To provide a real time clock capable of always performing correction of time-of-day even when a high frequency oscillator used for the correction discontinues oscillation.
A real time clock 1 utilizes an external high frequency oscillator 1000 that may discontinue oscillation. The real time clock 1 is provided with a low frequency oscillator 11. In the real time clock 1, a clock section 12 divides an oscillation frequency of the low-frequency oscillator 11 and generates time-of-day information, and an error measurement section 13 measures an error amount DF of the oscillation frequency of the low-frequency oscillator 11 on the basis of an oscillation frequency of the high frequency oscillator 1000 when the high frequency oscillator 1000 oscillates. The error amount DF is stored in a correction data storage section 14. A correction section 15 reads out the error amount DF from the correction data storage section 14 and changes a frequency division ratio of the clock section 12 to a frequency division ratio DV according to the error amount DF.
KARASUDA YUTAKA
OKUTO TOMOKI
Fujiwara Yasutaka
Hajime Yamashita
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