30 lines
729 B
NASM
30 lines
729 B
NASM
.cseg
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;***** Subroutine Register Variables
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.def drem8u =r15 ;remainder
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.def dres8u =r16 ;result
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.def dd8u =r16 ;dividend
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.def dv8u =r17 ;divisor
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.def dcnt8u =r18 ;loop counter
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;***** Code
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div8u:
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sub drem8u,drem8u ; clear remainder and carry
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ldi dcnt8u,9 ; init loop counter
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d8u_1:
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rol dd8u ; shift left dividend
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dec dcnt8u ; decrement counter
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brne d8u_2 ; if done
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ret ; return
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d8u_2:
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rol drem8u ; shift dividend into remainder
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sub drem8u,dv8u ; remainder = remainder - divisor
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brcc d8u_3 ; if result negative
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add drem8u,dv8u ; restore remainder
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clc ; clear carry to be shifted into result
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rjmp d8u_1 ; else
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d8u_3:
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sec ; set carry to be shifted into result
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rjmp d8u_1
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