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Multiple PHYs to a single MAC

Discussion in 'Electronic Design' started by Engin Ciftci, Apr 11, 2007.

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  1. Engin Ciftci

    Engin Ciftci Guest

    I need help on connecting multiple PHY controllers to a single MAC
    over an MII interface. In IEEE 802.3u it was mentioned that MII
    interface can support 32 different phy addresses. But most of the PHY
    controllers have an separate RXTRI or ISOLATE pin for tristating the
    output (RX) pins. I guess this will be a big problem in software
    because microprocessor must select which phy to enable and this is not
    controlled over MII interface. Also the configuration register 0.10
    bit can isolate the phy in the same manner and this becomes
    meaningless if a separate pin is used.

    If MII is tri stated over software control (register 0.10) there may
    be an collusion (short cct) at startup since both phys are sharing the
    same MII bus.

    I am wondering if any one of you has implemented this kind of
    application. I need your help on this subject.

    Engin Ciftci
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