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DP83TG721S-Q1: [DP83TG721S] Ethernet test modes and corresponding PHY functionality

Sebastian Seelmann
Prodigy 10 points
Part Number: DP83TG721S-Q1

Tool/software:

Hello all,

quick question: If I set a PHY into respective Ethernet compliance testmode 1 to 6 (lets take 6 for voltage droop as example)

what does the RGMII communication with the MAC do?

Does is go on as before, since the MAC will send its payload anyway, since it maybe does not know that the PHY is now in testmode, does the PHY itself stop its communication on the RGMII lines? Does it stop sending data but continue to clock the 125 MHz out, or is it completely stopped.

Thanks a lot for support.

Best wishes.

  • 0
    TI__Genius 14005 points

    Hi Sebastian,

    I'm not sure, we do not typically test RGMII communication during PMA compliance. Are you running into an issue with the PMA Compliance test? There is an Open Alliance script you should use before running the test, but I cannot post it on public forums since the DP83TG721 is a NDA Restricted part. If you would like to have it, please reach out to your Local Field representative.

    Best regards,

    Melissa

  • 0 in reply to Melissa Chang
    Prodigy 10 points

    Do you know someone who could know this, someone with the board maybe inf ront of him (also every other 1000 Mbit or also 100 Mbit device is representable for my issue, it is a generic question)

    I give you a little bit more background: I am doing EMC tests, and as you might know the 125 MHz RGMII signals cause a lot of trouble in emission testing since they are very sharp and usually 3.3V high up to 60 mA.

    So this 125 MHz can be seen up into the GHz range. Now to find out some root causes it is always nice to be able to shut down something (while sitting outside the EMC chamber) and luckily the Ethernet test modes can be set via software from an outside PC. So now I need to know (since I cannot measure it currently myself) if this testmodes really do shut down the RGMII 125 MHz communication, because if so, it is very easy for me to test the 2 cases in the EMC chamber., once with communication full functzionality, and once product partly disabled due to Ethernet PHY in test mode setting.

    I hope now its clear what I want to know.

    Thanks for your support.

  • 0 in reply to Sebastian Seelmann
    TI__Genius 14005 points

    Hi Sebastian,

    Are you using our Open Alliance initialiation script?

    If not, Can you reach out to a field representative from TI you can reach out to for your company? I can provide our previous EMC test results and recommended initialization script for EMC testing if I can confirm with the field rep you have NDA with us. 

    To rule out the RGMII interface, You can enable xMII Isolate mode in register 0x0[10]. Enabling xMII Isolate mode means RGMII transmit signals are ignored and receive signals are non-driving high impedance.

    Best regards,

    Melissa