126.96.36.199.1. 8B/10B Encoder Control Code Encoding
The tx_datak signal indicates whether the 8-bit data being sent at the tx_parallel_data port should be a control word or a data word. When tx_datak is high, the 8-bit data is encoded as a control word (Kx.y). When tx_datak is low, the 8-bit data is encoded as a data word (Dx.y). Depending upon the PCS-PMA interface width, the width of tx_datak is either 1 bit or 2 bits. When the PCS-PMA interface width is 10 bits, tx_datak is a 1-bit word. When the PCS-PMA interface width is 20 bits, tx_datak is a 2-bit word. The LSB of tx_datak corresponds to the LSByte of the input data sent to the 8B/10B encoder and the MSB corresponds to the MSByte of the input data sent to the 8B/10B encoder.