Clock selection for synchronous Ethernet

摘要

An Ethernet PHY may receive an indication from a local timing source that a local clock is suitable for propagation to a link partner. In response, a timer in the Ethernet PHY may be started. In instances that the Ethernet PHY receives, during a time period subsequent to starting the timer and before the timer reaches a predetermined value, an indication that the link partner is propagating a clock that is suitable for the Ethernet PHY to synchronize to, the Ethernet PHY may be configured as timing slave. In instances that the Ethernet PHY does not receive, during the time period subsequent to starting the timer and before the timer reaches a predetermined value, an indication that the link partner is propagating a clock that is suitable for the Ethernet PHY to synchronize to, Ethernet PHY may be configured as timing master upon the timer reaching the predetermined value.

主权项

1. A method, comprising:
receiving, by an Ethernet PHY, a first indication from a local timing source that a local clock is suitable for propagation to a link partner of said Ethernet PHY; starting a timer in said Ethernet PHY in response to the receiving of said indication; autonegotiating, by the Ethernet PHY with the link partner, to establish an active physical Ethernet layer connection between the Ethernet PHY and the link partner; configuring, after the establishment of the active physical Ethernet layer connection between the Ethernet PHY and the link partner, said Ethernet PHY as a timing slave when said Ethernet PHY receives a second indication during a time period after said starting said timer and before said timer reaches a predetermined value, said second indication including encoded symbols indicating that a clock signal suitable for synchronization is propagated by said link partner; configuring, after the establishment of the active physical Ethernet layer connection between the Ethernet PHY and the link partner, said Ethernet PHY as a timing master when said Ethernet PHY does not receive said second indication during said time period after said starting said timer and before said timer reaches said predetermined value; propagating, by said Ethernet PHY, said local clock signal to said link partner when said timer reaches said predetermined value and said Ethernet PHY is configured as said timing master; maintaining, when said Ethernet PHY is configured as said timing slave, the active physical Ethernet layer connection in response to a detected change in the clock signal propagated by said link partner; and maintaining, when said Ethernet PHY is configured as said timing master, the active physical Ethernet layer connection in response to the detected change in the local clock; transmitting, by the Ethernet PHY and when said Ethernet PHY is configured as said timing master, upon receiving a third indication from said local timing source that said local clock is no longer suitable for propagation to said link partner, a fourth indication to said link partner that said Ethernet PHY is no longer propagating said clock signal.