from Nikolai Golovchenko
;Division of 16bit by 8 bit with a result in Q16.16 form ; ; X_Int.X_Frac = X_Int / Y ; ; RAM  6 bytes (1 temp): ; X_Int = X_IntH:X_IntL 16 bit input/ output integer part ; X_Frac = X_FracH:X_FracL 16 bit output fractional part ; Y divisor / temporary ; Counter counter ; ; Size = 39 instructions ; Execution time = 6+16*141+3+16*141+3+2(return) ; = 460 instruction cycles ; ; 8July2000 by Nikolai Golovchenko ; 16February2001 fixed, reduced execution time and temporaries Div16by8to16_16 clrf X_FracL clrf X_FracH movlw 16 movwf Counter movf Y, w ;keep Y value in accumulator clrf Y ;and use Y register as temporary ;Find integer part Div16by8to16_16a rlf X_IntL, f ;shift next msb into temporary rlf X_IntH, f rlf Y, f rlf Counter, f ;carry has 9th bit of temporary ;copy carry to counter subwf Y, f ;substract Y (in w) from temporary skpnc ;if no borrow, set Counter.0 bsf Counter, 0 btfss Counter, 0 ;if Counter.0 clear (borrow) restore temporary addwf Y, f clrc ;restore counter rrf Counter, f ;at this point carry is the next bit of result decfsz Counter, f ;repeat 16 times to find integer part goto Div16by8to16_16a ;shift last integer bit rlf X_IntL, f rlf X_IntH, f ;Find fractional part bsf Counter, 4 ;Counter = 16 Div16by8to16_16b ;Shift zero bit into temporary rlf X_FracL, f rlf X_FracH, f rlf Y, f rlf Counter, f ;carry has 9th bit of temporary ;copy carry to counter subwf Y, f ;substract Y(in w) from temporary skpnc ;if no borrow, set Counter.0 bsf Counter, 0 btfss Counter, 0 ;if Counter.0 clear (borrow) restore temporary addwf Y, f clrc ;restore counter rrf Counter, f decfsz Counter, f ;repeat 16 times goto Div16by8to16_16b ;shift last fractional bit rlf X_FracL, f rlf X_FracH, f movwf Y ;restore divisor return
Questions:
See also:
file: /Techref/microchip/math/div/16by8lzfng.htm, 4KB, , updated: 2001/6/14 12:47, local time: 2015/8/29 16:32,
owner: NG944,

©2015 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? <A HREF="http://www.piclist.com/techref/microchip/math/div/16by8lzfng.htm"> PIC Microcontoller Math Method Division 16 bits by 8 with result as fraction rather than remainder </A> 
Did you find what you needed? 
PICList 2015 contributors:
o List host: MIT, Site host massmind.org, Top posters @20150829 RussellMc, IVP, James Cameron, Bob Blick, alan.b.pearce, embedded systems, Dwayne Reid, Neil, John Gardner, Isaac Marino Bavaresco, * Page Editors: James Newton, David Cary, and YOU! * Roman Black of Black Robotics donates from sales of Linistep stepper controller kits. * Ashley Roll of Digital Nemesis donates from sales of RCL1 RS232 to TTL converters. * Monthly Subscribers: Gregg Rew. ongoing support is MOST appreciated! * Contributors: Richard Seriani, Sr. 
Welcome to www.piclist.com! 
.