PURPOSE: To quickly make the frequency at the time of starting stable by setting the initial condition of a ROM (initial setting storage circuit) so that a temperature compensation code at rising of a power supply reaches a prescribed value.

CONSTITUTION: When a power supply rises, a readout signal is outputted from a terminal CE of a power-on clear sequencer 45 to a terminal CE of a ROM 43. Thus, a compensation code at +25°C is outputted to each input terminal B of multiplexers MUX1-MUX8 from output terminals DA1-DA8 of the ROM 43. Succeedingly, the power-on clear sequencer 45 brings an output terminal SEL to a high level. Thus, each output terminal X of the multiplexers MUX 1-MUX8 selects the input terminal B. Thus, a compensation code at +25°C is outputted to the input terminal D of the D flip-flops DFF1-DFF8 from each output terminal X. Then an error between the oscillated frequency of the VCXO and the rated frequency is decreased.