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Original question:

TLK10232: TLK10232

TLK10232: High Speed SERDES control settings - can we use the reserved fields?

Yannick Coquereau
Prodigy 100 points
Part Number: TLK10232

Hello,

We are facing optical bit errors with new SFP+ modules combined with a TLK10232 in a proven system. 1000+ units built and running.

When using a more recent SFP+ module, link errors increase (from BER test >10^12 downto  <10^5) with identical settings (same brand, newer version of SFP+ module)

the XAUI initialization sequence is the following:

        -- device address 0x07, register address 0x0000, register data 0x2000 (AN_CONTROL) (disable AN)

        -- device address 0x01, register address 0x0096, register data 0x0000 (LT_TRAIN_CONTROL) (disable training)

        -- device address 0x1E, register address 0x0004, register data 0x5500 (HS_SERDES_CONTROL_3) (Rx cursor changed to 101 =11/9 cursor amplitude)

        -- device address 0x1E, register address 0x000E, register data 0x000E (RESET_CONTROL)

After playing with the settings, we found better results by enabling the reserved field, like bit 7 and HS_CDRFMULT = 11 of HS_SERDES_CONTROL_3 register.

Question: is it OK and sustainable to use such settings? Can we know what effect have these settings (as we see improvements in the optical link BER) ?

Thanks a lot for your support!

  • 0
    TI__Genius 16240 points

    Hi Yannick,

    Enabling register 0x0004 bit 7 limits the HSRX equalizer DFE tap weights. I don't see any issues with enabling this bit. We don't have a great understanding of how setting register 0x0004 bits 11:10 to 11 affects the device, so I don't recommend using this setting. Out of curiosity, what prompted you to try using these settings?

    Do you have any information or characterization data on what changed between the older SFP module and the newer SFP module that you can share? It would be helpful to debug why the new module is causing a higher BER.

    I have some suggestions you can try which we typically recommend for applications with a short channel. Not sure if the newer SFP module has a shorter channel or not, but these might be worth trying.

    • Try enabling HS_ENTRACK (register 0x0004 bit 15)
    • Try using a high HS_EQPRE setting (register 0x0004 bits 14:12). 11/9 cursor amplitude is already a high setting, but it might be worth trying 13/9 too.
    • Try enabling HS_H1CDRMODE (register 0x0004 bit 5)

    Best,

    Lucas