Apple II | TOPIC -- Apple II -- Red Book Sweet-16 listing

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1 ***********************

2 * *

3 * APPLE-II PSEUDO *

4 * MACHINE INTERPRETER *

5 * *

7 * APPLE COMPUTER INC *

8 * *

10 * S. WOZNIAK *

11 * *

12 ***********************

13 ; TITLE "SWEET16 INTERPRETER"

14 R0L EQU $0

15 R0H EQU $1

16 R14H EQU $1D

17 R15L EQU $1E

18 R15H EQU $1F

19 SW16PAG EQU $F7

20 SAVE EQU $FF4A

21 RESTORE EQU $FF3F

22 ORG $F689

F689: 20 4A FF 23 SW16 JSR SAVE ;PRESERVE 6502 REG CONTENTS

F68C: 68 24 PLA

F68D: 85 1E 25 STA R15L ;INIT SWEET16 PC

F68F: 68 26 PLA ;FROM RETURN

F690: 85 1F 27 STA R15H ; ADDRESS

F692: 20 98 F6 28 SW16B JSR SW16C ;INTERPRET AND EXECUTE

F695: 4C 92 F6 29 JMP SW16B ;ONE SWEET16 INSTR.

F698: E6 1E 30 SW16C INC R15L

F69A: D0 02 31 BNE SW16D ;INCR SWEET16 PC FOR FETCH

F69C: E6 1F 32 INC R15H

F69E: A9 F7 33 SW16D LDA #SW16PAG

F6A0: 48 34 PHA ;PUSH ON STACK FOR RTS

F6A1: A0 00 35 LDY #$0

F6A3: B1 1E 36 LDA (R15L),Y ;FETCH INSTR

F6A5: 29 0F 37 AND #$F ;MASK REG SPECIFICATION

F6A7: 0A 38 ASL ;DOUBLE FOR TWO BYTE REGISTERS

F6A8: AA 39 TAX ;TO X REG FOR INDEXING

F6A9: 4A 40 LSR

F6AA: 51 1E 41 EOR (R15L),Y ;NOW HAVE OPCODE

F6AC: F0 0B 42 BEQ TOBR ;IF ZERO THEN NON-REG OP

F6AE: 86 1D 43 STX R14H ;INDICATE'PRIOR RESULT REG'

F6B0: 4A 44 LSR

F6B1: 4A 45 LSR ;OPCODE*2 TO LSB'S

F6B2: 4A 46 LSR

F6B3: A8 47 TAY ;TO Y REG FOR INDEXING

F6B4: B9 E1 F6 48 LDA OPTBL-2,Y ;LOW ORDER ADR BYTE

F6B7: 48 49 PHA ;ONTO STACK

F6B8: 60 50 RTS ;GOTO REG-OP ROUTINE

F6B9: E6 1E 51 TOBR INC R15L

F6BB: D0 02 52 BNE TOBR2 ;INCR PC

F6BD: E6 1F 53 INC R15H

F6BF: BD E4 F6 54 TOBR2 LDA BRTBL,X ;LOW ORDER ADR BYTE

F6C2: 48 55 PHA ;ONTO STACK FOR NON-REG OP

F6C3: A5 1D 56 LDA R14H ;'PRIOR RESULT REG' INDEX