Abstract: If there is neither a key input from a keyboard nor a command input from a CPU within a predetermined period of time, a keyboard controller generates an NMI request for sleep control. The CPU executes the NMI request in accordance with an NMI routine stored in a ROM. If the CPU is in an idle state, a sleep mode is set.

Abstract: A small electronic device includes first and second locking devices which releasably lock the batteries on a first and second mounting portions, first and second detectors which respectively detect that the locked conditions of first and second locking devices have been released, first and second switches for connecting the first and second batteries to a power supply node. The electronic device also includes a control unit which turns on the first switch to connect the first battery to the power supply node, and switches from an off state to an on state the second switch in response to a detection signal from the first detector.