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DP83822H: Why DP83822 has RGMII giga hertz protocol but maximum 100M

CHEN YAN
Intellectual 1430 points
Part Number: DP83822H

Hi, 

I have two questions about DP83822, sincerely ask for your help.

1. RGMII is a giga hertz protocol, why DP83822 support this protocol but only can reach 100Mbps?

2. If I want to do MII/RGMII compatibility design, can I leave the pins used in MII but not used in RGMII(pin27, CRS and pin29, COL) floating? What's the risk?

Thanks.

  • 0
    TI__Genius 11725 points

    Hi Chen Yan,

    The DP83822H, supports RGMII to give flexibility with MAC interface, as RGMII still supports lower speeds. When designing for MII, you cannot leave CRS floating. COL is required for half-duplex mode. Please review section 6 of the datasheet for more information. 

    Thank you,

    Nikhil