5.6.5. 64B/66B to 256B/257B Transcoder
If all four incoming blocks are data blocks:
- Remove the 2-bit headers of all four 66-bit data blocks.
- Append a header bit of 1 to the four 64-bit data payloads.
If there is at least one control block among the four-incoming blocks:
- Remove the 2-bit headers of all four incoming 66-bit blocks
- Append a header bit of 0 to the four payloads of the four blocks.
RS-FEC deletes the second 4-bit nibble in the block type field (BTF) of the first control block in a transcoded block. RS-FEC retains the first 4-bit nibble in the BTF of the first control block (indicating the type).
- Add the 4-bit header x1, x2, x3, or x4 following the overall header bit 0, where:
- x1 = Data block
- x2, x3, and x4 = Control block