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DP83867IR: The Ethernet link fail

shu wang
Prodigy 40 points

Part Number: DP83867IR
Other Parts Discussed in Thread: AM6422

Hi,

We recently hit an issue with DP83867 after board bring-up. The Ethernet link is not working on one board.

We are using RGMII mode with Gigabit auto-negotiation. The contorller is AM6422. The connection is same as the AM6422 evaluation board. MDC and MDIO are working fine, we could measured the singals.

However, after power-up, we observed that RX_CLK drops from 125 MHz to 25 MHz, while GTX_CLK stays at 125 MHz. We are not sure why this mismatch happens, and the link cannot come up.
 
Other boards with the same hardware, software, and configuration are working without any issue. The PHY core power comes up slightly later than the I/O power. We didn’t see any power sequnce requirements in the datasheet, but could this cause the issue?
 
Any ideas what might cause the PHY fail?
 
Best Regards,
Shu
  • 0
    TI__Mastermind 42565 points

    Hi Shu,

    The RGMII RX_CLK staying at 25MHz is indicative of no 1G linkup since this is an output of the device. GTX_CLK is an input from the MAC so it makes sense it to stay at 125MHz if the MAC is not aware that link was severed. 

    I would like to focus this on why is there a link issue. You had mentioned that other boards with the same hw/sw/configuration are working. Are these the exact same designs as this board (meaning different instances), or slightly different designs? I would like to understand differences between working and non-working instances which could attribute to this behavior; both on board as well as off-board.

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 40 points

    Hi Gerome,

    Yes, they are same hardware and software. The boards are newly received and has not been modified.

    Best Regards,

    Shu

  • 0 in reply to Gerome Cacho
    Prodigy 40 points

    Hi,

    Have you seen a similar issue in the past? We didn't make any changes to the board, so we're unsure what might have caused this problem. How should we troubleshoot this correctly?
    Thanks,
    Shu
  • 0 in reply to shu wang
    TI__Mastermind 42565 points

    Hello,

    I have not seen this issue in the past. As there are no changes to the board, I would suggest analyzing why this specific instance of the device is having issues and compare against other working boards. Is there difference in the clocking or supplies?

    Is the link partner in this instance okay when connecting to other instances of this design?

    Sincerely,

    Gerome