can imperfect power reset damage flash programmable HC08 ?


Dear all,

Can an imperfect power off reset,  with the power supply
going down to 0.5 V instead of required 0.1 V,
damage flash programmable HC08 chips?

I have made a board with a micro and a RS232 line driver
amongst other things, and I have been using Metrowerks to
download the code.  It worked ok for some time, it went to a
few dozens of programming/debugging cycles, say 30, and then it
become dead (for the Metrowerks).

Later on, trying to see what happened, I have noticed that
my power off reset did not bring the power supply for
the HC08 down to 0.1V but only down to about 0.5 V
(a leak from an overseen pull-up elsewhere on the board
- embarrassing).  The chip itself does not seem to have
shorted pins neither to the ground nor to the supply,
and I haven't been able to find any other electrical fault.

Another thing the chip suffered is that I tried
to perform bit set and bit clear using 2 byte addresses.
I had detected it while the chip was still ok, and corrected
it, went through two or three more programming cycles, and
then the chip stopped responding.

I shall try replacing the chip presently, but would anyone
care to comment on what could have gone wrong, and why?
All comments welcome.


.

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