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DP83867IRPAP-EVM: What is the cause of RX_ER in case of MII loopback mode?

user5815024
Prodigy 90 points
Part Number: DP83867IRPAP-EVM
Other Parts Discussed in Thread: DP83867IR

Hello,

I'm using DP83867IR.

For the debugging purpose, I tried MII loopback mode (Near-end loopback).

However when the signal loops back, the RX_ER signal was always asserted.

The MAC could receive the looped back frame by suppressing the RX_ER signal (setting register GPIO_MUX_CTRL2[0:3] = 1000 (constant "0")).

The speed was 10 and 100 Mbps. Both speed setting resulted in same.

My question is...

What is conceivable cause of the RX_ER in this case?

Best regards,

Tsunokawa

  • 0
    TI__Mastermind 19780 points
    Hi Tsunokawa-san,

    Were you in GMII operation when you did the MII loopback?

    I am not sure why the RX_ER was asserted, but in MII loopback mode, the DP83867 will not show a link indication.

    For GMII/MII loopback in 100M mode, the auto-mdix function must be disabled and no link partner connected.

    Best Regards,
  • 0 in reply to Rob Rodrigues
    Prodigy 90 points

    Hi Rob-san,

    Thank you very much for your response.

    #Were you in GMII operation when you did the MII loopback?

    > No, I was in MII operation.

    I found the cause of the RX_ER being asserted. It is my mistake for the MAC side. The TX_ER were always asserted by the MAC by mistake.

    After I set the MAC correctly so that TX_ER is not asserted, the RX_ER was no longer asserted.

    Sorry for taking your time.

    Best regards,

    Tsunokawa

    Rob Rodrigues