> I can see a possible consequential problem.  If the PIC is allowed to
> start operating in normal (non-programming) mode while the 5V supply is
> attached, then the outputs from the PIC may drive inputs of the other
> device to +5V, which will exceed the maximum input voltage ratings of
> the other device.

Will it, really?  Many devices which can't operate above, say, 3.5V,
will tolerate 5V+ on their I/O pins.  Check your device's Absolute
Maximum ratings.

I've always understood PICs to powerup with their I/O lines set to
input; i.e., high impedance.  If you write your code to respect this,
to not make the lines outputs and drive them high until after you
KNOW the device isn't being reprogrammed, then no worries.

Furthermore, you should check the spec again.  Usually, the only
time a voltage above Vmin is required is for a block erase, which
may not be a problem, because not all programmers perform a
block erase of the program memory before programming.

Mike H.

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