mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-12-03 03:52:16 +00:00
94 lines
2.1 KiB
NASM
94 lines
2.1 KiB
NASM
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]NACCUM EQU VARTAB
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]SIGN EQU VARTAB+4
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]NINDEX EQU VARTAB+6
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]STR EQU WPAR1
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INTASC2HEX
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LDY #0
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LDA (]STR),Y
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TAX
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LDA #1
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STA ]NINDEX ;
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LDA #0
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STA ]NACCUM
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STA ]NACCUM+1
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STA ]SIGN
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TXA
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BNE :INIT1
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JMP :EREXIT
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:INIT1
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LDY ]NINDEX
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LDA (]STR),Y
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CMP #173
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BNE :PLUS
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LDA #$0FF
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STA ]SIGN
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INC ]NINDEX
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DEX
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BEQ :EREXIT
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JMP :CNVERT
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:PLUS
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CMP #'+'
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BNE :CHKDIG
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INC ]NINDEX
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DEX ; DEC COUNT
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BEQ :EREXIT
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:CNVERT
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LDY ]NINDEX
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LDA (]STR),Y
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:CHKDIG
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CMP #$B0
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BMI :EREXIT
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CMP #$BA ; '9'+1
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BPL :EREXIT
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PHA
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ASL ]NACCUM
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ROL ]NACCUM+1
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LDA ]NACCUM
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LDY ]NACCUM+1
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ASL ]NACCUM
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ROL ]NACCUM+1
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ASL ]NACCUM
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ROL ]NACCUM+1
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CLC
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ADC ]NACCUM
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STA ]NACCUM
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TYA
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ADC ]NACCUM+1
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STA ]NACCUM+1
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PLA
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SEC
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SBC #$B0
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CLC
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ADC ]NACCUM
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STA ]NACCUM
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LDA #0
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ADC ]NACCUM+1
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STA ]NACCUM+1
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INC ]NINDEX ;INC TO NEXT CHARACTER
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DEX
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BNE :CNVERT
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LDA ]SIGN
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BPL :OKEXIT
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LDA #0
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SEC
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SBC ]NACCUM
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STA ]NACCUM
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LDA #0
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SBC ]NACCUM+1
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STA ]NACCUM+1
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:OKEXIT
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CLC
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BCC :EXIT
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:EREXIT
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SEC
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:EXIT
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LDA #2
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STA RETLEN
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LDX ]NACCUM+1
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LDA ]NACCUM
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STA RETURN
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STX RETURN+1
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RTS
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