titus-larsen-titus-1981-apple-interfacing

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20 POKE 4931 B, V 30 NEXT V 40 GOTO 10 ir;a"g"law 11pui l 0 FOR V = 0 TO 255 20 POKE 4931 B, V 30 NEXT V 40 FOR V = 254 TO l 50 POKE 4931 B, V 60 NEXT V 70 GOTO 10 STEP -1 You may wish to try either of these programs, or the ones you wrote. Why is the range in one of the triangular output lo 254 to 1 instead of 255 to O H the range is 255 to 0, these two values will be output twice, though you probably couldn't tell the difference on the meter. time delay, or delays, may be useful in these programs. Sile 4 Since you know that the voltage from 0 to 10 volts correspon to steps from 0 to 255, can you write a program that would allo you to enter a voltage from the keyboard and that would genera this voltage on the meter Use the following space for your progra We developed the following program, which you may wish to 10 INPUT "VOLTAGE ";V 20 R = V * 25.5 30 POKE 49318, R 40 GOTO 10 Step 5 Try your program, too. Does it generate a voltage from the converter that closely matches the voltage that you entered program seemed to work well, considering inaccuracies in the This program does not have any "error detecting" steps, so you also try and generate a + 15-volt signal from the converter. What you think will happen Will the converter burn out 130
e converter will not burn out, since it can only accept an 8-bit le, which corresponds to an output of + 10 volts. The "15" input 15 volts will cause an ILLEGAL QUANTITY ERROR, since we trying to transfer the value 382 to an 8-bit device. It just can't done with eight bits. t this point, you should be able to write a program that will alyou to enter an upper voltage and a lower voltage, and to have :tite Apple generate a triangular wave between them. Use your best togramming skills. e used the following program: INPUT "UPPER VOLTAGE"; H IF H = 0 THEN 40 PRINT "VOLTAGE OUT OF BOUNDS": GOTO 10 INPUT "LOWER VOLTAGE"; L IF L = 0 PRINT "VOLTAGE OUT OF BOUNDS": GOTO 40 IF H > L THEN 90 PRINT "UPPER V MUST BE HIGHER THAN LOWER V": GOTO 10 H = H * 25.5: L = L * 25.5 FOR V = l TO H POKE 49318, V NEXT V FOR V = H - 1 TO L + 1 STEP - 1 POKE 49318, V NEXT V GOTO 100 ";n your program and test it. You should be able to make the meter edle "swing" between the upper and lower voltages. You may use time delay, or delays, if you wish to slow the meter movement so t can easily watch it. experiment clearly shows you how a simple DI A converter y be interfaced to your computer. The NE5018 used internal tches, and much of the analog circuitry has been placed on the nverter chip. D/ A converters find use in applications that require e computer to control voltage-dependent devices, such as servo tors, amplifiers, etc. ou will not use the NE5018 D/ A converter again, so you may it from your breadboard. The SN7 402 NOR gate chip should retained, but the SN7 404 inverter may be removed. Power may turned off. Carefully remove the connections to the + 12- and 131
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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
Page 81 and 82: The actual ORing of these control s
Page 83 and 84: Fig. 5·10. Packaged version of the
Page 85 and 86: SIGNAL APPLE PfN INTERFACE PIN +12V
Page 87 and 88: ·.chips have rather slow access ti
Page 89 and 90: are possible, we think that one exp
Page 91 and 92: in most of the experiments unless o
Page 93 and 94: tep 3 You may wish to test other po
Page 95 and 96: ,..,,.,....,"'"' in the block from
Page 97 and 98: 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: e has been divided into 256 values,
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 and 150: INPUT "LAST TWO DIGITS ";A$ IF A$ =
Page 151 and 152: tfhe program first tests the reset
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---
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use of red LEDs is recommended, sin
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APPENDIX B Parts Required for the E
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APPENDIX 6502 Microprocessor Techni
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MC§f.500 IE1lriy {D"i) This input
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MCS6500 INSTilUCTION SH-ALPHABETICA
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,, ,, T!M!NG Il-01! READING DI\ TA
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MCS0t-20 PWH¢01 ns PWH¢2 ¢11ou11
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APPENDIX D Apple Interface Breadboa
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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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