From: Gerrit Heitsch <>
Date: Sun, 27 Apr 2014 17:25:07 +0200
Message-ID: <>
On 04/27/2014 05:08 PM, William Levak wrote:
> On Sat, 26 Apr 2014, Gerrit Heitsch wrote:
>> An EPROM that loses its contents due to age reverts back to $FF for
>> that cell.
> Not necessarily. It could lose the data one bit at a time. It could also
> be just on the edge of being 1 or 0, which could result it getting
> different results every time you read it.

Of course it's on a per bit basis. But when the programming is gone, the 
bit is always a '1' and never a '0'. So if you read a  '0' from a cell, 
it's the correct value. The problem starts when you read a '1'. Is it a 
'0' that suffered bit rot or is it supposed to be a '1'?

And the flipping bits that give different readings for every dump? 
That's why I suggested the 1N4148 to lower Vcc. That will stabilize such 
weak cells again, allowing you to read the correct data.


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Received on 2014-04-27 16:02:40

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