Instruction manual

ManualsBrandsRadio Shack ManualsVCR112

iii

rt:

Photograph

the completed

prolect

when burlt wrth the

recommended Radio Shack

parts

This

package

contains only

the

Printed Circuit Board, an

Integrated

Circuit

and

instructtons

This

PROJECT

BOARD ASCII KEYBOARD

ENCODER utrlizes TTL logic The ASCII

KEYBOARD

ENCODER

may be

used to

provide

inputs

alltypes

of equrpment designed

to operate

with

ASCII(American

Standard

Code

for

Information Interchange) rnputs

Examples

of such equipment are. T

V typewriters,

mini-computers,mrcro-processors

or any devrce whrch requires ASCII encoder

alpha-numeric

characters

Features

of the ASCII KEYBOARD

ENCODER include.

Repeat key

controls all characters

and

symbols

Negative-gorng

positive-going

data valid

strobe

Latch

outputs

(stores

last key

code)

Shift and

shift

lock

capabrlrty

True

false

ASCII

outouts

Six

extra

control kevs

Summary of content (29 pages)

PAGE 1
T h i s P R O J E C TB O A R D A S C I I K E Y B O A R DE N C O D E Ru t r l i z e sT T L l o g i c T h e A S C I I K E Y B O A R DE N C O D E R m a y b e u s e d t o p r o v i d ei n p u t st o a l l t y p e so f e q u r p m e n d t e s i g n e dt o o p e r a t ew i t h A S C I I ( A m e r i c a nS t a n d a r d Code for Information Interchange)rnputs Examples of such equipment are.
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ASCII ENCGIDEFI TABLE OF CONTENTS 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. fntroduction S p e c i f i c a t i o n. .s. Description Partslist AssemblyofthePrintedCircuitBoard P a r t s M o u n t i n .g. Testing T r o u b l e s h o o t i n. g T h e o r y oOf p e r a t i o n WaveForms S c h e m a t iDc i a g r a m ....2 . .... 3 . .... 4 .......5 ......6 .....6 ... .. ... 11 ....19 ........22 ...26 . .. .. . ..
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RAD|OSHACK ^ DtVtStONOF TANDYCORPORAflON E U.S.A.:FORTWORTH,TEXAS76102 C A N A D A :B A R R I EO , N T A R I OC. A N A D AL 4 M 4 W 5 T A NDY CORPORATION AUSTRALIA 2 8 03 r 6V T C T 0 R RToA A0 RYDALME NR SE W 2I16 ' 8 7 6 S p - 2 8 4 7- 9 9 0 - 0 I 8 4 ',) BE L GUI M PARCINDUSTRIELt]E NANINNE 5 1 4 0N A N I N N E UK E I L S T ORNO A I ] W S I O7 J N W E O N E S E USRTYA f F S P R I N T E DI N U S A . --.
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ASCII ENGC'E'EF SPECIFICATIONS l-- lnput Voltage: MrN. 4.7 E 5.O MAX. 5.
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ASiCII DESCRIPTION 5. Shift Logic R e f e rt o F i g u r e1 , B l o c kD i a g r a m . 6. Output Latches The ASCIIKeyboardEncoderusesthe scanprinciple to reduce the amount of logic necessaryto fully encodea 63 keytypewriterkeyboard.TheKeyboardis w i r e d i n t o a m a t r i xc o n s i s t i n g o f 1 6 c o l u m n sa n d 7 rows of keys.Sincethis typeof matrixcan handlea Keyboard with 112 switches. there are many locations that have no key.
