &RAMS

271627322764-2527C64-2521728-2027C128-2027256-2027C256-20

27C51227C0106115-106254-1062256-104164-1541256-10511000-8514256-8

L4.46L4.84£3.00£2.80£3.69L3.31£3.15L3.55

£3.69£4.97£1.53L3.06£4.83L1.78£2.80£5.61£5.61

DIL SOCKETS8 Pin14 Pin16 Pin18 Pin20 Pin24 Pin28 Pin40 Pin

£0.07£0.11£0.15£0.15£0.16£0.19£0.22£0.25

ELECTROLYTIC RADIAL CAPACITORS

uF 16V 25V 63V 100V 450V0 47 £0.05 £0.071 0 - - £0.05 £0.06 £0.152.2 £0.05 £0.06 £0.184 7 - - £0.05 £0.08 £0.3010 £0.05 £0.05 £0.06 £0.08 £0.4822 £0.05 £0.05 £0.0947 £0.06 £0.06 £0.11100 £0.06 £0.09 £0.11 - -220 £0.09 £0.12 £0.31470 £0.15 £0.19 £0.57 -1000 £0.22 £0.292200 £0.37 £0.57 -4700 £1.11

ELECTROLYTIC AXIAL CAPACI rORS

uF 16V 25V 63V 100V 450V0 47 £0.151.0 - £0.10 £0.10 £0.19

£0.10 £0.10 £0.22- £0.09 £0.10 £0.10 £0.34

£0.12 £0.12 £0.12 £0.4822 - £0.09 0.13 £0.17 £1.0647 £0.10 £0.11 £0.16 £0.20 £1.33100 £0.10 £0.13 £0.21 £2.46220 £0.13 £0.18 £0.42470 £0.21 £0.24 £0.691000 £0.33 £0.40 £1.052200 £0.52 £0.64

f1.14 4700 £0.90

224.7

10

SOLDERING IRONSAntex Soldering ironsM 12 WattC 15WattG 18WattCS 17WettXS 25WattST4 STAND35Watt Gas IronDesolder PumpAntistatic Pump225WG 0.5Kg Solder18SWG 0.5Kg Solder1mm 3 yds SolderDesolder Braid

£7.75£7.78£7.96£7.88£7,96£2.85

£11.58£3.00£4.30£7.40£6.60£0.62£0.87

RF CONNECTORSBNC Solder Plug 50RBNC Solder Plug 75RBNC Crimp Plug 50RBNC Crimp Plug 75RBNC Solder SktBNC Chassis SktPL259 5 2mmPL259 11 mmRND UHF socketSQR UHF socketF Plug RG58F Plug RG6N Plug BOBN Socket RG8BNC Crimp Pliers

£0.93£0.96£0.68£0.68£1.08£0.80£0.68£0.62£0.68£0.45£0.30£0.27£1.60£140

£15.50

PCB EQUIPMENTUV EXPOSURE UNITPLASTIC DEVELOPING TRAYPHOTO RESIST AEROSOL SPRAY (100m1)FERRIC CHLORIDE CRYSTALS (0.5Kg)TIN PLATING POWDER (90g)ETCH RESIST PENPCB POLISHING BLOCK

STRIPBOARD 0.1 PITCH64mm x 25mm £0.2764mm x 95mm £0.9064mm x 431 mm £3.2295mm x 127rnm f1.5095mm x 95mm £1.1095mm x 431 mm £4.80100mm x 160mm £1.60119mm x 454mrn £6.20

PHOTO RESIST BOARD(G. Fibre)

£0.86£1.62£2.09£2.41

CAPACITORSCeramic Mini Disc 100 & 63V

1 OpF to 100nF1 pF-1 nF £0.06. 1 n2 -2n7 £0.07,3n3 -4n7 f 0.12,10n & 12n £0.07

Polystyrene 160V 5% 47pF to 10nF47p -2n2 £0.09, 2n7 -10n £0.12

D CONNECTORSPlug Socket

9 Pin £0.29 £0.3015 Pm £0.39 £0.3915 Pin H D £0.81 £0.9023 Pin £0.40 £0.4925 Pin £0.48 £0.50

9 Way plastic cover E0.3015 Way plastic cover £0.3323 Way plastic cover £0.3625 Way plastic cover £0.36

BRIDGERECTIFIERS

W005 1 5A 50VW021 5A 200VBR32 3A 200VBR62 6A 200V100410A 400V

£0.19£0.20£0.36£0.64£1.39

£67.38£1.35£3.90£2.45

£10.80£0.72£1.84

BREADBOARD81mm x 60mm £3.06175mrn x 42mm £3.74175mm x 67mm £5.56203mm x 75mm Includesmounting plate & posts £7.36

COPPER BOARD (G. Fibre)100mm x 160mm £0.90110mm x 220mm £1.24

PHOTO RESIST BOARD(Paper)

£0.67£1.24£1.58

8" x 10'' £4.63

SWITCHES3amp 250v 6 4mm q mountingSPST ToggleSPDT ToggleSPOT CO TogDPDT ToggleDPDT CO ToggleDPDT CO Toggle(biased)

DPDT CO Toggle(biased 1 way)

DPDT mini slideRotary Wafer 1P12VV, 2P -6W.3P -4W, 4P -3W £0.78Key Switch SPST £2.70Push to make £0.25Push to break £0.28Latching Push Sqr £0.63PCB Tact 6 x 6mm £0.25

£0.60£0.64£0.68£0.76

£1.20

£1.20£0.15

RESISTORS0.25W 5% CF E12 Series £0.60/1000.5W 5% CF Et 2 Series £0.95/1000.25W 1% MF E24 Series £1.72/100POTS Log or Lin 470R 1 MO 25mm dia 0 25in

shaft £0.42PRESETS Enclosed Horz

or Vert 100R -- 1 MO 0 15W £0.15PRESETS Skeleton Horz

or Vert 100R 1 MO 0.1W £0.11* PLEASE STATE VALUE REQUIRED *

COMPUTER ACCESSORIES

Parallel Printer Lead 2mRS232 Lead (all pins) Male MaleRS232 Lead (all pins) Female MaleCentronics 36 Way Lead Male Male

Gender Changers9 Way D Mini Female to Female9 Way D Mini Male to Male25 Way D Mini Female to Female25 Way D Mini Male to Male9 Way D Female to Female9 Way D Male to Male25 Way D Female to Female25 Way D Male to Male

Adaptors9 Way Male to 25 Way Female25 Way Male to 9 Way Female25 Way D Male to 36 Way Centronic25 Way Null Modem Female Female25 Way Null Modem Male to Female25 Way Null Modem Male to MaleRS232 Surge Protector Male - FemaleRS232 Jumper Box Male to FemaleRS232 Tester (7 LEDs) Male - Female

Data Switch BoxesSerial Switch box - 2 Way A/BSerial Switch box - 3 Way A/B/CSenal Switch box 4 Way A/B/C/DSerial Switch box Cross overParallel box - 2 Way A/BParallel box -3 Way A/B/C/Parallel box 4 Way A/B/C/DParallel box Cross over

£6.90£3.60£3.60£4.78

£1.81£1.98£2.23£2.23£2.33£2.33£2.71£2.71

£2.33£2.33£3.56£3.02£3.02£3.02£6.12£3.02£6.59

£9.20£13.16£15.15£19.69£11.84£17.11£18.43£20.42

DIODESZener Diodes 2V7 -33VBZY88400Mw £0.08BZX85 1.3W £0.141 N4001 £0.061N4002 £0.071N4003 £0.071N4004 £0.071N4005 £0.071 N4006 £0.081N4007 £0.081N5400 £0.091N5401 £0.091N5402 £0.091 N5404 £0.111N5406 £0.111N5407 £0.141N5406 £0.151N914 £0.061N916 £0.061N4148 £0.05BY133 £0.130A47 £0.280A90 £0.070A91 £0.100A202 £0.27BA157 £0.10BA158 £0.10BA159 £0.101 N4149 £0.060A200 £0.10

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42

FIGURING IT OUTPART 12 BUILDING MODELS

By Owen Bishop

This series is intended to help you with the quantitative aspects of electronic design:predicting currents, voltage, waveforms, and other aspects of the behaviour of circuits.

Our aim is to provide more than just a collection of rule -of -thumb formulas.We will explain the underlying electronic theory and, whenever

appropriate, render some insights into the mathematics involved.

figure 103 shows a very sim-.1: ple circuit. The capacitor ispreviously charged to 9 V by anexternal source. The source is re-moved, current i flows throughthe resistor, and the pd acrossthe capacitor gradually falls. Weare asked to calculate how longit takes for the current to fall to1001.1.A.

930010 - XII - 103

Fig. 103

One way to answer this ques-tion is to set up the circuit, in-cluding a microammeter to mea-sure i, and measure the timewith a stop -watch. Timing is notthe difficulty; discharging takesseveral tens of seconds. The prob-lem is to find a capacitor of ex-actly 470 p F. We are driven to an-other way of answering the ques-tion - writing an equation whichbehaves in exactly the same wayas the theoretical circuit. Suchan equation is a model of the cir-cuit.

ModellingIt is easy to find the current atthe instant the external sourceis removed. At that instant, wehave a pd of 9 V across a 22 Id2resistor and

i = 9/22x103 = 409 µA.

But, as soon as that current startsto flow, the charge on the ca-

pacitor is reduced, causing thepd across it to be reduced, too.The effect of this is that the cur-rent is reduced. It decreases from490 µA, falling eventually to zero(at least, in practical terms: the-oretically, it never reaches zero).This circuit is one in which keyquantities are changing in time.This is the reason for using thelower-case symbols i and u; theyare to indicate quantities thatvary in time. By contrast, quan-tities such as C and R are con-stant and are represented bycapital letters.

The first step of building amodel of the circuit is to writeequations to express all the re-lationships we know. For thiscircuit, we know that

q = uC [Eq. 79]

where q is the charge on the ca-pacitor at any instant. We alsoknow that

u = iR (Ohm's law)[Eq. 80]

and

i = dq/dt [Eq.81]

The symbol dq/dt needs someexplanation. A symbol of thisform is know as a derivative,more particularly, a first deriva-tive (see Box 1). In this case,dq/dt is the rate of change ofthe charge on the capacitor incoulombs (C) per second (s). Bydefinition, the ampere is a flowof charge of 1 coulomb per sec-ond (1 C s-1) and Eq. 81 expressesthe loss of charge from the ca-pacitor in these terms.

Having jotted down the rele-vant equations, the next step isto relate q and dq/dt in a singleequation. Combining Eq. 79 and80 gives:

q = uC = iRC [Eq. 82]

Combining Eq. 81 and 82:

q = iRC = dq I dtxRC

dq I dt = -q RC [Eq. 83]

Equation 83 is a model of thecircuit, relating the instanta-neous current (represented bydq /dt) to the instantaneous charge,with R and C as constants. The

DerivativesGiven that y is a function of x(for example, y = 4 + 3x), thesymbol dy/dx stands for thefirst derivative of y with re-spect to x. It is the rate ofchange ofy with respect to x.Ifwe think of a graph in whichy is plotted against x, dy/dx isthe gradient ofthe graph at anypoint. Finding the derivative(sometimes called the differ-ential) of a function is knownas differentiation. There area number of simple rules forfinding derivatives, some ofwhich were given in Part 5.'When a function has been dif-ferentiated, the first derivativeis a new function, which canalso be differentiated. This givesthe second derivative, sym-bol d2y/dr2. We can go on anddifferentiate this again to ob-tain the third derivative,d3y/dx3, and so on.

Differential equations maycontain first, second, third orhigher derivatives. The orderof a differential equation isthat of the highest differen-tial present. Equation 83 is afirst -order equation. Nextmonth we shall look at somesecond -order equations.

Box 1

negative sign indicates that thecharge is decreasing with time.Readers will recognize the divi-sor RC as the time constant(z) of the circuit.

Because it contains a deriva-tive or differential, Eq. 83 is knowas a differential equation. Thedifferential terms in such an equa-tion express rates of change, sosuch equations are widely useda models for dynamic systems.They are ideal for modelling elec-

Solving the growth/decayequationEquation 83 is a typical ex-ample of the decay equation.It specifies the rate at whichthe charge diminishes or de-cays. With a positive coeffi-cient on the right of the equa-tion, it specifies growth.

Given a differential equa-tion, it maybe possible to writeit in the form

dy/dx = ky.

Note that the right-hand sideconsists of only a single termin y (no x, no y2, and so on).Also, k must be a constant, butmay be positive (growth) ornegative (decay). In Eq. 83,k = -1/RC. The solution ofsuch an equation is:

y =Asa",

where A is an arbitrary con-stant. The value of A may becalculated ifa set ofborder con-ditions is specified (see maintext).

Box 2


GENERAL INTEREST 43

= 1x 10'3

4 6 8

t [Si

Fig. 104

tronic circuits, and we shall usethem to build several models, thismonth and next.

Solving the equationThe next step is to solve the dif-ferential equation. We need to beable to find the value of q at anygiven time t. Having found q,we can easily find what u and iare at that time. There is nospace to go into the steps of solv-ing Eq. 83, but applying the rulesquoted in Box 2 gives us the so-lution:

q Ae-tIRC [Eq. 84]

For such a simple circuit, this ap-pears to be rather a complicatedsolution but, when looked at an-alytically, it makes sense. Wewill defer the original task offinding the current until we haveexamined in more detail the wayin which q varies with t. At pre-sent, we have what is called thegeneral solution to Eq. 83. Weneed to find the particular so-

4 -u p

930010 - XII - 105

Fig. 105

10

930010 XII - 104

lution which relates to the valuesand conditions of our circuit.

The key symbol in Eq. 84 ise, the exponential constant. Thishas a negative index, showingthat q is decreasing with time.The index is proportional tot, buthas R and C as divisors to takeinto account the effects of sub-stituting different capacitors andresistors in the circuit. With thevalues given in Fig. 103:

= Ae-0.0967t [Eq. 85]

The quantityA, known as the ar-bitrary constant, is the nextto be determined. This constantis there because the techniquefor solving Eq. 83 produces an in-finitely large number of generalsolutions, depending on the thevalue we allot to A. Figure 104shows just 10 ofthe possibilities.Which one of these representsthe circuit in our problem?

Border conditionsIf the values R and C were allthat were known, we could notfind A. Any of the curves inFig. 104, or any of many othersnot drawn there, fits the differ-ential equation. But we also knowthat the capacitor is charged to9 V when t= 0. These two valuesspecify the border conditions.When t= 0, C = 4701.iF and u = 9 V,by substitution in Eq. 79:

q = uC = 9x470x10-6

4.23x10-3 CSubstituting q = 4.23x10-3 Cand t = 0 in Eq. 84, the index ofe becomes zero:

4.23x10-3 = Ae0 = A.

We now have a value for A toput in Eq. 84:

= 4 .23e-0 .0967t X10-3

[Eq. 86]This is a particular solution ofEq. 83. Its graph is the curvedrawn as a heavy line inFig. 104, and shows how thecharge on the capacitor falls withtime at an ever -decreasing rate.

Knowing the instantaneousvalue ofq at any time, we can cal-culate u and i at the same instant.From Eq. 79 and 80:

i=u1R=q1RC.

From Eq. 86:

i = (4.23e-0.0067tx10-3)/RC

(4.23e-0.0067tx 10-3)/ 10.34

409.1e -0-0967x10-6.

We could plot a curve for i againstt, and this would have a similarform to the curve for Fig. 86. Inthis problem, we want to knowt when i = 100 µA. Substitutingi = 100 x 10-6 = 10-4:

0.2444 = e -0.0067t.

Taking natural logarithms:

In 0.2444 = -0.0967t

-1.4088 = -0.0967t

t = 14.57,

that is, the current falls to 100 µAafter 14.57 s.

Falling pdConsider the same circuit butwith C = 220µF and R = 100 Id).The capacitor is charged, then al-lowed to discharge for 10 s, afterwhich time the pd across it is2 V. Find the initial pd and thepd after 15 s.

The differential equation isEq. 83, and the general solutionis Eq. 84 as above. The borderconditions are that u = 2 V whent = 2 s.When u = 2, uC = 2x220 x10-6= 440x10-6. In Eq. 84, the indexof e is -10/RC = -0.4545.Substituting in Eq. 84:

440x10-6 = Ae-0 4545

Ax0.6348,

A = (440x10-6)/0.6348

6.931x10-4.

Having used the border condi-tions to find the arbitrary con-stant A, find the initial charge byputting t = 0 in Eq. 84:

q = A = 6.931x10-4.

This gives the initial pd:

u = q IC

= (6.931x10 -4)/(220x10-6)

= 3.15 V.

