V-Series Transceiver PHY IP Core User Guide

ID 683171
Date 7/26/2022
Document Table of Contents

9.13. PHY for PCIe (PIPE) Link Equalization for Gen3 Data Rate

Gen3 requires both TX and RX link equalization because of the data rate, the channel characteristics, receiver design, and process variations. The link equalization process allows the Endpoint and Root Port to adjust the TX and RX setup of each lane to improve signal quality. This process results in Gen3 links with a receiver Bit Error Rate (BER) that is less than 10-12.

Section 4.2.3 Link Equalization Procedure for 8.0 GT/s Data Rate” in the PCI Express Base Specification, Rev. 3.0 provides detailed information about the four-stage link equalization procedure. A new LTSSM state, Recovery.Equalization with Phases 0–3, reflects progress through Gen3 equalization. Phases 2 and 3 of link equalization are optional; however, the link must progress through all four phases, even if no adjustments occur. Skipping Phases 2 and 3 speeds up link training at the expense of link BER optimization.