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Link cannot be established once the fiber cable is disconnected and connected again

John11513
Expert 5720 points
Part Number: DP83822IF

Hi team,

My customer reported an issue with DP83822IF. The device is operated in 100BASE-FX mode. The problem is in sometime once the link dropped due to the fiber cable is disconnected, the link cannot recover automatically once the fiber is connected again until the PHY is reset.

I noted there is a NOTE in datasheet, it says "... if the electrical link between the fiber module and the DP83822 is broken, disconnected or otherwise disrupted, the link will recover only by initiating a soft
reset through MDIO/MDC interface."

I am not sure if this is the root cause of my customer's issue? If disconnection of the fiber cable results 'DISRUPTED' of the electrical link (between fiber module and the DP83822)?

Thank you!

John

  • 0
    TI__Guru**** 192079 points

    Hello John, 

    Thank you for the Query.

    Your observations are right and this is the probable cause. Do you know if the customer has connected the SD pin from the fiber transceiver.

    TI recommends connecting Signal Detect pin from the Optical Transceiver to the LED_1 pin and enable it using SD_EN bootstrap pin in 100BASE-FX mode. The LED_1 pin is not used in design and that, if the electrical link between the fiber module and the DP83822 is broken, disconnected or otherwise disrupted, the link will recover only by initiating a soft reset through MDIO/MDC interface.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    TI__Expert 5720 points

    Hi,

    Thank you for reply. 

    Yes, the LED_1 pin has been connected to fiber module and SD_EN has been enabled.

    Another think i want to clarify is that this issue only occurred when the port is operated in simplex mode. That is to say the Tx cable is removed and only a single Rx fiber cable is connected. The issue never occurred if both Tx and Rx fiber are connected.

    Thank you!

    John

  • 0 in reply to John11513
    TI__Guru**** 192079 points

    Hello John, 

    Thank you for providing additional details.

    In the case you described, doing s reset as you have mentioned would be recommended. 

    I could not see any other option available to detect only TX cable removed.

    Regards,

    Sreenivasa