From: Mike Keitz. There is a trick method that works for 4 bits. It replaces a 2-bit number in a variable with a 4-bit mask:
mov W, ++BitP ;W = 0001 0010 0011 0100 snb BitP.1 ;If 0 or 1, result is almost correct now. or BitP, W ;BitP = 0011 0111 inc BitP ;BitP = 0001 0010 0100 1000
It could be the core of an 8-bit routine thus:
; Convert 3-bit number (0-7) in INDEX to a 8-bit mask (00000001 ... ; 10000000) in BitP. mov W, INDEX and W, #%00000011 ;Start with half of the mask. mov BitP, W mov W, ++BitP ;The 4-bit converter snb BitP.1 or BitP, W inc BitP snb INDEX.2 ;Is it high 4 bits? swap BitP
two_to_n: and W, #$7 add PC, W retw $1 retw $2 retw $4 retw $8 retw $10 retw $20 retw $40 retw $80
;build MASK from INDEX.1-3 mov w,#1 sb INDEX.2 mov w,#4 mov MASK,w sb INDEX.3 swap MASK sb INDEX.1 rl MASK
|file: /Techref/scenix/lib/math/bit/mask_sx.htm, 1KB, , updated: 2004/6/10 14:40, local time: 2019/6/17 14:43,
|©2019 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.sxlist.com/techref/scenix/lib/math/bit/mask_sx.htm"> SX Microcontroller Bit Math Method Converting a 3-bit number to a 8-bit mask</A>
|Did you find what you needed?|
Welcome to sxlist.com!
& kind contributors
just like you!
Please don't rip/copy
Copies of the site on CD
are available at minimal cost.
Welcome to www.sxlist.com!