# SXMicrocontrollerMathMethod

## Divide 16 bit int by 16 bit int to 16 bit int with 16 bit int remander

; uint16 x = uint16 x / uint16 y
;
; Input:
;  x, x+1 - 16 bit unsigned integer dividend (x - lsb, x+1 - msb)
;  y, y+1 - 16 bit unsigned integer divisor
; Output:
;  x, x+1 - 16 bit unsigned integer quotient
; Temporary:
;  counter
;  x+2, x+3 - 16 bit remainder
;  temp - remainder extension
; Size: 36 instructions
; Max timing: 6+16*(5+14+4)-2+2+3=377 cycles

div16by16
clr	x+2	;clear
clr	x+3	;remainder
div16by16loopinit
clr	temp	;clear remainder extension
mov	W, #16
mov	counter, W
stc		;first iteration will be subtraction
div16by16loop
;shift in next result bit and shift out next
;dividend bit to remainder

rl	x	;shift lsb
rl	x+1	;shift msb
rl	x+2
rl	x+3
rl	temp

mov	W, y
sb	x.0

;subtract divisor from remainder
sub	x+2, W
mov	W, y+1
sc
movsz	W, ++y+1
sub	x+3, W
mov	W, #1
sc
sub	temp, W
jmp	div16by16next

mov	W, y+1
snc
movsz	W, ++y+1
mov	W, #1
snc

div16by16next
;carry is next result bit
decsz	counter
jmp	div16by16loop

;shift in last bit
rl	x
rl	x+1
ret

• /techref/scenix/member/NG--944/index.htm An improved version: smaller, faster, one fewer temp, and computes the remainder.
; uint16 x = uint16 x / uint16 y
;
; Input:
; x, x+1 - 16 bit unsigned integer dividend (x - lsb, x+1 - msb)
; y, y+1 - 16 bit unsigned integer divisor
; Output:
; x, x+1 - 16 bit unsigned integer quotient
; x+2, x+3 - 16 bit unsigned integer remainder
; Temporary:
; counter
; Size: 28 instructions
; Max timing: 4+16*(4+15+4)-2+2+3=375 cycles

div16by16
clr x+2 ;clear
clr x+3 ;remainder
mov W, #16
mov counter, W
div16by16loop
;shift in next result bit and shift out next
;dividend bit to remainder
rl x
rl x+1
rl x+2
rl x+3

;subtract divisor from remainder
mov W, y
sub x+2, W
mov W, y+1
sc
movsz W, ++y+1
sub x+3, W
;if no borrow, set next quotient bit
snc
jmp div16by16next

;if borrow, clear next quotient bit and restore the remainder

mov W, y
mov W, y+1
snc
movsz W, ++y+1
clc

div16by16next

decsz counter
jmp div16by16loop
;shift in last result bit
rl x
rl x+1

ret
• +

 file: /Techref/scenix/lib/math/div/16by16ng.htm, 3KB, , updated: 2006/9/18 13:00, local time: 2024/7/17 08:46, TOP NEW HELP FIND:  44.213.60.33:LOG IN

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