Jinx,
       I know it is not OK but what could it happen if within ISR there's a
GOTO to a Loop that makes microcontroller never goes back to the ISR so as
to get to the RETFIE???

       And if I enter a ISR, can that ISR be interrupted by a second ISR
before former ISR gets to the RETFIE???

       I think I've messed it up!!

:o)

On 9/7/07, Jinx <joecolquitt@clear.net.nz> wrote:
>
> > Something happens at the ISR and subrrutine called Loop has
> > to be executed, which is within MAIN. If this loop is entered,
> > microcontroller never gets out of this interrupt rutine
>
> Hi Carol,
>
> You can call any routine from within the ISR and as long as it's
> terminated with a return it should work. The stack stores the
> return/retfie addresses in LOFO (last on, first off) fashion. So
> the most recent call (the call from within the ISR) will be completed
> by PC going back into the ISR, then the retfie at the end of the ISR,
> returning PC to the main loop
>
> The ISR is basically a called routine, terminated with a return (plus
> GIE is automatically re-enabled), although it's generally h/w driven
>
> Where it's easy to come unstuck is using a branch or goto instead
> of a return or not clearing an IF
>
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