It is an object of the present invention to solve a problem that
malfunction of communication is generated by varying a frequency of a
clock due to noise from outside in a case where there is no supplied
signal in a circuit which performs negative feedback control so that the
supplied signal and the feedback signal can maintain a fixed phase
relationship between the signals. The present invention provides a
configuration including a PLL circuit and an oscillator circuit, where a
switch for switching an output between a signal from the PLL circuit and
a signal from the oscillator circuit to the signal output portion is
provided to switch from a connection to the PLL circuit to a connection
to the oscillator circuit in a case where there is no received signal.