Triple-Speed Ethernet Intel® FPGA IP User Guide

ID 683402
Date 11/25/2022

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Document Table of Contents

A.1. Basic Frame Format

Figure 88. MAC Frame Format

A basic Ethernet frame comprises the following fields:

  • Preamble—a maximum of 7-octet fixed value of 0x55.
  • Start frame delimiter (SFD)—a 1-octet fixed value of 0xD5 which marks the beginning of a frame.
  • Destination and source addresses—6 octets each. The least significant byte is transmitted first.
  • Length or type—a 2-octet value equal to or greater than 1536 (0x600) indicates a type field. Otherwise, this field contains the length of the payload data. The most significant byte of this field is transmitted first.
  • Payload Data and Pad—variable length data and padding.
  • Frame check sequence (FCS)—a 4-octet cyclic redundancy check (CRC) value for detecting frame errors during transmission.
  • An extension field—Required only for gigabit Ethernet operating in half-duplex mode. The MAC function does not support this implementation.