The pd after 15 s is found in asimilar way. The index of e is-15/RC = -0.6818.

q = 6.931x10-4xe-0 6818

3.505x10-4.

u = (3.505x10 -4)/(220x10-6)

= 1.59 V.

First -order equationsA first -order differential equa-tion has the form:

dyldx + f(x)y = g(x).

Both f(x) and g(x) are functionsof x, but one or both may be con-stants or zero, thus simplifyingthe equation.

An equation such as this isneeded for modelling the circuitof Fig. 105. Here the capacitoris being charged through a re-sistor by a variable pd, u. As be-fore, we write down relevant equa-tions:

uR = Ri =Rclq I dt;

uc = qic.

We can relate these by makinguse of the fact that, at any in-stant, KVL applies:

u = uR + uc

u=Rclqldt+q1C.

Rearranging terms and divid-ing by R to give dq/dt unity asits coefficient:

dq/dt + qIRC=u1R.[Eq. 87]

This is the first -order equation


44 FIGURING IT OUT - PART 12

that models the circuit.The equation may be solved

by the routine summarized inBox 3. This involves calculat-ing a quantity known as the in-tegration factor, the purposeof which is to produce an equa-tion that is easy to simplify later.The routine requires integra-tion: some of the procedures forthis were outlined in Part 5.

We identify the function f(t)as the constant 1/RC and g(t) asu I R.

F(t) = J 1/RC dt = t RC. Theintegration factor is et/RC.

G(t) = f (u/ R) el/RC-

If we assume that u is a con-stant, the integration is simpler.We will now refer to it as U.

G(t) = RC [(U /R) et /RC]

= CUeIIRC.

The solution is:

q= e-IIRCCUel IRC +

In the first term on the right,the indices of e total zero, ande° = 1:

q = CU + Ae-t/RC [Eq. 88]

This is the general solution. Ifthe capacitor has zero chargewhen t = 0, we have a bordercondition:

0 = CU + A,

A = -CU.

Equation 88 becomes:

q = CU (1-e-t/RC) [Eq. 89]

[C x10-4]4

0

q = 6 x10-4

This is the particular solution,assuming that the source isswitched on at t = 0 and holds aconstant value U. Figure 106shows the curve for this equationif U = 6. The charge on the ca-pacitor rises rapidly at first, butat a gradually decreasing rateuntil it almost, but never quite,reaches CU.

Charging timesA related equation is obtained bydividing Eq. 89 throughout byC. The pd across the capacitoris q / C, which we will refer to asuc. Then, dividing:

uc = U(1-e-IIRC)

.*. uclU =1-e-(IRC. [Eq. 90]

Equation 90 can be used to de-termine the time to reach anygiven pd uc expressed as a frac-tion of the applied pd U. In thestandard 555 timer circuit, themonostable period is the timetaken for the pd across the ca-pacitor to rise from U/3 to 2U/3,where U is the supply voltage.

uc/U = 1/3 at t1,

1/3 = 1-e-f1/RC

-2/3 =

Negating and taking logarithms:

In (2/3) = -t1/RC

t1 = 0.4055RC.

uc/U = 2/3; at t2:

2/3 = 1-e-t2/RC;

1/3 = -e-t2ffiC;

q= Cu (1 -e-tIRC)

2 3 4

t [S]5

930010 -XII- 106

In (1/3) = -t2/RC;

t2 = 1.0986RC.

The monostable period is t2 -t1=(1.0986-0.4055)RC = 0.6931RC.This is the period quoted in thedata sheet for this timer.

InductorsThe derivative which models theaction of an inductor is:

u = Ldildt.

The induced e.m.f., u, is propor-tional to the inductance L andthe rate of change of current, i.For the circuit of Fig. 107, theequations are:

uR = Ri;

uL = Ldildt.

By KVL:

u = uR + uL = Ri + Ldildt.

Rearranging terms and divid-ing throughout byL gives the dif-ferential equation:

di/dt + (R/L)i = u/L.

Applying the rules for solvingfirst -order equations, we have:

f(t) = R1L;

F(t)= Rt1 L.

Integrating factor is eRIIL.

g(t)= u /L;

G(t) = J (u L)eRIIL dt.

We make simplifying assump-

Solving first -order equationsGiven an equation in the formdy/dx + f(x) + g(x).

1. Integrate .if(x) dx and callit F(x).

2. The integrating factor isetifx).

3. Integrate ig(x) eF(x) dx andcall it G(x).

4. The solution la:y = e- '(z) G(x) Ae-P(x).

Note the negative indices atstage 4. A is the arbitrary con-stant; find it by using bound-ary conditions.

930010 - XII - 107

Fig. 107

tions in a moment. Here is thesolution at this stage:

e-RtIL J (u L) eRt/L dtAe-RtiL.

Note that the index of e is some-times + and sometimes -. If u isa function of t, for example, u isan alternating pd with a functionsuch as u = 2sin wt, we integratethe first expression on the right,and obtain a particular solution.Here we assume that u is con-stant and call it U. Integratingthe term gives:

e-RtIL (Li fL).eRtIL (L /R)

= u/R.

Now the solution is simplified to:

i = U/R + Ae-RtIL. [Eq. 91]

For the particular solution, takethe case in which the pd is 10 Vup to the time t = 0. The currentis steady (di/dt = 0), being de-termined only by the pd and theresistor:

i = 10/(220x103)= 45.45x10-6.

Substituting in Eq. 91:

IntegrationIntegrating a constant, VW:Table 1, Part 2, states thatthe integral of to = ta+1/(n+1),provided that n -1. Since tdoes not appear inthe expressionbeing integrated, n = 0. The in-tegral of t0 is t. Multiplied bythe constant 1IRC, the integralof 1IRC is t I RC.

Integrating etIRC : Table 1in Part 2 states that the inte-gral of eat is eat/a. Here, a= LIRCThe integral is

(or I RC)1(1IRC) = RCef

Fig. 106


Box 3 Box 4

FIGURING IT OUT - PART 12


45

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III s AI Its i 1. 1 I el

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A = 45.45x10-6 - U/R.

Putting this value ofA into Eq. 91,we have the particular solution:

i =U IR + (45.45x10-6 -U/R) e-RIIL [Eq. 92]

When t = 0, the applied pd is 10 Vand we have a constant currentof 45.45µA flowing through thecircuit. The voltage source issuddenly reduced to 0 V. To findwhat happens, insert U = 0 inEq. 92:

i = 0/R + (45.45x10-6 -0/R) e-RIIL;

i = 45.45x10-6xe-Rt/L. I Eq. 931

Figure 108 is the graph of this.It shows the current graduallydying away at a rate depend-ing on the inductance and re-

= 45 .

[pA]

0

sistance.We can also investigate what

occurs if the voltage is reducednot to zero, but to a lower volt-age, say, 5 V:

i = 5/R + (45.45x10 -6-5/R)xe-RtIL.

Or we can model a suddenly in-creased voltage to, say, 22 V:

i = 22/R + (45.45x10 -6-22/R)xe-Rt/L.

Figure 109 shows the graphs,which clearly reflect the actionof an inductor in resisting changesin the flow of current throughit. We could also modify Eq. 93by changing the value of L andseeing what effect this has onthe extent and timing of cur-rent changes.

Once a model has been built

mathematically, it is easy to in-sert new values and determineits behaviour. This is much eas-ier than building a circuit, thenreplacing resistors, capacitorsor inductors. Differential equa-tions are a powerful way of 'fig-uring it out'.

Next month we shall modelmore complicated circuits withsecond -order equations.

Test yourself1.

2.

Write the particular solutionfor the current in the circuitof Fig.103, but with C =150µF,R = 4.7 kS2 and an initial pdof 6 V. Find (a) the pd acrossthe capacitor 1 s after dis-charge has begun, and (b)the current 2 s after dischargehas begun.Find the rise time for the cir-cuit of Fig. 105, if U = 10 V,

C= 10 11F and R= 39 kaRise time is defined as timefor the pd across the capaci-tor to rise from 10% of U to90% of U.

3. In the circuit of Fig. 107, butwithR = 4.7 IcQ, andL = 20 mH,a steady voltage of 1 V is ap-plied until t = 0. Then thevoltage is changed instantlyto 5 V. Calculate the current2 ?As later.

Answers toTest yourself (Part 11)1. zn = 6.67 Q; z21 = 4 Q;

z12 = 4.67 Q; z22 = 7.47 Q.

2. z11 = 9.83 Z-5.57°;z21 = 1.17 Z77.590;gain = 0.12 Z83.16°.

3. hif =50 kQ;hzi = 125; hiz =1/3;h22 = 833 Ils

45 x 10 -6 x e -Rt / LAr

1 0 0 -

80 -

60 -

22+ (45 . 45 x 10

22-6 --R ) e -Rt / L

[pA]

40 -5

i= IT) +(45 .45 x5

)e-R1/L

20 -

110.4 0.6 0 0.2 0.4 0.6 0.8 1.0t 930010 - XII - 108 930010 - XII - 109

[Ns] t [1.(S]

Fig. 108 Fig. 109


46

SCIENCE &TECHNOLOGY

Coding for GSM

By Brian P. McArdle

1. IntroductionThe term GSM stood originally for Groupe Special Mobile. Themeaning Global System for Mobile communications has beenadopted recently as this is now considered to be a more accuratedescription. It is the new form of cellular telephone system in-tended to replace the present TACS. The purpose of this article is toreview the coding methods for voice and data.

The GSM projects was commenced in 1982 by CEPT in order to de-sign a pan-European cellular telephone system which could be op-erated throughout western countries. It was not the first cellularnetwork as systems, such as TACS, were already in operation by anumber of administrations. However, these other systems tendedto be confined and mobile units could not be used outside their owncountries. Since international travel, especially between countriesof the EC, had become commonplace, a clear requirement existedfor a pan-European system. There was the added advantage thatone system would reduce the difficulties of manufacturers whowere attempting to cater for the specifications of different nationalsystems. The EC wished to eliminate barriers to trade betweenmember states and, consequently, the concept of just one systemfitted in with these policies.

The TACS system uses narrowband frequency modulation (NsFm)for voice communication. The frequency range is 935-960 MHz forbase stations and 890-915 MHz for mobile units. During a call, themobile transmits on a specific channel and receives from the baseon another dedicated channel simultaneously. The frequency sep-aration between the two ranges permits duplex operation. In bothranges, the channel spacing is 25 kHz. The frequency deviation at9.5 kHz is unusually high, but frequencies are assigned to avoidinterference between adjacent channels. However, the system dif-fers from business radio in that specific channels are not assignedto individual users. Unknown to users, base and mobile stationsexchange control signals on control channels that are reserved forthis purpose and are not used for voice communications. A roam-ing mobile monitors the base control channels and selects thestrongest signal. It identifies itself to the selected base on a mobilecontrol channel in order to ensure that all appropriate calls are routedto that particular base. If the mobile moves away into another cellwhere a different base has a stronger signal, the procedure is re-peated. While the voice channels use frequency modulation, the con-trol signals are transmitted using digital modulation (Psx- phase -shift keying) at 8 kbits/second. Some control signals are sent overthe voice channels but, in general, the two operate separately.

In GSM, the voice and control channels both use digital modula-tion. It is an all digital system. The techniques for modulation andcoding are examined in sections 2 to 5. The comments expressedare purely personal.

2. Control channelsGSM has two basic types of channel: TRAFFIC for voice and data, andCONTROL. The term LOGICAL is sometimes applied. Both types useburst transmissions and Time Division Multiplexing (TDM) as re-quired. Every burst takes a total of 577 microseconds. A PHYSICALchannel means a sequence of such time slots for communication ofa full message between base and mobile stations. This is not aradio -frequency channel as the frequency can be altered. A frameis a prescribed sequence of eight bursts where a caller is assignedto one in every eight slots. Thus, eight callers are multiplexed to-

gether with respect to time. These points are further explained inSections 3 and 4. For operation of a GSM unit, a user is not awareof the complicated signalling procedures for implementation.

A control channel can be broadcast (3), common (3) or dedicated(8). The functions are not examined in this article as the empha-sis is on coding. Each channel can have more than one application.It could contain a combination of frequency correction, synchronizationand broadcast information (e.g., for base station identification). Forexample, a synchronization burst (148 bits) is transmitted by a baseon the Broadcast Synchronization Channel with the format

Tail Encrypted Synchronization Encrypted Tail Guardbits (3) bits (39) sequence (64) bits (39) bits (3) period (8.25)

577 microseconds156.25 bit periods

Tail bits can be taken as '0' unless otherwise stated. The guard pe-riod is to permit a unit to power down on termination of a burst.The first six bits after the tail bits represent the base's identifierand so on. The term'encrypted bits' refers to the information bitsthat are encrypted (Appendix 1) before modulation and transmis-sion. Alternatively, an access burst (88) is transmitted on a CommonControl Channel as follows

Tail Synchronization Encrypted Tail Guardbits (8) sequence (41) bits (36) bits (3) period (68.25)

In this particular case the tail bits are extended to length 8:00111010 and the 41 synchronization bits are also specified. Itshould be noted that the various signals do not contain the samenumber of useful bits, but the total duration remains constant.

An interesting point is that frequency hopping is in use. It is im-plemented on mobiles. However, this is not the spread spectrumform where a radiofrequency signal is deliberately spread acrossa bandwidth much larger than required for a message. In truespread spectrum the bandwidth is independent of a message, butis determined by a prescribed modulating signal. In GSM, the chan-nel does not remain the same for the duration of a message. Unknownto a user, the channel changes automatically on receipt of a spe-cific signal. The hopping occurs between the time slots when a mo-bile is not transmitting. The main purpose of hopping is to main-tain the maximum possible level of spectrum efficiency. However,the fact that a full message is transmitted on a number of chan-nels helps to minimize the effect of a poor channel (e.g., due to ahigh noise level or an interfering signal).

The control signals undergo encoding procedures similar, butnot identical, to those for voice and data. These are discussed inthe next two sections.

3. Voice communicationsGSM is an all digital system, which means that the speech signalsmust be digitized. At present, there is one speech codec, known asRPE-LTP, in use. Another codex, which would reduce the number ofbits by half, is still under development.

The full rate codex uses Linear Predicitive Coding (Appendix 3).It suffices to state that the codex is a good representation of humanspeech. The analogue audio signal is sampled every 20 millisecondsand a block of 260 bits is formed as follows

Class 1(182)do dI d2

Class 2 (78)d182 d183 d184 d259

where do and d259 are the MSB and LSB respectively. Class 1 is par-ticularly important and undergoes a series of encoding operations.


CODING FOR GSM 47

Class 2 remains unprotected. An analysis of the method of selec-tion of each class is not necessary to understand the coding proce-dure. Both classes eventually form a new block which is input tothe encryption unit (Appendix 1). The various steps can be sum-marized as follows

Input 1 -0-Convolutional A0-456Class -0 -Cyclic -.0-Permutationcode & tail bits code

260 182 185 189' 378Class 278

The cyclic encoder uses a generator polynomial (x3 + x +1) to de-duce three check bits from the polynomial (dox52 + d151 + d4 x3

+ cox2 +cix + c2). The check bits are chosen such that the residuepolynomial is (x2 + x + 1). Refer to Appendix 5 for the mathemati-cal background. If an error occurs in just one bit, there is a total of53 possibilities. However, the check bits are limited to a total of eightpossible combinations, including the case for no error. Obviously,further operations are required for an adequate level of protection.The new block is reordered according to

0 1 ...do d2

90d180

91c0

92 93c1 c2

94 95 ... 184d181 d179 ... dl

185 186 187 188

uo ugo u91 U92 u93 u94 u95 u184 0 0 0 0

The even -numbered data bits from 0 to 180 are placed in the first91 positions. The odd -numbered bits are in the last 91 locations inreverse order before the tail bits which are set to '0'. The convolu-tional encoder generates a new block according to the equations

v2n=(un + un_3 + un_4) mod 2v2n+1 = (un + un_i + un 3 + un_4) mod 2

for n = 0 to 188 and the block size is doubled. Class 2 bits are placedin positions 378 to 455. At this point, a fundamental data block isfully constructed. The blocks are interleaved by reordering and scat-tering the bits over a total of eight blocks. Transmission of a NORMALBURST is of the form

Tail3

Data Flag 157 1

Trainingsequence 26

Flag 2 Data1 57

Tail Guard3 8.25

encrypted encrypted

The effect of interleaving is that 57 bits are from the original blockand the remaining 57 are from the next block. A training sequenceis included between the useful information bits. This takes part inthe modulation, but not in the encryption process and need not beconsidered further. Two flags are added for control purposes sincecontrol signals are sometimes transmitted on traffic channels. Asper Section 2,GSM has very extensive signalling requirements and,consequently, traffic signals must double up as control channels whenthe deignated control channels have insufficient space for additionalsignals. For voice or data (Section 4), both flags are set to '0'. If flag1 or 2 is set to '1', then the even or odd numbered bits respectivelycarry control information. Hence, the term 'stealing flags' is applied.A full block of 456 bits has eight flags added to produce a final sizeof 464.

