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Original question:

AM335x RMII Ethernet connection without RX_ER

AM3354: RMII interface without RXER for PLC

Jack
Mastermind 9145 points
Part Number: AM3354

Hi TI

There's a question that a Customer wants to clarify.

My customer uses AM3354 with PLC via 10/100M RMII interface. 

According to them, their PLC device support MII and RMII, But RXER pin of PLC will be used for other purpose.

Please answer to the questions below.

1. Is is possible to communicate via RMII without RXER signal?

2. Original thread said MAC to MAC has not been verified. How about this PLC case? I don't have the information wherther their PLC has MAC and PHY mode.

3. Is it necessary to add Pull Up/Down to RXER pin even the pin is unused. I am confused by original thread. I am not sure the pin should be open-float or pulled down when RMII interface is used without RXER pin. 

4. If PU/PD is required when unused, Please suggest the appropriate value.

Regards, 

Jack

  • +1
    TI__Mastermind 27890 points

    Hello,

    1 ) Yes. Please see original thread.

    2) MAC to MAC has not been verified for any use-case.

    3) It needs to be held low. The original thread was suggesting that the internal PD could be used (depending on PinMux setting). I'd recommend an external PD to be extra safe.

    4) 10K PD should be sufficient. It's driven by the PHY so may be implementation-specific.

  • 0 in reply to -DK-
    Mastermind 9145 points

    Hi DK, 

    Thanks for your kind reply.

    Regards, 

    Jack

  • 0 in reply to -DK-
    Mastermind 9145 points

    Hi DK

    There're further question to be clarified. 

    There is still uncertainty regarding the case of "MAC to MAC has not been verified for any use-case".

    Customer uses the PLC chip in the following combination. 

    • PLC chip + PHY chip + RJ45 

    It seems their PLC chip itself does not support PHY mode.

    Please make clarification for better understanding. See the below questions.

    • Should I understand that MAC to MAC communication has never been omitted without connecting RXER for any use-case?
    • Does it mean that if RXER is not connected during MAC to MAC communication, TI cannot guarantee?
    • Is it possible for TI to provide with test result of MAC to MAC without RXER?

    Thanks.

    Regards, 

    Jack

  • +1 in reply to Jack
    TI__Mastermind 27890 points

    Hi Jack,

    TI has not verified MAC-MAC connections at all, so there is no data to provide, regardless of the RX_ER connection state.