PERIOD SIGNAL GENERATOR

PURPOSE: To generate the pulse width signals (period signals) of a cycle exceeding the circulation period of a counter while minimizing the processing loads of a CPU. CONSTITUTION: When a value set to a comparator 23 by the CPU 18 and the counted value of a free-running timer 24 match, the comparator 23 outputs matching signals to a pulse generation circuit 25 as trigger signals and outputs them to the CPU 18 as interruption signals. When the interruption signals are inputted, the CPU 18 sets the level of pulse signals to be outputted at the time of the input of the trigger signals at the next time to the pulse generation circuit 25 and sets the value corresponding to a time interval for outputting the matching signals next to the comparator 23. In the case of generating the pulse width signals of the cycle exceeding the circulation cycle of the free- running timer 24, the CPU 18 divides the cycle of the pulse width signals and sets the value to the comparator 23 so as to minimize the number of times of the matching signals outputted by the comparator 23.