GSM makes extensive use of Time Division Multiplexing. Successivebursts, as per the previous NORMAL BURST, are not from the samecaller. A traffic channel contains eight different callers in succes-sive time slots and a slot corresponds to a burst. Each caller hasone in every eight slots.

The reader is referred to ETSI Specification 1-ETS 300 031 for anexact description. The speech codec is an improvement onADPCM(Appendix 2) which is widely used for digital communications.Decoding procedures are not analysed as they are left to the manu-facturers. This is in line with normal practice of late. Most decod-ing algorithms will probably be based on the syndrome method. Aprevious article in this magazine7 has some relevant examples onthe above convolutional code.

GSM offers a major improvement in the level of confidentiality,

even without encryption, due to the complicated signalling arrange-ments, frequency hopping and multiplexing of messages. Low-costequipment, which can monitor the TACS system on NBFM, is uselessagainst GSM. Even with the speech codec and decoders installed, ascanner would still have to be capable of identifying the appropri-ate control signals and a particular burst among a total of eight overa complete cycle in order to eavesdrop on a particular conversation.It is quite likely that test and monitoring equipment will becomeso sophisticated that it could be designed and made only by the GSM

manufacturers.

4. Data communicationsGSM is not limited to speech, but has the facility to transmit dataat the following rates:

(a)(b)(c)

(d)(e)

full rate at 9.6 kbits/secondfull rate at 4.8 kbits/secondfull rate at 2.4 kbits/secondhalf rate at 4.8 kbits/secondhalf rate at 2.4 kbits/second.

Since the coding procedures are very similar, the analysis is con-fined to (a) and (b).

For (a), the information is input as 60 bits every five millisec-onds. Four blocks are chained together to generate a 240 bit blockwhich is processed as follows:

Input lo.4 blocks Am. -Tail Convolutional -op -Reduction to 456bits code

60 240 244 488 456

The convolutional code uses the same two equations as in Section3 to double the block size. The bits in locations 11 to 42 are removedto produce a reduced block of 456. This block is interleaved suchthat the bits are distributed over 19 blocks. Transmissions are inthe format of a NORMAL BURST.

For (b), the input is 60 bits every 10 milliseconds. The procedureis:

Input-Tail-0.2 blocks Am. Convolutional -10-Interleavingbits code

60 76 152 456

The tail bits are included within the 76 bit block as follows:

Data Tail Data Tail Data Tail Data Taild0 -d14 bits d15 -d29 bits d30 -d44 bits d45 -d59 bits15uo

4 15 4 15 4 15 4u75

Another block is generated as per above and entered into positions76 to 151. A convolutional code trebles the block to 456:

v3, = (un +un + un_3 +un_4) mod 2v3n+1 = (un + un_2 +un_4) mod 2

v3n+2 =(un un-1 + un_2 + un_3 + un_4) mod 2

and is interleaved, encrypted and transmitted in the format of aNORMAL BURST. A simplified decoding method is demonstrated inAppendix 6.

For voice and data, the encryption operation occurs after the otherencoding operations and just before the modulation process. Thisis not the standard configuration. Generally, error control encodersare the last step before modulation and transmission. The arrange-ment suggests some form of stream encryption where an error intransmission has no effect on the decryption operation. An errorin one bit remains a single error which can be corrected by the con-volutional code. (In block encryption, a single error could affect anentire block.) It also indicates that the radiofrequency signalsshould be transmitted on reliable interference -free channels.Frequency hopping (Section 2) should be of assistance in maintaining


48 SCIENCE & TECHNOLOGY

communications.

5. ModulationThe method of modulation is Gaussian Minimum Shift Keying(GMSK). The term 'Gaussian' refers to the shape of the modulatingwaveform. After the encryption unit, the bits are sent to the mod-ulator for digital modulation of a radio frequency carrier. In orderto indicate start and stop positions in the process, the modulatorhas the facility to add dummy bits to the stream of data bits. Thisconsists of a sequence of is before and after the data burst and themodulator behaves as if these dummy bits are input in the stan-dard manner. For electronic implementation, the bits are turnedinto bipolar form (1 and -1) as per the following equations and fil-tered to generate the modulating signal.

fln = (Pn + Pn_j) mod 2.

sn = 1- 2qn.

The last equation represents a differential operation since sr, be-comes the difference between the current bit at stage n and the pre-vious bit. In electronic terms, the sn s are Dirac pulses which areinput to a filter with very specific characteristics. Its response isdesigned to generate pulses with a Gaussian shape which, in turn,are used to phase -modulate a radiofrequency carrier. The trans-mitted signal in the time domain is of the form

x(t)= Ni(2E IT) cos [cot +0(0+ 00]

where 0 represents a random phase shift and can be assumed tobe constant for the duration of a burst. The modulation is 0(t) andproduces a phase shift and side bands in the unmodulated carrier.The other terms are

E = energy per modulation bitco = angular frequency of the carrierT = duration of one bitBT= 0.3 where B = 3 dB bandwidth.

The maximum phase shift per modulation bit is 90° and the mod-ulating index is less than 0.5. Hence, the term 'minimum' reflectsthe electronics restrictions of the modulation process. The effect isthat the radio frequency spectrum is compressed in comparison withthe older techniques of angle modulation (frequency and phase mod-ulation). For example, the first sidelobe is 23 dB below the level ofthe main transmission, whereas in PM this figure is 13 dB. Obviously,there must be a high level of precision in the interpretation ofphase changes. In the specification for radio transmission and re-ception, there is a requirement for phase accuracy. A burst in theprocess is 156.25 bit durations and the modulation rate is270.83 kbits/second. The reader is referred to ETSI SpecificationI-ETS 300 032 for a detailed analysis.

6. Radio frequency characteristicsGSM has two bands for dual frequency operation. Abase station trans-mits on one of the 124 channels in the range 935-960 MHz and re-ceives on another channel in the range 890-915 MHz. For mobileoperation, these two bands are reversed. To safeguard other ser-vices in adjacent bands, channels 1 and 124 are normally not used.In each band the channel spacing is 200 kHz with eight separatemessages, either voice or data, multiplexed on to the same chan-nel as per Sections 2 and 3. Each frame of a message is allocated atime slot of 577 microseconds for transmission of 156.25 bits. Thetransmission rate is so fast that adjacent channels cannot be op-erated within the same general area (e.g., between adjacent cells).It is recommended that a separation of at least 400 kHz be applied.

Due to the high frequency range, the transmitted signals arepropagated from base to mobile and vice versa by multipath ratherthan directly. They arrive in the general area of a mobile with ran-dom variations in level and different delays. In the immediate

vicinity of a mobile there are further variations mcaused by localreflections, diffractions and the arrival angle. Over distances of around10 metres, the criterion for a wide -sense stationary process is sat-isfied. For test purposes, propagation models have been developedfor different environments: urban, rural, and hilly terrain, but areoutside the scope of this paper. It suffices to state that special dif-ficulties are encountered for high bit rates at high frequencies andthe GSM system has been designed to cope with these problems. Thefrequency hopping mechanism (Section 3) is an attempt to maxi-mize the chances of reliable communications by moving a userthrough successive electronic channels during a full message.

There are various classes of units for different applications.Base stations are available in eight ranges from 2.5 watts to 320watts. There are five classes of mobile from 0.8 watts to 20 watts.Some are fitted with an integral antenna and others have a socketfor connection to an external antenna. In transmit mode, the ouputspectrum is determined by two main effects: modulation processowing to the use of burst type modulating signals and switchingtransients due to frequency hopping. For the first effect, there is atable of values for various power levels (e.g., an emission at 400 kHzfrom the nominal transmit frequency should be 58 dB down for aunit with an integral antenna and 60 dB for a unit with an antennaconnector). For the second effect, there can be inaccuracies in try-ing to distinguis between a transient and a spurious emission and,consequently, the two are considered together. The peak trans-mitted power in specific bandwidths (e.g., 10 kHz, 30 kHz and100 kHz) at designated frequencies (inside and outside the GSM bands)from the nominal transmit frequency must be within certain lim-its. A base or mobile in the transmit mode must not emit more than250 nanowatts at the designated frequencies in the range 9 kHz to1 GHz. For the range 1 GHz to 12.75 GHz, the level is increased to1 microwatt. For a mobile in the idle mode, the figures are 2 and200 nanowatts respectively. Both sets of test are quite complicatedand this explanation is only intended to present an overview of theoutput spectrum of a GSM system.

In general, the radio frequency characteristics are very in volvedand the reader is referred to ETSI Specification I-ETS 300 033.

7. SummaryThis article only covers the coding aspects of GSM from the point ofradio communications. The comments are purely personal and areader should consult the specifications for the exact position.

Although GSM was originally intended as a pan-European sys-tem, it will probably be a number of years before users can trans-fer automatically between states. Roaming by a mobile as it movesbetween states was included in the draft, but this could take someyears. The proposals were very ambitious, which resulted in com-plex equipment standards. Introducin g and developing any typeof new service, which must be operated on a national scale through-out a country,. will remain a major undertaking. The fact thatmany states already had cellular systems did not automatically turnGSM into a modification. Despite the difficulties, GSM is an out-standing achievement of design and development for the Europeof tomorrow.

References

1. Cellular Communications for Data TransmissionM. Flack and M. Gronow,NCC Blackwell (1990).

2. Digital Communications (3rd Edition)John G. Proakis,McGraw-Hill International Edition (1987).

3. Analog and Digital Signal Processing and CodingP.M. Grant, C.F.N. Cowan, B. Mulgrew and J.H. Dripps,Chartwell-Bratt (1989).

4. Error Control Techniques for Digital CommunicationsArnold M. Michelson and Allen H. Leveresque,


CODING FOR GSM 49

John Wiley and Sons. (1985)

5. ISDN ExplainedJohn M. Griffiths,John Wiley and Sons (1990).

6. Cryptography and Data SecurityDorothy Denning,Addison-Wesley (1982).

7. Elektor Electronics, January 1993

Appendix 1: Encryption techniquesThis article does not examine the method of encryption after theformation of the eight sub -blocks from the 456 bits as per Section 3.However, controversies have arisen over the A5 Encryption Algorithm.There is the difficulty that the encryption and decryption opera-tions have not been published as a specification in the usual man-ner. The algorithm is restricted to manufacturers and is availableonly to certain categories of personnel. A few general remarksshould provide an overview.

The most widely know encryption algorithm is the us DataEncryption Standard (DEs) introduced in 1977 for the encryptionof computer data. The input block is 64 bits and, in early applica-tions, was usually constructed from eight ASCII characters of eightbits per character. It is a block cryptosystem operating on groupsof bits rather than on individual bits (i.e., stream cryptosystem).The operation is fixed with the exception of a key block of 56 bits.Any combination of bits can be used and, therefore, there are 256possible keys. The particular key in use is the secret informationof the cryptosystem. The key block is sub -divided into 16 separateinternal keys, which are applied to the input block in 16 steps togenerate the output block of 64 bits. The decryption operation to

4 Feedback Logic

A

Shift - Register ofR stages

P

Key Bit

K

oc

940009 - 12

Fig. 1 a. Stream encryption system. The method of generating keybits is the secret information and must not be known by an unau-thorized user.

K, K, K, 3

940009 - 13

Fig. 1 b. Linear feedback shift register. The incoming bit on theleft is given by

JK r, jmod2j=1

L. = 1 or 0 for the latch closed or open respectively. Since addi-tion modulo 2 is a linear operation, the feedback logic is the lin-ear variety.

recover the original block is the same process, but the 16 sub-keysare applied in reverse order. Since the standard is over 16 yearsold, it is no longer considered suitable for many applications. ETSIis now developing new algorithms for its own particular require-ments. However, the DES remains a milestone in the developmentof modern secrecy systems and has been used as a basis for furtherdesigns. It should be around in updated versions until the year 2000.

GSM is believed to use sa shift register with non-linear feedbacklogic similar in principle to that in Fig.1. It does not use a DES typeblock system. For a shift register ofr stages (i.e., Jxflip-flops) thereare

1. 22r possible feedback arrangements. If r = 3, then 23 = 8 and28 = 256. The possible sequence of states in the operation of theshift register is

State : 000 001 010 011 100 101 110 111

Successor 1: 000 000 001 001 010 010 011 011Successor 2: 100 100 101 101 110 110 111 111.

Each state has two possible successor as an incoming bit is 1 or0. In reality, a shift register is designed such that each state hasa unique predecessor and successor. This means that each stateoccurs only once in a complete cycle of states (i.e., period). Thus,the number of different feedback arrangements is reduced to 221 1'.For r = 3, 24 = 16. If the logic required to implement a particu-lar sequence must consist of AND and OR operations, this isknown as NON-LINEAR. In mathematical terms, they are repre-sented by non-linear functions.

2. 2r feedback arrangements with linear logic. The arrangementconsists of latches and an EXCLUSIVE -OR operation to representaddition modulo 2. Each flip-flop of the register is connected througha latch, which is open or closed, to the addition operation.Obviously, if a latch is open, the corresponding state of the reg-ister has no effect on the generation of an incoming bit. It is thesimplest form of feedback logic and the most commonly used bycircuit designers. One of the principal applications is in the gen-eration of pseudo -random binary sequences.

3. (2r-1) linear feedback arrangements which do not generate thestate all zeros.

4. 4) (2r -1)/r linear feedback arrangements which generate max-imum length sequences of period (2r-1). 4) is Euler's ibtient Function.

The main reason for using non-linear logic is security. The tech-niques of cryptanalysis are considerably more effective againstlinear than non-linear logic. For example, the encryption operationof Figure 1 is given by C = (P + K) mod 2. Since the operation islinear, decryption is given by P = (C + K) mod 2. In the same man-ner, Kean be deduced from a known pair as follows: K= (C +P) mod 2and the secret information has been compromised. This could applyto a full sequence of key bits. It is a general guideline that linear-ity is the main cryptographic weakness in a system. It is the friendof hackers and the enemy of designers. Figure 1 is intended to il-lustrate the overall category and should not be taken as accuraterepresentation of the techniques in GSM.

Fig. 2. General arrangement for ADPCM.

940009-11


50 SCIENCE & TECHNOLOGY

Appendix 2: Adaptive differential pulse codemodulation (ADPCM)Figure 2 illustrates the general principles, but is not a detailedcircuit. The main point is that the output is not merely a sampledversion of the input sequence. The difference between the input anda prediction is quantized to produce another signal. It should benoted that xn, y, and en are digital numbers and not bits. The out-put, en, will always have at least a quantization error. In non -math-ematical terms, the original signal is sampled very often and thedifference between each sample and a predicted value of what thesample should be is quantized and transmitted.

The process of prediction is critical for accuracy and depends onthe assumption that any two successive samples and their corre-sponding predicted values do not differ too much. Consequently,the rate of sampling must be sufficiently high for this assumptionto remain valid. There can be a major variation over a large num-ber of samples. In fact, the process must be able to handle wide changesas a voice signal can vary substantially in level and frequency. Ingeneral, xn and xn_i should be very similar. Then, if the deductionof yn by the predictor is accurate, the difference (x, yn) is small.The difference signal is quantized into en, which is transmitted. Theresult is a reduction in the number of bits which would be requiredto transmit xn as ordinary PCM.

The simplest form of prediction is based on a recursive filter typeoperation as follows

Yn-laj=1

where r is the number of stages in the prediction process and theajs are the prediction coefficients. yn is an estimate of xn as per theprevious paragraph and xn is the reconstructed estimate of theoriginal input at stage (n-j). The coefficients are calculated by aminimization of the Mean Squared Error (MSE). Consider a simplifiedprocess where y n can be replaced by axn_i.

MSE = E (x, yn )2 = E (x, axn_i)2

= E (x772) 2aE (xnxn_i ) + a2E (x,42).

d/da(msE) = -2E(x, xn_/ ) + 2aE (x, 12) = 0.

The expectations can be replaced by autocorrelation functions de-duced from N input samples as follows

1N -k

R(k)=N Lixj j+k

j=1

for k =0 and 1. The same principle can be used for a predictor witha number of stages. Algorithms have been developed to allow au-tomatic calculation. In an adaptive configuration, the values wouldnot be constant.

