Sun Oct 21 10:16:39 EDT 2012
What to save in ISR?
The main question is, is it safe to use the stacks? I think so,
because none of the ASM instructions leave the stacks in an
inconsistent state. So the recipe is:
- dup is MOVWF which does not affect status flags, so WREG can be
- STATUS can then be copied into wreg.
The above are just STATUS @. To restore, care needs to be taken that
the drop doesn't mess up the flags after restoring it. So STATUS !
can't be used. There is a "nfdrop" that uses MOVFF to not affect
flags. This should work:
dup STATUS !
- save STATUS before doing any dup, since dup affects flags.
ther eis an