mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-11-28 18:50:09 +00:00
146 lines
3.2 KiB
Plaintext
146 lines
3.2 KiB
Plaintext
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*``````````````````````````````*
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* ZMSAVE :: SAVE 0-PAGE FREE *
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*- -*
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* STORES THE VALUES IN THE *
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* LITTLE FREE SPACE ON THE *
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* ZERO PAGE AT AN ALTERNATE *
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* MEMORY LOCATION TO BE *
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* RETRIEVED AND RESTORED AT A *
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* LATER POINT. *
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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 #>$6A00 *
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* PHA *
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* LDA #<$6A00 *
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* PHA *
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* JSR ZMSAVE *
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*- -*
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* ENTRY *
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* *
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* TOP OF STACK *
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* *
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* LOW BYTE OF RETURN ADDRESS *
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* HI BYTE OF RETURN ADDRESS *
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* LOW BYTE OF DESTINATION *
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* HIGH BYTE OF DESTINATION *
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*- -*
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* EXIT *
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* *
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* TOP OF STACK *
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* *
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* LOW BYTE OF RETURN ADDRESS *
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* HI BYTE OF RETURN ADDRESS *
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* *
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* Y = TRASH *
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* X = TRASH *
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* A = LOW BYTE OF RET ADDR *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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ZMSAVE
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*
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** LOAD ADDR1 ZERO PAGE AREA FIRST,
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** SINCE WE'LL BE USING THAT
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*
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** NOTE THAT THIS SHOULD ALWAYS BE
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** $06 AND $07, OR ELSE CODE WILL
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** HAVE TO CHANGE.
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*
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LDX ADDR1
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LDY ADDR1+1
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*
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** SAVE RETURN ADDRESS
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*
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PLA
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STA :RETADR ; LOCAL BECAUSE RETADDR
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PLA ; IS STORED ON ZERO PAGE
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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 ADDR1
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PLA
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STA ADDR1+1
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*
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** COPY ZERO PAGE TO SPECIFIED
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** NON-ZERO LOCATION (ONLY THE
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** FREE ONES..)
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*
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TYA ; STORE ADDR1 VALS
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LDY #1 ; FIRST
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STA (ADDR1),Y
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LDY #0
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TXA
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STA (ADDR1),Y
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LDY #2
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LDA $08
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STA (ADDR1),Y
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INY
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LDA $09
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STA (ADDR1),Y
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INY
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LDA $19
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STA (ADDR1),Y
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INY
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LDA $1E
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STA (ADDR1),Y
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INY
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LDA $E3
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STA (ADDR1),Y
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INY
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LDA $EB
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STA (ADDR1),Y
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INY
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LDA $EC
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STA (ADDR1),Y
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INY
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LDA $ED
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STA (ADDR1),Y
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INY
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LDA $EE
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STA (ADDR1),Y
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INY
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LDA $EF
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STA (ADDR1),Y
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INY
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LDA $FA
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STA (ADDR1),Y
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INY
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LDA $FB
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STA (ADDR1),Y
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INY
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LDA $FC
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STA (ADDR1),Y
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INY
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LDA $FD
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STA (ADDR1),Y
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INY
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LDA $FE
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STA (ADDR1),Y
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INY
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LDA $FF
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STA (ADDR1),Y
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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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RTS
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*
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** DATA
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*
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:RETADR DS 2
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*
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