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'[PIC] Corrupted flash on 877'
2002\11\08@134020 by Eric Bohlman

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[Resending with proper tagging that I had forgotten the first time]

Last week a prototype of a 16F877-based instrument started acting crazy
(naturally, this was while
my client was demonstrating it at a trade show).  It was as if the code
was running properly most
of the time, but jumping to the wrong places occasionally (for example,
menu items were getting
written to the wrong line of the LCD).  When I got it back, I verified the
chip and discovered that
it verified at 5V but failed the low-voltage verify.  It was both
programmed initially and verified
on a Needhams EMP-11.  Erasing it and reprogramming it cured the problem.
The EMP-11 uses the
"production" algorithm, so the chip had to have passed a low-voltage
verify when it was initially
programmed.

Has anyone seen anything like this before?  The chip has been programmed a
few tens of times,
nowhere near the write limit.

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2002\11\10@071732 by Roman Black

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Has it been exposed to high temperatures?
:o)
-Roman


Eric Bohlman wrote:

{Quote hidden}

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2002\11\14@033618 by Eric Bohlman

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11/10/02 6:10:01 AM, Roman Black <spam_OUTfastvidTakeThisOuTspamEZY.NET.AU> wrote:

>Has it been exposed to high temperatures?

Nope (client transported it as carry-on luggage on the plane to the show).

Followup: after reprogramming the chip, it worked for a few hours and then developed the same
problem.  OK, maybe we've got a bad chip.  I programmed another 16F877 (a 20MHZ rated part; the
first one was 4MHZ rated; it's actually being clocked at 3.58MHZ) and it worked.  For about a day.
Then it developed the same problem.

At this point I think I'm going to get the prototype back from the client and put a scope on all
the pins to see if there's noisy power or a solder joint that went bad.  I'm also going to contact
Microchip next week.

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