Hi Jez,

I'm far from the consummate embedded guy some around here are, but it seems to me that you'd reset the WDT anywhere in the code you might find the µcontroller spending some time. It seems plausible that an ISR could interrupt an ISR, or that two ISRs might cue up in succession (of equal priority), so that control could be some time returning to the Main loop.

On the other hand, Vista's security has demonstrated that you can take a good thing too far. So I guess I would come down on the side of resetting the WDT as often as possible without wasting machine cycles needlessly.

Man, that sounds like a non-committal politican answer. Strictly speaking I suppose one hopes that every WDT reset is a waste of cycles. And really they are, until your code hangs. Then they're brilliant. It's like cellphones and guns. They're only nuisances until you need one, then they're Godsends. Besides, isn't 90% of engineering, compromising between opposing considerations?