Dear Malcolm Peill,

Malcolm Peill <Malcolm@PEILL.ORG.UK> on 2001-06-18 11:04:51 AM admitted a lack
of knowledge when he said:
>I have to admit to never having used interrupts before, so it may be obvious
>to those who have.....
>
>My code includes the following:
>
>  ORG     0x000             ; processor reset vector
>    goto    main              ; go to beginning of program
>  ORG     0x004             ; interrupt vector location
>
>  bank_low
>  CLRWDT
>  btfss PIR1,TMR1IF ;return if it wasn't a timer1 interrupt


Yes, it's obvious. Interrupt routines need to save all kinds of stuff at the
beginning of the interrupt routine, then restore them at the end of the routine.
It's a little tricky, so everyone starts with the code in the
  _PIC16F87X data sheet_ by Microchip Technology Inc.
  http://www.microchip.com/0/lit/pline/picmicro/
  p. 132: Example 12-1: Saving Status, W, and PCLatH Registers
.
Also be sure to use
  http://piclist.org/techref/microchip/isrregs.htm
for a few improvements.

--
David Cary

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