On Wed, 16 Jul 1997 21:36:22 EDT Harold Hallikainen
<haroldhallikainen@JUNO.COM> writes:
(failure when interrupts are enabled during a certain segment of the main
program)
[...]
>ISR
>;       Determine cause of interrupt and do it.
>        saveContext             ; Save registers
>        btfsc   pir1,rcif               ; check for received character
>        call    RxSerial                ; Go get byte
>        btfsc   pir1,pspif              ; Parallel slave port write?
>        call    readPSP         ; Go handle it

Using gotos, calls, etc. in the ISR means saveContext needs to handle
PCLATH if you're using more than the first 2K code page (unless copies of
the routines are stored in the same place in every page).  Also it may be
overflowing the stack, if the main program is doing a lot of calling
around or the ISR continues to call deeper and deeper.   Since these
routines are almost certainly only called from one place, it may work
better to goto them, then go back to the next bit test when done rather
than return.  This will save on stack space but not help the PCLATH
problem.

-Mike