Date   : Fri, 25 Jul 2008 11:41:54 +0200
From   : kortink@... (John Kortink)
Subject: EEPROM writing in SW rom bank?

On Thu, 24 Jul 2008 15:33:35 +0100, Charlie.Robson@... wrote:

>John Kortink wrote on 24/07/2008 15:06:43:
>
>> Try pin 8 of IC77, which is a more 'correct' (i.e. actual)
>> write strobe.
>
>Hi John,
>
>thanks for replying.
>
>That's the pin I'm using. Unfortunately I just lost the use
>of a 'scope. I'll apply my parallel-port logic analyser to
>some pins later, though I don't think it has the resolution
>to show anything up.
>
>But from the sounds of it, at least by implication, this
>should work?

I gather you use a 28C<xxx>. According to a quick look in
the datasheets it is 'write inhibit' if nOE is active, in
contrast with most SRAMs, which are 'write' regardless of
nOE.

Unfortunately, nOE is active for writes as well as reads
on the model B (and Master). Only the B+ deasserts nOE
for writes.

I think this might be the cause of your writing problem.
You'll have to fabricate your own nOE.


John Kortink

-- 

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