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Observer
Observer
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Registered: ‎04-17-2020

### GTY : encoding necessary for robust transmission ? ###

Hello,

 

in a larger experiment I'm using GTY Wizard example design single lane @ 25Gbps on VCU129.

I'm using it in RAW 160b, i.e. w/o 8b10b or 64b66b etc. encoding.

I'm having my own comma detection and alignment scheme.

Now I've read that those encoding schemes are for comma alignment and for "DC balancing"

to make life easier for RX clock data recovery.

Question: do I have to expect increased BER or other GTY issues when running RAW w/o encoding

or will the bits be transmitted just fine, only shifted by some amount in the serial stream ?

ThanX a lot Oliver

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Xilinx Employee
Xilinx Employee
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Registered: ‎03-30-2016

Hello @Oliver_Hauck 

Usually for 25Gbps line-rate, channel insertion-loss will be high, so DFE will perform better than LPM on most cases.
But, as mentioned in UG578 Chapter4 DFE needs a random data for its auto adaptation module to work properly.
Without a random data sequence, BER may increased.
DFE_use_mode.png

Scrambling the RAW data before sending into GTY TX may help a lot. ( You don't need to scramble comma/alignment codes )

Thanks & regards
Leo