CCITT Recommendation G.721 gives the process required to turnstraight PCM at 64 kbits/second into ADPCM at 32 kbits/second. Theadaptive quantizer has 15 levels producing an output block of fourbits (three for magnitude and one sign bit) per input. For a sam-pling rate of 8 kHz, the transmission rate is 32 kbits/second. Thequality of speech is only slightly lower than PCM, but the consider-able reduction in the number of output bits more than compensates.Recommendation G.722 turns analogue voice in the range 50 Hz to 7 kHzinto SB-ADPCM at 64 kbits/second. The frequency band is split intotwo sub -bands and each is encoded using ADPCM. Further analysisis outside the scope of this paper and is not needed for GSM, whichuses Linear Predictive Coding (Appendix 3).

Appendix 3: Linear Predictive Coding (LPc)This is quite different from ADPCM in that the original signal or acompressed version is not transmitted. The input is sampled andthe samples processed as if they had been generated by an all -pole

digital filter type operation. In this requirement, LPC is very simi-lar to ADPCM at the input stage. However, the methods differ con-siderably beyond this point. The main advantage in LPC is that thenumber of bits required to represent a sam ple is greatly reducedwhen compared to PCM. At present, the principal application is inspeech codecs.

Figure 3 shows the general technique, but should not be takenas an accurate representation of a very complicated process. In PCM,the signals are analysed in the time domain. However, LPC uses thefrequency domain and the output block is primarily a representa-tion of the spectral information of the voice sample. Coarse spec-tral information is represented as the equivalent of filter coefficientssimilar to the overall model in the equations of Appendix 2.

Refer to voice communication in GSM. The codec is known asRPE-LTP. The voice is sampled every 20 ms and the actual outputsignal is a 260 bit block, which is processed as in Section 3 and inputto the modulator (Section 5). The block is a representation of a num-ber of different characteristics of human speech as per the previ-ous paragraph. Since the characteristics vary in importance, thebits are not of equal value. For signal processing, the block is di-vided into two main categories - 182 bits are knows as CLASS 1 andthe remaining 78 as CLASS 2. These two sub -blocks are processedseparately in accordance with the various operations in Section 3.There is a considerable difference between LPC at 260 bits every 20 ms(i.e., 13 kbits/second) and ADPCM at 32 kbits/second. LPC has majoradvantages and further research is needed.

Appendix 4: Integrated Services DigitalNetwork (IsDN)This has no direct connection with GSM, but it is envisaged that thetwo systems will be able to interface with each other. GSM is cellu-lar radio, whereas ISDN is designed to provide a very comprehen-sive range of telecommunication services, especially data, via thepublic telephone network. It does not have a radio facility. Althoughvoice is still the principal form of traffic, data has been growing steadilyover the years. The requirement for the integration of voice and datawithin the same service was essentially market driven.

ISDN is an all digital system from ened to enmd. The voice is dig-itized using ADPCM and transmitted along with other data on atraffic channel at 64 kbits/second. This type of channel is knownas the B Channel to signify bearer. Control signals are transmit-ted at 16 kbits/second on a different channel, called the D Channel.The standard interface consists of two B Channels, which are to-tally separae from one another, and one D Channel. Hence, the term2B+D is often used.

Appendix 5: Cyclic codesLet: n = block size

(xn + 1) = modulusg (x) = generator polynomialw (x) = code word represented by a polynomial of degree

(n - 1) or less.

In the majority of applications of such codes, g (x) and w (x) are fac-tors of (xn + 1). The check bits are chosen such thatg(x) divides w(x).In Section 3 the position is as follows:

Parameter Estimation

Frequency Detector forvoice Pitch

Control Logic

tgAOEb 10a.

Fig. 3. General arrangement for LPC codec.

OutputBit Block

940009 14



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n = 53 and (x53 + 1) is the modulus

g(x)= (x3 + x +1).

There is a total of eight residue polynomials: 0, 1, x, (x + 1), (x2 + 1),(x2 + x), (x2 + x + 1). The mathematical properties of the encodingoperation are:

(x53 + 1) = A (x) (x3 + x + 1) + (x2 + x + 1)

w(x) = do.x52 + dix51 + d2x50 + +d4gx3 + cox2 + cix + c2

= B (x) (x3 + x + 1) + (x2 + x + 1).

Thus, (x53 + 1) and w(x) have the same residue polynomial modulo(x3 + x + 1). In Set Theory, they are in the same equivalence class.Any element of such a class is fully representative of that class.

Appendix 6: Convolutional codeFrom the equations in Section 4:

un-2 = (v3n + v32) mod 2

un = (v36 + v38) mod 2.

The sequence of calculations at both ends is

Transmitter

v3=u,,+ un_i+ un_3 + u4 mod 2

v31 = un + un_2 + un-4 mod 2

v3,+2 = un + un_i + un_2 + un_3 + un_4 mod 2

Receiver

un_2 = v3, + v3n+2 mod 2

= v3n+3 + v35 mod 2

un = v3,+6 + v3,+8 mod 2

If an error occurs in v3,6 or v3,8, such that the calculated un is in-correct, this can be detected by calculating v3n, v31 and v3n+2 fromthe deduced un-4, u.3, un_2, un-1, and un. If these do not equal thevalues received, un should be corrected. END



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New test equipment, includes: 2.3GHz bench frequencycounter, EPROM emulator/programmer, portable 'scopesand bench function generators

Host of new components, including: compressiontrimmers, variable capacitors, connectors, fuses, andfuseholders, potentiometers, IC's, soldering irons andlead free solder

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54

MONOCHROME VGA ADAPTORToday, the choice of a monitor for your PC is limited tomonochrome VGA or colour VGA. Both types of monitor aredriven by a VGA video card which supplies analogue coloursignals. This article discusses a low-cost adaptor that gives asignificant improvement in grey value rendering when amonochrome display is connected to a VGA card.

Design by T. Scherer

THE decisive factor in the choice be-tween a colour and a monochrome

(black and white) monitor is usuallycost. If the budget is tight, most begin-ning computer enthusiasts opt for amonochrome display, which, they areinformed by shop assistants, is capa-ble of translating colour drive signalsinto corresponding shades of grey.

There are two good reasons tochoose a monochrome VGA display.Firstly, it is considerably cheaper thana colour type, the price differencebeing of the order of £100-200.Secondly, colour may not be required,for instance, if your work on the PC islimited to word processing.

Most modern PCs have a built-in256 -colour VGA card. Just in case youthink you have missed out on a few de-velopments in the PC scene, anything`below' VGA, i.e., CGA, EGA, MGA andHercules, is hopelessly out of date, ob-solete, and simply not used any more.Today's standard is the VGA videocard, which is almost invariably acolour system, and usually capable ofemulating all of the older standards.Although a monochrome mode is avail-able on most VGA cards, this is rarelyif ever used because it is a very poorlysupported feature. So, colour it is, but

how will it look on a monochromemonitor?

Unfortunately, if a monochromemonitor is connected to a VGA card,the resulting picture quality leavesmuch to be desired, mainly becausethe monitor translates the intensityvalue of a particular colour into a cor-responding grey level. Alas, this con-version is far from perfect, and somecolours are virtually lost. Even a cur-sory look at the problem reveals that itis caused by imperfections in the de-sign of the link between the VGA cardand the monochrome display. Thefault is fairly obvious: the monitorlooks at only one colour signal sup-plied by the VGA card, while the othercolour signals are simply not used.Fortunately, this shortcoming is easilyovercome with a circuit that costs nextto nothing, yet gives a significant im-provement in the quality of the pictureas it appears on your monochromeVGA screen.

The eyes have itThe picture quality on a monochromeVGA screen driven by a VGA card canbe optimized by ensuring that everycolour is properly converted into a cor-

Fig. 1. Luminance summing network in which input and output impedance requirements havebeen disregarded.

responding grey level. As already men-tioned, most inexpensive monochromeVGA monitors use only one colour sig-nal, usually red or green, to write thepicture. The result of this far too sim-ple conversion is that some picture de-tails are completely lost, while othersappear as black blocks.

A proper conversion of the three pri-mary colour signals, R, G and B, into amonochrome picture can be achievedat practically no cost. All you requireare a couple of resistors that combinethe three colours into a composite sig-nal. However, the signals can not becoupled just like that, and the valuesof the resistors need to be given someconsideration.

The human eye has different sensi-tivities for the three basic colours, red(R), green (G) and blue (B). Extensiveresearch has shown that the bright-ness, or luminance (Y), of a picturemust be composed as follows:

Y = 0.3R + 0.59G + 0.11B.

The equation shows clearly that up to40% of the picture contents are lost if,for instance, only the green componentis used to generate the Y signal.Obviously, a colour picture can only befaithfully displayed on a monochromemonitor if the colour components areadded (`summed") at the ratios given bythe above equation.

The circuitTurning the above theory into practice,i.e., implementing the summing net-work, is not as easy as one would ex-pect. A complicating factor is the needof maintaining an impedance of about70 Q at the monitor input and each of


MONOCHROME VGA ADAPTOR

Fig. 2. The same as Fig. 1, but taking into account a certain input and output impedance.

Fig. 3. From theory to practice. Circuit diagram of the monochrome VGA adaptor.

the outputs on the VGA card. Figure 1shows a network that complies withthe above luminance equation, butpays little attention to the characteris-tic impedance requirement. This cre-ates a mismatch between the monitorand the VGA card. Inevitably, some re-sistors have to be added to make surethat both the card and the monitor`see' an impedance of 70 S2. Figure 2shows an extended schematic in whichresistors R11, R112 and 12,,3 serve tocorrect the terminating impedance ofthe VGA card, while resistor Rms doesthe same for the source impedance ofthe monitor input.

The number crunching needed tocome up with the correct resistor val-ues was left to a computer. The resultis shown in Fig. 3. It will be noted thatRms and Rm2 shown in Fig. 2 are mis-sing. The reason is simple: they havesuch a high value (>10 kS2) as to haveno effect on the effective impedances.Fortunately, it was possible to roundoff the resistance values such that or-dinary resistors from the E 12 seriescould be used (resistor R3 consists oftwo 120-52 resistors connected in se-ries). Although 1% resistors may beused, the conversion accuracy of thenetwork is more than sufficient if youuse 5% types.

With some dexterity, the six resis-tors may be built into the monitor'ssub -D15 plug, provided this is not amoulded, riveted or otherwise com-pletely sealed type. To cut down cost,many monitor manufacturers omitnon -used pins on the D15 connector.Unfortunately, that means that youhave to purchase a new connector.

Before you start soldering, cover theinside of the connector with insulatingtape. This prevents short-circuits withthe metal layer which is often dampedonto the plastic connector hoods. Thephotograph in Fig. 4 shows the au-thor's prototype of the adaptor.

After installing the VGA adaptornetwork, the monitor should show apicture with perfect grey levels, and nopicture elements missing. If not, checkthe settings of the VGA card, and thoseof the brightness and contrast controlson the monitor. As regards the VGAcard, be sure to have this running in256 -colour mode, not, of course, inany of the (primitive) monochromemodes.

Fig. 4. Prototype of the adaptor network fitted into a 15 -way sub -D connector.



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58

TELEPHONE -CONTROLLED SWITCH

'Nos"

,'""`r.\ti.' '''A \'VW 410.1, 1.111011. AVM Ilk 46,w. 41i14010/Mkal.O.MINNMIPPONO.

Sea

sow ilk. ...wart.

The switching unit described here is capable of controlling upto seven mains -powered loads with the aid of commandsreceived via telephone. Any tone -dialling (DTMF) telephone setor hand-held tone dialler may be used to send commands tothe switching unit, and remotely control a wide range of mainsappliances in and around the home. With personal accesscode and system feedback!

Design by F. Zapf

THE circuit is connected to the tele-phone network* just like any nor-

mal telephone set. On being called, thecircuit waits a predetermined numberof ring signals, and then answers thecall (electrically, it 'lifts the receiver').Next, it waits for a pre-programmedsystem access code, which the callermust transmit with the DTMF keypadon his telephone.

The unit is capable of switching upto seven loads on and off. By virtue ofrelays, high voltages and currents maybe switched, so that loads may includemains -powered ones. Reception of thecorrect system code is acknowledgedwith a short tone, which the caller can

hear. Next, load number '1', for in-stance, a coffee machine, may beswitched on by pressing the '1' key twotimes. The same load is switched off bydialling 1 and then 0. The status ofload '1' (on or off) may be called up bypressing 1 and then 2 on the DTMFkeypad. The switching unit respondsto this by two short tones to signalthat the load is on, or a single longtone to signal that the load is off. Thecontrol of the other six loads is identi-cal to that of load '1', i.e., the channel(load) number is dialled first, then 0 or1 for switching off or on, or 2 to re-quest the channel status. An exceptionis formed by number 8: dialling this

* The term 'telephone network' in this article refers to a closed system installed in the home or office.The switching unit described here is not BT type -approved for connection to the Public TelephoneNetwork (PTN).

number allows you to switch all chan-nels on or off simultaneously. On/offstatus requesting does not work in thismode.

The circuitThe heart of the circuit diagram, givenin Fig. 1, is formed by an 8031 micro -controller. The computer control sec-tion sits between a telephone interfacecircuit and a power switching inter-face. An integrated DTMF decoderType MV8870 (Fig. 2) decodes the tonedialling codes received via the tele-phone line.

The telephone line interface con-sists of two parts: one to detect thering signals that enables the unit toanswer the call at the right moment,and another to receive and transmittones via the telephone line.

The ringing signal detector is rela-tively simple. A bridge rectifier, D3 -Ds,connected to the telephone lines (à'and 'b') turns the ringing signal (an al-ternating voltage) into a pulsating di-rect voltage, which is smoothed by C3,and limited to 15 V with the aid ofzener diode D7. The direct voltageacross D7 supplies the LED in opto-coupler IC7, with resistor Rs acting asa current limiter. During the ringingsignal, the collector of the phototran-sistor in the optocoupler (pin 8) is atground potential. The microcontroller,ICI, interrogates the state of the opto-coupler output signal via port lineP1.7. To suppress error pulses, the lowlevel at the optocoupler output is alsoused to trigger monostable multivibra-tor (MMV) ICs. The MMV's monotime isstarted by the ringing signal, and sup-plies a logic high level to microcon-troller pin INTO/P3.2 for about10 seconds. This is the period avail-able for transmitting codes to theswitching unit. As long as the circuithas not 'lifted the receiver', i.e., as longas relay Re i is not energized, the MMVis triggered again via the RET connec-tion.

The coupling with R7 -C2 ensuresthat the ringing signal detector re-sponds to alternating voltage only. Anydirect voltage levels that may exist be-tween terminals 'a' and 'b' are ignored.An LED, D o, provides a visual indica-tor for the call and DTMF signals.

When the microcontroller hascounted the programmed number ofringing pulses, it responds by pullingoutput P1.6 logic high, which causesrelay Rei to be energized via Rs and Ti.This means that the switching unit`lifts the receiver', i.e., answers the


TELEPHONE -CONTROLLED SWITCH 59

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Fig. 1. Circuit diagram of the telephone -controlled DTMF switching unit -a typical microcontroller application circuit based on a 8031.


60 TELECOMMUNICATIONS

VDD VSS VREF

IN+

IN -

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BIASCIRCUIT

CHIP CHIPPOWER BIAS

OSC1

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Fig. 2. Internal structure and pinning of the M-8870 DTMF decoder from Teltone (second source: Plessey Semiconductors).

call. Consequently, the series networkR4 -R5 and the primary winding of tele-phone line transformer Tn is con-nected to the 'a' and `b' lines via the

Resistors:2 8k122

10 10k0

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7 11(021 39k01 56k01 2701d)

Capacitors:4 100nF MKT11 100nF ceramic

1 22µF/35V radial1 101.1F/10V radial2 47pF1 4µF7/16V radial2 100gF/25V radial1 470µF/10V2 10nF/1500V MKT2 1000gF/35V radial

Semiconductors:1 B40C1500/10002 zener 5V6/400mW16 1N4148

Rl;R2R3;R6;R10;R17 -R23R4R5R7R8R9;R11R12;R13R14R15R16;R31;R32;R35R24 -R30R33R34R36

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D1;D2D3-D6;D8; D9;D11-019

relay contacts. The current flowingthrough this network is sufficientlylarge to maintain the connection. Oneend of the transformer secondary

' 1 zener 15V/400 mW1 LED red 3mm

(w. mounting clip)6 LED green 3mm

(w. mounting clip)9 BC5471 BC5161 8031 or 800312 74HC5731 27C64 (order code

6271; see page 70)74H000

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pitch 5mm1 14 -way box header and

IDC socket2 16 -way boxheader and

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pitch 7.5mm1 V23037 -A0002 -A101

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winding is connected to the positivesupply voltage via RI, while the otherend is connected to ground via R2 andT2. This means that rectangular volt -

1 Mains transformer 15V/8VA(e.g., Monacor/Monarch4VR8115) Tr2

1 Crystal 3.579545MHz X1

1 Crystal 12MHz X21 Heat -sink Ski 29/251 Type 'Power Manager' case;

Conrad6 order code 999008-111 Printed circuit board and EPROM

6271, set order code 934054 (seepage 70)

1 Chesilvale Ltd , 10 Woodland Road,Clifton, Bristol BS8 1 UQ Telephone.(0272) 736166, fax (0272) 736516.2 2001 Electronic Components {0438)742001; Celdis Ltd (0734) 585171, ESDDistribution (0279) 441144; FarnellElectronic Components (0532) 636311;Gothic Crellon Ltd. (0734); Semiconduc-tor Specialists (UK) (0895) 445522;Unite' Ltd. (0438) 312393.3 ElectroValue, Unit 3, Central TradingEstate, Staines, Middlesex TW18 4UXTelephone: (0784) 442253. Fax: (0784)460320.4 Monacor Nederland BV, P 0. Box 40,6580 AA Malden, Holland. Telephone:(+31) 80 585400 Fax: (+31) 80 584790.5 C -I Electronics, P.O. Box 22089,6360 AB Nuth, Holland. Fax: (+31) 45241877.6 Conrad Electronic Nederland By, P 0.Box 12, 7500 AA Enschede, HollandTel (+31) 53 282000 Fax: (+31) 53283075.


