Re: how to read unreliable eprom...
From: Frank Bemelman (f.bemelmanx_at_planet.invalid.nl)
Date: 06/20/04
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Date: Mon, 21 Jun 2004 01:18:55 +0200
"John Larkin" <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> schreef in
bericht news:5b4cd0pg2vbt5v202rf0gfdecpe1op0pn1@4ax.com...
> On Mon, 21 Jun 2004 00:19:11 +0200, "Frank Bemelman"
> <f.bemelmanx@planet.invalid.nl> wrote:
>
> >I have an old 2716 eprom, with some bits that are balancing
> >between 0-1. Everytime I read it, there are a handful of
> >addresses that have a different content.
> >
> >What is the best way to figure out what the bits probably are?
> >Reading the eprom at 4.5V, or at 5.5V? Should I cool it as much
> >as possible, or heat it up?
> >
> >Any other ideas?
>
> If a bit is undecided between 1 and 0, it's most likely 0, since 1 is
> the charge-lost (erased) state. Maybe.
The ones I see flipping are probably meant to be zeros.
> If it's a hard 1, it may already be lost!
Yes, since I see a only handful of random bits, there are
certainly also some bits that lost too much charge already
and thus '1'. I assume all cells are on the edge, let's
say at 50%, so I hoped there was a method to move them
a bit more in the good direction, for instance reading the
thing at 6 volt or at a low temperature, or at a high
altitude, whatever it takes to change the physics in my
favour.
>
> What's it do? Is there any way to evaluate functionality?
>
It's an eprom for an old PM3310 oscilloscope. The scope is
crashing, doing lots of funny things, resetting itself etc.
8085 code. When I disassemble it, I see quite a few 'undefined'
opcodes in the middle of what looks normal.
-- Thanks, Frank. (remove 'x' and 'invalid' when replying by email)
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