In a semiconductor integrated circuit comprising an internal circuit, a device for receiving a chip select signal from the outside, a device for receiving an input signal from the outside, and a voltage detecting circuit for detecting whether or not the potential of the input signal is higher than a reference potential; the voltage detecting circuit comprises a first device for differentially comparing the potential of the input signal with the reference potential and generating an output potential in accordance with the results of the comparison, a second device for detecting a predetermined edge of the chip select signal so as to trigger the first device, and a third device for latching the output potential of the first device to the third device when the first device is triggered by the second device, the internal circuit being switched from a first mode to a second mode, or vice versa, in accordance with the output potential of the third device.