61

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TELEPHONE -CONTROLLED SWITCH

ages generated by the controller online TO/P3.4 are coupled directly on tothe telephone network lines. Two zenerdiodes, Di and D2, limit the voltageacross the secondary winding to safelevels.

The received DTMF signals are ca-pacitively coupled to the decoder, 1C8.The external components that enablethe M8870 DTMF decoder to operatereliably are limited to four resistors, acapacitor and a quartz crystal. Thefour decoder outputs, Q1 -Q4, supply abit pattern that corresponds to the re-ceived DTMF number, sign or letter.The structure of the bit pattern isgiven in Table 1. The 4 -bit DTMF codeis applied to the microcontroller viaport lines P1.0 to P1.3.

The microcontroller has its externaladdress (EA) line tied to ground, andfetches its instructions from an exter-nal 8-KByte EPROM Type 27C64. Theaddress and data signals are demulti-plexed at port PO by an 8 -bit latchType 74HC573. A RAM IC is not foundin this application, since it is not re-quired to store large amounts of data.The only two user programmable para-meters, the number of ringing signalsand the 'access code', are convenientlystored in the controller's internal RAM.A second 8 -bit latch with three -stateoutputs, 1C2, allows the controller tooutput 8 -bit words. Seven of the eightlatch output bits Q I -Q8 are used tocontrol relays Re2 to Re8 and LEDs D20to D26 via driver transistors T4-Tio.Both the relays and the LEDs are'commoned' to the 12-V positive sup-ply rail. This enables 'true' logic to beused, i.e., a logic one at latch outputQ I -Q7 switches the associated relayon. Flyback diodes D 13-D 19 protect theswitching transistors against back-e.m.f. surges produced by the relaycoils when these are switched off.

The power supply of the telephone -

controlled switch is conventional, andbased on fixed voltage regulators. The12-V and 5-V supply voltages used forthe relay sections and the digital sec-tions respectively are derived from asingle mains transformer with a sec-ondary voltage of 15 V.

ConstructionThe artwork of the single -sided printedcircuit board designed for the tele-phone controlled switch is shown inFigs. 3a and 3b. The board consists oftwo parts. One accommodates themains transformer, the power supplyand the relays, the other, the tele-

Fig. 3a. Component mounting plan of theprinted circuit board designed for the tele-phone -controlled switch.



phone line interface and the microcon-troller circuit. Before you start fittingparts, separate the two boards by cut-ting.

Populating the boards is straightfor-ward since the component densitiesare fairly low. It is good practice tostart with the low -profile parts, fol-lowed by the taller and larger ones.

On the component overlay, smalltriangles indicate the position of pins`1' of boxheaders or pin headers K2, K3and K12. Boxheaders are preferredhere because of their greater stabilityand orientation notches, which makeit impossible to insert the flatcableconnector the wrong way around.

The channel activity LEDs, D20 toD26, are not fitted on to the board. It issuggested to mount these LEDs on tothe enclosure front panel, near the de-vice on/off switches, and connectthem to the board via a length of flat -cable and press -on (IDC) connectors.

The eight connectors marked withasterisks (*) in the wiring diagram inFig. 4 are the seven mains sockets towhich the loads are connected, andthe mains input socket.

Mechanical constructionThe presence of the mains voltage inthe circuit rules that the enclosure ofthe telephone -controlled switch beelectrically safe in all respects. To meetthis requirement, and to keep mechan-ical work to a minimum, the prototypeof the telephone -controlled switch wasbuilt into a 'Power Manager' case sup-plied by Conrad Electronics. This caseis basically an on/off switching unitfor seven mains powered devices. Thecase only contains wiring, a mainsinlet, seven switches plus neon lamps,and seven mains sockets to which ap-pliances are connected. The switcheson the front panel allow each appli-ance to be individually switched onand off. The case contains no elec-tronic parts, only electromechanicalparts and wiring.

The holes in the relay board are lo-cated such that the board is easily se-cured on to the mounting screws forthe mains socket strip in the PowerManager case. The board is securedwith the aid of M4 (4 -mm) PCB stand-offs and screws. The other board is fit-ted on to the enclosure bottom platewith the aid of PCB spacers, nuts andscrews. Finding a suitable location forthe board is not a problem becausethere is plenty of space.

The actual construction of the

Fig. 3b. Track layout (direct reading) of thePCB designed for the telephone -controlledswitch.



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Fig. 4. Circuit diagram of the power supply and mains/switching sections.

Power Manager case is a little un-usual. The switches and the mainssockets are fitted on to the angledfront and rear part, respectively, of thecover plate. Since all wires run under-neath the cover plate, travelling thedistance between the switches and thesockets, the free space inside the caseis almost fully crossed by wires. If youwant to construct your switching unitlike our prototype, it is, unfortunately,necessary to install completely newwiring, and bundle wires in neattrunks.

OperationApart from the central on/off switchand the channel on/off switches onthe front panel, the telephone -con-trolled switch has no local controls. Allcommands reach the unit via the tele-phone line in the form of DTMF codesgenerated on a telephone set with atone dialling keypad, or a pocket tonedialler. Commands are, obviously, onlyaccepted if the unit has answered thecall. Wrong commands or pauseslonger than 10 seconds cause the unitto transmit a long signal and then ringoff.

As already mentioned, the com-mands consist of two numbers pressedon the telephone keypad. The firstnumber is the channel number, 1

through 7, and the second number iseither 0 (channel off), 1 (channel on),or 2 to request the on/off status of thechannel.

Pressing 8 followed by 0 or 1

switches all channels off or on respec-tively.

The system access code is a kindof personal identification number (PIN)that prevents non -authorized use ofthe switching unit. To program or re-program the system access code, waitfor the unit to answer your call, andthen dial *1. The unit responds withtwo short signals. You now have sev-eral options. Pressing # disables theaccess protection, and clears the exist-ing access code. This is confirmed bythe unit producing a long and a shortsignal, and then ringing off.

To overwrite or program an accesscode for the first time, the desired codeis entered following the *1. The codecan have up to eight numbers, and theunit confirms reception of each ofthese by a short signal. The sequenceis terminated by pressing the # key,which, consequently, can not be partof the system access code. On receiptof the # tone, the unit transmits a longand a short signal. Pressing # is notrequired if the access code consists ofexactly eight numbers. The new accesscode is retained until it is overwritten,or the unit is switched off and onagain. When this happens, the access


TELEPHONE -CONTROLLED SWITCH 65

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spond by transmitting two short sig-nals. Next, enter the desired number ofringing pulses before the unit will an-swer a call. First enter the tens (0, 1 or2), then the units (1 through 9). Each

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acceptable entry is confirmed by theunit transmitting a short signal.Reception of a wrong number causesthe unit to transmit a long signal andthen break the telephone connection.If the number of ringing pulses is ac-cepted, the unit responds with an in-terrupted signal, whereupon it ringsoff. The programmed number is re-tained until it is overwritten, or resetto the default value of 6 when the unitis switched off and on again.

The third special function is theDTMF transmitter test, which is in-voked by calling the unit, and pressing*3. In this mode, the unit responds tothe number pressed on the telephoneby generating a corresponding numberof short signals, for instance, four ifyour press the '4' on your telephone.Pressing the *, # or letter code (A -D)keys should produce 11, 12 or 13through 16 short signals. A pauselonger than 10 seconds prompts theswitching unit to ring off.

Table 1. M8870 DTMF decoder output codes as a function of received tone pair. The OE (output enable) input allows all outputs to be switched to high -impedance.



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STX High-periormance Room TransmitterHi performance transmitter with a buffered output stage for greater stability and range.Measures 22mm x 22mm including mic. 6-12V operation, 1500m range £15.45

VT500 High -power Room TransmitterPowerful 250mW output providing excellent range and performance. Size 20mm x40mm. 9-12V operation. 3000m range £16.45

VXT Voice Activated TransmitterTriggers only when sounds are detected. Very low standby current. Variable sensitivityand delay with LED indicator. Size 20mm x 67mm. 9V operation. 1000m range £19.45

HVX400 Mains Powered Room TransmitterConnects directly to 240V AC supply for long-term monitoring. Size 30mm x 35mm.500m range £19.45

SCRX Subcarrier Scrambled Room Transmitter

Scrambled output from this transmitter cannot be monitored without the SCDM decoderconnected to the receiver. Size 20mm x 67mm. 9V operation. 1000m range £22.95

SCLX Subcarrier Telephone TransmitterConnects to telephone line anywhere, requires no batteries. Output scrambled sorequires SCDM connected to receiver..Size 32mm x 37mm. 1000m range £23.95

SCUM Subcarrier Decoder Unit for SCRXConnects to receiver earphone socket and provides decoded audio output toheadphones. Size 32mm x 70mm. 9-12V operation £22.95

ATR2 Micro Size Telephone Recording InterfaceConnects between telephone line (anywhere) and cassette recorder. Switches tapeautomatically as phone is used. All conversations recorded. Size 16mm x 32mm.Powered from line £13.45

*** Specials ***OLVIMIAX Radio Control SwitchRemote control anything around your home or garden, outside tights, alarms, pagingsystem etc. System consists of a small VHF transmitter with digital encoder and receiverunit with decoder and relay output, momentary or alternate, 8 -way dil switches on bothboards set your own unique security code. TX size 45mm x 45mm. RX size 35mm x90mm. Both 9V operation. Range up to 200m.Complete System (2 kits) £50.95Individual Transmitter DLTX £19.95Individual Receiver DLRX £37.95

MOM 11141 Micro BroadcasterNot technically a surveillance device but a great idea! Connects to the headphone outputof your Hi-Fi, tape or CD and transmits Hi-Fi quality to a nearby radio. Listen to yourfavourite music anywhere around the house, garden, in the bath or in the garage andyou don't have to put up with the DJ's choice and boring waffle. Size 27mm x 60mm.9V operation. 250m range £20.95

A

UTLX Ultra -miniature Telephone TransmitterSmallest telephone transmitter kit available. Incredible size of 10mm x 20mm!Connects to line (anywhere) and switches on and off with phone use.All conversation transmitted. Powered from line. 500m range £15.95

TLX700 Micro -miniature Telephone TransmitterBest-selling telephone transmitter. Being 20mm x 20mm it is easier to assemble thanUTLX. Connects to line (anywhere) and switches on and off with phone use. Allconversations transmitted. Powered from line. 1000m range £13.45

STLX High-performance Telephone TransmitterHigh performance transmitter with buffered output stage providing excellent stabilityand performance. Connects to line (anywhere) and switches on and off with phone use.All conversations transmitted. Powered from line. Size 22mm x 22mm.1500m range £16.45

TKX900 Signalling/Tracking TransmitterTransmits a continous stream of audio pulses with variable tone and rate. Ideal forsignalling or tracking purposes. High power output giving range up to 3000m. Size25mm x 63mm. 9V operation £22.95

CD400 Pocket Bug Detector/LocatorLED and piezo bleeper pulse slowly, rate of pulse and pitch of tome increase as youapproach signal. Gain control allows pinpointing of source. Size 45mm x 54mm. 9Voperation £30.95

CD600 Professional Bug Detector/LocatorMulticolour readout of signal strength with variable rate bleeper and variable sensitivityused to detect and locate hidden transmitters. Switch to AUDIO CONFORM mode todistinguish between localised bug transmission and normal legitimate signals such aspagers, cellular, taxis etc. Size 70mm x 100mm. 9V operation £50.95

QTX180 Crystal Controlled Room TransmitterNarrow band FM transmitter for the ultimate in privacy. Operates on 180 MHz andrequires the use of a scanner receiver or our ORX180 kit (see catlogue). Size 20mm x67mm. 9V operation. 1000m range £40.95

QLX180 Crystal Controlled Telephone TransmitterAs per OTX180 but connects to telephone line to monitor both sides of conversations.20mm x 67mm. 9V operation. 1000m range £40.95

QSX180 Line Powered Crystal Controlled Phone TransmitterAs per OLX180 but draws power requirements from line. No batteries required. Size32mm x 37mm. Range 500m £35.95

GRX180 Crystal Controlled FM ReceiverFor monitoring any of the '13' range transmitters. High sensitivity unit. All RF sectionsupplied as a pre -built and aligned module ready to connect on board so no difficultysetting up. Outpt to headphones. 60mm x 75mm. 9V operation £60.95

A build-up service is available on all our kits if required.UK customers please send cheques, POs or registered cash. Please add£1.50 per order for P&P. Goods despatched ASAP allowing for chequeclearance. Overseas customers send sterling bank draft and add £5.00 perorder for shipment. Credit card orders welcomed on 0827 714476.

OUR LATEST CATALOGUE CONTAINING MANY MORE NEWSURVEILLANCE KITS NOW AVAILABLE. SEND TWO FIRSTCLASS STAMPS OR OVERSEAS SEND TWO IRCS.

- 1:


. I :

68

DX TELEVISI N

A two -monthly column by Keith Hamer and Garry Smith

SUSTAINED openings throughoutAugust gave way to a dramatic drop

in sporadic -E activity within the first fewdays of September. On the whole, theseason has been a satisfying one for mostlong-distance TV enthusiasts, despite itbeing a comparatively short one.

Reception from the Middle East hasbeen less favourable for DX-ers in theUnited Kingdom this season, whereas inEurope Iranian transmissions have beenregularly identified on channels E2, E3and E4. To make up for this, enthusiastsin the United Kingdom have witnessedat least three transatlantic openings thisseason, albeit short ones. Although lateAugust is not traditionally an 'exotic' pe-riod, the 22nd brought in 525 -line signalson channels A2 and A3 for ten minutesfor Simon Hamer in New Radnor(Powys). During the same opening,Band III sporadic -E signals were evidentfrom Iceland on channels E6 and E7, andlater from Denmark on channel E5. Thisis the only reported incidence of Band IIIsporadic -E reception so far this season.Simon had virtually an identical patternof reception in early June 1988, and twodays later signals from Algeria, Libyaand Tunisia were seen in Band III.Unfortunately, these signals were notaround on this particular occasion!

August 21st was also an action -packed day, with continuous receptionfrom early morning until late at night.Signals were first noted fromScandinavia, then Central Europe, withfavourable reception from stations to thesouth-east and south during the earlyevening.

September saw a sudden decline in ac-tivity with signals mainly from the southon the 4th and 5th. The last opening ofany significance occurred on the 10thwith signals from Scandinavia and Spainin evidence throughout the day.

Reception reportsTim Webbs (New Romney) watched ex-cellent -quality tropospheric signals fromBelgium, France and the Netherlands onSeptember 8th, using an AntiferenceXG14 wideband array, without a mast-head amplifier. Of particular importancewas his reception of 'Zuid-Holland TV', anew regional station on channel E49with an ERP of around 10 kW. At thetime of his reception (1845 UTC), colourbars were being transmitted.

lain Menzies (Aberdeen) has recentlyreturned from the French Alps, withnews of DX -TV possibilities there.During his visit, lain logged NRK, TVE,RTP and some stations from the formerYugoslavia in Band I. Tropospheric re-ception on channel E4 from La Dole inSwitzerland, and a French station justabove E4 (channel L4) were evident. RAIUno on channels IA and IB also appearedby tropospheric enhancement on someevenings.

