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Clock selection for synchronous Ethernet

  • US 9,215,092 B2
  • Filed: 06/10/2011
  • Issued: 12/15/2015
  • Est. Priority Date: 06/10/2010
  • Status: Active Grant
First Claim
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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.

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