Real-time clock generation device and real-time clock generation method

Abstract

A first ring oscillator outputs a reference clock signal. A table acquirer acquires a control-value table representing a correspondence between time zones in which the first ring oscillator operates and division ratios of the reference clock signal. In accordance with the control-value table, a divider generates an RTC signal by changing a division ratio of the reference clock signal for each time zone in which the first ring oscillator operates. During execution of calibration of the control-value table, a second ring oscillator outputs a measurement clock signal that oscillates more accurately than the reference clock signal. A frequency measurer measures a frequency of the RTC signal based on the measurement clock signal. In a case in which a frequency of the RTC signal exceeds an allowable error, an update determiner updates at least part of division ratios in the control-value table.