Chris Howles (Erdington) reports amystery `JRT BGRD-1' (Serbia) PM5544test card seen on channel R2 during thesecond half of August. The test patternwas floating with other known channelR2 signals, thus confirming the fre-quency. One possible explanation is thatan Eastern European country was relay-ing Serbian TV from Eutelsat II -F4. TheSerbian TV logo `PTC B1' has also beenseen on channel R1 by other enthusiasts.

Marc Vissers (Belgium) has receivedmost of the ùsuals' this summer, such asTVE-1, RTP-1, RAI UNO, OK -1 (Russia)and HTV-1 (Croatia). In addition, somerarer signals were noted including MRT-1 (Macedonia), and surprisingly TVShqiptar (Albania) on channel C. Thislatter transmitter is no longer listed inthe WRTH 1993, but the station wasidentified by the PM5534 test card, indi-cating that it is still on -air.

Stephen Michie (Bristol) commentsthat August was quite reasonable withCIS programmes being seen fromLatvian transmitters. Stephen queriesLatvia's TV transmitters listed in publi-cations such as the WRTH, and wonderswhether these are locally produced ser-vices or relays of Ostankino TV (Russia).The identifications used on the G-204test pattern are also causing concern formay DX-ers. The different idents seemmeaningless, and do not indicate thecountry of origin.

At 1237 UTC on August 15th, Stephennoticed an announcer on channel E4 withthe initials `MRT' in the top right-handcorner of the picture. This signal isthought to have originated from thePelister transmitter in the south ofMacedonia.

Bernd Trutenau (Lithuania) has cor-rected a news item concerningLithuania. The channel R11 transmitteris no longer atop the parliament buildingin Vilnius (it was originally installedthere for security purposes during the

/ * ,

#

Swedish programme schedule received byBob Brooks via sporadic -E on channel E2.

period of occupation of the facilities ofLithuanian Radio and TV in 1991).Channel R11 programmes are nowbroadcast from the main TV/FM tower inVilnius from where the other TV pro-grammes are also aired.

Log for AugustSporadic -E reception occurred on mostdays throughout the month, but only themore prolonged openings are shownbelow.12.08.93: Sporadic -E signals between0605 and 1447 UTC; Sweden E3; NorwayE3 and E4; Spain E3; Denmark E3;many unidentified signals on channelsR1 and R2.14.08.93: Reception from 0705 until1705 UTC: Spain E3 and E4; Italy IA andIB; Czech Republic R2; Hungary R2;Poland R1; Switzerland E2.21.08.93: An excellent all -day openingbetween 0844 and 2250 UTC with sig-nals from Sweden E2 and E3; NorwayE3; Poland R1, R2 and R3; Denmark E3;Hungary R2; Italy IA and IB; Spain E2,E3 and E4; Portugal E4; Czech RepublicR1; Corsica on channel L3.15.08.93: Signals between 0719 and0815 UTC: Czech Republic R1; AustriaE2a; Italy IA and IB; Norway E2 and E3;Macedonia E4; Germany E2.22.08.93: Sporadic -E reception between0851 and 1916 UTC included: NorwayE2, E3 and E4; Sweden E2, E3 and E4;Denmark E3, E4 and E5; Poland R1, R2and R3; Czech Republic R2; Slovakia R2;Spain E2; CIS R1, R2, R3 and R4;Albania IC; USA/Canada A2 and A3;Iceland E3, E4 and E6.23.08.93: Reception from 0715 until 1330UTC included: Iceland E4; Portugal E2and E3; Spain E2, E3 and E4; Italy IA;Hungary Rl.25.08.93: Sporadic -E noted between 0740and 2105 UTC included: Sweden E2, E3and E4; CIS R1, R2, R3 and R4; Italy IAand IB; Rumania R3; Poland R1; FinlandE4.26.08.93: Reception between 0845 and2030 UTC: Norway E2 and E3; SwedenE2 and E3; Portugal E3; Spain E2 andE3; Czech Republic R1; Slovakia R2;Slovenia E3; Germany E2.


DX TELEVISION 69

30.08.93: Countries identified from 0619until 1700 UTC included: Italy IA andIB; Corsica L2; Spain E2 and E3; CzechRepublic R1; CIS R2; Sweden E2, E3 andE4; Norway E2 and E3; Finland E3;Iceland E3.

Log for September04.09.93: Sporadic -E reception mostlyaround midday: Norway E4; France L2and L3; Spain E2, E3 and E4.10.09.93: Norway E3; Sweden E2; SpainE2 and E3 (including various regionalnews programmes around midday).

The DX -TV logs were kindly supplied byAndrew Jackson, Stephen Michie, SimonHamer, Bob Brooks, Garry Smith andBarry Bowman.

German DAB plansshelvedPlans for the introduction of DAB(Digital Audio Broadcasting) in 1995have been shelved by ARD due to a short-age of funds. It seems that 1997 will bethe earliest possible starting date, de-pending on whether the EC or theGerman government will help to financethe project. It will cost at least DM30 million just to vacate channel E12,which is the part of Band III where DABtransmissions would be.

Service informationBelgium: BRTN is to reduce its airtimeas part of a drastic cost-cutting exercise.Needless to say, plans for the introduc-tion of morning television and the exten-sion of afternoon transmissions havebeen shelved. This is mainly as a resultof fierce competition from its commercialrival, VTM, with the resultant loss of ad-vertising revenue. BRTN intends to re-main committed to information,education and general entertainmentprogrammes rather than move down-market, presumably resisting Americanimports and 'satellite -style' TV.However, BRTN could face further prob-lems when new rules allow Dutch ser-vices to be distributed by cable.

The Belgian government is to allow anincrease in power (400 W maximum) for50 MHz amateur operation, with no re-strictions on the type of transmittingaerial used.France: Two new channels (one educa-tional, the other news) may soon belaunched by TF1. The educational chan-nel will broadcast during the day via theformer La Cinq transmitters, which atpresent broadcast ARTE from late after-noon onwards.Netherlands: Programmes are beingshown as early as 0700 local time via theNED-1 network.

Omroep Fryslan, a local TV service inthe province of Friesland, is planning to

Identification caption received by BobBrooks from the Eesti TV (Estonia)transmitter at Tallinn on channel E2.

be on the air from January 1994, but ini-tially the service will only be availablevia cable. The proposed channels for theservice (from the Franeker transmitter)are E22, E25 and E28 with a maximumERP of 300 kW.

'Zuid-Holland TV' (`ZH-TV') is now ontest on channel E49 with an ERP of ap-proximately 10 kW. The proposed start-ing date was September 1st, 1993, but bylate September test transmissions, con-sisting of colour bars (with the identifica-tion `NOZEMA', `KANAAL 49' and'ZUID-HOLLAND TV') were continuing.At present, a temporary 'standby'Marconi transmitter is in use, but thefinal transmitter will be located at thePTT tower at Rotterdam-Waalhaven,with the aerials mounted at a height of200 m ASL.

The Dutch publisher VNU and theLuxembourg television company CLT arelaunching the country's second commer-cial channel, RTL5, which will offersport, films and 'adult' entertainment.This new service will originate inLuxembourg.Germany: SW -3 is now showing aVetterpanorama' after closedown for thebenefit of tourists. The information cov-ers many areas of southern Germany. Anew private regional TV service called`Schamoni-TV' is coming on -air soon inthe Berlin area. The studios are locatedat the foot of the Alexanderplatz TVtower.Austria: ORF-2 now shows aVetterpanorama' programme during themorning.Luxembourg: The Dudelange transmit-ter on channel E7 is currently operatingwith an ERP of 130 kW.Switzerland: Only the SSR-1 (Frenchlanguage) network seems to show theFuBK test card at switch -on; the DRSand TSI networks show text pages (TextVision). All three networks open at0600 UTC without an opening sequenceor identification logo, and switch straightto 'Euronews'. The same pictures areshown via the three networks with soundstraight in the appropriate langauge, ei-ther French, German or Italian, depend-ing on the network.

Sweden: SVT-1 has been showing colourbars with a special test transmission an-nouncement. A PM5544 test patternheaded `TV1' has been radiated, as wellas the usual 'SVERIGE' PM5534.Portugal: The new names for thePortuguese first and second networksare 'Canal 1' and `TV -2' respectively.Finland: MTV has launched a specialnews programme called `Talousuutiset',which reports on various issues aboutthe economy. It commenced in August,and is screened after the regular news onMTV -3 on Mondays at 1920 (local time)and on Tuesday to Friday at 2220 (localtime). Local television broadcasts havecommenced in Narpio. They have alsobeen available in Kristiinankaupunkifrom August 16th.Slovakia Republic: The STV-1 trans-mitter at Bratislava/Kamzik is nowusing CCIR system B with 5.5 MHzsound spacing.Poland: TVP-2 will commence using thePAL colour system from January 1st,1994. There are many SECAM-only re-ceivers still in existence, but the type ofcompensation for viewers with these setshas yet to be agreed.Moldova: TV Moldova is relaying vari-ous satellite services at the followinglocal times: 1000-1015: news from TRT(Wednesday and Friday Euronews);1700-1715: News from TV5. The channelR3 transmitter at Chisinau/Straseni isreported to have an ERP of 800 kW!Jordan: A teletext service has now beenintroduced.Iraq: Iraq Television International plansto establish a DBS satellite service usingArabsat and Eutelsat transponders fromthe end of 1993. Coverage will extend tomore than 35 countries in Asia andEurope.Israel: The franchises for a commercialsecond network (Channel 2) have beenawarded to three of the seven groupsthat tendered for the licence - after await of more than 15 years!. The pro-posed opening of Channel 2 is plannedfor October. Each franchise owner will beallocated two days per week for broad-casting, with Saturdays assigned to thethree groups in rotation.Samoa: The TV New Zealand PacificService and its transmission subsidiaryBCL have helped establish 'TeleviseSamoa', which went on -air last May.

This month's service information waskindly supplied by Gosta van der Lindenand the BDXC, Netherlands; Reflexion,Germany; Garry Smith, UK; PerttiSalonen, Finland; Roger Bunney, UK;Andrew Emmerson, UK; Thomas Pahlke,Germany; Bernd Trutenau, Lithuania.

Please send any news about DX -TV inyour part of the world to: Keith Hamer, 7Epping Close, Derby DE3 4HR, England.


70

READERS SERVICESExcept in the USA and Canada, all orders, except forsubscriptions and past issues (for which see below),must be sent BY POST to our Dorchester office usingthe appropriate form opposite. Please note that wecan not deal with PERSONAL CALLERS, as no stockis carried at the editorial and administrative office.Readers in the USA and Canada should send orders,except for subscriptions (for which see below), to OldColony Sound Lab, Peterborough, whose full addressis given on the order form opposite. Please includeshipping cost according to total order value. For sur-face delivery in the USA, if order is less than $50, in-clude $3; $50+, $4. For Canada surface, if less thanUS$50, include US$5; US$50+, US$7.50. For air orother deliveries, please inquire. Please allow 4-6weeks for delivery.All other customers must add postage and packingcharges for orders up to £25.00 as follows: UK andEire £1.95; surface mail outside UK £2.45; Europe(airmail) £2.95; outside Europe (airmail) £3.70. For or-ders over £25.00, but not exceeding £100.00, thesep&p charges should be doubled. For orders over£100.00 in value, p&p charges will be advised.

SUBSCRIPTIONS & PAST ISSUESSubscriptions and past issues, if available, should beordered from Worldwide Subscription Service Ltd,Unit 4, Gibbs Reed Farm, Pashley Road, TICE-HURST TN5 7HE, England. For subscriptions, usethe order form on the opposite page. Prices of past is-sues (except July/August and December), includingpostage for single copies, are £2.70 (UK and Eire);£3.00 (surface mail outside UK); £3.20 (air mailEurope); £3.95 (airmail outside Europe). Prices of pastJuly/August and December issues, including postagefor single copies, are £3.75 (UK); £4.00 (surface mailoutside UK); £4.25 (airmail Europe); and £5.00 (air-mail outside Europe).

PAST ARTICLES

Photocopies of articles from January 1978 onwardscan be provided, postage paid, at £1.95 (UK and Eire),£2.10 (surface mail outside UK), £2.45 (airmailEurope), or £2.70 (airmail outside Europe). In case anarticle is split into instalments, these prices are applic-able per instalment. Photocopies may be orderedfrom our editorial and administrative offices.

COMPONENTS

Components for projects appearing in Elektor Elec-tronics are usually available from appropriate advertis-ers in this magazine. If difficulties in the supply ofcomponents are envisaged, a source will normally beadvised in the article. It should be noted that thesource(s) given is (are) not exclusive - other suppli-ers may also be able to help.

BOOKSFor book availability, see advertisement on page 23.

SHELF BOX

Elektor Electronics shelf box £2.95 $6.00

FRONT PANELS

PROJECT

Timecode interfaceDigital functiongenerator

4 -Megabyte printerbufferFM tuner4MB printer buffer cardLC meterGuitar tunerNICAM decoder12VDC to 240VACinverter

Audio DACDig. audio/visual system

1.2 GHz multifunctionfrequency meterU2400B NiCd batterycharger

No.

910055-F

910077-F

910110-F920005-F920009-F920012-F920033-F920035-F

920038-F920063-F

920022-F1920022-F2920022-F3

Price Price(£) (US$)

8.80 17.60

10.60 21.20

11.45 22.9013.20 26.408.25 16.50

11.45 22.908.80 17.608.25 16.50

16.15 32.3010.00 20.0010.00 20.0019.40 38.8028.80 57.60

920095-F 13.80 27.60

920098-F 8.75 17.50

PROJECT No. Price Price(£) (US$)

Workbench PSU 930033-FInexpensive phase meter 930046-FMIDI channel monitor 930059Ah meter w. digital readout 930068Autoranging frequencyreadoutElectronic loadAF rms voltmeter

930034930088

930108-F

17.00 34.0017.25 34.50Not availableNot available

Not availableNot available17.25 34.50

EPROMS / PALS / MICROCONTROLLERSAmiga mouse/joystickswitch (1 x GAL 16V8) 6001 8.25 16.504 -Megabyte printer buffer(1 x 2764) 6041 15.30 30.608751 emulatorincl. system disk (MSDOS) 6051 29.40 58.80Connect 4 (1 x 27C64) 6081 15.30 30.60EMON51 (8051 assemblercourse) (1 x 27256 +disk 1661) 6061 20.00 40.00EMON51 (8051 assemblercourse) (1 x 27256 +disk 1681) 6091 20.00 40.00FM tuner (1 x 27C256) 6101 20.00 40.00Multi -purpose Z80 card:GAL set (2 x GAL 16V8) 6111 11.15 22.30Multi -purpose Z80 card:BIOS (1 x EPROM 27128) 6121 15.30 30.601.2 GHz multifunctionfrequency meter(1 x 27C256) 6141 11.45 22.90Digital audio/visual system(1 x 27C256) 6171 10.30 20.60TV test pattern generator(1 x 27256) 6151 13.00 26.00DiAV system. Package:1 x 27512; 2 x GAL; 1 xfloppy disk (MSDOS) 6181 30.50 61.00PAL test pattern generator(1 x GAL 20V8-25) 6211 9.40 18.60Watt-hour meter (1 x 27256) 6241 10.00 20.00Four fold DAC (1 x GAL) 6251 10.75 21.50Multipurpose display decoder(1 x 2764) 6261 11.50 23.00Telephone -controlled switch(1 x 2764) 6271 14.50 29.00Relative humidity meter(1 x 2764) 6301 14.50 29.00535 card w. EPROM emulator(1 x PAL; 1 x GAL) 6311 26.00 52.00RDS decoder (1 x 27C64) 6331 14.50 29.00I2C tester (1 x GAL 6001) 6341 30.75 61.508751 programmer (1 x 8751) 7061 46.40 92.80Microcontroller NiCd charger(1 x ST62E15) 7071 10.00 20.00Maxi micro clock (clock) 7081 11.50 23.00Maxi micro clock (darkroom timer) 7091 11.50 23.00Maxi micro clock (cooking timer) 7101 11.50 23.00Mini micro clock (clock) 7111 11.50 23.00Mini micro clock (darkroom timer) 7121 11.50 23.00Mini micro clock (cooking timer) 7131 11.50 23.00VHF/UHF TV tuner(1 x 87C51) 7141 25.75 51.50Microntroller-driven UART(1 x ST62T10) 7151 17.25 34.50

DISKETTES

Plotter driver (D. Sijtsma) 1541 11.15 22.30I/O interface for Atari 1571 7.65 15.30Tek/Intel file converter 1581 7.65 15.30B/W video digitizer 1591 11.15 22.30Timecode interface 1611 7.65 15.30RTC for Atari ST 1621 7.65 15.3024 -bit colour extensionfor video digitizer 1631 11.15 22.30PC controlled weatherstation - 3 (supersedesdisks 1551 and 1561) 1641 7.65 15.308051/8032 Assembler course(IBM version) 1661 7.65 15.308051/8032 Assemblercourse (Atari version) (3.5") 1681 7.65 15.30AD232 converter 1691 7.65 15.30GAL programmer (3 disks;upgrade: June 1993) 1701 11.15 22.30Multi -purpose Z80 card 1711 7 65 15.30Fuzzy Control One 1721 7 75 15.50Pascal library for MMC 1751 9 70 19.40Speech/sound memory 1771 7 65 15.30

PROJECT No. Price Price(£) (US$)

PC -aided transistor tester 1781 7.50 15.00IR receiver and DTMF decoderfor 80C32 SBC 1791 9.00 18.00I2C opto/relay card 1821 7.65 15.30Video digitizer for PCs 1831 14.50 29.00GAL programmer for Amiga 1841 11.00 22.00I2C alphanumerical display 1851 8.50 17.00Philips preamplifier 1861 8.50 17.00GAL programmer (excl. OpalJr. disks) 1881 10.75 21.50Precision clock for PCs 1871 8.50 17.00X2404 -to -8751 interfacing 1891 8.50 17.00SIM - an 8051 emulator 1931 34.25 68.50

PRINTED CIRCUIT BOARDSPrinted circuit boards whose number is followed by a+ sign are only available in combination with the as-sociated software item, and can not be supplied sepa-rately. The indicated price includes the software.

