Meanwhile, CPU-based safety-related control circuits are utilized in the industry. These CPU-based safety-related control applications, however, require some subsidiary safety measures, e.g. diagnostic function and redundant hardware structure, and their circuits are not simple. Moreover, CMOSs [39], which are widely used and [easily] available, are not normally applicable to safety-related control because of self-oscillation in the case of CMOS input open-failures.