Synchronization of clock domains on a data network

Patent metadata

Field	Value
Publication number	US-12273186-B2
Application number	US-202217652002-A
Country	US
Kind code	B2
Filing date	Feb 22, 2022
Priority date	Feb 22, 2021
Publication date	Apr 8, 2025
Grant date	Apr 8, 2025

Abstract

A network includes a first plurality of nodes operating in a first clock domain based on a first clock source, a second plurality of nodes operating in a second clock domain based on a second clock source, and synchronization circuitry accessible to both of the clock domains without requiring network traffic between the clock domains. The synchronization circuitry is configured to periodically calculate a drift rate between the time of day in the respective clock domains. Each node in one of the clock domains is configured to, when sending a message to a node in the other of the clock domains, calculate a time of day in the other of the clock domains based on an actual time of day in the one of the clock domains and the drift rate, and to include, in the message to the node in the other clock domain, the calculated time of day.

First claim

What is claimed is:

1. A data network comprising:
a first plurality of nodes operating in a first clock domain based on a first clock source;
a second plurality of nodes operating in a second clock domain based on a second clock source; and
synchronization circuitry accessible to both the first clock domain and the second clock domain without requiring network traffic between the first clock domain and the second clock domain, the synchronization circuitry including time-of-day capture circuitry and drift calculation circuitry, and being configured to periodically calculate a rate of drift between time of day in the respective first and second clock domains; wherein:
each node in one of the first and second clock domains is configured to, when sending a message to a node in another of the first and second clock domains:
calculate a time of day in the another of the first and second clock domains based on an actual time of day in the one of the first and second clock domains and the rate of drift between time of day in the respective first and second clock domains, and
include, in the message to the node in the another of the first and second clock domains, the calculated time of day in the another of the first and second clock domains; and
the data network further comprises:
a plurality of storage locations configured to store previous indications of the time of day as indicated by the first clock source and the second clock source, and previous values of the rate of drift, to provide consistent values of the time of day and the rate of drift during writing of subsequent values of the time of day, and a subsequently calculated rate of drift.

2. The data network of claim 1 wherein:
the time-of-day capture circuitry is configured to determine, at each of two different moments, time-of-day as indicated by the first clock source and time-of-day as indicated by the second clock source; and
the drift calculation circuitry is configured to calculate, from the time-of-day as indicated by the first clock source at a first of the two different moments and the time-of-day as indicated by the second clock source at the first of the two different moments, and the time-of-day as indicated by the first clock source at a second of the two different moments and the time-of-day as indicated by the second clock source at the second of the two different moments, the rate of drift between time of day in the respective first and second clock domains.

3. The data network of claim 2 wherein the plurality of storage locations comprises:
a first set of storage locations for storage of the time-of-day as indicated by the first time source at the second of the two different moments, the time-of-day as indicated by the second time source at the second of the two different moments, and the rate of drift calculated by the drift calculation circuitry; and
a second set of storage locations for storage of copies of the time-of-day as indicated by the first time source at the second of the two different moments, the time-of-day as indicated by the second time source at the second of the two different moments, and the rate of drift calculated 1 by the drift calculation circuitry, such that during writing of subsequent values of the time of day as indicated by the first clock source, the time of day as indicated by the second clock source, and a subsequently calculated rate of drift, into the first set of storage locations, the node in the one of the first and second clock domains that is sending a message to the node in the another of the first and second clock domains has access, from the second set of storage locations, to consistent values of the time of day as indicated by the first clock source at the second of the two different moments, the time of day as indicated by the second time source at the second of the two different moments, and the rate of drift.

4. The data network of claim 3 wherein the second one of the at least two different moments is later than the first one of the at least two different moments by 10 ms.

5. The data network of claim 3 wherein the drift calculation circuitry is configured to update the rate of drift between the first time source and the second time source at drift calculation intervals that are longer than an interval between the first one of the at least two different moments and the second one of the at least two different moments.

6. The data network of claim 5 wherein the drift calculation circuitry is configured to update the rate of drift between time of day in the respective first and second clock domains at drift calculation intervals of at least 1 second.

7. The data network of claim 1 wherein:
the first clock domain is an Ethernet Precision Time Protocol domain; and
the second clock domain is a Peripheral Component Interconnect Express Precision Time Measurement domain.

8. Synchronization circuitry for synchronizing between two clock domains in a data network having a first clock domain based on a first clock source, and a second clock domain based on a second clock source, the synchronization circuitry comprising:
time-of-day capture circuitry configured to determine, at each of two different moments, time-of-day as indicated by the first clock source and time-of-day as indicated by the second clock source;
drift calculation circuitry configured to calculate, from the time-of-day as indicated by the first clock source at a first of the two different moments and the time-of-day as indicated by the second clock source at the first of the two different moments, and the time-of-day as indicated by the first clock source at a second of the two different moments and the time-of-day as indicated by the second clock source at the second of the two different moments, the rate of drift between time of day in the respective first and second clock domains; and
a plurality of storage locations configured to store previous indications of the time of day as indicated by the first clock source and the second clock source, and previous values of the rate of drift, to provide consistent values of the time of day and the rate of drift during writing of subsequent values of the time of day, and a subsequently calculated rate of drift.

9. The synchronization circuitry of claim 8 wherein the plurality of storage locations comprises:
a first set of storage locations for storage of the time-of-day as indicated by the first clock source at the second of the two different moments, the time-of-day as indicated by the second clock source at the second of the two different moments, and the rate of drift calculated by the drift calculation circuitry; and
a second set of storage locations for storage of copies of the time-of-day as indicated by the first clock source at the second of the two different moments, the time-of-day as indicated by the second clock source at the second of the two different moments, and the rate of drift calculated by the drift calculation circuitry, such that during writing of subsequent values of the time of day as indicated by the first clock source, the time of day as indicated by the second time source, and the subsequently calculated rate of drift, into the first set of storage locations, a node in one of the first and second clock domains that is sending a message to a node in another of the first and second clock domains has access, from the second set of storage locations, to consistent values of the time of day as indicated by the first clock source at the second of the two different moments, the time of day as indicated by the second clock source at the second of the two different moments, and the rate of drift for calculating, from the time of day in the one of the first and second clock domains, the

Assignees

• Marvell Asia Pte Ltd

Inventors

• Mater Olaf
• Reinbold Lukas
• Ning Xiongzhi
• Dolling Steffen

Classifications

• H04L7/0008

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

• G06F1/14

  Time supervision arrangements, e.g. real time clock · CPC title

• G06F1/12

  Synchronisation of different clock signals {provided by a plurality of clock generators} · CPC title

• H04J3/0658 Primary

  Clock or time synchronisation among packet nodes · CPC title

• H04J3/0635 Primary

  Clock or time synchronisation in a network (timer in protocols H04L69/28) · CPC title