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DS90UB928Q-Q1: Could you tell me how much Bit Error Rate that is possible to cause loose lock for DS90UB928Q-Q1?

K.Yaita
Guru 29720 points
Part Number: DS90UB928Q-Q1

Hi Team,

Could you tell me how much Bit Error Rate that is possible to cause loose lock for DS90UB928Q-Q1?
Is there any data?

Best Regards,
Yaita / Japan disty

  • 0
    TI__Genius 10475 points
    Yaita-san,
    Please refer to the DS90UB928 datasheet for details on the link error count register (addr 0x65).

    If the link error count is enabled in this register, then the deserializer loses lock when the error count reaches the threshold set in this register.
  • 0 in reply to Palaniappan Manickam
    Guru 29720 points

    Hi Palaniappan-san,

    Thank you for your support.
    I believe my customer can enable Link Error Count not only prototype but although mass-production depending on his application.
    Is my understanding correct?
    I concern about it because the default value is 0x03(Link Error Count is disabled), so would like to ask just in case.

    Best Regards,
    Yaita / Japan disty

  • 0 in reply to K.Yaita
    TI__Genius 10475 points
    Yes it can be enabled and used in normal mode.
  • 0 in reply to Palaniappan Manickam
    Guru 29720 points

    Hi Palaniappan-san,

    Thank you for your support.
    My customer wants to enable Link Error Count and has two questions as the following.

    1)
    Does "Link Error Count" value accumulate only when link error is occured consecutively?
    Or does it accumulate even if link error is occured intermittently?

    2)
    Is it possible to reset "Link Error Count" value?
    My customer don't want to loose lock even if link errors are occured.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 10475 points
    Hello,
    The link error counter is pixel clock based and it doesn't need to be consecutive for the error count to accumulate. It counts up until the threshold is reached if enabled.
    The error threshold can be set to a high enough value so a few errors do not cause loss of lock, but at the same time it can help detect if something catastrophic happens.
  • 0 in reply to Palaniappan Manickam
    Guru 29720 points

    Hi Palaniappan-san,

    Thank you for your support.
    Regarding question 2), I believe "Link Error Count" value can be reset if toggling 0x41 bit4 (Link Error Count Enable bit).
    Is my understanding correct?
    --------------------------------------------
    2)
    Is it possible to reset "Link Error Count" value?
    My customer don't want to loose lock even if link errors are occured.
    --------------------------------------------

    My customer don't want to loose lock even if link errors are occured many times, so I would like to confirm if setting "Link Error Count Threshold (bit[3:0])" to 1111b and periodically toggling "Link Error Count Enable (bit4)" can be applicable to achieve it.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 10475 points
    Reg 0x41 bit 4 enables or disables the link error count, so when you set to high the link error count accumulates errors. When you toggle it and set to low, the error count is disabled and deserializer loses lock with 1 error. If you set it back to high again, the prev error count should be lost and it should start counting again from 0 until the threshold is reached (max value 1111b in your example).
  • 0 in reply to Palaniappan Manickam
    Guru 29720 points

    Hi Palaniappan-san,

    Thank you for your continuous support.
    I understood.

    Can error count be reset to 0 if we rewrite the value of Link Error Count Threshold (bit 3:0)?
    My customer wants to reset the error count to 0 with maintaining link error count enable.



    Best Regards,
    Yaita / Japan disty

  • 0 in reply to K.Yaita
    TI__Genius 10475 points
    Hello,
    We are looking at setting up some hardware testing on bench to confirm the behavior. We should be able to provide you a timeframe for results in a couple of days.
  • 0 in reply to Palaniappan Manickam
    Guru 29720 points

    Hi Palaniappan-san,

    I really appreciate for your effort to this inquiry.
    I will wait for your feedback.

    If the following answer is yes, my customer also wants to know if reset is occured even if rewrite the same value (0x41 bit3-0 : 1111b - > 1111b).  
    ----------------------------------------------
    - Can error count be reset to 0 if we rewrite the value of Link Error Count Threshold (bit 3:0)?
    ----------------------------------------------

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 10475 points
    Hello,

    We tested this on the bench with the 928 board and the observation is that LOCK will go down upon the error count hitting the threshold but will re-lock automatically and lose lock again and so on. The LOCK continues to toggle as long as the error condition persists.

