Instant Interrupts - Revisited

[SteveB]

RETFIE FAST works on the low-priority interrupt, too.

Just to clarify one important item. Here is snippet from the PIC18F8722 Datasheet under Memory Organization:

5.1.4 FAST REGISTER STACK
...
If both low and high priority interrupts are enabled, the
stack registers cannot be used reliably to return from
low priority interrupts. If a high priority interrupt occurs
while servicing a low priority interrupt, the stack register
values stored by the low priority interrupt will be
overwritten. In these cases, users must save the key
registers in software during a low priority interrupt.

So, more accurately, RETFIE FAST works when low-priority interrupts are enabled, as long as software saves & restores key registers during the low priority interrupts, and RETFIE FAST is only used to return from high-priority interrupts.

Steve