At 03:48 PM 12/13/2012, Bob Blick wrote: >Hi Dwayne, > >I also used external circuitry for reset/power supervision on designs >that used 16C7x parts. Why? Because I observed lockups etc in the very >scenarios you describe. But I have not needed it on newer parts. Many thanks, Bob. This is exactly the kind of feedback that I need. I may not have been clear enough in my first message - I've tried to=20 make these newer PICs mess up but I haven't yet succeeded. So: I'm=20 looking for both good and bad feedback in regards to hanging or=20 lock-ups in any situation that any of you may have seen. Part of my problem is that I simply have NOT yet done any=20 hazardous-location projects without including an external=20 watchdog. Most of those past projects involve copious amounts of=20 Natural Gas (the largest ovens that we have done run at 30 million=20 BTUs) and I simply won't do a controller that doesn't have redundant=20 watchdogs. But that limits my experience with modern PICs, simply=20 because most projects DO have watchdogs. I'm willing to take a chance with these tiny heaters because a=20 failure won't cause a hazardous situation (the extra hardware=20 over-temperature cutout protects against this) - a failure would just=20 cause customers to be unhappy with us. But if anyone can tell me=20 that they did something to make one of these newer PICs to lock up or=20 hang, I would very much like to hear about it so that I can try to=20 duplicate the situation here. Moving to a small PIC lets me to reduce the BOM cost by a few percent=20 and allows me to do some neat things that the current all-analog=20 design can't do. But I don't want to jeopardize reliability by=20 making the change. Thanks again! dwayne --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .