To provide a method for enabling a microprocessor to be restarted after rewriting a program without providing a dedicated circuit and an apparatus using the method, a timer for counting a predetermined clock is controlled in the following first and second modes, where in the first mode, the timer is reset (count-cleared) at predetermined intervals by a program so as to monitor an operating status of the program, and in the second mode, the microprocessor is restarted without resetting the timer at predetermined intervals by the program.