Sorry to post on this old theme. But what you suggested, Scott, seems not to
be only a little trick to shorten the processing time. Sometime it is
crucial. If two interrupts flags are set - and you want only one interrupt
to trigger the ISR - AND you have interrupt routines for both interrupts,
you have to ask, if the interrupt enable flag AND the corresponding
interrupt flag are set.

To avoid problems I always use your code to determine which interrupt source
has triggerd the ISR:

          btfsc   intcon,t0ie
           btfss  intcon,t0if
            goto  check_intb0
                goto    handle_tmr0_int
check_intb0
            btfsc       intcon,inte
             btfss      intcon,intf
              goto      check_tmr1
                goto    handle_intb0_int

Martin


> From: Scott Dattalo [mailto:scott@dattalo.com]
> Sent: Tuesday, April 11, 2000 12:31 AM
> One little trick I and  others use to speed up the ISR is this:
>         btfsc   intcon,peie
>          btfss  pir1,rcif
>           goto  check_next_int_in_list
> If the interrupt is not enabled, then it can't be the source.
> So the first BTF
> will skip the second and the next possible interrupt source
> is checked. If the
> interrupt is enabled but the interrupt flag is cleared, then
> this interrupt
> isn't the source.