Maintaining a time of day in a physical layer circuit including compensating for drift away from a grandmaster time

Abstract

A physical layer circuit includes registers and a timing circuit. The registers are configured to store a future time of day, a local hardware time and a compensation value. The timing circuit is configured to: determine a relationship between the local hardware time and a grandmaster time; select the future time of day; determine a difference between a local clock and a grandmaster clock and set the compensation value equal to the difference; subsequent to determining the difference, enable maintenance of a current time of day; when the local hardware time matches the future time of day, begin updating the current time of day based on the compensation value to match the grandmaster time; and adjust the compensation value to compensate for drift between the current time of day and the grandmaster time.