Hardware Clock Accuracy Check via Built-In Test Circuit
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Solution Overview
Problem
Existing network devices lack an efficient and scalable method for accurately testing the precision of hardware clocks, particularly in large-scale networks, as external test equipment is unsuitable for frequent or widespread accuracy checks.
Innovation Solution
A network device with built-in accuracy test circuitry that samples the network time from a hardware clock using an external reference signal, such as a Pulse-Per-Second (PPS) signal, to assess the clock's accuracy, allowing for continuous monitoring without external equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external test equipment is used to check hardware clock accuracy, then measurement precision can be achieved, but device complexity and cost increase significantly for large-scale networks
Solution Approach 1:
The patent combines the test circuit functionality directly into the hardware clock device itself. The test circuit is integrated within the same device that contains the hardware clock, eliminating the need for separate external test equipment. This merging allows the hardware clock to perform self-testing by comparing its output against an internal reference, thereby maintaining measurement precision while significantly reducing device complexity and cost for large-scale network deployments
Solution Approach 2:
The hardware clock device performs its own accuracy testing through an integrated test circuit that compares the clock output against a reference signal. This self-service capability eliminates dependency on external test equipment, allowing the device to autonomously monitor and verify its own timing accuracy. The self-testing mechanism maintains measurement precision while simplifying the overall system architecture and reducing costs across large networks
2Reliability
If external test equipment is deployed for widespread clock accuracy checks, then reliability of time synchronization can be improved, but loss of time and productivity decrease due to setup and maintenance overhead
Solution Approach 1:
The integrated test circuit enables the hardware clock to perform continuous self-testing without requiring external equipment setup or maintenance. The device autonomously compares its clock output against a reference signal and generates accuracy indicators, eliminating the time loss associated with deploying and maintaining external test equipment across large networks while ensuring reliable time synchronization
Solution Approach 2:
The self-testing mechanism enables continuous monitoring of hardware clock accuracy without interruption to network operations. The test circuit operates continuously, comparing clock output against reference signals and providing ongoing accuracy verification, thereby maintaining high reliability of time synchronization while eliminating the periodic setup and maintenance interruptions that would occur with external test equipment
3Ease of operation
If built-in test circuitry is added to hardware clocks, then ease of operation for accuracy checking is improved, but device complexity increases
Solution Approach 1:
The test circuit functionality is merged into the existing hardware clock device structure, sharing common components such as the reference signal input and output interfaces. This integration approach improves ease of operation by providing built-in self-testing capabilities without adding significant external complexity, as the test functions utilize existing device resources and infrastructure
Data Source
Figure 1~2
AI summary
A network device includes one or more ports for connecting to a communication network, packet processing circuitry and clock circuitry. The packet processing circuitry is configured to communicate packets over the communication network via the ports. The clock circuitry includes a hardware clock configured to indicate a network time used for synchronizing network devices in the communication network, and a built-in accuracy test circuit configured to check an accuracy of the hardware clock.