titus-larsen-titus-1981-apple-interfacing

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Step7 Wire· the SN7493 counter as shown in Fig. 6-19. You will nee use the input port and the output port from the previous steps this experiment. You will also need two NOR gates, as shown Fig. 6-19. A single SN7402 chip will provide these gates. Do +5 SN7402 49317 14 12 INP A A DO WR INP B B DI TO INPUT RO D2 49319 PORT* 11 RO D D3 10 SN7493 *GROUND INPUT BITS D7-D4 Fig. 6-19. Test circuit schematic used to check SN7493 counter chips. substitute an SN74L93 counter for the SN7493. Remember to gro the unused inputs on the input port. Step 8 Write a short test program that will exercise the reset functi on the counter, and one that will test the ability of the comput to clock the counter and increment its count by one. We used the following program: 10 POKE 49318,0 20 IF PEEK(49319) > 0 THEN 1000 30 PRINT "RESET TEST OK" 40 FOR C = 1 TO 15 50 POKE 49317, 0 60 IF PEEK(49319) C THEN 1010 70 NEXT C 80 PRINT "COUNT TEST OK": END ' 1000 PRINT "RESET FAILURE":END 1010 PRINT "COUNT FAILURE AT "; C: END 148
tfhe program first tests the reset and then starts the necessary tests to test the ability of the chip to increment its count by one for each p ulse that is received at the INP A pin, Step 9 This program does not test all 16 counter states, The last count om llll to 0000 is not tested, Could you change the program to ke care of this should not be difficult for you to add the final test to the program, here are several ways in which you could do this, Here is one: 90 POKE 49317,0 JOO IF PEEK(49319) 0 THEN 1010 110 PRINT "COUNT TEST OK": END this case, a final count has been generated and the "wrap-around" from 1111 to 0000 has been tested, The output port will not be used again, so you may remove it your breadboard, The input port will be used again, The power be turned o:ff, since the program will not be used again, EXPERIMENT NO, 15 SIMPLE fl.AG CIRCUITS The purpose of this experiment is to demonstrate the construction d use of simple Hag circuits, Flags are signals that are used by the computer and If 0 devices sb that their operations are synchronized, Flags are commonly used oindicate one of two possible conditions, ready/busy, full/empty, ,}xot/ cold, and other combinations that relate the conditions of an. 0.nterface to the computer, Experiment No, 6 illustrated the use of nput ports to transfer nonnumeric information to the computer, his experiment will develop this concept further, An 8-bit input is :required in this experiment,
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lJ. 21862 APPLE® INTERFACING JONAT
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APPLE® INTERFACING by Jonathan A.
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Preface The purpose in writing this
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make no attempt to provide much det
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Contents CHAPTER 1 6502 PROCESSOR 9
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CHAPTER 1 6502 Processor The Apple
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Fig. 1- 1. 6502 Microprocessor chip
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locate the memory "cell" that is to
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IR.,view At this point, you should
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Gei'!eral-fi!Jrp@S('; I/ 0 Commaru:
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of an examined memory location. Fro
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will now explore the actions that e
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transfers will require more than ei
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grams are probably easier to write
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·when the Apple computer is progrn
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Y@bie ::!1. VNth i
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DECODED OUTPUT puter systems, the R
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1 1 1 Using Decoders In many cases,
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used in PEEK commands, for example
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An alternate approach is to use bot
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sections, but the address inputs, A
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fUNCTlON TABLES COMPARING CASCADING
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flexible decoding scheme, as shown
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until the power is turned off. Ther
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the logic zero state. In most cases
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ue in sequence (in binary), 255, 25
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DATA BUS DATA A SN74125 DATA B DATA
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R gates that control the enabling o
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state of the unused bits cannot be
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CHAPTER 4 Flags and Decisions n alm
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VALUE 00111010 00011010 11110000 00
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•• Addrss Byte Da;a Syie Mexacl
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INPUT DEVICE RD 49321 - READY/BUSY
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INPUT DEVICE INPUT PORT Dl Dl ' D3
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y-language programming will also be
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CHAPTER 5 Breadboarding 01 With the
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5 IN4001 (4) 6 ,.___'-'' N:...J LM3
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A15 AIO A13 Al2 Al4 All A9 AfJ D .L
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In the memory address mode, must pl
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PIN CONFIGURATION DJ, LOGIC DIAGRAM
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The actual ORing of these control s
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Fig. 5·10. Packaged version of the
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SIGNAL APPLE PfN INTERFACE PIN +12V
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·.chips have rather slow access ti
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are possible, we think that one exp
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in most of the experiments unless o
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tep 3 You may wish to test other po
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,..,,.,....,"'"' in the block from
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None of the outputs should be activ
Page 99 and 100: ---" 2 CLR 20 2 CK Si\17474 The dev
Page 101 and 102: entered and run, It first asks you
Page 103 and 104: +5 Gl\ID LOGIC SWITCHES A B c D 16
Page 105 and 106: PR INT "O"; GOTO 65 If you wish to
Page 107 and 108: am, and the two-byte decimal calcul
Page 109 and 110: for each value that is input to the
Page 111 and 112: of the monitor screen each time the
Page 113 and 114: A = 128 420 B = PEEK(493 l 9) 430 F
Page 115 and 116: il!!lie -2. 0 THEN . . .
