mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2025-02-18 15:30:36 +00:00
9b12b6fd9b
- getting ready for major changes for 0.6.0. - be sure to download the 0.5.0 release to ensure proper functionality, as these rountines will not work together in the SRC or BIN folder during the transition - Beginning to significantly alter documentation
101 lines
3.2 KiB
NASM
101 lines
3.2 KiB
NASM
*
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*``````````````````````````````*
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* AGET161 (NATHAN RIGGS) *
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* *
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* GET DATA IN ARRAY ELEMENT *
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* *
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* INPUT: *
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* *
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* WPAR1 = ARRAY ADDRESS *
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* WPAR2 = ELEMENT INDEX *
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* *
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* OUTPUT: *
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* *
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* .A = ELEMENT LENGTH *
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* .X = ELEMENT ADDR LOBYTE *
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* .Y = ELEMENT ADDR HIBYTE *
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* RETURN = ELEMENT DATA *
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* RETLEN = ELEMENT LENGTH *
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* *
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* DESTROY: AXYNVBDIZCMS *
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* ^^^^^ ^^^ *
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* *
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* CYCLES: 126 *
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* SIZE: 135 BYTES *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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]AIDX EQU WPAR2
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]ADDR EQU WPAR1
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*
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]ESIZE EQU VARTAB ; ELEMENT LENGTH
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]ESIZEB EQU VARTAB+1 ; ^BACKUP
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]ASIZE EQU VARTAB+2 ; NUMBER OF ELEMENTS
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]IDX EQU VARTAB+6 ; INDEX BACKUP
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*
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AGET161
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LDA ]AIDX
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STA ]IDX
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LDA ]AIDX+1 ; GET INDEX HIBYTE
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STA ]AIDX+1
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STA SCRATCH
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LDY #0 ; RESET INDEX
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LDA (]ADDR),Y ; GET NUMBER OF
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STA ]ASIZE ; ARRAY ELEMENTS
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LDY #1 ; GET HIBYTE OF
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LDA (]ADDR),Y ; # OF ARRAY ELEMENTS
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STA ]ASIZE+1
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INY ; INCREASE BYTE INDEX
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LDA (]ADDR),Y ; GET ELEMENT LENGTH
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STA ]ESIZE
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STA ]ESIZEB
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*
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** MULTIPLY INDEX BY ELEMENT SIZE, ADD 3
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*
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LDY #0 ; RESET .Y AND .A
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LDA #0
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BEQ :ENTLPA ; IF ZERO, SKIP TO LOOP
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:DOADD
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CLC ; CLEAR CARRY
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ADC ]AIDX ; ADD INDEX TO .A
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TAX ; HOLD IN .X
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TYA ; LOAD HIBYTE
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ADC SCRATCH ; ADD HIBYTE
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TAY ; HOLD IN .Y
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TXA ; RELOAD LOBYTE
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:LPA
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ASL ]AIDX ; MULTIPLY INDEX BY 2
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ROL SCRATCH ; ADJUST HIBYTE
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:ENTLPA
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LSR ]ESIZE ; DIVIDE ELEMENT LENGTH BY 2
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BCS :DOADD ; IF BIT 1 SHIFTED IN CARRY, ADD MORE
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BNE :LPA ; CONTINUE LOOPING IF ZERO FLAG UNSET
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STX ]IDX ; STORE LOBYTE
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STY ]IDX+1 ; STORE HIBYTE
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LDA #3 ; ADD 3 TO INDEX LOBYTE
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CLC ; CLEAR CARRY
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ADC ]IDX
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STA ADDR2 ; STORE ON ZERO PAGE
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LDA ]IDX+1 ; ADJUST HIBYTE
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ADC #0
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STA ADDR2+1
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*
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LDA ADDR2 ; ADD ARRAY ADDRESS
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CLC
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ADC ]ADDR ; LOBYTE
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STA ADDR2
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LDA ADDR2+1 ; HIBYTE
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ADC ]ADDR+1
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STA ADDR2+1
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LDY #0 ; RESET BYTE INDEX
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:LP
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LDA (ADDR2),Y ; GET BYTE FROM ELEMENT
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STA RETURN,Y ; PUT INTO RETURN
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INY ; INCREASE BYTE INDEX
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CPY ]ESIZEB ; IF INDEX != ELEMENT LENGTH
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BNE :LP ; CONTINUE LOOP
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LDA ]ESIZEB ; .A = ELEMENT SIZE
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STA RETLEN ; STORE IN RETLEN
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LDY ADDR2+1 ; .Y = ELEMENT ADDRESS HIBYTE
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LDX ADDR2 ; .X = ELEMENT ADDRESS LOBYTE
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RTS
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