GTS Ethernet Intel® FPGA Hard IP User Guide

ID 817676
Date 8/05/2024
Public
Document Table of Contents

4.4.1.1. Drive the Ethernet Packet to the TX MAC Avalon Streaming Client Interface with Disabled Preamble Passthrough

The following figure shows the composition of an Ethernet Frame. Be aware of this while you make connections to the TX MAC Avalon Streaming Client Interface.

Figure 30. Fields and Frame Boundaries in an Ethernet Packet

When Preamble Passthrough is turned off, do not drive the Preamble of the Ethernet frame on the i_tx_data bus. Drive the first clock cycle with the destination address, as shown in the table below.

Table 26.  Ethernet Frame Field Positions in i_tx_data with Preamble Passthrough Disabled Attention: 10GE/25GE requires multiple transfer cycles for header data.
i_tx_clk (Cycle) i_tx_data Ethernet Frame Field Description
1-> D0 [63:56]' Dest Addr[47:40] The first octet of the Destination Address, follows Start Frame Delimiter (SFD).
[55:48]' Dest Addr[39:32] -
[47:40]' Dest Addr[31:24] -
[39:32]' Dest Addr[23:16] -
[31:24]' Dest Addr[15:8] -
[23:16]' Dest Addr[7:0] -
[15:8]' Src Addr[47:40] When you turn on Source Address Insertion, content is replaced by the source address that is configured in the txmac_saddr register unless i_tx_skip_crc is high.
[7:0]' Src Addr[39:32]
2->D1 [63:56] Src Addr[31:24]
[55:48] Src Addr[23:16]
[47:40] Src Addr[15:8]
[39:32] Src Addr[7:0]
[31:24] Length/Type[15:8] -
[23:16] Length/Type[7:0] -
[15:0] -
Note: The byte order flows from left to right on the bus – the first byte of the MAC destination address is the leftmost byte; the MAC treats this as the first byte after the Start Frame Delimiter (SFD). The bit numbered 0 in the Ethernet Specification is the rightmost bit of each byte.