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Original question:

DP83822I: AUTO-MDIX can be used when auto-negotiation is disabled?

DP83822I: AUTO-MDIX not working.

Hisao Uchikoshi
Genius 14870 points
Part Number: DP83822I

Hi Experts,

Customer fails Auto-MDIX. Below is the register configuration.

BMCR(0x0000)
Bit13 (Speed Selection)        : 1 (100 Mbps)
Bit12 (Auto-Negotiation Enable): 0 (Disable Auto-Negotiation)
Bit 8 (Duplex Mode)            : 1 (Full-Duplex)

PHYCR(0x0019)
Bit15 (Auto MDI/X Enable) : 1 (Enable Auto-Negotiation Auto-MDIX capability)

Link cannot be established every time. The pear NIC is Intel I219-LM.

Are there any missing for register setting? 

Regards,

Hisao Uchikoshi

  • 0
    TI__Expert 7040 points

    Hello Hisao,

    Since you have disabled Auto-Negotiation, you will need to enable Robust Auto MDIX in order to ensure the Auto-MDIX resolves properly in all situations. You can enable Robust Auto MDIX through register 0x0009[5]=1.

    Regards,
    Justin 

  • 0 in reply to Justin Lazaruk
    TI__Genius 14870 points

    Hi Justin,

    Thank you for your answer.

    The datasheet says that "Robust Auto-MDIX" is used when the link partner does not support the "normal" Auto-MDIX. Could you please explain what is the case to use it? What is the device not supporting "normal"? By setting this bit, are there any affects to other functions?

    Regards,

    Hisao Uchikoshi

  • 0 in reply to Hisao Uchikoshi
    TI__Expert 7040 points

    Hi Hisao,

    "Normal" Auto-MDIX is meant to work in conjunction with auto-negotiation. When auto-negotiation is disabled but auto-MDIX is desired, the IEEE spec is not specifically defined so "normal" Auto-MDIX is not always sufficient. We have included Robust Auto-MDIX for this scenario, which will not affect other functions of the PHY.

    Regards,
    Justin