Patent ID: 7093143

Claim:
A semiconductor integrated circuit comprising: a CPU; a clock generation circuit which supplies an operational clock signal to the CPU, a frequency of the operational clock signal being specified from the CPU; and a power supply circuit including: a voltage regulator which is coupled to receive an external power supply voltage and which provides an internal power supply voltage from the external power supply voltage, a voltage value of the internal power supply voltage being specified from the CPU, and a determination circuit which is coupled to receive the internal power supply voltage and which determines whether a voltage value of the internal power supply voltage provided from the voltage regulator has been changed to a voltage value specified from the CPU, wherein the determination circuit is coupled to receive a first signal output from the CPU for requesting a change of the voltage value of the internal power supply voltage, and provides to the CPU a second signal for indicating that the voltage value of the internal power supply voltage provided from the voltage regulator has been changed to the voltage value specified from the CPU.