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Original question:

DS250DF810: ds250df810

DS250DF810: When ds250df810 improves the 100g interface between switching chip and optical module, there are a lot of wrong packets in 100g interface

sailchang
Prodigy 20 points
Part Number: DS250DF810

hi

We use ds250df810 between switch and optical module to improve 4 * 25g signal！At the beginning, the 100g port of the switch chip could not be linked. 

Later, we modify the RX output emphasis control register parameters of the optical module from 3dB to 0d；

The 100g port of the switch chip can link, and there is no wrong packet.

Can we change the parameters of ds250df810 instead of configuring the optical module so that the 100g port of the switch chip is linked and correct！

I tried to modify the following parameters of ds250df810 from Ti forum：

reg     value    mask

0x13  0x04     0x04

0x1a  0x00     0x08

The 100g port of the switch chip can link up, but there are many wrong packets when receiving data！

The ds250df810 is configured according to the document ffront-port ingress；

Now the value of CTLE is 0x00；

Is there any other configuration that can improve the stability of the interface and eliminate the wrong packets？

thanks

  • 0
    TI__Mastermind 19235 points

    Hi,

    In my assessment, for your case reducing the optical module output de-emphasis from 3dB down to 0db is the cleanest and most effective way to eliminate the retimer Rx over-equalization problem that you are observing. Most likely the channel insertion loss in between the optical module and retimer Rx is too low.

    Forcing CTLE = 0x00 combined with limiting mode and reduced CTLE bias current (i.e. the retimer settings which you have already tried) are the typical recommendation that TI make for cases of over-equalization due to very low insertion loss channel. usuallly these settings are sufficient. My guess is that the retimer input channel loss is much less than 3dB for your system case, TI's recommended minimum loss. You could try manually applying DFE tap 1 attenuation (refer to retimer datasheet), but again disabling unnecessary optical module output de-emphasis is easier and more effective.

    Cordially,

    Rodrigo Natal

    HSSC Applications Engineer

    ,