Triple-Speed Ethernet Intel® FPGA IP User Guide

ID 683402
Date 11/25/2022
Public

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4.2.3.3. Frame De-encapsulation

The frame de-encapsulation state machine detects the start of frame when the /I/ /S/ sequence is received and replaces the /S/ with a preamble byte (0x55). It continues decoding the frame bytes and transmits them to the MAC function. The /T/ /R/ /R/ or the /T/ /R/ sequence is decoded as an end of frame.

A /V/ character is decoded and sent to the MAC function as frame error. The state machine decodes sequences other than /I/ /I/ (Idle) or /I/ /S/ (Start of Frame) as wrong carrier.

During frame reception, the de-encapsulation state machine checks for invalid characters. When the state machine detects invalid characters, it indicates an error to the MAC function.