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ASC|! ENCC'E,EFI PARTSLIST T h i s p a c k a g e c o n t a i n s a c o m p l e t e c i r c u i t c a r d ( P r o j e c tB o a r d 2 7 7 - 1 1 7 1 r e a d y f o r p a r t s t o b e a d d e d . l t a l s o c o n t a i n s I n t e g r a t e dC i r c u i t , R S 7 4 H 1 0 3 ( 2 1 ) T o c o n s t r u c t y o u r A S C I I K e y b o a r dE n c o d e r ,y o u w i l l n e e d t h e f o l l o w i n g p a r t s . A l l p a r t s a r e a v a i l a b l ef r o m y o u r R a d i o S h a c k S t o r e .
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ASCII ENCC'ElEFI A S S E M B L Y O F T H E P R I N T E DC I R C U I T B O A R D Assembling of the Printed Board consists of m o u n t i n g c o m p o n e n t s t o t h e B o a r d .T h e P A R T SL I S T notes the parts you'll need The Board contains l e t t e r i n g i d e n t i f y i n g w h e r e t h e c o m p o n e n t sa r e t o b e m o u n t e d .
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-4 ru 0 NK]LHTE D o -Q m { FIGURE2.
PAGE 9
ASCil Mount the followingIntegratedCircuits: 424,R57475, 4-bit BistableLatch NOTE: DZs, R57475, 4-bit BistableLatch Y o um a y w a n t t o u s e s o c k e t s f o r t h e l C ' s if so now is the time to mount them. ENCC'E'EFI f l 2 6 , R S 7 4 1 3 ,D u a l ,4 - i n p u t S c h m i t tT r i g g e r 1. Install the IntegratedCircuits (lC) in their correctpositions. 2. The pins protrudethrough the holes in the PrintedCircuitBoard. 3. NOTE: A dot or indentation at one end i n d i c a t e sp i n 1 . 4.
PAGE 10
@ D o o lrl z o o m 0 (o F I G U R E3 .
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AETCII ENCC'EIEFI You are now ready to install the Keyboard to the P r i n t e dC i r c u i t B o a r d .M o u n t a s f o l l o w s : ! Ensure that all of the pins on the Keyboardare STRAIGHT! nThe Keyboardcontainsthree plastic alignment pins on its basewhich mate into alignmentholes in the PrintedCircuitBoard Placethe Kevboard with keys facing a f lat Position the the down on surface. Printed Circuit Board (componentside down) approximatelythree inches above Keyboard.
PAGE 12
ASC|| ENCC|E'EFI TESTING LED Cathode ldentification T o t e s t t h e A S C I I K e y b o a r dE n c o d e ry o u ' l l n e e d s o m e f o r m o f d i s p l a y t h a t v e r i fi e s t h e c o d e s .l f y o u h a v e t h i s e q u i p m e n t a v a i l a b l e ,u s e i t t o t e s t y o u r E n c o d e r .S e e Connector Pin ldentification on page 12 for pin c o n fi g u r a t i o n .
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@ ASCII Fabrication Procedures fJ X n n ! Carefullybend the connector'sletteredpins (up)as shown in Figure4. Mount the LED'sbetweenthe followingpairs of pins: (All cathodes of the LED's are connectedto oDD numberedpins.)2-3,4-5, 6 - 7 , 8 - 9 , 1 0 - 1 1 , 1 2 - 1 3 , 1 4 - 1 5 ,1 6 - 1 7 a n d 18 - 19 . M o u n t t h e n i n e , 1 8 0 o h m r e s i s t o r sb y solderingthem to pins as shown. Bend the free lead of the resistorsolderedto pin 18 toward the resistorconnectedto pin 16 and solder.
PAGE 14
ASCII BLUE J U M P E R S( 4 } ENCG'EIEFI +5.0 VDC l80a 180cl 1 8 0s , 1 8 0s l I t 8 00 I 1 8 0s , 1 8 0s , 1 8 00 IED L^.,^ S C H E X I A I I CD I A G R A A I RED J U M P E R S( 5 ) NOTE: F I G U R E4 . Be sure to coat the tip of your soldering iron with a layer of melted solder before soldering the component leads and wires to the connector terminals.
