Timekeeping Circuit Using Hardware Counter and External Sync
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Solution Overview
Problem
Software clocks in electronics devices have lower timekeeping accuracy compared to hardware clocks due to processing load and noise reduction circuits, and equipping devices with hardware clocks increases circuit size and manufacturing costs.
Innovation Solution
An electronics device determines the present time using time information acquired from an external device and a hardware counter circuit, updating reference time and measuring elapsed time to calculate the current time, eliminating the need for a hardware clock circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a software clock is used for timekeeping, then the circuit scale is reduced and manufacturing cost is lowered, but the timekeeping accuracy deteriorates due to CPU processing load
Solution Approach 1:
The timekeeping function is segmented into two independent parts: a hardware counter circuit that accurately counts clock cycles, and a software component that calculates elapsed time and determines present time. This segmentation allows the hardware counter to operate independently without being affected by CPU processing load, thereby maintaining high timekeeping accuracy while keeping the overall circuit scale reduced.
Solution Approach 2:
A hardware counter circuit is introduced as an intermediary component between the clock signal source and the software timekeeping logic. This counter circuit acts as a mediator that accurately measures elapsed time by counting clock cycles, isolating the time measurement function from CPU processing variations and ensuring high precision without requiring a full RTC circuit.
2Measurement precision
If an RTC circuit is equipped for accurate timekeeping, then the timekeeping accuracy is improved, but the circuit scale is enlarged and manufacturing cost increases
Solution Approach 1:
The essential timekeeping function is extracted from the complex RTC circuit, retaining only the necessary hardware counter component. This extracted counter circuit is sufficient for accurate elapsed time measurement, while the present time calculation is performed by software, thereby achieving high timekeeping accuracy without the need for the complete RTC circuit structure.
Solution Approach 2:
Instead of using an expensive and complex RTC circuit, the invention employs a simple and inexpensive hardware counter circuit that performs the critical time measurement function. The counter circuit is resource-efficient and can be easily integrated, providing accurate timekeeping at a fraction of the cost and complexity of a full RTC circuit.
3Device complexity
If a software clock is used, then the device configuration is simplified, but the timekeeping accuracy deteriorates due to noise reduction circuits affecting the clock signal
Solution Approach 1:
The invention replaces the software-based time measurement mechanism with a hardware counter circuit that directly counts clock cycles. This hardware-based approach is insensitive to noise reduction circuits and signal processing variations, providing stable and accurate time measurement while maintaining simplified device configuration.
Data Source
AI summary
An electronics device comprising a time information acquisition unit which acquires time information representing present time from an external device, an update unit which updates reference time stored in a reference time storage unit to time represented by the latest time information acquired by the time information acquisition unit each time the time information is acquired, a counter circuit which is formed by hardware and updates its count value at fixed cycles, an elapsed time measurement unit which measures an elapsed time since the update of the reference time by use of the counter circuit, a present time calculation unit which calculates present time by adding the elapsed time to the reference time stored in the reference time storage unit, and a response unit which makes the present time calculation unit calculate the present time and outputs the calculated present time if a present time output request is issued.