from by Nikolai
Golovchenko
Don't know how to explain its operation, but what it does is approximate calculation of 32768/x using linear interpolation between points where x=1,2,4,8,16,32,64,128,256.
The routine can be extended for other number of bits in x.
;test cblock x, yh, yl endc clrf x ; movlw 129 ; movwf x again call Reciprocal8 nop incf x, f goto again ;**************************************************** ; ; Approximate calculation of 32768/x ; Input: x ; Output: y = 256 * yh + yl ~= 32768/x ; ; To calculate reciprocal, linear interpolation ; is used between points, where x=1,2,4,8,16,32,64,128 ; ; Size: 19 instructions ; Execution speed(worst case including return): ; 6+4*8-1+4+4+2=47 ; ; 4 Aug 2000 by Nikolai Golovchenko ;**************************************************** Reciprocal8 movf x, w skpnz retlw 1 ;error - division by zero movwf yh clrf yl setc Reciprocal8a rrf yl, f rlf yh, f skpc goto Reciprocal8a clrc rrf yh, w clrf yh subwf yh, f Reciprocal8b rrf yh, f rrf yl, f skpc goto Reciprocal8b retlw 0 ;ok ;****************************************************
file: /Techref/microchip/math/div/recip32k-ng.htm, 1KB, , updated: 2000/8/8 18:21, local time: 2024/8/31 23:34,
3.12.160.97: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? <A HREF="http://techref.massmind.org/Techref/microchip/math/div/recip32k-ng.htm"> PIC Microcontoller Math Method Reciprocal 32768/x</A> |
Did you find what you needed? |
Welcome to massmind.org! |
Ashley Roll has put together a really nice little unit here. Leave off the MAX232 and keep these handy for the few times you need true RS232! |
.