| 摘要 |
For suppressing increase of terminals in number, a semiconductor device is proposed which includes an input terminal to which an external clock is to be inputted. The semiconductor device further includes a crystal oscillating circuit, a storing circuit, and a selecting circuit. The crystal oscillating circuit generates an internal clock on the basis of the vibrating frequency of a crystal oscillator. The input terminal is inputted with a using information signal for indicating using information of the external clock and an input signal composed of the external clock. The storing circuit holds the using information signal being inputted into the input terminal when a reset signal is being inputted into a reset terminal and then outputs the signal. The selecting circuit is inputted with the internal clock and the external clock inputted at the input terminal and then outputs one of the clocks in response to the using information signal outputted from the storing circuit. This operation allows the input terminal to be used as the terminal to which the external clock and the using information signal are to be inputted, thereby being able to suppress the increase of the terminals in number.
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