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cs8900a always returning 0x5555

Discussion in 'Embedded' started by Markus Zingg, Jun 23, 2003.

  1. Markus Zingg

    Markus Zingg Guest

    Dear all

    I'm trying to use a CS8900a ethernet controller in one of my designs.
    I connected it to the CPU according to the app notes (16 bit IO mode,
    CPU's /CS conneced to AEN and /SBHE, I try to use IO mode). I tripple
    checked everything against the checklist in the app note an83-3 and so
    far everything looks ok. Hooking up a logic analyzer showes that
    timeings are ok also. When I plug in a 10BaseT cable from the RJ-45 on
    my board, the LINK-LED on both sides light. But when i try to read the
    signature from the register IOBASE+OAh, i always get 0x5555. In fact,
    i only get the value 0x5555 for all addresses between 0x300 and 0x30e.

    I'm now struggling with this problem for days and would really
    apreciate any help on this. I searched the net and found an old thread
    about the same issue, but there was no solution to the problem posted.
    I'm currently realy out of ideas, so any hints on what to check etc.
    are welcome.


    Markus Zingg, Jun 23, 2003
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  2. Markus Zingg

    Gary Kato Guest

    I tripple checked everything against the checklist in the app note an83-3 and
    Well, we didn't think it was timing because you assured us that it wasn't. :)

    Good work finding the bug!!
    Gary Kato, Jun 25, 2003
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  3. Markus Zingg

    Markus Zingg Guest

    You are of course right here. What I was lookign fore (since I
    consider myself being a beginner) were some general tips/hints what
    else to check. After this post I did the folowing things

    - solder out the oszilator. The lan link went away which for me was
    some indication that the osizlator seemed to do it's work.
    - Used a scope to check the oscilaotor oszilating. It did, but I heard
    that due to the capacitance of the probe it could oszilate during
    measure and not before and after. Anyways, I then concluded that the
    oscilator most likely woule work.
    - replaced the cs8900a with aother one. Since this gave the same
    results, and since the wireing was ok not much more other than the
    timeing (IMHO) was left over.

    I probably would have expected from the experts some advice like well,
    what you describe leaves open 1) a malfuncitoning chip, 2) oszilator
    not working or 3) you are worng with your asumptions or 4) any other
    advice. Being a newbee, one soon feels sort of trapped from such a
    situation if no one answers. In general I'm keen to learn and even if
    an advice would not have hit the nail it surely would have helped
    learning. Not geting a single reply in such a crisis (sorry but to me
    it was sort of) just makes you feel dumb / even more lost if other
    questions around your own post are answered within minutes.
    Yeah, you have no idea how lucky I am now. The hardware design for
    this project is now complete and I'm now happy to complete the

    Many thanks for your reply. It's highly apreciated! :)

    Markus Zingg, Jun 25, 2003
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