8B/10B decoding after serial transmission problem?

Hello,

I run into a problem/bug where I currently don't see a solution, probably somebody can give me some hints.

I encoded data frames with 8B/10B, filled the gaps between the data with K28.5 characters and then transmitted the data stream via a serial line. On the receiver side I did the same backwards and run their into a problem: The serial data stream of the following bytes (0x6E, 0x74, 0x77, 0x65 or D14.3, D20.3, D23.3, D5.3) contains a bit sequence that is identical to the K28.5 character and therefore my receiver recognises also this K char instead of the intended data byte.

No valid D character sequence should produce the K28.5 sequence! Check your generation logic and make sure you are following the rules for running disparity.

Gabor

(posting via Xilinx website - Google groups seems broken today)

Your running disparity is the most likely culprit. I believe you are encoding the D20.3 symbol with either positive or negative disparity and then using the opposite to encode the D23.3 symbol.

Colin Hankins