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DP83TG720S-Q1: CRC errors when plug the cable

Giuseppe CAVALLARO
Prodigy 40 points
Part Number: DP83TG720S-Q1

Hello Support

On the setup discussed in the ticket:

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1041288/dp83tg720s-q1-dp83tg720s-q1-crc-errors/3880382#3880382

I am facing a new issue.

If the PHY is in loopback (SGMII/Digital or Analog) the whole communication is always ok and no errors are seen.

As soon as I plug the cable to connector I got errors inside the PHY (e.g. CRC).

Do you have any idea?

regards

peppe

  • 0
    TI__Mastermind 39785 points

    Hi Peppe,

    Just for my understanding, this is a custom board of DP83TG720S-Q1 connected to MAC via SGMII, correct?. And that when unconnected, the PHY is working in MII, Digital, and Analog loopback, correct?

    What is the PHY connect to on the cable?

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 40 points

    Hi Gerome, 

    please I ask you to take a look at the ticket I mentioned in my previous command, here you will get all the necessary details.

    In summary, it is a custom board where the DP83TG720S-Q1 connected to MAC via SGMII. If the PHY loopback is used, the MAC and PHY are able to communicate w/o any issue. As soon as I plug the cable I get CRC issue inside the PHY registers.

    Regards

    peppe

  • 0 in reply to Giuseppe CAVALLARO
    TI__Mastermind 39785 points

    Hi Peppe,

    I have read over the ticket you linked to. So everything is working (Loopback-wise) when no cable is connected but once a cable is connected, then you see these CRC issues.

    Is the PHY is in loopback mode when the cable is plugged in, or is it under normal operation? If under normal operation, what is on the other side of the cable, or is it unconnected on that side? If loopback works fine and the data communication is problematic when connecting to a link partner, then this could lead to looking at issues on that link partner's board.

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 40 points

    Hello Gerome

    the scenario changed, so I was able to fix the CRC errors but I cannot see the link up.

    I am using the SGMII mode w/o any loopback

    regards

    peppe

  • +1 in reply to Giuseppe CAVALLARO
    TI__Mastermind 39785 points

    Hi Peppe,

    I am having a difficult time understanding your setup when it is working and when it isn't working. Could you provide a block diagram of these scenarios?

    How did you fix the CRC errors? I recall you had some sensitivity with capacitors on SGMII lines. In addition, are you sure that the SGMII traces are as length matched as possible? What are you plugging into as a LP? Or is it unconnected? Do you have MDI link?

    Could you please try out some steps outlined in section 2.10 in SNLA246?

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 40 points

    Hi

    I fixed that so the ticket can be closed, many thx for your support.

    regards

    peppe