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DP83869HM: Interfacing with an external switch over an SGMII (SerDes) link

Souvik Sarkar
Prodigy 100 points
Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869

Tool/software:

Hello,

I have a custom design in which the PHY DP83869 is connected to an external RJ and its SGMII is connected to the SGMII SerDes of an external switch. When autonegotiation is enabled on the SerDes side, the link on the switch comes up as 1000BASE-KX. The link works fine at 1G. However, when I fix the copper side to work on 100BASE-TX, the copper side of the link works (tested through PHY loopback) but the link with the SerDes side does not work. Any help with this is greatly appreciated.

Thank you all.

  • 0
    TI__Genius 12916 points

    Hi,

    Could you send me the register dump from 0x01 to 0x1F and 0x31 and 0x37 when the link is supposed to happen?

    In addition, have you had the chance to look at our SGMII troubleshooting guide?

    Best,

    J

  • 0 in reply to J
    Prodigy 100 points

    Hi J,

    Thank you for your reply. Regarding the SGMII troubleshooting guide, I did not have the chance yet to look into it.

    However, I tested further on this. The link is working when I turn off auto-negotiation and fixed the speed on the SGMII side (i.e. Writing 0x2100 on the register C00 instead of writing on register 0x0). Also for this, auto-negotiation was turned off and speed was fixed on the switch side too. In this case the switch side interface reflected itself as instead of 1000BASE-KX. 

    Seems to me it is a switch issue in its auto-negotiating behavior. I may be wrong but the observations till now is suggesting me that.

  • 0 in reply to Souvik Sarkar
    TI__Genius 12916 points

    Hi Souvik,

    Good to hear. The switch may not have sent auto-negotiation page to the PHY. You can verify if the autonegotiation next page is received by the PHY by register 37h bit 1. Please note that this bit clears once read so the second read will result in 0.

    Best,

    J