mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-12-02 12:52:03 +00:00
96 lines
2.1 KiB
Plaintext
96 lines
2.1 KiB
Plaintext
*
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*``````````````````````````````*
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* DIVD8 :: 8BIT DIVISION (8BR) *
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*- -*
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* DIVIDE ONE 8BIT NUMBER BY *
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* ANOTHER TO GET AN 8BIT *
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* RESULT. UNSIGNED ONLY. *
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* *
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* ORIGINAL AUTHOR IS WHITE *
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* FLAME, AS SHARED ON *
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* CODEBASE64. MINOR CHANGES. *
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*- -*
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* CLOBBERS: *
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* *
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* FLAGS: ????---- REG: AXYM *
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*- -*
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* CYCLES: ??? *
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* SIZE: *
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*- -*
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* USAGE: *
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* *
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* LDA #200 *
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* PHA *
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* PDA #10 *
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* PHA *
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* JSR DIV8 *
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*- -*
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* ENTRY *
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* *
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* LOW BYTE OF RETURN ADDRESS *
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* HIGH BYTE OF RETURN ADDRESS *
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* SECOND NUM TO BE MULTIPLIED *
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* FIRST NUM TO BE MULTIPLIED *
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*- -*
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* EXIT *
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* *
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* .Y = REMAINDER *
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* .X = UNCHANGED *
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* .A = QUOTIENT *
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* *
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* [RETURN] = QUOTIENT *
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* [RETLEN] = 1 (QUOT LENGTH) *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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DIVD8
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*
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** GET RETURN ADDRESS
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*
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PLA
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STA RETADR
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PLA
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STA RETADR+1
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*
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** GET PARAMETERS
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*
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PLA
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STA :DVEND
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PLA
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STA :DVSOR
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*
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LDA #$00
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LDY #8
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ASL :DVSOR
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:L1 ROL
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CMP :DVEND
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BCC :L2
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SBC :DVEND
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:L2 ROL :DVSOR
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DEY
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BNE :L1
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STA :REM
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*
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** RESTORE RETURN ADDRESS
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*
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LDA RETADR+1
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PHA
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LDA RETADR
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PHA
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*
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** LOAD QUOTIENT INTO A, REMAINDER INTO X
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*
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LDY :REM ; REMAINDER TO Y
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LDA #1
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STA RETLEN
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LDA :DVSOR
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STA RETURN
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*
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RTS
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*
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** DATA
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*
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:REM DS 1
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:DVEND DS 1
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:DVSOR DS 1
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*
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