I'm sure this is simple but I can't find the answer (even with the new improved search engine) so perhaps I'm phrasing the question wrong.

I want a 16F628 to go to sleep when inactive for say 60secs.
The code I'm using is constantly looping looking for a trigger signal to go low before firing a camera but I'd like it to power down completely if nothing happens for say 60secs and wake up again and start monitoring the trigger if a PORTB pin changes state.

Thanks, Andrew