PURPOSE: To reduce interruption handling by an outside trigger so as to reduce an interruption load, and also facilitate the structure of hard ware.

CONSTITUTION: A reference position (G) latch signal detecting flag XGL is set to '1' on the basis of a G signal from an air cylinder discriminating sensor, and returned to '0' by timer interruption handling per a constant period corresponding to a program in practice. A G latch signal memory flag XGLM is set to '1' when the G latch signal detecting flag XGL is set to '1', and returned to '0' on the basis of execution of interruption handling based on an NE signal from a rotational angle sensor corresponding to the program in practice. Therefore, an NE signal abnormality flag XFNE ms set to '1' when the G latch signal detecting flag XGL is set to '1' during the executing period of the timer interruption handling and the G latch signal memory flag XGLM is set to '1' so that the rotational angle sensor is judged as abnormal. At this time, an interruption request port is facilitated as one of ports for inputting the NE signal.