Low Latency 40-Gbps Ethernet IP Core User Guide

ID 683745
Date 3/08/2021
Document Table of Contents

3.2. LL 40GbE IP Core Functional Description

The LL 40GbE IP core implements the 40 GbE Ethernet MAC in accordance with the IEEE 802.3ba 2010 High Speed Ethernet Standard. This IP core handles the frame encapsulation and flow of data between a client logic and Ethernet network via a 40 GbE Ethernet PCS and PMA (PHY).

In the transmit direction, the MAC accepts client frames, and inserts inter-packet gap (IPG), preamble, start of frame delimiter (SFD), padding, and CRC bits before passing them to the PHY. The PHY encodes the MAC frame as required for reliable transmission over the media to the remote end.

In the receive direction, the PHY passes frames to the MAC. The MAC accepts frames from the PHY, performs checks, updates statistics counters, strips out the CRC, preamble, and SFD, and passes the rest of the frame to the client. In RX preamble pass-through mode, the MAC passes on the preamble and SFD to the client instead of stripping them out. In RX CRC pass-through mode (bit 1 of the CRC_CONFIG register has the value of 1), the MAC passes on the CRC bytes to the client and asserts the EOP signal in the same clock cycle with the final CRC byte.

The LL 40GbE IP core includes the following interfaces:

  • Datapath client-interface–The following options are available:
    • With adapters—Avalon-ST, 256 bits
    • Custom streaming, 128 bits
  • Management interface—Avalon-MM host slave interface for MAC management. This interface has a data width of 32 bits and an address width of 16 bits.
  • Datapath Ethernet interface—XLAUI interface: Four 10.3125 Gbps serial links
  • In Arria 10 variations, an Arria 10 dynamic reconfiguration interface—an Avalon-MM interface to read and write the Arria 10 Native PHY IP core registers. This interface supports dynamic reconfiguration of the transceiver. LL 40GbE IP cores that target an Arria 10 device use the Arria 10 Native PHY IP core to configure the Ethernet link serial transceivers on the device. This interface has a data width of 32 bits. This interface has an address width of 12 bits.

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