On Wed, Jun 3, 2009 at 9:52 PM, Jesse Lackey wrote: > The DC bench supply is flawless, the scope and a DMM agree it is at 5.05V. > > The board I used to debug this insanity has only the PIC, a crystal and > a LED to blink on it. No decoupling caps or anything else. > > The original board (with all required caps and other circuitry) with > this problem now works fine, of course, reprogrammed to not have > brownout @ 4.6V. > > Done wasting time on this problem! > If you don't have a decoupling cap, in theory a very short transient, shorter than what your scope can measure, might trigger the brownout reset as soon as the chip tries to power on. Granted, your target (non-debug) circuit probably does have the decoupling caps, so it's not clear why there is an issue there. Without decoupling caps, I would be worried about unpredictable, un-reproducible, scratch-your-head-'til-you-get-to-the-gooey-stuff mystery bugs further down the road, exactly because transient power spikes could corrupt internal PIC states. It's unlikely, but not impossible. - Marcel -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist