Intel Corporation
Method and apparatus for synchronous signaling between link partners in a high-speed interconnect

Abstract:

Loop timing is performed in a Reconciliation Sublayer (RS) so that the transmit clock frequency can be adjusted to be equal to the receive clock frequency for the entire PHY (including the physical coding sublayer (PCS)). One of two partners is selected to be the timing Slave to the other. If only one partner is capable of loop timing, that partner becomes the Slave. If both partners are capable of loop timing, symmetry breaking can be used to determine which partner should become Slave.