US Patent 7583556 Switching circuit for CMOS circuit

A controlling circuit for controlling on-off switching of a power supply for a CMOS circuit includes a CMOS circuit (20) and a switch (30). The CMOS circuit includes a first circuit (50) for storing the system time of the computer and a second circuit (70) for storing other system settings of the computer. One terminal of the switch is connected to the first circuit and a power supply (10) in parallel via a resistor (R2). The one terminal of the switch is connected to the second circuit, and another terminal of the switch is connected to ground. When the one terminal of the switch is connected to the another terminal, the data stored in the second circuit is cleared while the system time stored in the first circuit remains.