GTS Ethernet Intel® FPGA Hard IP User Guide

ID 817676
Date 4/01/2024
Public

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4.3.1.1. TX MAC Avalon Streaming Client Interface with Disabled Preamble Passthrough

Figure 28. Fields and Frame Boundaries in an Ethernet PacketWhen you turn off Preamble Passthrough in the parameter editor, i_tx_data must be written as shown in the figure for the first cycle of data presented to the MAC.
Table 21.  TX MAC Field Positions in i_tx_data with Preamble Passthrough Disabled Attention: 10GE/25GE requires multiple transfer cycle for header data.
i_tx_clk (Cycle) i_tx_data MAC Field Description
1 [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, contents are replaced by txmac_saddr unless i_tx_skip_crc is high.
[7:0]' Src Addr[39:32]
2 [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: It is important to note the bit and byte order.

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 order is such that the bit numbered 0 in the Ethernet Specification is the rightmost bit of each byte.