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Original question:

DP83822I: About RGMII mode strap pin in DP83822I

DP83822I: About the MDC and MDIO timing issue under RGMII mode communication between DP83822IRHBR and AM4376

Kevin,Shen
Prodigy 230 points
Part Number: DP83822I
Other Parts Discussed in Thread: AM4376

Hi Pimentel,

When DP83822IRHBR and AM4376 are configured as RGMII mode, there is no communication as I described in the last message, and I found that there existed timing issue between MDC and MDIO, which is red marked in the below picture, when in the rising edge of MDC, the setup time is not enough for MDIO, which leads to unclear state(0 or 1) . So do you have met with similar issue before, and would you like give me some suggestion on how to solve this issue? Thanks!

  • 0
    TI__Mastermind 23675 points
    Hi Kevin,

    Do you see incorrect data when you read register 0x0, 0x1, 0x2 and 0x3?
    The timing for MDIO/MDC is tight since the interface supports up to 25MHz.
    Are you inducing any delay on MDC?
    Can you show me the timing for the part of the coms when the AM is sending a bit stream and then show me the PHY response timing?