68HC12D60A self-erasing

Started by James M. Knox May 30, 2005

Some of you may recall that a while back I asked if anyone else was having
problems with the flash memory in a D60A getting erased. I had only seen
the problem in field units, never with good documentation. The units
themselves were always good, and could be reprogrammed. Further, a
bootloader in protected flash was okay. One theory was that somehow the
bootloader was getting executed when it shouldn't be, and that this was
erasing flash -- but there was no evidence either way.

Well, now a similar but different board is doing it on the bench, under
much more limited conditions. There is no bootloader, no code anywhere in
memory that knows how to erase flash (intentionally <G>). Although it
probably only does it something like 0.2% of the time, the sequence is:

Using P&E Prog12Z
o Erase Module
o Program Module
o Verify Module
o Exit (which turns off the unit)

All steps work fine, and the program steps step through the correct memory
ranges.

I then switch to IDC12Z and turn on the unit. The IDC12Z shows nothing but
FF's in flash. I can switch back to Prog12Z, and it confirms that the
entire memory is erased.

The only unusual thing I see with IDC12Z is that it always fails to connect
the first (and sometimes second) time. But a couple of RETRY's always work.

On the bench it's not that big a deal to just reprogram it again. But I
would REALLY like to eliminate any risk of self erasure in the field. Any
ideas???

jmk

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James M. Knox
TriSoft ph 512-385-0316
1300 Koenig Lane West fax 512-371-5716
Suite 200
Austin, Tx 78756 jknox@jkno...
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