Отправлено Linuxoid 29 августа 2002 г. 16:15 В ответ на: У Atmel в аппнотах avr200.asm, avr200b.asm деление/умножение двухбайтовых целых (+) отправлено Linuxoid 29 августа 2002 г. 16:07

;***************************************************************************
;*
;* "div16s" - 16/16 Bit Signed Division
;*
;* This subroutine divides signed the two 16 bit numbers
;* "dd16sH:dd16sL" (dividend) and "dv16sH:dv16sL" (divisor).
;* The result is placed in "dres16sH:dres16sL" and the remainder in
;* "drem16sH:drem16sL".
;*
;* Number of words :39
;* Number of cycles :247/263 (Min/Max)
;* Low registers used :3 (d16s,drem16sL,drem16sH)
;* High registers used :7 (dres16sL/dd16sL,dres16sH/dd16sH,dv16sL,dv16sH,
;* dcnt16sH)
;*
;***************************************************************************

;***** Subroutine Register Variables

.def d16s =r13 ;sign register
.def drem16sL=r14 ;remainder low byte
.def drem16sH=r15 ;remainder high byte
.def dres16sL=r16 ;result low byte
.def dres16sH=r17 ;result high byte
.def dd16sL =r16 ;dividend low byte
.def dd16sH =r17 ;dividend high byte
.def dv16sL =r18 ;divisor low byte
.def dv16sH =r19 ;divisor high byte
.def dcnt16s =r20 ;loop counter

;***** Code

div16s: mov d16s,dd16sH ;move dividend High to sign register
eor d16s,dv16sH ;xor divisor High with sign register
sbrs dd16sH,7 ;if MSB in dividend set
rjmp d16s_1
com dd16sH ; change sign of dividend
com dd16sL
subi dd16sL,low(-1)
sbci dd16sL,high(-1)
d16s_1: sbrs dv16sH,7 ;if MSB in divisor set
rjmp d16s_2
com dv16sH ; change sign of divisor
com dv16sL
subi dv16sL,low(-1)
sbci dv16sL,high(-1)
d16s_2: clr drem16sL ;clear remainder Low byte
sub drem16sH,drem16sH;clear remainder High byte and carry
ldi dcnt16s,17 ;init loop counter

d16s_3: rol dd16sL ;shift left dividend
rol dd16sH
dec dcnt16s ;decrement counter
brne d16s_5 ;if done
sbrs d16s,7 ; if MSB in sign register set
rjmp d16s_4
com dres16sH ; change sign of result
com dres16sL
subi dres16sL,low(-1)
sbci dres16sH,high(-1)
d16s_4: ret ; return
d16s_5: rol drem16sL ;shift dividend into remainder
rol drem16sH
sub drem16sL,dv16sL ;remainder = remainder - divisor
sbc drem16sH,dv16sH ;
brcc d16s_6 ;if result negative
add drem16sL,dv16sL ; restore remainder
adc drem16sH,dv16sH
clc ; clear carry to be shifted into result
rjmp d16s_3 ;else
d16s_6: sec ; set carry to be shifted into result
rjmp d16s_3