Tony Nixon quotes the Microchip datasheet for the 16f8xx (and Robert Rolf added comments):
movwf w_temp ;given multiple banks, and no global memory ;you need to make a w_temp in each because you cannot change status prior to saving it. swapf status,w ;The swapf instruction, unlike the movf, affects NO status bits, which is why it is used here. clrf status ;point to bank 0 and clear all the flags movwf status_temp movf pclath,w ;save PCLath movwf pclath_temp clrf pclath ;assume that this ISR is in page 0 ;bcf status,irp ;This bcf is redundant & unnecessary unless the clrf status (above) is removed movf fsr,w movwf fsr_temp ; ISR ;The example fails to restore FSR here. ;One should movf fsr_temp,w movwf fsr ;to complete the restore sequence. movf pclath_temp,w movwf pclath swapf status_temp,w movwf status swapf w_temp swapf w_temp,w
Tom Handley says:
...one of the nice things about the 16C76/77 and 16F876/877 devices is that the upper 16 Bytes are aliased to Bank 0. This is a good place to keep a copy of W, STATUS, PCLATH, FSR, etc, during an ISR routine.
Timer tutorial (incl prescalers) by Andrew Warren
David A Cary of Motorguide Pinpoint Says:
Up: PIC Micro Controller Interrupt Routine Library http://piclist.com/techref/microchip/ints.htm
|file: /Techref/microchip/isrregs.htm, 4KB, , updated: 2011/2/2 14:11, local time: 2018/8/21 03:32,
|©2018 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/isrregs.htm"> Saveing register state in an Interrupt Service Routine</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!