PAGE 15
@ ASCII TESTPROCEDURE 1. Installthe Heep Test Module on the Printed CircuitBoard. 2. Connect +S-volt DC power to pin 1 of test moduleconnector. 3. Connect ground return to pin Z of test module. 4. Perform test using Output Code Table and observe test module LED indications.The followingis a descriptionand explanationon how to use the tableand how to interpretthe test moduleindications. Lookingat the OutputCodingTable,youseethereare two separategroupsof output codingidentifiedas NORMALand SHIFT.
PAGE 16
@ ASCII ENGclElEFI O U T P U TC O D I N G T A B L E T h e O U T P U TC O D I N G T A B L E i s d i v i d e d i n t o t w o m a j o r s e c t i o n s- N O R M A L a n d S H I F T I n N O R M A L , t h e l e f t - h a n d c o l u m n l i s t s t h e l o w e r c a s e s y m b o l so f t h e k e y b o a r d I.
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ASCII NORMAL SYMBOL SHIFT HEX O U T P U TC O D E E 26 2 5 24 23 22 SYMBOL O U T P U TC O D E E 2 1 20 26 HEX 2 s 24 2 3 2 2 2 1 20 o o 1 o 1 o o o 1 51 * SOH o o o o o o o 1 o1 W o 'l o 1 o 1 1 1 57 * BEL o o o o o 1 1 1 07 E o 1 0 o o 1 o 1 45 * ENO o o o o o 1 o 1 o5 R o 1 o 1 o o 1 o 52 * STX 0 o o o 0 o 1 o o2 T o 1 o 1 o 1 0 o 54 * EOT 0 o o 0 1 o 0 o4 o 1 o 1 1 o 0 1 59 o o o o 1 o o 1 o9 o 1 o 1
PAGE 18
ASCII SHIFT NORMAL CODE OUTPUT SYMBOL E 26 24 23 22 2 1 o 1 o 0 1 1 o o o 0 1 1 1 o 1 1 3B @ o 1 o o o o 0 0 40 l 0 1 1 o 1 5D CLEAR 1 o o o o 1 0 o2 H E R EI S 1 o o n 0 o I 1 L BLANK "l o 0 0 0 Z o 1 o 1 X o I o \- o 1 V o B 1 0 1 4C *FF T CR * srx o3 - 1 o o o4 * I o o 5A 1 I o o o 58 0 o 0 o 1 1 43 ETX 1 o "l o 1 1 o 56 n 1 o o o o 1 o 42 N 0 'l 0 o 4E M U 1 o o 0 0 1 o o 0 SPACE
PAGE 19
ASiCII ENCCIEIEFI OUTPUTCODINGTABLE The following is a definitionof symbolabbreviationsof ASCIIcode in the SHIFTmodeof the OUTPUTCODING TABLE.Physicallythe keysare not identifiedas such.They are the samekeysthat are usedin the NORMAL mode. NORMAL mode key labelsare noted in bold face type. ESC = ESCAPE SO = SHIFTOUT n BACK SPACE BS = BACK SPACE TAB O, CTRL, A W. G R B L A N K ,E , U TAB HT = HORIZONTAL SOH=STARTOFHEADING BEL= RINGSTHE BELL E N O= E N O U I R Y B.
PAGE 20
ASiCII TROUB LESHOOTING Negativeor FalseASCII: lf you checkedyour KeyboardEncoderby connecting it to a TV typewriter and typed RADIOSHACK and obtain the following W display:-)i 60*,7) <4 insteadof RADIOSHACK,troubleexistsbetweenthe Encoder and the equipment it is connectedto. Incorrectdatasuchas this indicatesthatthe Encoder is supplyingtypeddata into a systemthat isdesigned to acceptASCIIin a code oppositeof that which you have connected into it.
PAGE 21
ASiCII the brokencopperrun or the pad and solderit. Cutoff the excesswire. Once you have confirmedthat you have repairedthe hole,protectthe wire and looserun or the pad with epoxy or some non-conductive cementor glue. Step-by-Step Troubleshooting: Thereare four main stepsin troubleshooting: Step 1. Step 2. Step 3. Step 4. Verifythe problem. lsolatethe problem. lsolatethe component. Repairthe problem. Step 1. Verify the Problem. Step 1 is easy.You have been doing just that.
