Link Training

Introduction

Link training is the process of obtaining link synchronization between two ports attached via a 1x, 4x, or 12x link.

Link training is initiated when a port's receive logic receives a TS1 Ordered Set (referred to as the beacon sequence) from the port at the other end of the link. This happens when a port's Physical Layer receives a PowerOnReset, a LinkPhyReset (from the Link Layer), or when a hot plug event occurs.

The link training process includes:

  • Symbol synchronization.

  • Lane-to-lane de-skew.

  • Link width and speed negotiation.

  • The training sequence handshake.

  • Error recovery from transient link errors.

During the training process, the ports at each end of the link learn each other's capabilities and configure the following ...

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