> Van: Peter Schultz <schupet@dvp.com>
> Aan: PICLIST@MITVMA.MIT.EDU
> Onderwerp: Re: Un-erasable memory in a 16C74A
> Datum: donderdag 12 maart 1998 2:33
>
> Hi,
> Exactly as You stated, one of address line blown by ESD.

Sorry to but in, but it couldn't be _a_ addressline, becouse of the fact
that to
get the effect i've mentioned you would need _two_ address-lines destroyed.
And, if you destroy an address-line you would (normally) see copies of your
first code-block, not Zero's.

But, to agree with you, it (the  ESD) could have affected the Code-protect
hardware, in such a manner that the code-protect was enabled _without_
regards to the fuses that normally steer that function.

> The strange thing is all the time the same lines blown, probably the
> most sensitive and weaker as ESD goes.
> I have 4 device with absolutely the same problem and same addresses not
> deletable. So it can not be the circuit because it quaranteed I have
> different one.
>
> Peter
>
[Cut]
Greetz,
   Rudy Wieser