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DS280DF810: PRBS Testing in Retimer Device

AMAN BANOLIA
Prodigy 50 points
Part Number: DS280DF810

Hello, 

I am running PRBS in the given setup

With the Following setup 

Retimer 1 

Data Rate 27.95 Gbps and Post-Lock Output as PRBS Generator (as suggested in Programming Guide Line)

Channel 4 PRBS-7 Enable

 

I am configuring the retimer 1  with the above setting but am not able to detect any signal on the optical side. 

Regards,

Aman

  • 0
    TI__Mastermind 27157 points

    Hi Aman,

    Our retimer requires CDR lock in order to generate a PRBS pattern.  If a data signal at 27.95 Gbps is not available, we often work around this by using a subrate clock.  Does your test setup allow for use of an external clock?  If so, I would recommend the following:

    • Configure retimer CDR for 27.95 Gbps.
    • Set clock to subrate of  27.95 Gbps.  For clock generators we have available in lab, this would probably be div 8 or div 16, so 3.49375 GHz or 1.746875 GHz.
    • Set amplitude to 800 mVpp.
    • Use balun to split 50 Ohm singled ended signal into 100 ohm differential signal.  If balun is unavailable, you can probably use a single ended signal.  If you do this, use 400 mVpp signal.
    • Connect differential signal to differential input of retimer.  If using single ended signal, connect to P or N.
    • Verify CDR lock.
    • For testing multiple channels at once, you can fanout the signal using internal 2x2 crosspint.
    • Enable PRBS generator.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 50 points

    Dear Miller 

    As shown in figure all CDR is locked but as I am enabling the PRBS for channel 4 the output of the Retimer is getting turned off 

    I am doing the following setting

  • 0 in reply to AMAN BANOLIA
    TI__Mastermind 27157 points

    Hi,

    You should be able to enable PRBS generator without manually adjusting the POST LOCK Output.  Does this the device behavior?  Are you able to enable the PRBS generator on other channels?

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 50 points

    Hello Miller,

    How we can make sure whether the Output is retimed data or PRBS pattern without manually setting the POST LOCK Output? 

    For all the channels behavior is the same.

    Thanks,

    Aman 

  • 0 in reply to AMAN BANOLIA
    TI__Mastermind 27157 points

    Hi Aman,

    Typically I just select the channel and press the "enable" button in the PRBS tab.  This has worked fine in my experience.

    When you say that the output turns off, how are you measuring this?  Is it from a scope, or signal detect from another retimer?

    I haven't run into issues where enabling the PRBS generator causes output to stop.  Does the retimer maintain lock after enabling the PRBS generator?

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 50 points

    Hello Miller,

    I am measuring the output by signal detection in another retimer.  When I press the enable button in PRBS tab, signal is getting detected only when POST LOCK Output is set to Retimed Data as soon as I switch the POST LOCK Output setting to PRBS Generator signal doesn't get detected at the other retimer.

    I am referring to step 8 of this procedure.

    Thanks,

    Aman

  • 0 in reply to AMAN BANOLIA
    TI__Mastermind 27157 points

    Hi Aman,

    Using SigCon architect, I would recommend configuring PRBS just using the "Enable" button in the PRBS tab.  I think that the "Enable" button and the "Post-Lock Output" configuration options have a couple additional register writes associated with each of them besides just basic enable / post lock register writes as detailed in the programming guide.

    If enabling the PRBS generator results in signal detect, that's a good start.  Are you able to lock to the data on the RX retimer?  If so, you can use the pattern checker to confirm that you are receiving PRBS data.

    Thanks,

    Drew