Low Latency 40G Ethernet Intel® FPGA IP User Guide: Agilex™ 5 FPGAs and SoCs

ID 813652
Date 7/22/2024
Public
Document Table of Contents

6.2. RX MAC Interface to User Logic

The RX MAC provides an Avalon® streaming interface to the FPGA fabric. The datapath comprises 2, 64-bit words. A valid FCS for a packet results in l2_rx_error bit 1 being low when l2_rx_endofpacket is high. An FCS violation is indicated when l2_rx_error bit 1 is high when l2_rx_endofpacket is high.
Table 17.   Avalon® Streaming RX MAC Interface Signals All interface signals are clocked by the clk_rxmac clock.

Signal

Direction

Width

Description

clk_rxmac Output 1 Clock for the RX MAC. Generated from the incoming data and is an output from the core (312.5 MHz).
l2_rx_data Output 128

Data output from the MAC. Bit 127 is the MSB and bit 0 is the LSB. Bytes are read in the usual left to right order. The IP reverses the byte order to meet the requirements of the Ethernet standard.

l2_rx_preamble Output 64

Received preamble data. Available when you select PREAMBLE PASS-THROUGH mode.

Valid when l2_rx_startofpacket is asserted.
l2_rx_valid Output 1 When asserted, indicates that l2_rx_data[127:0] is driving data. When this signal is low, the IP ignores l2_rx_data, l2_rx_startofpacket, l2_rx_endofpacket, l2_rx_empty, and l2_rx_error.
l2_rx_startofpacket Output 1

When asserted, indicates the first byte of a frame.

l2_rx_endofpacket Output 1 When asserted, indicates the last data byte of a frame, before the frame check sequence (FCS). In CRC pass-through mode, it is the last byte of the FCS. The packet can end at any byte position.
l2_rx_empty Output 4 Specifies the number of empty bytes when l2_rx_endofpacket is asserted.

The packet can end at any byte position. The empty bytes are the low-order bytes.

l2_rx_error Output 6

When asserted in the same cycle as l2_rx_endofpacket, indicates the current packet should be treated as an error packet. It is valid when l2_rx_endofpacket is high.

l2_rxstatus_valid Output 1 When asserted, indicates that l2_rxstatus_data is driving valid data.
l2_rxstatus_data[39:0] Output 40

Specifies information about the received frame.