PAGE 22
ASICII IC MAJOR SECTION ENCC'EIEFI P R O B A B L EC A U S E , / I N D I C A T I O N 23 Keyboardscanner 1 Outputsneverchange. 2 Keyboardnot scanned. 3 Defectiveboard. 24 Output latches 1. The four ASCIIoutput bits 20,21,22,23 neverchange. Z5 Output latches 1. The three ASCII output bits 24, 25,26 never change. ZG Keyboardscannerand encoder 27 Keyboardscanner,key pressed detector,and encoder ZB Encoder Zg Shift logic 1 . Defective board (does not oscillate). 2 .
PAGE 23
ASCII THEORYOF OPERATION The following is a detailedTheoryOf Operationof the ASCII KeyboardEncoderand its associatedcircuitry. Referto the SchematicDiagramandWaveformChart while readingthis Theory. Scanner The Scannercircuitryis made up of 76,23, 22 and 212. Partof ZGis usedas the master oscillatorf or the rest of the system.23, togetherwilhZ,2,forms a base 18 counter. Z3 supplies BCD data to Keyboard Scanner Decoder 212 and generatesthe four least significantdigits of the ASCII code.
PAGE 24
ASCII Noticefine K on the chart.Zl pin 12 will go high on the fallingedgeof the cTRsignal.ThisFlip-Flopstores the Key Pressedcommand until the Keyboard is disabledduring Keyboard Disabled Time. During this time, on the rising edge of 22 pin 9, 21 pin 9 storesthe K line data.Thisstorageis shownon lineL of the Waveform Chart. Duringthe positivepulse shown on line G, the next time the 6iR signalgoeslow, Flip-Flop21 pin 12goes back low.
PAGE 25
ASCII In the normal mode,a high out of 215, pin 1, causes Z9 and Z8 to be disabled.This causesdata, listed in the encoder table, to be routed to the two NAND Gates,27 and the other half of 26. The data is then sent to the three data latches in 25. In the shifted mode,215 pin 1 is low, which disables the three NAND Gatesin 216. NANDGatesZ9 and Z8 now become active.Thesethree Gates do two major things. First they decode incoming data.
PAGE 26
@ ASCll The shift lock circuit modifies the codes just as the shift function. The method of holding the shift lock instructions is slightly different in Flip-Flop213. W h e n t h e " S h i f t L o c k " k e y i s p r e s s e d .F l i p - F l o p2 1 3 pin 9 goes high. When the Shift Lockkey is released, p i n 9 o f 2 1 3 s t a y s h i g h .
PAGE 27
r I I I I N o @ prlru^L^-' I KEYBOARDI DTSABLE I KEY PRESSED BOt2 ol23t5A 15A lrllll I A rlll crK -,rl-fL,rL,r\Wpt-t-,rLrt-,r\FfL_J-LJ-t-f\ c B crK --r-lfi-t--rtffi m c 66', J D DI o ! D!s € m 'n F z2prNr2 o v 3 o G z2PrNe I H z?PrNrr I zrgPrN. ---{ T { J zrPlN 14 H rl I BO15ABO r1 8ot5AB ltrlr tr-rr-rrnrth-,r-rnnn \-n-,nJl.d h-l--].r-t-J h-r-lF-l-t-t Ft-r--r h-r- r-til Fl-,(-t hf f-\ Tl 1.
PAGE 28
( EOGT C0illtCTOB- ?1,,,-n, .lE 26 -lI OF ^ l/- c , 4 Ir '{' 25 25 ,l'./ ge llow' 0 vcc A S C irl ( E Y 8 0 A Rt C 0 ',S USr t { 0 T t s u t { r t s so r H t n w r sst P r c rrft 0 I A [ [ N E S I S T O RASB E I / 4 W A T T txP8tssrD tr{ oHMs lx = 10001 2 ARE II{ MICROTARAOS CAPACIIONS {9f = PIC0fARADS) Rtf DTS zr 22, zr3 2 3 ,z f l 2 4 .z 5 26 z?,216 28,zD 2 9 .
PAGE 29