"STRONG, Neil -Syntegra" wrote:
>Am I correct in assuming that if you write code that is greater that 1
>page, then you must duplicate the ISR in both pages anyway - regardless
>of whether my ISR changes PCLATH.

No, you only need one copy of the ISR.  If your background is in page 1
when you get an interrupt, execution is vectored to h'0004'.

What you need to avoid is a GOTO ISR instruction at address h'0004'.  A
goto instruction at that location will put you back to page 1.  Locate
the start of your ISR at h'0004', save and restore context as has been
previously described and you should have no problems.

If your ISR has no calls or gotos you can get away without saving PCLATH
but I would regard this as poor practice.  You may make an 'improvement'
later on and forget to add the instructions to save PCLATH.

--
Bob Fehrenbach    Wauwatosa, WI     bfehrenb@execpc.com