Re: Fat40 RAM problem?

From: William Levak <*wlevak_at_SDF.ORG*> Date: Fri, 29 Aug 2014 11:15:37 +0000 (UTC) Message-ID: <Pine.NEB.4.64.1408291111480.6252@sdf.lonestar.org> · wlevak_at_SDF.ORG

On Fri, 29 Aug 2014, A. Fachat wrote:

> Hi there,
>
> I've analyzed the RAM problem on my Fat40 a bit more. I've recorded the broken
> addresses - which are stable - and measured the RAM chip in question (UA16 )
> with the scope.
>
> See https://www.flickr.com/photos/afachat/sets/72157646409152698/
>
> What looks interesting is that the data I/O pins of the RAM even stays high
> when I write a zero into it! I.e. either the RAM is broken and pulls the line
> high, or the driver (or something else) is broken. However, I cannot see why
> the combination of address bits should create a driver failure.

Internal short in the driver chip.  I've run into this before.  Only 
certain combinations of bits produce the error.

wlevak@sdf.lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org

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