Hi,

I guess PCLATH remains unchanged upon interrupt. The manual states: "PC is
loaded with 0004h". If PCLATH would be changed on entry to interrupt, how
could you save this since it should happen BEFORE the IT? And a practical
experience: I never dealt with PCLATH on IT and I have seen no trouble. Of
course, if you have an GOTO or CALL (maybe a PCL operation) in the ISR, it
is a completely different thing and you should manage PCLATH as in other
cases.

Facit: if you do not change PCLATH in the ISR, do not need to take care
of it.

This is my 2 cent.

Imre


On Tue, 27 Jul 1999, Andy Kunz wrote:

> >What happens to PCLATH? If the interrupt occurrs when PCLATH is non-zero,
> >having been set by the code prior to a goto, is PCLATH unchanged?
> >
> >If so, will a GOTO executed by the interrupt service routine apply PCLATH
> >in computing the address (baaddd thing?)?
>
> Yep.
>
> >On interrupt, does one need to save PCLATH and set it to whatever is
> >appropriate for the ISR, then restore it when exiting the ISR?
>
> Yep.
>
> Andy
>
> ==================================================================
> Andy Kunz               Life is what we do to prepare for Eternity
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> andy@rc-hydros.com      http://www.rc-hydros.com     - Race Boats
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