SEPTEMBER 1993Fuzzy logic multimeter - 1 920049-2Linear temperature gauge 920150Digital output for CD players 920171

20.00 40.007.05 14.10

Not availablePC -aided transistor tester 920144 9.75 19.50Harmonic enhancer 930025 13.50 27.00I2C alphanumerical displayincl. disk (1851) 930044+ 14.25 28.50

Mini micro clock 930055 7.50 15.00950-1750 MHz converter UPBS-1 1.95 3.90

OCTOBER 1993Stereo mixer UPBS-1 1.95 3.90MIDI channel monitor 930059 14.00 28.00Ah meter with digital display 930068 14.00 28.00Autoranging frequencyreadout 930034 12.50 25.00ROM -gate switchover forAtari ST 930005 30.25 60.50Microntroller-driven NiCdbattery charger (incl.programmed ST62E15) 920162+ 25.50 51.00Fuzzy logic multimeter - 2incl. disk (1721) 920049-1+ 23.75 47.50

NOVEMBER 1993Fuzzy logic multimeter - 3(four boards)

Precision clock for PCsincl. disk (1871)

VHF/UHF TV tunerboards -1 and -2, and

87C51 (7141)Output amplifier with AFbandpass filterElectronic loadDigital hygrometerincl. EPROM (6301)

Power MOSFET tester

920049 Not available

930058+ 12.25 24.50

930064+ 57.25114.50

930071 6.75 13.50930088 Not available

930104+ 28.00 56.00930107 32.50 65.00

DECEMBER 1993535 card w. EPROM emulatorincl. GAL and PAL (6311) 930103+AF rms voltmeter 930108I2C power switch 930091Medium power HEXFETamplifier 930102Microcontroller driven UART 930073SCART switching box 930122Low -power NBFM transmitter 914114Photographic workshop light 930116Stereo PWM output amplifier 934076

JANUARY 1994Digital dialRDS decoderincl. EPROM (6331)

I2C testerincl. GAL (6341)

Telephone -controlled switchincl. EPROM (6271)

47.50 95.0012.25 24.506.25 12.50

12.75 25.504.75 9.50

14.25 28.50Not availableNot availableNot available

930161 12.75 25.50

930121+ 23.75 51.50

930128+ 36.25 72.50

934054+ 37.25 74.50

A list of all PCBs, software products and front panels available through the Readers Services ispublished in the March, June, September and December issues of Elektor Electronics


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TERMS OF BUSINESSHOW TO PAYUnless you have an approved credit accountwith us, all orders must be accompanied bythe full payment, including postage and pack-ing charges as stated on page 70, section I .

Payment may be made by cheque drawnon a London clearing bank (but see para. 4below), postal order, VISA, ACCESS, MAS-TERCARD or EUROCARD (when paying bycredit card, the order must go to the card-holder's address). Do not send cash throughthe mail. Cheques and postal orders should hecrossed and made payable to 'Elektor Electronics(Publishing)'.

Payment may also be made by direct trans-fer from a private or business Giro account toour Giro Account No. 34 152 3801 by com-pleting and sending to the National Giro Centre,in a National Giro postage paid envelope, aNational Giro transfer/deposit form. Do not sendGiro transfers direct to us, as this will delay yourorder.

If you live outside the UK, payment mayalso he made by Bankers' sterling draft drawnon a London clearing bank, Eurochcque madeout in pounds sterling (with holder's guaran-tee card number written on the back), or US orCanadian dollar cheque, but such cheques, ac-cepted at the exchange rate prevailing at thetime your order is received, must be increasedby the equivalent of £15.00 to cover our bankers'negotiating fee.

If you pay by Bankers' sterling draft, makeclear to the issuing bank that your full nameand address MUST be communicated to theLondon clearing bank.

Our bankers are National WestminsterBank PLC, 100 High Street, BRENTFORD

r

TW8 8AY, England. Our account number is4285 0134.

DELIVERYAlthough every effort will be made to dispatchyourorder within 2-3 weeks from receipt of yourinstructions, we can not guarantee this time scalefor all orders.

RETURNSFaulty goods or goods sent in error may be re-turned for replacement or correction, but notbefore obtaining our consent. All goods re-turned should he packed securely in a paddedbag or box, enclosing a covering letter statingthe dispatch note number. If the goods are re-turned because of a mistake on our part, wewill refund the return postage. Goods returnedfor refund must he in resaleable condition Andwill be subject to a 10% handling charge witha minimum charge of £250.

DAMAGED GOODSClaims for damaged goods must be received atour Dorchester office within 10 days (UK); 14days (Europe) or 21 days (all other countries)from the date on our "Recorded Delivery" slip.

CANCELLED ORDERSAll cancelled orders will be subject to a 10%handling charge with a minimum charge of£2.50.

PATENTSPatent protection may exist in respect of circuits,devices, components, and soon, described in ourbooks or magazines. Elektor Electronics (Publishing)

do not accept responsibility or liability for fail -

ing to identify such patent or other protection.

COPYRIGHTAll drawings, photographs, articles, printed -cir-cuit boards, EPROMS, and cassettes published inour books or magazines (other than in third -partyadvertisements) are copyright and may not bereproduced or transmitted in any form or byany means, including photocopying and record-ing, in whole or in part, without the prior per-mission of Elektor Electronics (Publishing) inwriting. Such written permission must also beobtained before any part of these publicationsis stored in a retrieval system of any nature.

Nothwithstanding the above, printed -circuithoards may be produced for private and personaluse without prior permission.

LIMITATION OF LIABILITYElektor Electronics (Publishing) shall not beliable in contract, tort, or otherwise, for anyloss or damage suffered by the purchaser what-soever or howsoever arising out of, or in con-nexion with, the supply of goods or services byElektor Electronics (Publishing) other than tosupply goods as described or, at the option ofElektor Electronics (Publishing), to refund thepurchaser any money paid in respect of thegoods.

LAWAny question relating to the supply of goodsand services by Elektor Electronics (Publishing)shall be determined in all respects by the lawsof England.

April 1993

Annual subscription rates (1994)

United Kingdom 27.00Rest of the world (surface mail) £33.00AIRMAILEurope & Eire £34.00USA & Canada $57.00Middle East & North Africa £43.00Central & southern Africa £43.00Central & South America £43.00Australia & New Zealand £45.00Far East & South Pacific regions £45.00

Payment may be made by cheque in sterling drawnon a London clearing bank (but see below), postalorder, VISA, ACCESS, MASTERCARD or EUROCARD (in whichcase the subscription must be sent to the cardholder's ad-dress) or by direct transfer to our Giro Account no. 34152 3801. Do not send cash through the mail. Chequesand postal orders should be made payable to ÈlektorElectronics Publishing'. Giro transfers should be made bycompleting and sending the appropriate transfer/depositform to the National Giro Centre (UK) or to your nationalGiro Centre.

If you live outside the United Kingdom, payment mayalso be made by Bankers' sterling draft drawn on a Londonclearing bank or Eurocheque. Eurocheques should bemade out in pounds sterling and have the holder's guaranteecard number written on the back.

only may pay in $US cheques.

The standard subscription order period is twelve months.If a permanent change of address during your subscrip-tion period means that copies have to be dispatched by amore expensive service, no extra charge will be made.Similarly, no refund will be made, nor expi ry date extended,if a change of address allows the use of a cheaper service.

Student applications, which qualify for a 10% (ten percent) reduction in current rates, must be supported by ev-idence of studentship signed by the head of the college,school or university faculty.

Please note that new subscriptions take about four weeksfrom receipt of order to become effective.

Cancelled subscriptions will be subject to a charge of25% (twenty-five per cent) of the full subscription price or£7.50, whichever is the higher, plus the cost of any issuesalready dispatched. Subscriptions cannot be cancelled afterthey have run for six months or more.

Our bankers are National Westminster Bank PLC, SortingCode 60-03-23, 100 High Street, Brentford TW8 8AY,England. Our account number is 4285 0134.

June 1993

US dollar cheques. Subscribers in the USA and Canada



Surplus alwayswanted for cash! THE ORIGINAL SURPLUS WONDERLAND! Surplus always

wanted for cash!,

LOW COST PC SPECIALISTS - ALL EXPANDABLE - ALL PC COMPATIBLE8088 XT - PC99

,

irsAittri 256k RAM - expandable Factory burnt -in

to 640k Standard 84 key 4.7 Mhz speed keyboard 360k 5-1/4" floppy 12" green screen 2 serial & 1 parallel ports included

MS-DOS 4.01 In good used condition

Optional FITTED extras: 640K RAM £39. 12" CGA colourmonitor with card £39. 2nd 5-1/4" 360K floppy £29.95. 20mbyte MFM hard drive £99.

°nIY 99 .00,,,FLOPPY DISK DRIVES

51/4 " from £22.95 - 31/2" from £21.95!Massive purchases of standard 51/4" and 312" drives enables usto present prime product at industry beating low prices! All units(unless stated) are removed from often brand new equipmentand are fully tested, aligned and shipped to you with a 90 dayguarantee and operate from standard voltages and are of stand-ard size. All are IBM-PC compatible (if 31/2" supported).3.5" Panasonic JU363/4 720K or equivalent £29.95(B)3.5" Mitsubishi MF355C-L. 1.4 Meg. Laptops only` £29.95)B)3.5" Mitsubishi MF355C-D. 1.4 Meg. Non laptop £29.95(B)5.25" EXTRA SPECIAL BRAND NEW Mitsubishi MF501B

360K. Absolutely standard fits most computers £22.95)B) Data cable included in price.

Shugart 800/801 SS refurbished & tested £175.00)E)Shugart 851 double sided refurbished & tested £275.00)E)Mitsubishi M2894-63 double sided switchable

hard or soft sectors- BRAND NEW £250.00)E)Dual 8" drives with 2 mbyte capacity housed in a smart casewith built in power supply! Ideal as exterior drives! £499.00)F)End of line purchase scoop! Brand new NEC D2246 8" 85megabyte of hard disk storage! Full CPU control and industrystandard SMD interface. Ultra hi speed transfer and access timeleaves the good old ST506 interface standing. In mint conditionand comes complete with manual. Onl £299(E)

THE AMAZING TELEBOX!Converts your colour monitor into a

QUALITY COLOUR TV!!

TV SOUND& VIDEOTUNER!

The TELEBOX consists of an attractive fully cased mainspowered unit, containing all electronics ready to plug into a hostof video monitors made by manufacturers such asMICROVITEC, ATARI, SANYO, SONY, COMMODORE,PHILIPS, TATUNG, AMSTRAD and many more. The compositevideo output will also plug directly into most video recorders,allowing reception of TV channels not normally receivable onmost television receivers (TELEBOX MB). Push button controlson the front panel allow reception of 8 fully tuneable 'off air' UHFcolour television or video channels. TELEBOX MB covers vir-tually all television frequencies VHF and UHF including theHYPERBAND as used by most cable TV operators. Compositeand RGB video outputs are located on the rear panel for directconnection to most makes of monitor. For complete compatibility- even for monitors without sound - an integral 4 watt audioamplifier and low level Hi Fi audio output are provided asstandard.Telebox ST for composite video input monitors £32.95Telebox STL as ST but with integral speaker £36.50Telebox MB as ST with Multiband tuner VHF -UHF -Cable.

& hyperband For overseas PAL versions state5.5 or 6mhz sound specification. £69.95

Telebox RGB for analogue RGB monitors (15khz) £69.95Shipping code on all Teleboxes is (B)

RGB Telebox also suitable for IBM multisync monitors with RGBanalog and composite sync. Overseas versions VHF & UHF call.

286 AT - PC286

640k RAM expandable 2 serial & 1 parallelwith standard SIMMS ports

12 Mhz Landmark speed MS-DOS 4.01 20 meg hard disk Co -processor socket 1.2 meg 5-1/4" floppy Enhanced 102 keykeyrd 1.4 meg 3-1/2" floppy

Clock & calendar with EGA driver on board batteryback up

BRAND NEW AND BOXED!

Only £249.00(,)The Philips 9CM073 is suggested for the PC286 and the\CM8873 for the PC386. Either may use the SVGA MTS-9600if a suitable card is installed. We can fit this at a cost of £49.00for the PC286 and £39.00 for the PC386.

POWER SUPPLIESPower One SPL200-5200P 200 watt (250 w peak).Semi openframe giving +5v 35a, -5v 1.5a, +12v 4a (8a peak), -12v 1.5a,+24v 4a (6a peak). All outputs fully regulated with over voltageprotection on the +5v output. AC input selectable for 110/240vac. Dims13" x x 2.5". Fully guaranteed RFE. £85.00 (B)

Power One SPL130. 130 watts. Selectable for 12v (4A) or 24 v(2A). 5v @ 20A. ± 12v @ 1.5A. Switch mode. New. £59.95(B)Astec AC -8151 40 watts. Switch mode. +5v @ 2.5a. +12v @2a. -12v @ 0.1a. 6-1/4" x 4" x 1-3/4".New £22.95(B)Greendale 19ABOE 60 watts switch mode.+5v @ 6a,±12v (4)la,+15v @ 1 a. RFE and fully tested.11 x 20 x5.5cms. £24.95(C)Conver AC130. 130 watt hi -grade VDE spec.Switch mode.+5v

15a, -5v @ 1a,±12v @ 6a.27 x 12.5 x 6.5cms.New. £49.95(C)Boshert 13090.Switch mode.ldeal for drives & system. +5v@ 6a,+12v CO 2.5a, -12v @ 0.5a, -5v @ 0.5a. £29.95(B(Farnell G6/40A. Switch mode. 5v @ 40a.Encased £95.00(C)Farnell G24/5S. As above but 24v @ 5a. £65.00(C)

BBC Model B APM Board£100 CASH FOR THE

MOST NOVELDEMONSTRATABLE

APPLICATION!BBC Model B type computer on a board. A major purchaseallows us to offer you the PROFESSIONAL version of the BBCcomputer at a parts only price. Used as a front end graphicssystem on large networked systems the architecture of the BBCboard has so many similarities to the regular BBC model B thatwe are sure that with a bit of experimentation and ingenuity manyuseful applications will be found for this board!! It is suppliedcomplete with a connector panel which brings all the I/O to 'D'and BNC type connectors - all you have to do is provide +5 and± 12 v DC. The APM consists of a single PCB with most majoric's socketed. The ic's are too numerous to list but include a6502, RAM and an SAA5050 teletext chip. Three 27128EPROMS contain the custom operating system on which wehave no data, On application of DC power the system boots andprovides diagnostic information on the video output. On boardDIP switches and jumpers select the ECONET address andenable the four extra EPROM sockets for user software. Appx.dims: main board 13" x 10". I/O board 14" x 3". Supplied testedwith circuit diagram, data and competition entry form.

