> This would be an extraordinarily useful thing to have for checking out
> emulator pods that get "OOPSed" or "OUCHed".  Any ideas?

You could probably resort to cold junction testing. This is basically a
controlled current source/sink and an A/D for each pin to be tested. The
source can be a D/A. The DUT has all its inputs tested over a defined DC
range and the analyzer draws conclusions about whether any structures
close to the IO pins has damage. It is not foolproof and it tells nothing
of the inner workings of the chip, however if it was damaged by something
external, then it should have a fair rate of success in finding the fault.

Such analyzers can be trained using a good chip and then tell if others
are good or bad (more exactly 'like' the probe or different). Based on the
comparison idea a simple one could be built using a bucket of window
comparators and AC low voltage applied through a pound of resistors to
each pin of the two parts, perhaps in two groups to generate a potential
difference between some pins. Obviously a complete sequence PRNG with as
many bits as pins on the device, and with a supply 1.2 V larger than the
device's test voltage is better. Each window comparator would compare a
reference and a DUT pin and light a LED if they were different.

This works for any 'black box' device, but it is necessary to keep the
black boxes in sync if they are FSMs (like microprocessors) and I think
that it cannot be used for nondeterministic black boxes, like random
number generators, noise source, etc.

Peter

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