Page History

...

Like 8B/10B, the code table is split into two parts. The 7 least significant bits are encoded using a 7B/8B encoding table, and the 5 most significant bits are encoding using a 5B/6B table.

Also like 8B/10B, a running disparity is output with each code, and fed back to the input for use in selecting the next code.

The 7/8 encoding is considered first, along with a running disparity count. The code is looked up in the 7B/8B table. Then it is optionally inverted if doing so would bring would bring the running disparity closer to 0. Some codes naturally have 0 disparity (4 ones and 4 zeros), and these are never inverted.

...