Low Latency Ethernet 10G MAC Intel® FPGA IP User Guide

ID 683426
Date 3/01/2022
Public
Document Table of Contents

4.5.5.2. Payload Length

The MAC IP core checks the payload length for frames other than control frames when the VLAN and stacked VLAN detection is disabled. The MAC RX keeps track of the actual payload length upon receiving a frame and checks the actual payload length against the length/type or client length/type field. The payload length must be between 46 (0x2E) and 1500 (0x5DC). For VLAN and stacked VLAN frames, the minimum payload length is 42 (0x2A) or 38 (0x26) respectively and not exceeding the maximum value of 1500 (0x5DC).

For an invalid payload length, the MAC RX sets the avalon_st_rx_error[4] bit to 1. This error occurs when the actual payload length is less than the value of the length/type field. If the actual payload length is more than the value of the length/type field, the MAC RX assumes that the frame contains excessive padding and does not set this error bit to 1. If the value of the length/type field is more than the actual payload length, the MAC RX sets the avalon_st_rx_error[4] bit to 1, and the packet content will not be accurate.

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