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DP83849I: Link up, Link down swing

Hattie Spetla
Intellectual 335 points
Part Number: DP83849I

Hello,

I have several boards that are showing 'link-up -100Mbps/Full - flow control off', link-down' swings. The device repeats this continuously.

This happens after the boards have been used for some time. I will leave it connected over the weekend and when I come back I see the behavior. 

This is unrecoverable on reset, other boards with the same hardware are fine on the same network connection. 

Replacing the phy resolves the issues.(Will need to confirm.) 

I am seeing signal on the RX lines, and I occasionally see data on the TX lines. I'm also seeing some <1us pulses on the TX lines, which seems way too fast to be the FLP.

This is all on A, the other port does not  seem to be affected. The signal levels look OK. 

What would you look at first? What do you recommend as first steps in debugging/ finding root cause?

  • 0
    TI__Mastermind 18425 points
    Hi Hattie,

    It looks like you are seeing some link instability where the link keeps switching between up and down. The devices that show this issue, only show it on port A and not on B.
    In this case, I would recommend doing a schematic check between port A and port B and see if there are any differences. If there are no differences in schematics, then checking the layout would be the next step.
    To verify that the schematics and layout are correct, please use the design guide: www.ti.com/.../snla079d.pdf

    -Regards,
    Aniruddha
  • 0 in reply to Aniruddha Khadye
    TI__Mastermind 18425 points
    Hi Hattie,

    I am closing this thread for now. If there are still pending questions, you can open a new thread and provide information about the open issues. You can also provide a link to this thread if the questions are related.

    -Regards,
    Aniruddha