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

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

4.2.1. Order of Transmission

The IP core transmits bytes on the Ethernet link starting with the preamble and ending with the FCS in accordance with the IEEE 802.3 standard. On the transmit client interface, the IP core expects the client to send the most significant bytes of the frame first, and to send each byte in big-endian format. Similarly, on the receive client interface, the IP core sends the client the most significant bytes of the frame first, and orders each byte in big-endian format.

Figure 28. Byte Order on the Client Interface LanesDescribes the byte order on the Avalon® streaming interface. Destination Address[40] is the broadcast/multicast bit (a type bit), and Destination Address[41] is a locally administered address bit.


For example, the destination MAC address includes the following six octets AC-DE-48-00-00-80. The first octet transmitted (octet 0 of the MAC address described in the 802.3 standard) is AC and the last octet transmitted (octet 5 of the MAC address) is 80. The first bit transmitted is the low-order bit of AC, a zero. The last bit transmitted is the high order bit of 80, a one.

The preceding table and the following figure show that in this example, 0xAC is driven on DA5 (DA[47:40]) and 0x80 is driven on DA0 (DA[7:0]).

Figure 29. Octet Transmission on the 25GbE Avalon® Streaming SignalsIn the following diagram Preamble pass through and CRC pass through mode are disabled.

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