; 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 jmp div16by16add ;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 div16by16add ;add divisor to remainder add x+2, W mov W, y+1 snc movsz W, ++y+1 add x+3, W mov W, #1 snc add temp, W div16by16next ;carry is next result bit decsz counter jmp div16by16loop ;shift in last bit rl x rl x+1 ret

See also:

- /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

;add divisor to remainder

mov W, y

add x+2, W

mov W, y+1

snc

movsz W, ++y+1

add x+3, W

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, |

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