Low Latency 40G for ASIC Proto Ethernet Intel® FPGA IP User Guide

ID 683221
Date 11/10/2022
Public
Document Table of Contents

6.4. RX PCS Interface to User Logic

The Low Latency 40G for ASIC Proto Ethernet IP core RX client interface in PCS Only variations employs the Media Independent Interface (MII) protocol.

The RX PCS acts as a source and the client acts as a sink in the receive direction.

Table 16.  Signals of the MII RX Client Interface

Signal Name

Description

clk_rxmac The RX MAC clock. This clock is recovered from the incoming data. The frequency of this clock is 312.5 MHz. All RX MAC interface signals are synchronous to clk_rxmac.
rx_mii_d[127:0]

RX MII data. Data is in MII encoding. o_rx_mii_d[7:0] holds the first byte the IP core received on the Ethernet link. o_rx_mii_d[0] holds the first bit the IP core received on the Ethernet link.

When o_rx_mii_valid has the value of 0 or o_rx_mac_am has the value of 1, the value on o_rx_mii_d is invalid.

rx_mii_c[15:0] RX MII control bits. Each bit corresponds to a byte of rx_mii_d. rx_mii_c[0] corresponds to rx_mii_d[7:0], rx_mii_c[1] corresponds to rx_mii_d[15:8], and so on.

If the value of a bit is 1, the corresponding data byte is a control byte. If the value of a bit is 0, the corresponding data byte is data.

The Start of Packet byte (0xFB), End of Packet byte (0xFD), Idle bytes (0x07), and error byte (0xFE) are control bytes, but the preamble bytes, Start of Frame (SFD) byte (0xD5), CRC bytes, and payload bytes are data bytes.

When rx_mii_valid has the value of 0 or rx_mac_am has the value of 1, the value on rx_mii_c is invalid.

rx_mii_valid Indicates that rx_mii_d, rx_mii_c, and rx_mac_am are valid.
rx_mac_am Indicates the IP core received a valid alignment marker on the Ethernet link.

When rx_mii_valid has the value of 0, the value on rx_mac_am is invalid. The value of rx_mii_valid may fall while the IP core is asserting rx_mac_am.

Figure 19. RX MII Client Interface for Low Latency 40G for ASIC Proto Ethernet IP Core