LOW-POWER HIGH-PRECISION CLOCK CIRCUIT FOR INTEGRATED CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide the clock circuit which is of low power, but has high precision. SOLUTION: A high-precision oscillator 12 is used to clock a timer A circuit 16 and a low-power oscillator 24 is used to clock a timer B circuit 22. This timer B circuit is synchronized with a processor clock, and the processor makes use of the timer B circuit even if the processor clock is asynchronous with the timer B circuit. The high-precision oscillator is selected as a timing source for the processor and timer A circuit, and when the low-power oscillator clocks the timer B circuit, the processor is able to measure the frequency of the on-chip low-power oscillator under program control in terms of the frequency of the high-precision clock.