Only £29.95 or 2 for £53 (B)SPECIAL INTEREST

Trio 0-18 vdc bench PSU. 30 amps. NewFujitsu M3041 600 LPM band printerDEC LS/02 CPU boardRhode & Schwarz SBUF TV test transmitter

25-1000mhz. Complete with SBTF2 Modulator £6500Calcomp 1036 large drum 3 pen plotter £ 650Thurlby LA 160B logic analyser £ 3751.5kw 115v 60hz power source £ 950Anton Pillar 400 Hz 3 phase frequency converter 75Kw POANewton Derby 400 Hz 70 Kw converter POANikon PL -2 Projection lens meter/scope £750Sekonic SD 150H 18 channel Hybrid recorder £2000

SECAM I NTSC not available. HP 7580A Al 8 pen high speed drum plotter £1850 justable internal fixing struts, readyKenwood DA -3501 CD tester, laser pickup simulator £ 350 punched for any configuration of equipment mounting plus ready

- - - : ' , 8 . - mounted integral 12 way 13 amp socket switched mains distribu-Brand new and boxed 230 volts uninterruptable power supplies Lion strip make these racks some of the most versatile we havefrom Densei. Model MUK 0565-AUAF is 0.5 kva and MUD Microline 183. NLQ 17x17 dot matrix. Full width. £139 (D) ever sold. Racks may be stacked side by side and therefore1085-ANBH is 1 kva. Both have sealed lead acid batteries. MUK Hyundai HDp-620. NLQ 24x18 dot matrix full width. £149 (D) require only two side panels or stand singly. Overall dimensionsare internal, MUD has them in a matching case. Times from Qume LetterPro 20 daisy. Qume QS -3 interface. £39.95 (D) are 77-1/2"H x 32-1/2"D x 22"W. Order as:interrupt are 5 and 15 minutes respectively. Complete with full Centronics 152-2 9 x 7 dot matrix. Full width. £149 (D) Rack 1 Complete with removable side panels £275.00 (G)operation manuals MUK £249 (F) MUD £525 (G) Centronics 159-4 9 x 7 dot matrix.Serial. 9-1/2" width £ 99 (D) Rack 2 Less side panels £145.00 (G)

1992 Winter Issue of Display News now available - send large SAE - PECKED with bargains!

386 AT - PC386LA3.31r9700 el WOW -M.gra

2 meg RAM expandedby slots

20 Mhz with 32k cache.Expandable to 64k

40 meg hard disk 1.2 meg 5-1/4" floppy VGA card installed

2 serial & 1 parallelports

MS-DOS 4.01 Co -processor socket Enhanced 102 keyboard Kwik Disk Accelerator

Software - FREEBRAND NEW AND BOXED!

Only £425.00(F)MONITORS

14" Forefront Model MTS-9600 SVGAmultisync with resolution of 1024 x 768.0.28pitch. "Text" switch for word processing etc.

' Overscan switch included. Ideal for the PC-. 386 or PC -286 with SVGA card added. Also

Ariii compatibe with BBC, Amiga, Atari (includingthe monochrome high resolution mode), Ar-

chimedes etc. In good used condition (possible minor screenburns). 90 day guarantee. 15" x 14" x 12". Only £159(E)

14" Philips Model CM8873 VGA multisyncwith 640 x 480 resolution. CGA, EGA orVGA, digital/analog, switch selectable.Sound with volume control. There is also aspecial "Text" switch for word processing,

d, spreadsheets and the like. Compatible withIBM PC's, Amiga, Atari (excluding themonochrome high resolution mode), BBC,

Archimedes etc. Good used condition (possible minor screenburns) 90 day guarantee. 15' x 14" x 12". Only £139(E)Philips 9CM073 similar (not identical) to above for EGA/CGAPC and compats. 640 x 350 resolution. With Text switch withamber or green screen selection. 14" x 12' x 13-1/2" £99(E)KME 10" high definition colour monitors. Nice -

tight 0.28" dot pitch for superb clarity andmodern styling. Operates from any 15.625 khzsync RGB video source, with RGB analog andcomposite sync such as Atari, CommodoreAmiga, Acorn Archimedes & BBC. Measuresonly 13.5" x 12" x 11". Also works as quality Tv witn our HUBTelebox. Good used condition. 90 day guarantee. Only..£125 (E)KME as above for PC EGA standard £145 (E)Brand new Centronic 14" monitor for IBM PC and compatiblesat a lower than ever price! Completely CGA equivalent. Hi-resMitsubishi 0.42 dot pitch giving 669 x 507 pixels. Big 28 Mhzbandwidth. A super monitor in attractive style moulded case.Full90 day guarantee. Only £129 (E)NEC CGA 12" IBM-PC compatible. Highquality ex -equipment fully tested with a 90day guarantee. In an attractive two toneribbed grey plastic case measuring 15"L x13"W x 12"H. The front cosmetic bezel hasbeen removed for contractualreasons. Only.......... (E)

20" 22" and 26" AV SPECIALSSuperbly made 'UK manufacture. PIL all solid state colourmonitors, complete with composite video & sound inputs. Attrac-tive teak style case. Perfect for Schools,Shops,Disco, Clubs.In EXCELLENT little used condition with full 90 day guarantee.

20"....£135 22"....£155 26"....£185 (F)CALL FOR PRICING ON NTSC VERSIONS!

Superb Quality 6 foot 40u

19" Rack Cabinets

O00 OillO MPS.

SODS

-ELECTRONICS-

MAIL ORDER & OFFICESOpen Mon -Fri 9.00-5.30Dept EL, 32 Biggin Way,

Upper Norwood,London SE19 3XF.

LONDON SHOPOpen Mon -Sat 9-5.30Thursday till 9.00pm

215 Whitehorse Lane,South Norwood,London, SE25 .

£ 470£2950£ 150

Esc

Massive ReductionsVirtually New, Ultra Smart!

Less Than Half Price!Top quality 19" rack cabinets made in UKby Optima Enclosures Ltd. Units featuredesigner, smoked acrylic lockable frontdoor, full height lockable half louvered backdoor and removable side panels. Fully ad -

DISTEL © The OriginalFree dial -up database!

1000's of items+info on lineV21, V22 & V22 bis

081-679-1888

ALL ENQUIRIES

081167914414Fax- 081-679-1927

All prices for UK Mainland. UK customers add 17.5% VAT to TOTAL order amount. Minimum order 210. PO orders from GovernmenLUniversities.Schools & Local Autho tieswelcome -minimum account order £30. Carriage charges (A)=22.00. (A1)=23.75. (9)=25.50. (C)=28.50. (0)=211.50. (E)=214.00 (F)=218.00 (G)=Call Scotland surcharge: call.All goods supplied subject to our standard Condiiions of Sale and unless otherwise stated guaranteed for 90 days. All guarantees on a retum to base basis.Rights reserved tochange prices & specifications without prior notice. Orders subject to stock. Quotations willingly given for higher quantities than those stated. Bulk surplus always wanted forcash.


74

ELEKTOR ELECTRONICS is available from, among others:

CRICKLEWOODELECTRONICS LIMITED40 Cricklewood Broadway,

London NW2 3ETTelephone 081 450 0995

Fax 081 208 1441

L.P. HANNEYYour electronic componentspecialist for Avon, Wilts &

Somerset.

77 Lower Bristol Road, Bath,Avon, Telephone 0225

424811

AAGE NIELSEN1 Sorted= DosseringenDK-2200 Copenhagen,

Denmark,Telephone 01 39 30 10

Fax 031 39 05 02

TABACCARIA BRITANICAPraca do Duque da

Terceira 191107 Lisboa, PortugalTelephone 932 4752

MK KNJIGARNASlovenska 29

LjubljanaSlovenia

Telephone 061 150 196

THE ELECTRONIC SHOPElectronic components, test

equipment, telephoneaccessories, computer

accessories, microphones,disco lighting, speakers, turntables, mixers, meters, stylus.

29 Hanging Ditch,Manchester M4 3ES,


HELMHOLT ELEKTRONIKFarvevej 2

DK-7600 Struer, DenmarkTelephone 97 85 26 11

D.P. HOBBS (NORWICH)LTD

Electronic componentspecialists. Amateur radio

equipment.13 St. Benedict Street,

Norwich NR2 4PE,Telephone 0603 615786

RCE ELECTRONICCENTRE

Boulevarden 34DK-9000 Aalborg, Denmark

Telephone 98 16 07 10

TECHNICAL BOOKS &MAGAZINES

289-299 Swanston StreetMelbourne, Australia 3000

Telephone 663 3951

GREENWELD27 Park Road

Southampton SO1 3TBEngland

Telephone (0703) 236 363Fax (0703) 236 307

MANCOMP240 Platt Lane

Manchester M14 7BSEngland


VEJLE RC ELEKTRONIKSdr Brogade 42

P 0 Box 332DK-7100 Vejle, DenmarkTelephone 75 83 25 33

INEL Co.P.O. Box 1397

JL. Hariang Banga No. 3Bandung 40116

Indonesia

OMNI ELECTRONICSStock a wide range of

electronic components.174 Dalkeith Road,

Edinburgh EH 16 5DX,Telephone 031 667 2611

BEBEK ELECTRONICSHirsimetsantie 26SF -15200 Lahti 11

FinlandTelephone (18) 33 99 46

Advertising Standards AuthorityBadger BoardsB K ElectronicsBull ElectricalCanal Bridge AudioCirkit DistributionCricklewood ElectronicsDisplay ElectronicsElectronics - the Maplin MagazineElectroValueElektor ElectronicsESR Electronic ComponentsICE TechnologyIntegrated Measurement SystemsJ P DistributionKare ElectronicsLabcenterLloyd ResearchMaplin Electronic SuppliesMicroAmpsMicrogem SystemsMorrison MicrosMQP ElectronicsNumber One Systems LtdPico Technology LtdPOWERwareRobinson Marshall

INDEX OF ADVERTISERS

23, 656519

32525345734051

23, 7438

Inside back cover574331

7

56Back cover

51

5365524

6656

Inside front cover

Roline SystemsSpeaker BuilderSquarewave ElectronicsStewart of ReadingSuma DesignsTsien (UK) LtdUltimate TechnologyViewcom ElectronicsWhite House Systems

39

575257676341

12, 1365

ADVERTISING SPACEfor the February 1994 issue may be reserved not later than10 December 1993 by

Elektor Electronics (Publishing)Advertisement Office

3 Crescent TerraceCheltenham GL50 3PE

EnglandTelephone (0242) 510 760; Fax (0242) 226 626

to whom all correspondence, copy instructions and artworkshould be addressed.


THE BEST LOW COST PROGRAMMERSDESIGNED & MANUFACTURED IN THE UK

SPEEDMASTER 1000SPEEDMASTER 1000E

UNIVERSAL PROGRAMMER Superfast PC based programmer Programmes; EPROMS UP TO 8M BIT,

FLASH EPROMS, EEPROMS, BPROMS,NVRAMs, MICROs (8748/51),PALs, GALs, EPLDs, PEELS, viMACHS, MAPLs, MAX oi

III Plugs directly into ciettWparallel port

1111000E Version has ROM/RAMemulator built in: 128k(1 Mbit) standard, 0

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MICROMASTER 1000MICROMASTER 1000E

UNIVERSAL PROGRAMMER Programmes: EPROMS UP TO 8M BIT.

FLASH EPROMS, EEPROMS,BPROMS, NVRAMs, PALs,GALs, EPLDs, PEELs, Os. ISMACHs, MAPLs, MAX etc. SiS

PLUS over 80 different Microsincluding 8748/51, 68HC705, 68HC711,PICs, Z86, TMS320, TMS370 etc DIPsWITHOUT ADAPTORS ORPERSONALITY MODULES!

III Package adaptors available.III 1000E Version has ROM/

RAM emulator built in:128K (1Mbit) standard,optional 512K (4 Mbit)

SPEEDMASTER 8000GANG/SET PROGRAMMER

8 way, Pc or stand aloneII Super -fast programming times,

manufacturer recommendedalgorithms

II 32 pin devices as standard Support for 8748,51,

TMS370, PIC Micros and40 pins.

WHY BUY AN INFERIOR IMPORTED PROGRAMMER WHEN YOU CAN HAVE A MANUFACTURERAPPROVED UNIVERSAL PROGRAMMER/EMULATOR DIRECT FROM ICE TECHNOLOGY!

Li We offer the best range of low-cost programmers available, now including our uniqueUNIVERSAL PROGRAMMERS WITH BUILT IN EMULATORS

E Unrivalled device support, for example the Micromaster 1000 programmes PICS, Z86, 87C705, 68HC705,TMS370, 77C82 ETC WITHOUT ADAPTORS, as well as the full range of Eproms, PLDs etc supported byall our universal programmers.

Li Approved by National Semiconductor for their full range of PALs, GALs, and MAPLs - other programmersclaiming approval are often only approved for EPROMs -a much less exacting specification!

El All our programmers and programme/emulators work off the standard parallel port with any IBMcompatible PC, even laptops

El Unbeaten programming times: Programme a 27256 in just 5 SECONDS including download and verify.7 Easy upgrade path between Models. 0 G Y

FOR MORE DETAILS, DEVICE LIST AND DEMO DISK CALL NOW ON

TEL +44 (0)226 767404 FAX +44 (0)226 370434ICE TECHNOLOGY LTD, UNIT 4. PENISTONE COURT, STATION BUILDINGS, PENISTONE, S. YORKS, S30 6HG, UK.

A T1MFJDIVc POSMON

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220

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A INI 01TAGG

)

STORAGE TAM TAX n Sat

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F-41 1114

VCLTS/DP/

Model OS -3020 illustrated above

Star Quality, Reliability,and World ClassPerformancef=g; £269-95

Maplin Electronics are pleased toannounce their superb new range

of precision, laboratory gradeOscilloscopes from Goldstar.

.0.cif The range starts with the superNr, value -for -money, 20MHz Dual -trace

Oscilloscope, OS -9020A. Featuresinclude a large 6in., high luminanceCRT with internal 8 x 10cm graticule,TV field or line triggering and X -Ymode producing Lissajous patternsfor phase shift measurements.

NEWForhigher frequency applications,

the 40MHz Dual -trace Oscilloscope,OS -9040D, is ideal for TV and videosignals and a trigger delay facility allowsobservation of fast leading edges.

f,Ni For RF signals and high-speed logicNr, applications, the highly specified

100MHz triple -trace Oscilloscope,OS -9100D, has 3 independent inputchannels and is ideal for simultaneousdisplay of 3 logic pulse trains fortiming comparison.

.v The dual -trace, 40MHz Oscilloscope,NE OS-904RD, is similar in specification

to OS -9040D, but with the additionalfacility of a digital readout on the CRTThe readout displays information suchas timebase and attenuator settings,and on -screen measurements can beperformed using movable cursors, thevalue appearing on the CRT screen.

NE 20MHzTop -of -the -range is the excellent

Nir' 20MHz Digital Storage Oscilloscope,OS -3020, with on -screen digital read-out and measurement facilities. Thedigital storage function enables one-offevents to be captured and stored fordetailed analysis. Stored waveforms canbe printed out on a suitable X -Y plottervia the built-in RS232 interface.Repetitive high-speed waveformsup to 20MHz can be digitised usingequivalent sampling techniquesand pre -trigger mode allows eventsoccurring before the triggering pointto be captured.

All models are supplied complete with probes, mains lead, spare fuses and detailed operating manual. Full detailsand specifications can be found in the 1994 Maplin Full Colour Catalogue, available from WH SMITH andselected branches of RSMcColl in Scotland for £2.95 (£3.45 by post direct from Maplin). To order, Phone the CreditCard Hotline, 0702 554161, or send your Mail Order to P.O Box 3, Rayleigh, S.S6 2BR, or visit your local Maplin store.Please note latest models all now cream in colour as Model OS -3020.

ffMCIplin ELECTRONICS. UK AGENTS FOR GOldStarVisit our stores in: Birmingham, Brighton, Bristol, Cardiff, Chatham, Coventry, Edinburgh, Glasgow, Ilford, Leeds,Leicester, London (Edgware, Forest Hill and Hammersmith), Manchester (Oxford Road and Cheetham Hill),Middlesbrough, Newcastle-upon-Tyne (The Metro Centre, Gateshead), Nottingham, Portsmouth, Reading,Sheffield, Slough, Southampton, Southend-on-Sea, Stockport, plus a NEW store opening soon in Milton Keynes.Phone 0702 552911 for further details.All items subject to availability, prices include VAT and may change after Feb. 28 1994. Carriage charge per order £5.70.

Handling charge £1.40 per order. Overseas customers please phone 0702 552911.

OS 9020AGWO3D £269.95

OS -9040D GWO4E £399.95

CUL-JIM_

METIMMM=IMMIMMETC1=10

e

OS -904R1) GW06G1499.95

0 VI r

OS -9100D GWO5F £699.95

OS -3020 GWO7H £749.95

GoldStarTechnology with the human touch

AUDIO & HI -Fl COMPUTERS & MICROPROCESSORS ......AUDIO & HI -Fl COMPUTERS & MICROPROCESSORS DESIGN IDEAS RADIO, TELEVISION & COMMUNICATIONS SCIENCE & TECHNOLOGY TEST & MEASUREMENT

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