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Original question:

DP83TC811R-Q1: External interface link re-connection issues after disconnect

DP83TC811R-Q1: PHY sending runt or short frame

Sven Schuchmann
Prodigy 45 points
Part Number: DP83TC811R-Q1
Other Parts Discussed in Thread: DP83TC811

Hello Adrian,

regarding this: https://e2e.ti.com/support/interface-group/interface/f/interface-forum/977492/dp83tc811r-q1-external-interface-link-re-connection-issues-after-disconnect

we checked our hardware and cannot find anything wrong.

Can we send our hardware over to you so you can check?

Best Regards,

   Sven

  • 0
    TI__Expert 5425 points

    Hi Sven,

    You stated you checked your hardware, but could you try performing the following experiments to make sure? This will help isolate whether the issue is on the MAC side or MDI side.

    1. Can you set the DP83TC811 PHY in xMII loopback, send data from the MAC and see if you properly receive the data back?
    2. Can you set the DP83TC811 PHY in reverse loopback, send data from the link partner and see if you properly receive the data back?

    Regarding seeing runt frames during a link status change, it is possible that a frame was parsed (resulting in a smaller frame) as the connection was cut during the transmit process. So there does not seem to be anything wrong on that front.

    In addition, would you be have to answer the questions I left on the thread? I have it reposted below:

    1. Can you check the data to clock skew timing/settings and see if it is correct? It is possible that both the MAC and PHY introduced some skew internally, which causes the data to be sampled incorrectly.
    2. Do you take the slave down while the slave is in the middle of transmitting packets? If so, then the detected runt frame could be caused by the interrupted transmission when the slave is taken down while transmitting.
    3. You can double check the pins and see if there is an overvoltage. If I recall correctly, you did not seem to find any issues there. In the end, even if the overvoltage/ESD interrupt is set, it should not affect the functionality of the PHY if it is a false positive. Is it possible that a spike was detected on power-up and that is why the overvoltage interrupt is set?

    Regards,

    Adrian Kam