220.127.116.11. 8B/10B TX Disparity Control
The Disparity Control feature controls the running disparity of the output from the 8B/10B Decoder.
- tx_forcedisp—a control signal that indicates whether a disparity value has to be forced or not
- tx_dispval—a signal that indicates the value of the running disparity that is being forced
The following figure shows the current running disparity being altered in Basic single-width mode by forcing a positive disparity /K28.5/ when it was supposed to be a negative disparity /K28.5/. In this example, a series of /K28.5/ code groups are continuously being sent. The stream alternates between a positive running disparity (RD+) /K28.5/ and a negative running disparity (RD-) /K28.5/ to maintain a neutral overall disparity. The current running disparity at time n + 3 indicates that the /K28.5/ in time n + 4 should be encoded with a negative disparity. Because tx_forcedisp is high at time n + 4, and tx_dispval is low, the /K28.5/ at time n + 4 is encoded as a positive disparity code group.