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TLK10232: tlk10232 PMA link down

TOSHIO NOZAKI
Prodigy 20 points
Part Number: TLK10232

Tool/software:

Hello.

I am testing the TLK10232 by connecting it as shown below.

I am monitoring the following registers:

・CHANNEL_STATUS_1

・PMA_STATUS_1

・PMA_STATUS_2

・PCS_STATUS_1

・PCS_STATUS_2

・KR_PCS_STATUS_2

I have confirmed that the following errors occur about once every 1 to 2 days.

・PMA_STATUS_1 (PMA_LINK_DOWN)

・PCS_STATUS_2 (PCS_RX_FAULT)

・KR_PCS_ATATUS_2 (PCS_HI_BER_LH)

What is the cause of such errors?

I don't know if it's the optical cable or the SFP module that is bad.

  • 0
    TI__Mastermind 36423 points

    Hi,

    This indicates that there is an issue with the signal the TLK10232 is receiving.

    Do you have SFP loopback modules?  You could use these to test out each TLK10232 to see if issue is correlated with one of these devices.  If issue is not observed with loopback modules, this implies that there is something relating to the optical signal chain (SFP modules + optical cable) causing this behavior.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 20 points

    Thank you for your advice.

    I got a loopback module and tested it.

    As a result, no link down occurred.

    I tested it again with the following configuration.

    If one side is a general switch, the problem does not occur even if the same SFP and cable are used.

    Why does a link down occur between TLK10232s?

    I want to prevent link down from occurring even when connecting TLK10232s together.

    Will it improve if I adjust the optical transmission level, etc.?

  • 0 in reply to TOSHIO NOZAKI
    TI__Mastermind 18950 points

    Hi Toshio,

    Drew is out of the office and will be back next week. I do not cover TLK products but in the meantime I have some thoughts that might assist the debug:

    • Two TLK10232s are being used - did you use the loopback module to test the activity of both TLK10232s by themselves, if such a method was physically possible? The problem only happens in the hardware arrangement with two TLK10232s?
    • The three error flags you reported are related to a link down event, a fault condition on the RX path, and a high BER condition
      • In your diagrams it seems the TLK10232 on the right hand side is the one being checked for errors. Do we know if the TLK10232 on the left hand side has the same or different errors?
      • Have you noticed any other symptoms of the link down and errors while the system is operating, or only when checking the flags?
    • If the PMA errors are really a random event (nothing significant is happening in terms of external disturbances), then one possibility is that the signal quality between the two TLK10232s is marginal and random noise can sometimes be enough to cause signal errors or link drop. If you have methods to adjust the signal integrity settings of the PMA link, that could be a useful to experiment with.

    Best,

    Evan Su