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I am reading this document : https://www.nxp.com/webapp/Download?colCode=AN3869 I got this link from NXP support, but I did not get a precise answer to my questiosn and I would like to be sure :

  • The NXP support told me that link training exists between MAC and PHY over SGMII. By reading this document, I assume that the link training is about auto-negotiation. However, link training is usually not about auto negotiation, but about having a proper signal on the cable, so I am a bit confused

  • MAC does necessarily have a MDIO connexion with PHY if SGMII is used. Indeed, auto negotiation is based on the 1000BASE-X standard and capabilities ares exchanged over the SGMII cable. But there are plenty of other registers in the MDIO that you can/should configure. How do you do this ? Does the information go through the SGMII connexion too, or is there ALWAYS a MDIO connexion between MAC and PHY?

Thank you for your time!

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  • \$\begingroup\$ You have to be registered to have access to the AN you are referring to. And what was the question that you asked? \$\endgroup\$
    – nickagian
    Jun 26, 2017 at 14:17
  • \$\begingroup\$ Also, you don't mention any information at all regarding which PHY you use. \$\endgroup\$
    – nickagian
    Jun 26, 2017 at 14:26
  • \$\begingroup\$ It was a general question about the SGMII standard \$\endgroup\$
    – pierre123
    Jun 26, 2017 at 14:47

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I don't know the specific PHY (now that I think of it, you don't even mention which PHY you have) and cannot tell you if these apply to your case. But from my experience from other PHYs I can tell you these:

There are normally both of these methods supported to configure a link between PHY and MAC. Either you have to provide every necessary parameter from the MAC to the PHY over the MDIO interface, or you configure both sides in auto-configuration (usually this is by default done at the PHY after power-up) over SGMII and the two sides automatically exchange information and agree on a configuration (meaning speed, full-duplex etc.).

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  • \$\begingroup\$ It was a general question about the SGMII standard, but thank you for your answer, I doubted it was possible not to have a MDIO connexion on the PHY since the auto negotiation process over SGMII only allows to transfer speed/duplex/link status... \$\endgroup\$
    – pierre123
    Jun 26, 2017 at 14:56

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