Microcomputer Sleep Mode Clock Correction via Reference Measurement
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Solution Overview
Problem
Conventional techniques for correcting the clock frequency in sleep mode of a microcomputer are inadequate as they rely on indirect data estimation, leading to uncertainty in achieving high accuracy.
Innovation Solution
A microcomputer configuration where count data from a high-frequency reference clock is measured and stored, allowing direct correction of the clock signal upon transitioning to sleep mode, ensuring accurate oscillating frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a CR oscillating circuit is used for the sleep mode clock to reduce power consumption and cost, then power consumption and cost are reduced, but frequency accuracy deteriorates with large oscillation errors up to 5%
Solution Approach 1:
The patent measures and stores the actual oscillation frequency of the CR circuit before the CPU enters sleep mode while the high-accuracy reference clock is still running. This preliminary measurement captures the real frequency characteristics under current temperature and voltage conditions, which is then used to correct the clock counter value during sleep mode, ensuring accurate timing despite the CR circuit's inherent frequency variations.
Solution Approach 2:
The patent implements a feedback mechanism where the high-accuracy reference clock continuously monitors and measures the actual oscillation frequency of the CR-based sleep mode clock. This measured frequency information is fed back to adjust the clock counter correction value, creating a closed-loop system that compensates for frequency drift and maintains timing accuracy throughout sleep mode operation.
2Ease of manufacture
If conventional correction techniques using pre-measured characteristics or profiles are used, then correction can be implemented, but accuracy is insufficient because indirect estimation cannot verify conformity with current state
Solution Approach 1:
The patent enables the sleep mode clock system to self-measure and self-correct its frequency errors. The CR circuit's actual frequency is measured by the reference clock, and the correction value is automatically calculated and applied to the clock counter based on this real measurement, eliminating the need for external calibration or pre-stored characteristic data.
Solution Approach 2:
The patent replaces indirect estimation methods (based on pre-measured temperature-voltage-frequency characteristics) with direct electronic measurement using the reference clock. This substitution of measurement methodology provides real, verifiable frequency data rather than relying on theoretical models or indirect calculations.
Data Source
AI summary
ProblemA sub clock for a sleep mode in a a microcomputer is retained to be operable with high accuracy.SolutionA sub clock 20 counts oscillating pulses of a CR oscillating circuit 21 by a loop counter 22, and outputs a clock signal each time the oscillating pulses reach a target count Pm. A CPU 11 counts oscillating pulses of the CR oscillating circuit 21 in a predetermined time measured by a time counter 25 in response to a clock signal of a main clock 13 by a crystal oscillator, and corrects the target count Pm according to a pulse count P thereof. Since the real count state is obtained based upon the clock signal of the main clock having high frequency accuracy without the estimation of the sub clock 20, the high accuracy of the sub clock is retained even if environmental changes such as temperatures occur.