>     I've just pulled my second 'F874 out of the ESD-proof packaging and
put
> it in my programmer. I programmed Wouter van Ooijen's WLoader boot-loader
> into it and then loaded my iButton test code into the PIC using the
loader.
> After trying to add a random noise generator to another breadboard (on the
> same power bus, with the wallwart unplugged during tweaks) and
subsequently
> giving up, I decided to pull the RNG off and continue playing with the
PIC.
> After about five minutes of being powered up, the PIC decided "No more!"
and
> then proceeded to overheat my 7805, then started heating up itself (I have
> never seen a PIC of any kind get hot, least of all one running at only
> 4MHz)... There is no way this can be an isolated incident - I changed most
> of the RS232 linedriver circuitry, the PSU circuitry, etc. Was there a
> faulty batch of PIC16F874s made?

This really smells like the parasitic SCR got turned on.  Is there any
chance that any of the I/O lines could be externally driven above the PIC
supply, even for a short glitch?  Are any lines tied to ground externally
that could be accidentally driven high by the firmware?


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