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Original question:

DS110DF410: Link tranining support with DS110DF410S

DS280DF810: Link Training Support?

Mohamed Irfanulla MOHAMED ABDULLA
Prodigy 10 points
Part Number: DS280DF810
Other Parts Discussed in Thread: DS280BR820, DS280MB810

Hi TI experts,



According to this table it states that DS280DF810 does not support link training. I need few more clarification on the description. Does it mean that the coefficient update training frames from the link partner will never be received by the host in the following setup?

Secondly, Is there any possibility for the signal to pass through the retimer without applying the TX FIR settings? Moreover is there a procedure to pass the signal through the retimer without retimer manipulating the signal?
Does these sequence have any effect?

  1. Select CH0
  2. Write for all channels
  3. Reset all channel registers to power-on default values
  4. Set adapt mode 0: no adaption
  5. Put device into RAW mode (Writing 0x1E register)
  6. Enable EQ boost override
  7. Set EQ boost value as

Thank you in advance for your response,

  • TI__Mastermind 36363 points

    Hi Mohamed,

    The retimer is not protocol aware, so it would not distinguish between actual data and link training data.  I expect that link training frames can pass through the retimer, but the training pattern will not have any of the pre/post adjustments set by the host/link partner since it has a non-linear signal chain.  Because of this, link training is not supported.

    When the retimer is in "RAW" mode, TX FIR settings are not applied.  However, the signal chain through the device does not have the linearity that DS280BR820, DS280MB810 have.  Because of this, we would not recommend using link training with DS280DF810.

    Often, hosts have an option to disable link training.  I would recommend disabling link training with DS280DF810.

    Thanks,

    Drew

  • in reply to Drew Miller1
    Prodigy 10 points

    Hi Drew,

    Thanks for your explanation. I would like to know the best possible method for tuning the TX FIR coefficients.
    I see the recommended procedure is to sweep through the main,pre,post values listed in the Programming Guide and identify a setting with which on RX side VEO > 198 and HEO > 0.5 (I am not sure about these values please correct them if it is wrong).

    Are there any other method to simplify this procedure as for different cables the insertion loss are different and it requires different settings.

    Thanks,

  • in reply to Mohamed Irfanulla MOHAMED ABDULLA
    TI__Mastermind 36363 points

    Hi Mohamed,

    Your understanding is correct, the best TX FIR coefficients can be identified through sweeping values.  Please see the app note listed below for more details on this.

    https://www.ti.com/lit/pdf/slyt678

    We have empirically observed that our retimer has good BER for VEO > 200mVpp and HEO > 0.4 UI.  I would target achieving this eye measurement on the retimer.

    In our datasheet, Figures 11, 12, and 13 show a range of suggested FIR settings depending on insertion loss.  These can be used as a starting guideline for any FIR tuning.

    Thanks,

    Drew