25G Ethernet Intel® Stratix® 10 FPGA IP User Guide

ID 683154
Date 9/15/2021
Document Table of Contents

4.1.1. 25G Ethernet Intel FPGA IP Core TX MAC Datapath

The TX MAC module receives the client payload data with the destination and source addresses. It then adds, appends, or updates various header fields in accordance with the configuration specified. The MAC does not modify the destination address, the source address, or the payload received from the client. However, the TX MAC module adds a preamble, if the IP core is not configured to receive the preamble from user logic. It pads the payload of frames greater than eight bytes to satisfy the minimum Ethernet frame payload of 46 bytes. By default, the MAC inserts the CRC bytes. The TX MAC module inserts IDLE bytes to maintain an average IPG of 12.

Figure 13. Typical Client Frame at the Transmit InterfaceIllustrates the changes that the TX MAC makes to the client frame. This figure uses the following notational conventions:
  • <p> = payload size, which is arbitrarily large
  • <s> = number of padding bytes (0–46)
  • <g> = number of IPG bytes
Figure 14. TX MAC Functions

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