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DP83867IS: Why the PHY did not return a valid PHY ID?

WENBO LI
Intellectual 440 points
Part Number: DP83867IS

Hi,

I am using DP83867ISRGZR to design 10/100/1000 Ethernet port.

When I read the PHY ID through the mdio interface, one of my PHY devices did not return a valid ID (phy id=0 or an invalid number). Any possible reasons why?

Should be the PHY ID returned always the same among all the devices of the same type (same part number)? If so, what's the PHY ID that should be for my phy device DP83867ISRGZR?

Thanks,

Wenbo

  • 0
    TI__Mastermind 26320 points

    Hi Wenbo,

    DP83867 defines straps to configure the Phy Id of the device. Default Phy address without external straps is 00. Refer to section 8.5.1 to understand the strapping options available and external straps resistor values needed to configure them.

    Regards,
    Geet

  • 0 in reply to Geet Modi
    Intellectual 440 points

    Thank you Geet.

    I am afraid I have misled you. I was not referring to the PHY address strapping. I was using non-strap (phy address 0), and a pull up resistor (phy address 3) for the two phy devices that are sharing the same mdio bus.

    The problem that I had was that when I read the PHY Identifier Register #1 (PHYIDR1), it was supposed to return 0x2000 (section 8.6.3), but it returned 0x0000 or other value other than 0x2000. The PHY Identifier Register #1 value is Read Only, Permanently set to a default value. I am wondering how the PHY returns other values when querying its PHY Identifier Register#1. Any thoughts? Is it possible the PHY device was getting damaged for some reason.

    By the way, we feed the XI clock pin with a 2.5V squarewave. Is this going to damage the phy device?

    Thanks,

    Wenbo

  • 0 in reply to WENBO LI
    TI__Mastermind 26320 points
    Hi,

    If Phy MDIO is returning 0x000, means it not able to read the registers.

    XI with external clock reference shall be limited to 1.8V. Datasheet recommends to have capacitor divider circuit for swings above 1V8. With high voltage, part behaviour is not guaranteed, in some cases it may do permanent damage as well. Please reduce swing and retry.

    Regards,
    Geet