MACsec Intel® FPGA System Design User Guide

ID 767516
Date 3/31/2024
Public
Document Table of Contents

2.2.1.3. Order of Ethernet Transmission

The TX MAC 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. Whereas the MACsec IP sends and expects frames to be in least significant bytes first and each byte in little-endian format. The AVST-AXI-ST bridge handles this ordering between the MACsec and E/F-tile IP.
Figure 9. Ethernet Frame Octets
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 7 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 following figure shows that in this example, 0xAC(DA5) is driven on [511:504] in case of AVST and on[7:0] in case of AXI-ST and 0x80(DA0)is driven on [471:464] in case of AVST and on [47:40] in case of AXI-ST.
Figure 10. E/F-tile AVST Interface for 100G
Figure 11. MACsec AXI-ST Interface for 100G