please dont rip this site

SX Microcontroller Math Method

Divide 48 bit int by 23 bit int to 48 bit int

by Nikolai Golovchenko

Dividend	DS 6
Divisor		DS 3
Temp		DS 3
BitCount	DS 1


;**********************************************************************
;
;48 BY 23 BIT UNSIGNED DIVISION (Non-restoring method)
;
;**********************************************************************
;
;     Input: Dividend, 6 bytes (Dividend+0 MSB, ... , Dividend+5 LSB)
;            Divisor, 3 bytes (Divisor+0 MSB, ... , Divisor+2 LSB)
;
;    Output: Dividend, 6 bytes (Dividend = Dividend / Divisor)
;            Z  - division by zero
;            NZ - okay
;
; Temporary: Temp, 3 bytes - remainder
;            BitCount, 1 byte - counter
;
;      Size: 52 instructions
;
;Max timing: 3+5+6+28*48-2+7+3=1366 cycles
;
;**********************************************************************

DIVIDE_48by23

        ; Test for zero division
	mov	W, Divisor
	or	W, Divisor+1
	or	W, Divisor+2
	snz
	ret			; divisor = zero, not possible to calculate -
				; return with set zero flag (Z)

        ; clear remainder
	clr	Temp
	clr	Temp+1
	clr	Temp+2

	mov	W, #48		; initialize bit counter
	mov	BitCount, W

	stc			; set carry to perform subtraction
				; first in the following loop
DIVIDE_LOOP_48by23
	; shift in next result bit and
	; shift out next bit of dividend
	rl	Dividend+5
	rl	Dividend+4
	rl	Dividend+3
	rl	Dividend+2
	rl	Dividend+1
	rl	Dividend
        ; shift in highest bit from dividend through carry in temp
	rl	Temp+2
	rl	Temp+1
	rl	Temp

	mov	W, Divisor+2	; load w with LSB of divisor
				; to use it in subtraction or
				; addition afterwards

	; If previous result bit was set (subtraction was performed
	; without borrow or addition made the remainder positive),
	; subtract divisor from remainder,
	; else add divisor to remainder
	sb	Dividend+5.0
	jmp	Div48by23_add

        ; subtract 23 bit divisor from 24 bit temp,
        ; divisor LSB is in w
        sub	Temp+2, W	; subtract LSB

	mov	W, Divisor+1	; get middle byte
	sc			;  if overflow ( from prev. subtraction )
	movsz	W, ++Divisor+1	; incresase source
	sub	Temp+1, W	; and subtract from dest.

	mov	W, Divisor	; get top byte
	sc			;  if overflow ( from prev. subtraction )
	movsz	W, ++Divisor	; increase source
	sub	Temp, W		; and subtract from dest.

	jmp	DIVIDE_NEXT_48by23 ; jump to loop end

Div48by23_add
        ; add 23 bit divisor to 24 bit temp
        ; divisor LSB is in w

	add	Temp+2, W	; add LSB

	mov	W, Divisor+1	; middle byte
	snc 			; check carry for overflow from previous addition
	movsz	W, ++Divisor+1	; if carry set we add 1 to the source
	add	Temp+1, W	; and add it if not zero

	mov	W, Divisor	; MSB byte
	snc			; check carry for overflow from previous addition
	movsz	W, ++Divisor
	add	Temp, W		; add

DIVIDE_NEXT_48by23
	; carry contains next result bit
	decsz	BitCount	; decrement loop counter (carry not influenced)
	jmp	DIVIDE_LOOP_48by23 ; another run

        ; finally shift in the last carry
	rl	Dividend+5
	rl	Dividend+4
	rl	Dividend+3
	rl	Dividend+2
	rl	Dividend+1
	rl	Dividend

	clz                     ; done, clear zero flag (NZ) and
	ret			; return

;**********************************************************************




file: /Techref/scenix/lib/math/div/48by23ng_sx.htm, 3KB, , updated: 2004/6/10 13:40, local time: 2024/11/24 09:18, owner: NG--944,
TOP NEW HELP FIND: 
3.142.172.190:LOG IN

 ©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE!

<A HREF="http://sxlist.com/techref/scenix/lib/math/div/48by23ng_sx.htm"> SX Microcontroller Math Method - Divide 48 bit int by 23 bit int to 48 bit int</A>

After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type a nice message (short messages are blocked as spam) in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.


Link? Put it here: 
if you want a response, please enter your email address: 
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
Did you find what you needed?

 

Welcome to sxlist.com!


Site supported by
sales, advertizing,
& kind contributors
just like you!

Please don't rip/copy
(here's why

Copies of the site on CD
are available at minimal cost.
 

Welcome to sxlist.com!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  .