Time-of-day correction for network clock protocol

Patent metadata

Field	Value
Publication number	US-12395261-B2
Application number	US-202217659869-A
Country	US
Kind code	B2
Filing date	Apr 20, 2022
Priority date	Apr 20, 2021
Publication date	Aug 19, 2025
Grant date	Aug 19, 2025

Abstract

In a network having at least one slave node including a slave clock, a method of adjusting the slave clock relative to a master clock of a master node includes, at the slave node, correcting a time of day of the slave clock using (a) a slave pulse signal having a known slave pulse rate, (b) a time-of-day counter of the slave node, and (c) a master pulse signal, based on values of the slave clock at nearest corresponding edges of the slave pulse signal and the master pulse signal, and correcting a frequency of the slave clock using the slave pulse signal, a clock signal of the slave node, and the master pulse signal, based on values of the slave clock at nearest corresponding edges of the master pulse signal. No other clock signal from outside the slave node is used for the corrections.

First claim

What is claimed is:

1. In a network having at least one master node, the master node having a master clock and outputting a master “pulse-per-second” signal having a known master pulse rate, the network further having at least one slave node including a slave clock, a method of adjusting the slave clock relative to the master clock, the method comprising, at the slave node:
correcting a time of day of the slave clock using (a) a slave “pulse-per-second” signal of the slave node, the slave “pulse-per-second” signal having a known slave pulse rate, (b) a time-of-day counter of the slave node, and (c) the master “pulse-per-second” signal, without receiving any other clock signal from outside the slave node, based on values of the slave clock at nearest corresponding edges of the slave “pulse-per-second” signal and the master “pulse-per-second” signal; and
correcting a frequency of the slave clock using the slave “pulse-per-second” signal of the slave node, a clock signal of the slave node, and the master “pulse-per-second” signal, without receiving any other clock signal from outside the slave node, based on values of the slave clock at nearest corresponding edges of the master “pulse-per-second” signal.

2. The method of adjusting the slave clock according to claim 1 , wherein:
using the slave “pulse-per-second” signal comprises using a slave “pulse-per-second” signal that is a “pulse-per-second” signal having a slave pulse rate of 1 pulse per second; and
using the master “pulse-per-second” signal comprises using a master “pulse-per-second” signal that is a “pulse-per-second” signal having a master pulse rate of 1 pulse per second.

3. The method of adjusting the slave clock according to claim 1 , wherein:
using the slave “pulse-per-second” signal comprises using a slave “pulse-per-second” signal that is a “pulse-per-second” signal having a slave pulse rate of 1,000 pulses per second; and
using the master “pulse-per-second” signal comprises using a master “pulse-per-second” signal that is a “pulse-per-second” signal having a master pulse rate of 1,000 pulses per second.

4. The method of adjusting the slave clock according to claim 1 , wherein:
using the slave “pulse-per-second” signal comprises using a slave “pulse-per-second” signal that is a “pulse-per-second” signal having a slave pulse rate of 62,500 pulses per second; and
using the master “pulse-per-second” signal comprises using a master “pulse-per-second” signal that is a “pulse-per-second” signal having a master pulse rate of 62,500 pulses per second.

5. The method of adjusting the slave clock according to claim 1 wherein correcting the time of day of the slave clock comprises:
retrieving a first counter value from a slave time-of-day counter on occurrence of an edge of the slave “pulse-per-second” signal;
retrieving a second counter value from the slave time-of-day counter on occurrence of an edge of the master “pulse-per-second” signal that is the nearest corresponding edge to edge of the slave “pulse-per-second” signal;
subtracting the first counter value from the second counter value to yield a time-of-day correction; and
adding the time-of-day correction to a current counter value.

6. The method of adjusting the slave clock according to claim 5 , further comprising, before adding the time-of-day correction to the current counter value:
determining whether the time-of-day correction exceeds one-half an interval of the slave “pulse-per-second” signal; and
when the time-of-day correction exceeds one-half an interval of the slave “pulse-per-second” signal:
inverting algebraic sign of the time-of-day correction, and
performing again the retrieving the first counter value, the retrieving the second counter value, and the subtracting.

