Patent ID: 7277039

Claim:
A microcomputer comprising: a central processing unit which carries out a predetermined operation process according to a program; a random access memory which is used as a work area for the central processing unit; a nonvolatile memory to which the program is stored; an A/D converter capable of converting an analog signal into a digital signal; an internal bus; and a bus state controller for bus state control, the internal bus being coupled to the central processing unit, the bus state controller, the random access memory, the nonvolatile memory and the A/D converter, the A/D converter including: a ladder-type resistor providing a reference voltage selected by a decoder, a first operational amplifier which receives the selected reference voltage, a switch which is capable of short-circuiting an input terminal and an output terminal of the first operational amplifier, and a comparator circuit which compares an output voltage of the first operational amplifier with an analog signal.