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 ORG x DS 1 yh DS 1 yl DS 1 clr x ; mov W, #129 ; mov x, W again call reciprocal8 nop inc x jmp 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 mov W, x snz retw 1 ;error - division by zero mov yh, W clr yl stc reciprocal8a rr yl rl yh sc jmp reciprocal8a clc mov W, >>yh clr yh sub yh, W reciprocal8b rr yh rr yl sc jmp reciprocal8b retw 0 ;ok ;****************************************************
| file: /Techref/scenix/lib/math/reciprocal.htm, 1KB, , updated: 2004/11/4 14:31, local time: 2024/12/26 08:49,
13.59.183.77: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/scenix/lib/math/reciprocal.htm"> SX Microcontroller Basic Division Math Method s</A> |
| Did you find what you needed? |
Welcome to massmind.org! |
Welcome to techref.massmind.org! |
.