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- .define Ror4
- .sect .text
- .sect .rom
- .sect .data
- .sect .bss
- .sect .text
- ! This subroutine rotates right a fourbyte word.
- ! The number of rotates is in X.
- Ror4:
- txa
- bne 1f ! a zero rotate skip
- rts
- 1: tay
- jsr Pop
- stx ARTH
- sta ARTH+1
- jsr Pop
- stx ARTH+2
- sta ARTH+3
- 2: lsr ARTH+3 ! rotate word
- ror ARTH+2
- ror ARTH+1
- ror ARTH
- bcc 1f ! no carry
- lda #0x80 ! put carry in leftmost bit
- ora ARTH+3
- sta ARTH+3
- 1: dey
- bne 2b
- lda ARTH+3
- ldx ARTH+2
- jsr Push
- lda ARTH+1
- ldx ARTH
- jmp Push ! push result onto the stack
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