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Original question:

DP83TG720S-Q1: SGMII auto-negotiation

DP83TG720S-Q1: What does SGMII auto-negotiation do?

Cameron Wutzke
Expert 4077 points

Part Number: DP83TG720S-Q1

I see the 720S is a single/fixed speed PHY (1Gbps) and hence there is no auto-negotiation. It will always link-up in 1Gbps mode

leads me to my question: what is the “SGMII auto negotiation” negotiating? Master / slave ?

thanks,

Cameron

  • 0
    TI__Expert 4620 points

    Hello Cameron,

    In SGMII control information is transferred from the PHY to the MAC to signal the change of the control information. This is achieved by using the Auto-Negotiation functionality. This control information comprises of various statuses such as link , duplex mode, speed, as well as EEE capability for example. 

    Regards,
    Avtar

  • 0 in reply to Avtar Dhaliwal
    TI__Expert 4077 points

    Can any version of the DP83TG720 be setup to negotiate master/slave roles on the T1 link?

  • +1 in reply to Cameron Wutzke
    TI__Expert 4620 points

    Hello Cameron, 

    In the auto-negotiation process between two SGMII PHY's the concept of master-slave configuration doesn't typically apply as it does in the other interfaces. There is no explicit master or slave designation between the two PHY's, instead the auto-negotiation process determines the highest common denominator of their abilities such as speed, duplex mode, and other features supported by the PHY.

    Once auto-neg is complete both PHY's agree on a common set of parameters for communication. So while auto-neg is important for establishing communication, it doesn't involve configuring one PHY as master and one PHY as slave in the traditional sense. 

    Regards,

    Avtar