| 摘要 |
PURPOSE:To reduce the size of a frequency control signal applied from outside and also to attain a setting action of a frequency with high resolution, by using the 1st and 2nd latch circuits, a selector, an adder/subtractor, the 1st and 2nd D/A converters, an addition amplifier and an oscillator which performs the control of oscillation frequency. CONSTITUTION:The frequency control signal of N bits containing a control direction discriminating flag in a fine control mode and an initialization/fine control discriminating flag which are given to the 1st latch circuit 1 from outside is selected to an initialization mode. Then the frequency control signal is given to the following circuit from the circuit 1 for initialization of the oscillation frequency of an oscillator 7. For the fine control of the oscillation frequency, the initialization/fine control discriminating flag is set to a fine control mode to apply the frequency control signal to the circuit 1. Thus an adder/ subtractor 2 performs the addition or subtraction for the frequency control signal and another frequency control signal which is applied previously and held by the 2nd latch circuit 4. The result of this addition or subtraction is given to the following circuit for control of the oscillation frequency of the oscillator 7. |