Page 117 and 118: program. You may forgotten steps to
Page 119 and 120: The A output, RD 49319, has already
Page 121 and 122: used the following program: FOR A =
Page 123 and 124: · numbers would have to be "split"
Page 125 and 126: tep 1 The input port and output por
Page 127 and 128: 0'"""c"y'·i- the relative values t
Page 129 and 130: and output ports are simply additio
Page 131 and 132: e has been divided into 256 values,
Page 133 and 134: e converter will not burn out, sinc
Page 135 and 136: 07 DATA BUS DO 3 4 7 a 13 14 17 18
Page 137 and 138: each decade. The bed code is used i
Page 139 and 140: LED BIT RED } D3 YELLOW EL M D4 GRE
Page 141 and 142: : : FOR T = 0 TO 770 NEX T T NEX T
Page 143 and 144: Thus, by testing the value input fr
Page 145 and 146: he six LEDs should be removed from
Page 147 and 148: Yo'1 should be able to develop the
Page 149: INPUT "LAST TWO DIGITS ";A$ IF A$ =
Page 153 and 154: would you program the computer so t
Page 155 and 156: Yes. Simply reverse the commands at
Page 157 and 158: · computer to measure analog volta
Page 159 and 160: he minimum value should be in the r
Page 161 and 162: 130 Y2 = PEEK(49319)/ 1.594 140 HPL
Page 163 and 164: You probably will not see much chan
Page 165 and 166: D7 D6 D5 D4 D3 D2 Dl DO 'b- • "A"
Page 167 and 168: ll'i!i Name 1 1/0 SELECT 2- 17 A 15
Page 169 and 170: ADDRESS BUS A7-AO :> MEMORY 256 x 8
Page 171 and 172: !n!erfac" Slel Addwess lta"%Je 0 C0
Page 173 and 174: 28 INT IN SLOT 6 +5 lK Lr LOCAL INT
Page 175 and 176: USER 1 This input will allow you to
Page 177 and 178: puts. You must be careful in your d
Page 179 and 180: CONTROL/ DATA input at pin 12 ( C/D
Page 181 and 182: 93427 OR EQUIV ROM ADDRESS BUS 1---
Page 183 and 184: use of red LEDs is recommended, sin
Page 185 and 186: APPENDIX B Parts Required for the E
Page 187 and 188: APPENDIX 6502 Microprocessor Techni
Page 189 and 190: MC§f.500 IE1lriy {D"i) This input
Page 191 and 192: MCS6500 INSTilUCTION SH-ALPHABETICA
Page 193 and 194: ,, ,, T!M!NG Il-01! READING DI\ TA
Page 195 and 196: MCS0t-20 PWH¢01 ns PWH¢2 ¢11ou11
Page 197 and 198: APPENDIX D Apple Interface Breadboa
Page 199 and 200: APPENDIX E Printed-Circuit Board Ar
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!'i9. E-2. Printecl-
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F t • I +: a... :::> 0 a: (!> 0 (
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Controllers, 14 Converter analog-to
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Pin configuration-cont SN7474, 150
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The Blacksburg Group According to B
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