F-Tile Ethernet Intel® FPGA Hard IP User Guide

ID 683023
Date 4/03/2023
Public

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4.2.2.6. RX Undersized Frames, Oversized Frames, and Frames with Length Errors

The RX MAC flags RX frames that arrive with fewer than 64 bytes as undersized, and are not checked for FCS. The RX MAC marks undersized frames by asserting o_rx_error[2] or sets o_rx_mac_error[2:0] = 2'b2 on the EOP segment when the frame ends.

The RX MAC marks RX frames that arrive with more bytes than the RX Maximum Frame Size value you specify in the parameter editor as oversized. The RX MAC marks oversized frames by asserting o_rx_error[2] or sets o_rx_mac_error[1:0] = 2'b2 when the frame ends.

If you turn on Enforce maximum frame size in the parameter editor, oversized frames are not allowed through the RX client interface. When the frame reaches the maximum size, it is ended, and the RX MAC asserts both o_rx_error[2] and o_rx_error[1] to indicate the frame was truncated.

RX Frames that arrive with a valid Length field (Length/Type ≤ 1500) are checked for length errors. If the length of the packet advertised in the Length/Type field is larger than the length of the frame that actually arrived, the RX MAC asserts o_rx_error[4] or sets o_rx_mac_error[1:0] = 2'b3 on the EOP segment to indicate that there was a length error.