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DS110DF111: SBT

Brian Gosselin
Expert 4585 points
Part Number: DS110DF111

Hello,

Can you please provide some details regarding what SBT does?

My customer found that they need to disable SBT in order to achieve a link in a 10GBase-SR application using SFP+ transceivers.

Best Regards,
Brian

  • 0
    TI__Genius 16680 points

    Hi Brian,

    SBT checks the number of bit transitions within a window of time. If the number of transitions do not meet the required threshold, then SBT prevents CDR lock. I would guess your customer's pattern has a low number of bit transitions, which would explain why disabling SBT is necessary to obtain CDR lock.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    TI__Expert 4585 points

    Hi Lucas,

    Thank you.  Follow-up questions:

    How many transitions is the DS110DF111 looking for and how long is the window of time?

    Would you expect SBT not to work in the case of 10GBase-SR during the linkup stage?

    Best Regards,
    Brian

  • 0 in reply to Brian Gosselin
    TI__Genius 16680 points

    Hi Brian,

    Brian Gosselin said:
    How many transitions is the DS110DF111 looking for and how long is the window of time?

    Unfortunately I don't have a clear answer to give here as this is confidential design information.

    Brian Gosselin said:
    Would you expect SBT not to work in the case of 10GBase-SR during the linkup stage?

    I would normally expect the single bit limit to be reached with ordinary 64b/66b encoded 10GbE data. If the data/pattern being transmitted has an especially low number of bit transitions, then this would explain why the single bit limit isn't being reached. Disabling SBT is a common debug/workaround step for CDR lock issues, so I don't have any concern if it is necessary for the customer to obtain CDR lock.

    Best,

    Lucas