titus-larsen-titus-1981-apple-interfacing

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operations that can be used to obtain the decimal equivalent for·· two-byte binary number Since the MSBY is "offset" by a factor of 256, you can use the follow; ing relationship: VALUE = (M * 256) + l where VALUE is the final decimal value of the 16-bit word. Step 3 To test this equation, enter the following program into the puter: 200 INPUT "SET MSBY ON SWITCHES ";A$ 210 M = PEEK(49319) 220 INPUT "SET LSBY ON SWITCHES ";A$ 230 L = PEEK (49319) 240 V = (256 * M) + l 250 PR INT V 260 GOTO 200 Now run the program, starting it by entering GOTO 200, and pressing the RETURN key. When the computer asks, "SET MSBY ON SWITCHES" set the eight bits for the value of the MSBY on the eight switches. Depress the RETURN key on the keyboard. When the computer asks, "SET LSBY ON SWITCHES" change the eight switches so that they represent the eight bits that you wish to enter for the LSBY value. When the switches have been set, depress the RETURN key so that the computer will know that you are ready. Now the decimal value should be displayed on the video monitor, Some typical 16-bit values that you might wish to try are listed below. Fill in the decimal value for each, as generated by the Apple. You should be able to check these fairly quickly with the aid of a calculator. MSBY 11001010 11000111 00000001 SBY 11000001 0001l l01 10000001 You should find values of 51905, 50973, and 385. Sep 4 The following program is a combination of the binary output pro-
am, and the two-byte decimal calculation program. It will allow u to input two 8-bit bytes to represent a 16-bit value, display the ecimal value and the binary value. A = 32768 FOR S = l TO 2 FOR Q = l TO 8 IF B-A
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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
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 and 70: y-language programming will also be
Page 71 and 72: 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: PR INT "O"; GOTO 65 If you wish to
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 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
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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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