Re: strange 2001N fault

From: Francesco Messineo <francesco.messineo_at_gmail.com>
Date: Tue, 20 Feb 2018 20:24:31 +0100
Message-ID: <CAESs-_y-2Bi9iDp-K1ZLrApFW4MUdXCWCgTuvJJxyJKTToXjxA@mail.gmail.com>
On Tue, Feb 20, 2018 at 7:37 PM, Gerrit Heitsch
<gerrit@laosinh.s.bawue.de> wrote:
> On 02/20/2018 07:28 PM, Gerrit Heitsch wrote:
>>

>
>
> Oh.... If your scope is analog, try to set it to 'chop' instead of
> 'alternate'. The reason for that is that 'alternate' will do a full trace of
> one signal and then a full trace of the other. If you switch to 'chop', it
> will quickly alternate between both inputs while doing the traces. This way
> you get to see what is happening on both inputs at the same time while
> 'alternate' will introduce a lag. With digital signals that will suggest a
> relationship between 2 signals that might not actually be there.

yes, I already knew that. I routinely use chop mode to look at the
relationship between two digital signals.
Thank you for the /RAS suggestions, it wasn't clear to me that the
corruption could happen only close to /RAS being asserted,
I was also trying to check what was happening before /CAS going low.
One big problem with analog scopes like mine, is that I can't see
what's before the trigger, so if an address line is changing right
before /RAS edge, I won't see it.
I'll see how close is too close for a 4116 anyway, maybe I'm lucky if
I can have a couple of /RAS cycles on the same sweep and still
measure when an address is changing too close (if any).

Frank

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Received on 2018-02-20 20:00:04

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