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DS280DF810: OTU4 datapath testing

AMAN BANOLIA
Prodigy 50 points
Part Number: DS280DF810

Hello ,

I am using DS280DF810 with the above setup with 100GE Ethernet and OTU4 data rates. In which 100GE data rate is working fine but getting FAS error in analyzer with OTU4 datarate,

I am using the following settings for DS280DF810 retimer. Please suggest in which direction should I change the pre-cursor and post-cursor value to solve the FAS error.

1. CDR settings to Manual Mode with Data Rate of 27.95Gbps.

2. Adaptive Mode 2

3. TX FIR settings for Lower Retimer are ( Pre Cursor Tap +0, Main Cursor +12, Post Cursor Tap +0)

    TX FIR settings for Upper Retimer are ( Pre Cursor Tap +0, Main Cursor +16, Post Cursor Tap +0)

 Please provide some suggestion how to solve the problem or some extra settings need to be done

Regards,

Aman

 

  • 0
    TI__Mastermind 18911 points

    Hi Aman,

    I have a couple questions related to this.

    • Is it possible to provide a retimer register dump while operating with OTU4 data?
    • Does your ASIC have the ability to take eye measurements / eye diagrams?  If so, can you share these?  This is helpful for understanding if retimer TX settings are well optimized.
    • Do you have any insertion loss estimates for ASIC <-> Retimer and Retimer <-> QSFP?
    • Do you have the ability to transmit PRBS patterns from your ASIC and OTU4/100 GbE analyzer?  Since the retimer has a built in PRBS checker, this can help us understand where errors in your link are originating from.

    In general, the fact that 100 GbE works well seems to suggest that your physical link is working well.  Unless there are key electrical requirements that differ between 100 GbE and OTU4, it's not immediately clear why there are errors in the OTU4 link.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 50 points

    Hi Miller,

    Currently, we are not able to measure the eye diagram in ASIC so we changed the test setup to physical loopback as shown in the figure with Insertion Loss of 13dB. In this setup 

    In this setup as well we are getting the FAS and Inv. Marker error with FEC enabled.

    Please check the device status of Retimer 1 

    Device status of Retimer 2 

    Also attached the register dumps of both the retimers.

    Retimer1.cfgRetimer2.cfg

    Please go through this and help me to clear FAS error 

    Regards

    Aman

  • 0 in reply to AMAN BANOLIA
    TI__Mastermind 18911 points

    Hi Aman,

    Are you able to enable the PRBS generator on retimer 2 and check for PRBS errors on retimer 1?  In general, the HEO/VEO you are observing is smaller than what we would typically target.  Typically, it is recommended to have at least 0.4UI, 200mV for HEO/VEO.  You could try adjusting TX settings to see if this can be improved.

    In general, the HEO/VEO you are observing is surprising.  If you transmit Ethernet data instead of OTU4, does this change the observed HEO/VEO?

    Thanks,
    Drew