Low Latency 40-Gbps Ethernet Intel® Stratix® 10 IP Core User Guide

ID 683600
Date 6/20/2023
Public
Document Table of Contents

4.1.2.3. Length/Type Field Processing

This two-byte header represents either the length of the payload or the type of MAC frame.
  • Length/type < 0x600—The field represents the payload length of a basic Ethernet frame. The MAC RX continues to check the frame and payload lengths.
  • Length/type >= 0x600—The field represents the frame type. The following frame types are possible:
    • Length/type = 0x8100—VLAN or stacked VLAN tagged frames. The MAC RX continues to check the frame and payload lengths.
    • Length/type = 0x8808—Control frames. The next two bytes are the Opcode field that indicates the type of control frame. For pause frames (Opcode = 0x0001) and PFC frames (Opcode = 0x0101), the MAC RX proceeds with pause frame processing.
      Note: Pause frame processing is not available in the Quartus Prime Pro 17.1 Stratix 10 ES Editions software. In this release, the IP core passes these frames to the RX client interface and updates the appropriate l2_rxstatus_data bits. However, the IP core does not implement flow control.
    • For other field values, the MAC RX forwards the receive frame to the client.