Help with a busted MSV11-L?

Noel Chiappa jnc at
Sun Dec 7 13:43:13 CST 2014

    >> From: Jon Elson

    >> The 2V level sounds like maybe NO chip is driving that node. A shorted
    >> output (or input) would likely pull one way or the other, 2V is about
    >> the resting point of a TTL input.

    > The way the two output data laches are wired, the output control on one
    > is wired with the negation of the output control on the other, so one
    > or the other ought to be trying to drive the line at all times. So
    > perhaps the one that _should_ be driving the line normally is the bad
    > one, then

After thinking about this tip for a few minutes, it dawned on me that there's
a simple way to see if the data latch is bad: read the CSR! That will try and
drive that line from the other latch. So I did, and ... I can read 0 from
that bit in the CSR! So it's the data latch that's bad.

Thanks for the tip!


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