H-tile Ethernet Hard IP User Guide: For Intel® Stratix® 10 Devices

ID 683430
Date 2/16/2022
Public
Document Table of Contents

4.2.8. 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.

Figure 12. Byte Order on the Client Interface Lanes Without Preamble Pass-ThroughThe figure describes the byte order on the Avalon-ST interface when the preamble pass-through feature is turned off. 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 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 preceding table and the following figures show that in this example, 0xAC is driven on DA5 (DA[47:40]) and 0x80 is driven on DA0 (DA[7:0]).

Figure 13. 100-Gbps Octet Transmission on the Avalon-ST Signals Without Preamble Pass-ThroughThe figure illustrates how the octets of the client frame are transferred over the TX datapath when preamble pass-through is turned off.
Figure 14. Byte Order on the Avalon-ST Interface Lanes With Preamble Pass-ThroughThe figure describes the byte order on the Avalon-ST interface when the preamble pass-through feature is turned on.

Destination Address[40] is the broadcast/multicast bit (a type bit), and Destination Address[41] is a locally administered address bit.



Figure 15. 100-Gbps Octet Transmission on the Avalon-ST Signals With Preamble Pass-ThroughThe figure illustrates how the octets of the client frame are transferred over the TX datapath when preamble pass-through is turned on. The eight preamble bytes precede the destination address bytes. The preamble bytes are reversed: the application must drive the SFD byte on i_tx_data[455:448] and the START byte on i_tx_data[511:504].

The destination address and source address bytes follow the preamble pass-through in the same order as in the case without preamble pass-through.

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