| 摘要 |
<p>PURPOSE:To make it possible to change system clock frequency according to power source voltage by providing a power source voltage detecting section, an oscillator, and terminals that connect plural resistors and external capacitors that determine the time constants. CONSTITUTION:A power source voltage detecting section 7 and a switching circuit 4 are set to select a resistor R1 when power source voltage is above V1, to select a resistor R2 when V1-V2, and to select a resistor R3 when the voltage is above V2. Further, the resistance value is set to make oscillation frequency f1 when the resistor R1 is selected, to make the frequency f2 when the resistor R2 is selected and to make the frequency f3 when the frequency R3 is selected when the value of an external capacity is made C0. When the device is operated in this state, oscillation frequency of an oscillator 5, that is, system clock frequency is switched according to power source voltage. Thus, system clock frequency can be switched according to power source voltage.</p> |
