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Original question:

DP83867CS: auto-polarity inversion of the MDI lanes

DP83867CS: With automatic MDI polarity correction, how does this affect what the PHYSTS register read out?

Max Luc Balen
Intellectual 830 points

Part Number: DP83867CS

Tool/software:

Hi Team,

Following on from this thread; following on the explanation regarding the IEEE802.3 standard for MDI polarity reversal, does it really not matter that the polarities of MDI differential signals are reversed in individual pair(s) when the chip is bootstrapped to mirror mode because the chip should be able to detect the polarity per each channel?

If I have reversed polarity on channel A and normal polarity on channel B, what will bit 8 of PHYSTS register be read out? Will it indicate resolved as MDI or MDIX for channel A and B?

Thanks

  • 0
    TI__Expert 8105 points

    Hi Max,

    MDI and MDIX are not referring to the individual channel polarity changes, but instead to connecting one channel to another. Please refer the following table for more information.

    MDI Config Main PHY Channel Link Partner Channel
    MDI (PHYSTS[8]=0) A A
    B B
    MDIX (PHYSTS[8]=1) A B
    B A

    The polarity changes are represented by bits [5:2] of the same register PHYSTS, each bit representing each channel, where bit 2 is for Channel A and bit 5 is for Channel D.

    Regards,

    Vivaan