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DP83867IR: Why does MDIO always need pull up?

H Jayaraj
Intellectual 590 points
Part Number: DP83867IR

Irrespective of ethernet PHY manufacturer, In all the phys MDIO needs pull up whereas MDC May or may not need pull up?

  • 0
    TI__Expert 3595 points

    Hi Harsh,

    Many serial communication lines need a pullup resistor in order to enable communications. The pull up is what gives you the 1's and the open-drain interface pulls the line to 0. Without the pull-up, the line would always be 0.

    MDIO is a two directional line, while MDC is only one direction. The output side of MDC would need a pull-up, but the input should work fine in most designs without a pull-up. 

    Thanks,
    Lysny