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LMK05318B: Switchover event issue

Allen Lu
Expert 3140 points

Part Number: LMK05318B
Other Parts Discussed in Thread: LMK05318

hi team:

 My customer use LMK05318B and have a switchover issue when hot plug in/out the fiber optic, can you help to share the function of BIT5 of the 0xFC register ?

 And also, pls help to share the a method, when the optical fiber is reinserted, how the LMK05318 can automatically lock again.

here attached the issue description and config file for your reference.

 RU plugging fiber optic， LMK05318B clock out of lock issue.docx

lmk05318_cpri_cfg_12G.tcs

  • 0
    TI__Genius 17025 points

    Hi Allen,

    Some comments/questions:

    1. My understanding is that the customer cannot attain lock again when the DPLL reference input (PRIREF) goes from present to lost to present. Is this correct?
    2. Is the customer able to regain lock after performing this sequence: R252 (0xFC) = 0x2D -> 0x09 -> 0x2D?
    3. When R252[5] is enabled, then phase cancellation (hitless switching functionality) is enabled after switchover.
    4. Please have the customer try these debugging steps: 
      • Test with this config (I only reran the Run Script).
      • Currently, manual holdover mode is set. This means that if the CPRI input returns but the LMK05318B does not detect the PRIREF as valid, then the device will remain in holdover mode. Please confirm the following registers at the point after the CPRI input returns.
        • PLL1_VM_INSIDE, R357[5]
        • PLL1_VM_INSIDE, R367[5]
        • PRIREF_VALSTAT, R411[2]
        • DPLL_REFSEL_STAT, R167[1:0]

    Regards,

    Jennifer

  • 0 in reply to Jennifer Bernal
    TI__Expert 3140 points

    hi Jennifer:

    Jennifer Bernal said:
    Is the customer able to regain lock after performing this sequence: R252 (0xFC) = 0x2D -> 0x09 -> 0x2D?

    yes , as below log show the connection is lock again.

     i will let customer try your comments , tks again.

  • 0 in reply to Allen Lu
    TI__Genius 17025 points

    HI Allen,

    That is interesting. Yes, it would be good to get insight on the PRIREF validation status at time of lost signal.

    Regards,

    Jennifer