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[TDA4M] RMII pinmux double check

Peter Li79
Expert 8940 points

Hi, Experts:

In the TI J721E EVM, the QUAD-PORT ETHERNET EXPANSION BOARD uses QSGMII.

But my customer wants to use 6 RMII ports (will connect external ethernet PHY).

I think the customer has made the correct configuration.

Would you please kindly double check whether it is okay? 

J721E_alpha.zip

  • 0
    TI__Mastermind 27743 points

    Hello Peter,

    Can you please share customer schematic via mail (pls dont post here)? 

    Below are some comments about pinmux

    • Is customer using external or internal RMII 50MHz clock? Internally SOC can provide clock on CLKOUT pin whereas external oscillator or PHY can also provide clock on RMII_REF_CLK. I see both are configured in the pinmux.
    • Is any GPIO used for PHY reset/interrupt? If yes, I don't see it configured in pinmux

    Rest of pinmux seems correct.

  • 0 in reply to Prasad Jondhale
    TI__Expert 8940 points

    Hi, Prasad:

    The schematics is still under development.

    Customer plans to use internal CLK_OUT pin to provide clock, and also will use GPIO from another MCU on board to control the PHY reset pin.

    So, customer doesn't need to ball out the RMII_REF_CLK?  Or the CLK_OUT should be connected to  RMII_REF_CLK from the board?

    Many thanks and appreciate.

  • 0 in reply to Peter Li79
    TI__Mastermind 27743 points

    Hello Peter,

    Your understanding is correct. If internal clock is used, no need to configure/connect RMII_REF_CLK.

    But in my opinion, having it balled out can be back up option for alpha EVM in case we see any issues (I can't think of any at this point), and external clock needs to be used.

    Let me know your thoughts.