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DS125DF1610: No pattern with on-chip eye monitor

Part Number: DS125DF1610

Hi,

Our customer faced a issue during test of DS125DF1610. They used the re-timer connected with optical module. The optical signal is input, then it is converted to electric signal and goes through the re-timer. Finally it's converted to optical signal again.

During the test, they could see the eye pattern with optical signal. Also the system worked normally and CDR was locked. But they couldn't get eye pattern through the on-chip eye monitor. Customer has used the on-chip eye monitor in previous project, but this issue happened first time. Customer wants to know if that means the signal received by chip isn't good or it's caused by some other reasons.

They tested several different ICs on their board. They couldn't see the eye pattern with several re-timers (all the channels), but they could see the pattern with some others.

From the block diagram of datasheet, we can see that the eye opening monitor is before CDR, after EQ and DFE. Did that mean the effects of the re-timer in this application relied on the CDR function? So customer couldn't get eye pattern with on-chip eye monitor?

Thanks,

Andrew

  • Hi,

    If the retimer CDR is locked then the Eye Opening Monitor (EOM) function should work. Though the EOM plots capture the eye quality after EQ is applied and prior to CDR, CDR lock is still required for the EOM to work. Can you provide a full dump of the retimer channel registers for the test case in question?

    Thanks,

    Rodrigo Natal

    HSSC Applications Engineer

  • Hi Rodrigo,

    Since I think this case isn't urgent for customer now and I'll close this thread. If there's more request from customer, I'll create a new thread then.

    Thanks,

    Andrew