7. The method of adjusting the slave clock according to claim 5 wherein adding the time-of-day correction to the current counter value comprises adding all of the time-of-day correction to the current counter value in a single operation.

8. The method of adjusting the slave clock according to claim 5 wherein adding the time-of-day correction to the current counter value comprises adding each of a plurality of portions of the time-of-day correction in a corresponding plurality of operations spread over time.

9. The method of adjusting the slave clock according to claim 1 wherein correcting the frequency of the slave clock comprises:
retrieving a first counter value from a slave time-of-day counter on occurrence of a first edge of the master “pulse-per-second” signal;
retrieving a second counter value from the slave time-of-day counter on occurrence of a second edge of the master “pulse-per-second” signal that is the nearest corresponding edge to the first edge of the master “pulse-per-second” signal;
subtracting the first counter value from the second counter value to yield a first intermediate correction value;
subtracting the first intermediate correction value from duration of an interval of the master “pulse-per-second” signal to yield a second intermediate correction value; and
dividing the second intermediate correction value by the first intermediate correction value to yield an interval correction for the slave “pulse-per-second” signal.

10. The method of adjusting the slave clock according to claim 9 wherein correcting the frequency of the slave clock further comprises adding the interval correction to the slave “pulse-per-second” signal.

11. A slave node in a network, the network including at least one master node having a master clock and outputting a master “pulse-per-second” signal having a known master pulse rate, the slave node comprising:
a clock signal generator configured to output a slave clock signal, the slave clock signal having a slave clock frequency;
a time of day counter configured to increment at each interval of the slave clock signal to indicate a time of day;
a slave “pulse-per-second” signal generator configured to output a slave “pulse-per-second” signal, the slave “pulse-per-second” signal having a known slave pulse rate lower than the slave clock frequency; and
clock correction circuitry configured to:
correct the time of day using the slave “pulse-per-second” signal and the master “pulse-per-second” signal, without receiving any other clock signal from outside the slave node, based on values of the slave clock at nearest corresponding edges of the slave “pulse-per-second” signal and the master “pulse-per-second” signal; and
correct the slave clock frequency using the slave “pulse-per-second” signal, the slave clock signal, and the master “pulse-per-second” signal, without receiving any other clock signal from outside the slave node, based on values of the slave clock at nearest corresponding edges of the master “pulse-per-second” signal.

12. The slave node of claim 11 wherein:
the slave “pulse-per-second” signal generator is configured to output a slave “pulse-per-second” signal that is a “pulse-per-second” signal having a slave pulse rate of 1 pulse per second; and
the clock correction circuitry is configured to use a master “pulse-per-second” signal that is a “pulse-per-second” signal having a master pulse rate of 1 pulse per second.

13. The slave node of claim 11 wherein:
the slave “pulse-per-second” signal generator is configured to output a slave “pulse-per-second” signal that is a “pulse-per-second” signal having a slave pulse rate of 1,000 pulses per second; and
the clock correction circuitry is configured to use a master “pulse-per-second” signal that is a “pulse-per-second” signal having a master pulse rate of 1,000 pulses per second.

14. The slave node of claim 11

Assignees

• Marvell Asia Pte Ltd

Inventors

• Fu Yao
• Patra Lenin Kumar
• Chen Jeng-Jong Douglas
• Ma Xiaoqing
• Hofman-Bang Joergen P R
• Zhang Yangyang

Classifications

• H04J3/0685

  Clock or time synchronisation in a node; Intranode synchronisation · CPC title

• H04J3/062

  Synchronisation of signals having the same nominal but fluctuating bit rates, e.g. using buffers (pulse-stuffing H04J3/07; asynchronous-synchronous conversion H04L5/24; speed conversion H04L25/05; speed conversion in computers G06F5/06) · CPC title

• H04L7/0008

  Synchronisation information channels, e.g. clock distribution lines · CPC title

• H04J3/0679 Primary

  by determining clock distribution path in a network · CPC title

• H04J3/0658 Primary

  Clock or time synchronisation among packet nodes · CPC title