Abstract: A time measuring circuit is provided with an oscillating circuit configured to generate a low-speed clock signal and a high-speed clock signal; and a measuring circuit configured to measure target time based on clock number of the low-speed clock signal and the high-speed clock signal outputted from the oscillating circuit, wherein the low-speed clock signal has a relatively low frequency and the high-speed clock signal has a relatively high frequency. The oscillating circuit is configured to switch from outputting the low-speed clock signal to outputting the high-speed clock signal when elapsed time from when a measurement of the target time started reaches a set value, and the set value is calculated by subtracting a predetermined value from a preliminary value which is provided by a preliminary measurement measuring the target time using only the low-speed clock signal.

Abstract: A time measuring circuit is provided with an oscillating circuit configured to generate a low-speed clock signal and a high-speed clock signal; and a measuring circuit configured to measure target time based on clock number of the low-speed clock signal and the high-speed clock signal outputted from the oscillating circuit, wherein the low-speed clock signal has a relatively low frequency and the high-speed clock signal has a relatively high frequency. The oscillating circuit is configured to switch from outputting the low-speed clock signal to outputting the high-speed clock signal when elapsed time from when a measurement of the target time started reaches a set value, and the set value is calculated by subtracting a predetermined value from a preliminary value which is provided by a preliminary measurement measuring the target time using only the low-speed clock signal.