Hi all.

I've just come across a problem that I've never had happen before.
Likely that was due to luck. Now I'm not sure what the best way to
solve it is.

At the start of my ISR, I save WREG, STATUS, and BSR (this is a
PIC18F) to temporary registers. I then restore them on exit. I've been
tracking a bug that seems to be manifesting itself due to incorrect
bank selection. Here's why I think this is happening, look at the
addresses of the following registers:

W_Temp     0x080
PORTA       0xF80

The other registers have similar overlapping low byte addresses.
So...going into my ISR I might not be in the correct bank. But if I
change the bank, I've upset the current state and things won't get
restored correctly.

I'm not really sure what to do on this one. I suppose I could use a
lot of banksel commands (and that's likely what I'm going to try while
waiting to see what everyone else thinks), but is there a better way?
I'm currently using code Microchip put in the data sheet for context
saving, which means it might not be the best. I'd like to keep using
my own registers rather than the fast return stack as I'd like the
capability of moving to two priority interrupts later on.

Thanks!

Josh

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