    So it looks like the error count gets reset automatically upon reaching the threshold.
  • 0 in reply to Palaniappan Manickam
    Guru 29720 points

    Hi Palaniappan-san,

    Thank you for your kind support.
    I understood it looks like the error count gets reset automatically upon reaching the threshold.

    Can error count be reset to 0 if we rewrite the different value of Link Error Count Threshold (bit 3:0)? (ex: 0x41 bit3-0 : 1110b - > 1111b)
    My customer wants to reset the error count to 0 without loose lock.

    If the answer is yes, I also wants to know if we can reset the error count to 0 even if rewrite the same value (ex: 0x41 bit3-0 : 1111b - > 1111b).  

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 10475 points
    Yaita-san,
    Based on our testing, neither re-writing or overwriting the error count threshold value nor disable/re-enable error count can help with keeping the lock high.
    To summarize, the error counts gets reset automatically and will count up again until threshold, then LOCK drops low and this process repeats causing the LOCK to toggle. This matches the expected behavior of LOCK, i.e. if there are continuous errors in the system exceeding the error count threshold LOCK will go low and then toggle as long as the error condition persists. The correct course of action would be to identify the underlying error condition and rectify that.
  • 0 in reply to Palaniappan Manickam
    Guru 29720 points

    Hi Palaniappan-san,

    Thank you for your support. I will inform your comments to my customer.

    I would like to confirm just in case.
    You referd "continuous errors" as the following. 
    ---------------------------------------------
    i.e. if there are continuous errors in the system exceeding the error count threshold LOCK will go low and then toggle as long as the error condition persists.
    ---------------------------------------------

    However I got the following reply from you the other day.
    ---------------------------------------------
    The link error counter is pixel clock based and it doesn't need to be consecutive for the error count to accumulate. It counts up until the threshold is reached if enabled.
    ---------------------------------------------

    I think these are conflicting contents.
    Which is correct?
    I think it is ideal if link error count value accumulates only when link error is occured consecutively.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 10475 points
    Sorry for any confusion. The link error count is pixel clock based and the errors do not need to happen in consecutive cycles for it to keep counting.
    What I mean by continuous errors is if there are still errors in the system (let's say for many many pixel clock cycles), the error count will go up, reach the threshold, reset and count up again and this will keep repeating causing the LOCK to drop again and again.
  • 0 in reply to Palaniappan Manickam
    Guru 29720 points

    Thank you Palaniappan-san,

    According to your comments, loose lock is certainly occured in terms of long term even if Link Error Count Threshold (bit 3:0) is max setting (1111b).
    I believe there is an application that loose lock shouldn't be occured even if link errors is occured.
    Is there recommended countermeasure for such application?
    (Is there such requirement from any other customer?)

    In addition, default value 0x03 (Link Error Count disable) of 0x41 register is too strict to set in terms of above.
    What do your team think about it?


    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 10475 points
    The default (setting of '3') is just set to a value higher than the 1 error that will trigger the lock to go low if this feature is not used.

    It is ok to set the value to max (4'b1111) when using this feature and if there are more errors then LOCK will go low. It is not typical for an application to want to maintain LOCK high even when there are so many errors, so this is not something we typically see customers ask for.
  • 0 in reply to Palaniappan Manickam
    Guru 29720 points

    Hi Palaniappan-san,

    I would like to confirm test condition about the following result.
    -------------------------------------------------------------
    Yaita-san,
    Based on our testing, neither re-writing or overwriting the error count threshold value nor disable/re-enable error count can help with keeping the lock high.
    To summarize, the error counts gets reset automatically and will count up again until threshold, then LOCK drops low and this process repeats causing the LOCK to toggle. This matches the expected behavior of LOCK, i.e. if there are continuous errors in the system exceeding the error count threshold LOCK will go low and then toggle as long as the error condition persists. The correct course of action would be to identify the underlying error condition and rectify that.
    -------------------------------------------------------------
    Has loose lock been occured many times per second in your evaluation system?
    If so, my customer think the yellow part is reasonable.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Genius 10475 points
    I am not sure if I understand the question, but yes the lock keeps toggling based on the testing (lock monitored on LED on the EVM).