Cyclone V Device Handbook: Volume 2: Transceivers

ID 683586
Date 10/24/2018
Public
Document Table of Contents

1.3.1.3.1. 8B/10B Encoder in Single-Width Mode

In single-width mode, the 8B/10B encoder generates 10-bit code groups from 8-bit data and 1-bit control identifier with proper disparity according to the PCS reference diagram in the Clause 36 of the IEEE 802.3 specification. The 10-bit code groups are generated as valid data code-groups (/Dx.y/) or special control code-groups (/Kx.y/), depending on the 1-bit control identifier.

Figure 23. 8B/10B Encoder in Single-Width Mode

The IEEE 802.3 specification identifies only 12 sets of 8-bit characters as /Kx.y/. If other sets of 8-bit characters are set to encode as special control code-groups, the 8B/10B encoder may encode the output 10-bit code as an invalid code (it does not map to a valid /Dx.y/ or /Kx.y/ code), or unintended valid /Dx.y/ code, depending on the value entered.

In single-width mode, the 8B/10B encoder translates the 8-bit data to a 10-bit code group (control word or data word) with proper disparity. If the tx_datak input is high, the 8B/10B encoder translates the input data[7:0] to a 10-bit control word. If the tx_datak input is low, the 8B/10B encoder translates the input data[7:0] to a 10-bit data word.

Figure 24. 8B/10B Conversion FormatThe LSB is transmitted first.