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

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

  • 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

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

  • 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