Triple-Speed Ethernet Intel® FPGA IP User Guide

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ID 683402
Date 5/30/2022
Public
Document Table of Contents

4.1.4.4. Frame Type Validation

The MAC function checks the length/type field to determine the frame type:
  • Length/type < 0x600—the field represents the payload length of a basic Ethernet frame. The MAC function continues to check the frame and payload lengths.
  • Length/type >= 0x600—the field represents the frame type.
    • Length/type = 0x8100—VLAN or stacked VLAN tagged frames. The MAC function continues to check the frame and payload lengths, and asserts the following signals:
      • for VLAN frames, rx_err_stat[16] in MAC variations with internal FIFO buffers or pkt_class_data[1] in MAC variations without internal FIFO buffers
      • for stacked VLAN frames, rx_err_stat[17] in MAC variations with internal FIFO buffers or pkt_class_data[0] in MAC variations without internal FIFO buffers.
    • Length/type = 0x8088—control frames. The next two bytes, the Opcode field, indicate the type of control frame.
      • For pause frames (Opcode = 0x0001), the MAC function continues to check the frame and payload lengths. For valid pause frames, the MAC function proceeds with pause frame processing. The MAC function forwards pause frames to the user application only when the PAUSE_FWD bit in the command_config register is set to 1.
      • For other types of control frames, the MAC function accepts the frames and forwards them to the user application only when the CNTL_FRM_ENA bit in the command_config register is set to 1.
  • For other field values, the MAC function forwards the receive frame to the user application.

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