titus-larsen-titus-1981-apple-interfacing

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Step 7 Enter our program, or yours, into the computer and test it. Yo will have to press the RETURN key to display the MSBY on t LEDs, and you must press it a second time to display the LSB Can you enter values greater than 65535 Can they be converte and displayed Yes, you can enter them, and they will be converted, but you c,aJurnJ')!lf!l display them, since they will generate results that are greater • .,··cl§J
tep 1 The input port and output port described previously will be used this experiment. By now, you should be familiar with these types ports, but we refer you to Experiment Nos. 2, 3, and 8 for the cessary details. If you have not performed these experiments, we ommend that you do so before going on with this experiment. In this experiment, you will use the computer to acquire and disay a set of values that are acquired from the input port. While ese may be acquired with software steps such as: INPUT A$ Q = PEEK(49319) INPUT A$ R = PEEK(49319) ·stakes a great number of software steps to acquire a small amount information. Can you suggest an alternative ist of values can be acquired by using a loop, and an array can used to store the information, so that a new variable need not assigned to each new data value. Can you write a short program t could be used to acquire 10 data points used the following program, which should look somewhat like s. Note the use of an array to store the information. 0 DIM A(lO) PRINT "START" FOR P = 1 TO 10 INPUT A$ A(P) = PEEK(49319) NEXT P PRINT "START DISPLAY • • ." 123
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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
Page 73 and 74: 5 IN4001 (4) 6 ,.___'-'' N:...J LM3
Page 75 and 76: A15 AIO A13 Al2 Al4 All A9 AfJ D .L
Page 77 and 78: In the memory address mode, must pl
Page 79 and 80: 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: · numbers would have to be "split"
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 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
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USER 1 This input will allow you to
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puts. You must be careful in your d
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CONTROL/ DATA input at pin 12 ( C/D
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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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