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66AK2H06: 1Gb SGMII RX initial calibration

Seppo Pyorret
Prodigy 20 points

Part Number: 66AK2H06

Hello experts,

We are having issues with rx align errors in 1Gb ethernet and using 66AK2H06 SOC. 

My question concerns the initial calibration of serdes during powerup. The silicon errdata SPRZ402F has on pages 84 & 85 a section 'SerDes Fails to Adapt RX BOOST Equalization'. There it explains that the calibration is not done if 8/10b decoding is used. The peripherals listed does not show the 1.25GHz SGMII but the decoding is exactly same 8/10b in 1Gb Ethernet.

According to SPRUHO3A, section 15.3 describes the initial calibration and after PHY startup sequence is complete and it will be done only once. But, taking the silicon errdata into account, is the SOC RX calibrated at all since the 8/10b decoding is being used?

  • 0
    TI__Expert 7340 points

    Hi,

    Could you please elaborate more on the background of the issue?

    Let me know which SDK version you are currently using?

    Are you using TI's default MCSDK SerDes configuration/a custom initialization?

    Seppo Pyorret said:
    According to SPRUHO3A, section 15.3 describes the initial calibration and after PHY startup sequence is complete and it will be done only once. But, taking the silicon errdata into account, is the SOC RX calibrated at all since the 8/10b decoding is being used?

    Will check this internally and get back to you.

    Regards,

    Betsy Varughese

  • 0 in reply to Betsy Varughese
    TI__Guru 64420 points

    Hi Seppo,

    That errata section only applies to the data rate of 5Gbps and beyond. The SGMII at 1.25G would be unaffected by the errata note 28.

    Would a PRBS pattern perform without errors? Have you tried out hardcoding the ATT/Boost values to see the errors increase or decrease? 

    usually for lower rate at <1G, it should work (low BER) for wide range of RX (TX) EQ values. What are the Boost values seen currently?   

  • 0 in reply to ShreyasRao
    TI__Guru 64420 points

    Seppo,

    Looking at the errata document, I think you could be affected by the advisory 44, where the Boost value maybe at 0 (for lower speed interfaces) which does not experience significant high frequency loss. You would need to manually set it to a different number. 

    "it may be possible to reduce the high-frequency content of the incoming signal by lowering the slew-rate of the remote TX" could also be tried.