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PICList Thread
'Damage by undererase? Was Re: How to use Datarase '
1998\02\20@080449 by Morgan Olsson

picon face
At 09:16 1998-02-18 +0100, Rudy Wieser wrote:

>> What is the best time to erase PIC16c74A with Datarase II (Walling Co)?
>
>Any time beyond about 15 minutes (short distance between EPROM & UV-Lamp).
>Too short will cause a Memory-effect (so I am being told) like with
>NiCad's, wich
>will disable your (on-board) EPROM in time.
>

Very strange. I don«t understand how it can happen.
Undererase woild just, I believe, just not reset some bit(s), or make them
uncertain (under some conditions read as 0, sometimes 1. That will be hard
to detect, so always erase long time is best, and when verifying after
programming veryfying should be carried out both at max and min Vdd, to
check both for badly programmed and badly reset cells.  ("Production
programmer")  But for testing so far I just use Picstart Plus.

Althougt it looks like you are right; I have reprogrammed four PIC14000
about fifteen times each, and usually with just enough time to erase it,
and often no essential margin.  (When the programmer said "chip not blank"
I just erased a few more minutes and then programmed)  Now one of the PIC
is working weird.  When running it it frequently restarts (more than five
times per second i believe) start correct, then running garbage code,
restets etc.  If I cover the window it seem to reset a little less
frequently.  When i verify program eprom it is correct.  I have also tried
to erase very long time, then reprogram, with same result.  

As I cant understand why this happen I will later try to erase a very very
long time, then try again, maybe try to run it under different clock
frequency and voltage.

Has anyone else experienced the same?
/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  spam_OUTmrtTakeThisOuTspaminame.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

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