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DP83822I: About RGMII mode strap pin in DP83822I

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

Hi,

I use DP83822I and AM4376 to communicate in RGMII mode.

When I set RX_ER as mode 3, then RGMII_EN is set as 1. But in this mode, there is no TX_CLK, when I set RX_ER as mode 4, then RGMII_EN is set as 0, there is TX_CLK. So why? What else should I configure about the PHY? Is the problem of DP83822I datasheet?

  • 0
    TI__Mastermind 23675 points
    Hi Kevin,

    That is the correct behavior though.
    There should be no output of TX_CLK when in RGMII operation.
    Only RX_CLK is outputted by the PHY in RGMII operation.
    Please see the section on RGMII in the DP83822I datasheet.
  • 0 in reply to Ross Pimentel
    Prodigy 230 points
    Hi Pimentel,
    Thank you for your information.
    In RGMII operation, TX_CLK is output from MAC.
    So when will TX_CLK in RGMII operation output the clock signal? Is that related to the software in the CPU(We haven't downloaded the SW)?
    Thank you again!
  • 0 in reply to Ross Pimentel
    Prodigy 230 points
    Hi Pimentel,
    Another question, what's the operation mode for the DP83822 when it communicates with AM4376? Force mode or advertised mode? Thanks!
  • 0 in reply to Kevin,Shen
    TI__Mastermind 23675 points
    Hi Kevin,

    The CPU will output the TX_CLK when its firmware allows it to.
    I am not sure what the CPU is configured for. I suggest reaching out to the CPU group to understand the timing on this.

    Are you referring to forced and advertise with another PHY that is connected to AM4376? Can you show me a block diagram of this connection?
    A PHY can communicate with another PHY in either forced or advertise mode on the MDI (cable interface).
    There is no forced or advertise mode on the xMII (MII, RMII or RGMII).