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DP83822I: Can't switch to RGMII mode using the HW bootstraps on DP83822 EVM .

Yue TANG
Expert 8705 points
Part Number: DP83822I
Other Parts Discussed in Thread: USB-2-MDIO

Hi,

We  pull-up and pull down the pins to configure the MAC interface following the datasheet as below[P1].Target mode is RGMII, then, didn't connect to the external processor, just power up the DP83822 EVM, by my understanding, the TX_CLK should not output clock if in RGMII mode[P2], but still can observe clock from TX_CLK pin. please suggest if there is anything wrong? thanks.

P1:

P2:

  • 0
    TI__Mastermind 19780 points

    Hi Yue,

    You are correct that in RGMII mode, the TX_CLK will not be sourced by the PHY.

    The datasheet tables for the RGMII mode can be confusing.  To place the DP83822 into RGMII mode by straps, leave RX_DV pin floating, or apply a pull-down.  RX_ER must be set to mode 2 or mode 3.  This can be done by placing a pull-up of 6.2k on R60 and a pull-down of 1.96k on R66 using the EVM.

    If you are still having problems, I would recommend trying to read the registers of the DP83822 on the EVM by MDIO.  You can do this using the USB-2-MDIO tool.

    Best Regards,