Low Latency 40G for ASIC Proto Ethernet Intel® FPGA IP Design Example User Guide

ID 683599
Date 10/05/2020
Public

2.3. Functional Description

This section describes the 40G Ethernet MAC/PCS and 40G Ethernet PCS IP core using the Intel device. You can choose to configure MAC within the IP or implement a separate MAC outside of this IP.

Configuring the 40G Ethernet IP with MAC and PCS

In the transmit direction, the MAC accepts client frames and inserts inter-packet gap (IPG), preamble, the start of frame delimiter (SFD), padding, and CRC bits before passing them to the PHY. The PHY encodes the MAC frame as required for reliable transmission over the media to the remote end.

In the receive direction, the PHY passes frames to the MAC. The MAC accepts frames from the PHY, performs checks, strips out the CRC, preamble, and SFD, and passes the rest of the frame to the client.
  • In RX preamble pass-through mode, the MAC passes on the preamble and SFD to the client instead of removing them out of frames.
  • In RX CRC pass-through mode, the MAC passes on the CRC bytes to the client and asserts the EOP signal in the same clock cycle with the final CRC byte.

Configuring the 40G Ethernet IP with PCS Only

The PHY encodes the user MAC frame to ensure reliable transmission over the media to the remote end via the Media-Independent Interface (MII).