In general, you just save the prior state of the port, register, etc.. then compare the current state to that state to check for changes.
Bob Fehrenbach has passed on a number of his snippets for inclusion in my web page and have shown up in this book. The first detects the change in a bit and saves the new data for later execution. This code can be used to detect changes in the I/O Ports, Timers, or other registers that can be updated externally to the software execution.movf Reg, w andlw Mask ; Mask out unused bits xorwf old, w ; Compare to previous value btfsc STATUS, Z ; If Zero set, bits are the Same goto no_change xorwf old ; Bits are different, Store New ; pattern in "old"
|file: /Techref/microchip/regchg.htm, 1KB, , updated: 2004/12/6 11:49, local time: 2020/12/2 15:04,
|©2020 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/microchip/regchg.htm"> PIC Microcontoller Methods Detecting a change in a register</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!