mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-11-28 18:50:09 +00:00
164 lines
3.7 KiB
Plaintext
164 lines
3.7 KiB
Plaintext
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*
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*``````````````````````````````*
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* MEMSWAP :: MEMORY SWAP *
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*- -*
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* SWAPS THE VALUES STORED IN *
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* TWO BLOCKS OF SEQUENTIAL *
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* MEMORY. *
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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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* LDA #>$300 *
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* PHA *
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* LDA #<$300 *
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* PHA *
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* LDA #$100 *
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* PHA *
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* JSR MEMSWAP *
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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 FIRST ADDRESS *
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* HIGH BYTE OF FIRST ADDRESS *
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* LOBYTE OF SECOND ADDRESS *
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* HIBYTE OF SECOND ADDRESS *
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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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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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MEMSWAP
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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 VARIABLES
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*
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PLA
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STA :LENGTH
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PLA
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STA ADDR1
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STA :A1
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PLA
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STA ADDR1+1
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STA :A1+1
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PLA
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STA ADDR2
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STA :A2
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PLA
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STA ADDR2+1
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STA :A2+1
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*
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********************************
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*
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* ERROR CONTROL
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*
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********************************
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*
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LDA ERRCTRL
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CMP #1
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BEQ :CHKERR
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JMP :ERREND
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:CHKERR
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LDA ADDR2+1 ; IF #>A2 => #>A1
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CMP ADDR1+1
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BCS :CHKLO ; CHECK LOW BYTES
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JMP :A1GTA2 ; ELSE, A1 > A2
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:CHKLO
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LDA ADDR2
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CMP ADDR1
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BCS :A2GTA1
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JMP :A1GTA2
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:A2GTA1
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LDA ADDR2 ;CALC DEST-SRC
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SEC
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SBC ADDR1
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TAX
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LDA ADDR2+1
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SBC ADDR1+1 ; MOD 64K AUTOMATIC
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; -- DISCARD CARRY
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TAY
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TXA ; CMP WITH # OF BYTES TO MOVE
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CMP :LENGTH
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TYA
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SBC :LENGTH+1
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BCS :ERREND ; BRANCH IF NO OVERLAP
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JMP :OVF
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:A1GTA2
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LDA ADDR1
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SEC
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SBC ADDR2
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TAX
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LDA ADDR1+1
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SBC ADDR2+1
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TAY
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TXA
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CMP :LENGTH
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TYA
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SBC :LENGTH+1
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BCS :ERREND
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:OVF
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_ERR :E_SID;:E_OVF;:E_DUMP;:LENGTH;#6
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*
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********************************
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*
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:ERREND
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*
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********************************
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*
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LDY #255 ; COUNTER
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:LP
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INY
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LDA (ADDR1),Y
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TAX ; X CONTAINS ADDR1 VAL
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LDA (ADDR2),Y ; A CONTAINS ADDR2 VAL
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STA (ADDR1),Y
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TXA
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STA (ADDR2),Y
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CPY :LENGTH
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BNE :LP
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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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** VARIABLES
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*
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:LENGTH DS 2
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:A1 DS 2
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:A2 DS 2
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*
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:E_SID ASC "MEMSWAP (MSWAP MACRO)",00
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:E_DUMP ASC "DUMPING LENGTH (2) A1(2) A2(2)",00
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:E_OVF ASC "OVERFLOW! ADDRESSES OVERLAP.",00
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*
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