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- .define Com
- .sect .text
- .sect .rom
- .sect .data
- .sect .bss
- .sect .text
- ! This subroutine performs a one complement on
- ! a group of atmost 254 bytes (number in register Y).
- ! This group is on the top of the stack.
- Com:
- lda SP+1
- sta ADDR+1 ! address (highbyte) of first byte
- lda SP+2
- sta ADDR ! address (lowbyte) of first byte
- 1: dey
- lda (ADDR),y
- eor #0x0FF ! one complement
- sta (ADDR),y
- tya
- bne 1b ! do it n times
- rts
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