titus-larsen-titus-1981-apple-interfacing

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must POKE the MASK ' and DATA bytes before you call the sub tine. The object here has been to show you a bit more of the powe the Apple computer and how it can handle different tasks. The path isn't often the most interesting or educational. 68
CHAPTER 5 Breadboarding 01 With the Apple It has always been our philosophy that computers should be easy :use, both for program development and for hardware or interface velopment. Since the necessary signals for interfacing most comters are readily available. somewhere in the computer system, it s decided to develop some general-purpose interface circuits that d be used with a number of different computers. These circuits fairly simple and are easily constructed and adapted to many puters besides the Apple. A printed circuit was developed coning all of the necessary circuits for interfacing purposes. A photoph of the interface is shown in Fig. 5-1. A standard 40-conductor cable is used to connect the interface breadboard to various comers. While the interfacing circuits could have been breadboarded then used for the experiments, it was thought that this would provide additional points at which problems could surface. BASIC BREADBOARD e basic breadboard contains a number of useful circuits that alinterface designs to be easily set up and tested. The basic secs are Power Supply, Logic Probe, Device and Memory Decoders, Buffers, and Control Circuitry. er Supply e power supply section of the breadboard may be operated in of two ways. An external +5-volt power supply may be used, as 69
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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
Page 19 and 20: Gei'!eral-fi!Jrp@S('; I/ 0 Commaru:
Page 21 and 22: of an examined memory location. Fro
Page 23 and 24: will now explore the actions that e
Page 25 and 26: transfers will require more than ei
Page 27 and 28: grams are probably easier to write
Page 29 and 30: ·when the Apple computer is progrn
Page 31 and 32: Y@bie ::!1. VNth i
Page 33 and 34: DECODED OUTPUT puter systems, the R
Page 35 and 36: 1 1 1 Using Decoders In many cases,
Page 37 and 38: used in PEEK commands, for example
Page 39 and 40: An alternate approach is to use bot
Page 41 and 42: sections, but the address inputs, A
Page 43 and 44: fUNCTlON TABLES COMPARING CASCADING
Page 45 and 46: flexible decoding scheme, as shown
Page 47 and 48: until the power is turned off. Ther
Page 49 and 50: the logic zero state. In most cases
Page 51 and 52: ue in sequence (in binary), 255, 25
Page 53 and 54: DATA BUS DATA A SN74125 DATA B DATA
Page 55 and 56: R gates that control the enabling o
Page 57 and 58: state of the unused bits cannot be
Page 59 and 60: CHAPTER 4 Flags and Decisions n alm
Page 61 and 62: VALUE 00111010 00011010 11110000 00
Page 63 and 64: •• Addrss Byte Da;a Syie Mexacl
Page 65 and 66: INPUT DEVICE RD 49321 - READY/BUSY
Page 67 and 68: INPUT DEVICE INPUT PORT Dl Dl ' D3
Page 69: y-language programming will also be
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
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used the following program: FOR A =
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· numbers would have to be "split"
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tep 1 The input port and output por
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0'"""c"y'·i- the relative values t
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and output ports are simply additio
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e has been divided into 256 values,
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e converter will not burn out, sinc
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07 DATA BUS DO 3 4 7 a 13 14 17 18
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each decade. The bed code is used i
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LED BIT RED } D3 YELLOW EL M D4 GRE
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: : FOR T = 0 TO 770 NEX T T NEX T
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Thus, by testing the value input fr
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he six LEDs should be removed from
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Yo'1 should be able to develop the
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INPUT "LAST TWO DIGITS ";A$ IF A$ =
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tfhe program first tests the reset
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would you program the computer so t
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Yes. Simply reverse the commands at
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· computer to measure analog volta
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he minimum value should be in the r
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130 Y2 = PEEK(49319)/ 1.594 140 HPL
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You probably will not see much chan
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D7 D6 D5 D4 D3 D2 Dl DO 'b- • "A"
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ll'i!i Name 1 1/0 SELECT 2- 17 A 15
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ADDRESS BUS A7-AO :> MEMORY 256 x 8
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!n!erfac" Slel Addwess lta"%Je 0 C0
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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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