> From jnewport@MAIL.ORION.ORG Wed Jun 24 12:12:45 1998
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> Date:         Wed, 24 Jun 1998 13:14:41 -0500
> From: "Jonathan M. Newport" <jnewport@MAIL.ORION.ORG>
> Subject:      after I return from an interupt...
> To: PICLIST@MITVMA.MIT.EDU
>
> sorry, I'm kind of new to this, but say I've got something in a continuous
> loop like:
>
> circle  goto    circle
>
> waiting for an interupt.  when the isr is finished and I use the retfie
> command, will it increment the program counter to execute the instruction
> after this one?

No, you return to the same loop.

> or if it doesn't is there a way that I can increment the
> program counter myself? thanks

No, you can't change the content of an item on the stack.  But you can
just re-enable interrupts at the end of your interrupt handler, and do
a goto to the instruction after the circle instruction, as long as you
don't need any addresses on the stack.  But if circle is in a subroutine
that you need to return from, you can't use this hack.  By the way, unless
you disable the watchdog timer, this loop will eventually cause a watch-
dog reset unless you clear the watchdog timer in the interrupt routine
and have the interrupt occur often enough.

Usaully what people do is have the interrupt routine send a flag for the
base level reoutine to continue.  For example

        bcf     some_status_byte,0;
circle  btfss   some_status_byte,0;
        goto    circle


and in the interrupt routine:

        ...
        bsf     some_status_byte,0;
        ...

>
> Jonathan Newport
>