AUTOMATIC TIME CONTROL METHOD FOR INTERNAL TIMER OF CPU

摘要

PURPOSE:To automatically control the time of an internal timer of a CPU which can automatically control the variance among the lots of the CPU. CONSTITUTION:A watchdog timer 2 applies the reset signals outputted in a fixed cycle as the external clocks to an input port PIN of a CPU 1. The CPU 1 counts these external clocks as the external clocks by an internal counter and at the same time actuates an internal timer to count the internal clocks. When the count value of the external clocks reaches a set level, the CPU 1 sets the reference time value based on the count value. At the same time, the CPU 1 stops the time limit operation of the internal timer and checks the time limit period of this timer. Then the CPU 1 calculates a constant to decide the time of the internal timer based on the difference if detected between the time limit period and the reference time. The calculated constant is set and the automatic control operation is complete for the timer time.