Maintaining a time of day in physical layer circuit of a network device while periodically compensating for drift away from a master time of a grandmaster clock

Abstract

A network device operative to maintain a first time of day (ToD) synchronized to a grandmaster clock is provided and includes a physical layer (PHY) circuit and a processor. The PHY circuit: maintains the first ToD in a first format and a second ToD in a second format; initially sets the second ToD based on a master ToD of the grandmaster clock; and updates the second ToD to maintain synchrony with a master time of the grandmaster clock by incrementing a counter based on a local clock, periodically updating the first ToD responsively to a counter value of the counter, and based on the updated first ToD and a compensation value, periodically adjusting the second ToD to more closely match the master time. The processor ascertains whether the second ToD has drifted from the master time and adjusts the compensation value based on whether the second ToD has drifted.