1984-12-17 11:03:13 +00:00
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.define Rol
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1987-01-30 18:41:42 +00:00
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.sect .text
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.sect .rom
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.sect .data
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.sect .bss
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.sect .text
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1984-12-17 11:03:13 +00:00
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! This subroutine rotates left an integer n times
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! N is in register X.
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! The result is returned in registerpair AX.
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Rol:
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txa
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bne 1f
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jmp Pop ! zero rotate return input
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1: tay ! Y contains number of rotates
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jsr Pop
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stx Ytmp ! save lowbyte
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2: clc
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rol Ytmp ! rotate lowbyte
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rol a ! rotate highbyte
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bcc 1f ! no carry
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inc Ytmp ! put carry in rightmost bit
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1: dey
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bne 2b
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ldx Ytmp ! store lowbyte in X
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rts
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