40- and 100-Gbps Ethernet MAC and PHY MegaCore Function User Guide

ID 683114
Date 6/15/2022
Public
Document Table of Contents

3.2.14. MAC – PHY XLGMII or CGMII Interface

The PHY side of the MAC implements the XLGMII or CGMII protocol as defined by the IEEE 802.3ba standard. The standard XLGMII or CGMII implementation consists of 32 bit wide data bus. However, the Altera implementation uses a wider bus interface in connecting a MAC to the internal PHY. The width of this interface is 320 bits for the 100GbE IP core and 128 bits for the 40GbE IP core.

Table 27.  XL/CGMII Permissible Encodings Lists XL/CGMII permissible encodings. Memorizing a few of the XL/CGMII encodings greatly facilitates understanding of Ethernet waveforms. The XL/CGMII encodings are backwards compatible with older Ethernet and have convenient mnemonics. The DATAPATH_OPTION RTL parameter instantiates TX and RX backwards compatibility and is set by default.

Control

Data

Description

0

xx

Packet data, including preamble and FCS bytes.

1

07

Idle.

1

fb

Start of Frame (fb = frame begin).

1

fd

End of Frame (fd = frame done).

1

fe

XL/CGMII Error. Typically a bit error which switched a 66‑bit block between data and control, or corrupt control information (fe = frame error).