Harold :

I don't have the manual now neither remember the details, but the answer
is there. Search for "context saving" on the manual. The C18 compiler
only automatically saves the basic registers, others used as the table
pointers are not automatically saved during interrupts. There is a
pragma instrucction to especify whitch registers must be saved during
context saving.

There is also a "feature" related to a non safe return values greater
than 4 bytes when using interrupts. (It's on the README file).


Oscar T.=20



-----Mensaje original-----
De: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]
En nombre de Harold Hallikainen
Enviado el: Mi=E9rcoles, 30 de Junio de 2004 10:30 a.m.
Para: PICLIST@MITVMA.MIT.EDU
Asunto: [PIC:] C18 and Interrupts

I think I'm running into problems with variable corruption during
interrupts. This MAY be due to bank switching going in and out of
interrupts (forcing the variables used in the ISR into access RAM seems
to
fix the problem). Generally, I want some global variables that the
interrupts can change (things like ram timers that are decremented by
timer interrupts, uart buffers, etc.). The Microchip C18 manual does not
seem to give very thorough information on interrupts (and the manuals
seem
to be getting worse... the older manuals I have are more complete). So,
can someone give me a definitive list of what I need to do in declaring
variables in a C interrupt service routine to have them work right? Does
the interrupt pragma set up and restore the bank register so my main
line
code still knows where its variables are?

THANKS!

Harold


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