Arria® 10 Transceiver PHY User Guide

ID 683617
Date 4/01/2024
Public
Document Table of Contents

2.6.1.4. Rate Match FIFO for GbE

The rate match FIFO compensates frequency Part-Per-Million (ppm) differences between the upstream transmitter and the local receiver reference clock up to 125 MHz ± 100 ppm difference.
Note: 200 ppm total is only true if calculated as (125 MHz + 100 ppm) - (125 MHz - 100 ppm) = 200 ppm. By contrast, (125 MHz + 0 ppm) - (125 MHz - 200 ppm) is out of specification.

The GbE protocol requires the transmitter to send idle ordered sets /I1/ (/K28.5/D5.6/) and /I2/ (/K28.5/D16.2/) during inter-packet gaps (IPG) adhering to the rules listed in the IEEE 802.3-2008 specification.

The rate match operation begins after the synchronization state machine in the word aligner indicates synchronization is acquired by driving the rx_syncstatus signal high. The rate matcher deletes or inserts both symbols /K28.5/ and /D16.2/ of the /I2/ ordered sets as a pair in the operation t