Patent ID: 7277037

Claim:
A microcomputer comprising: a central processing unit which carries out a predetermined operation process according to a program; an external terminal for receiving an analog signal; an A/D converter capable of converting the analog signal received from said external terminal into a digital signal; an internal bus; and a bus state controller for bus state control of the internal bus, the internal bus being coupled to the central processing unit, the bus state controller and the A/D converter, the A/D converter including: a ladder-type resistor, a first operational amplifier which receives a reference voltage of said ladder-type resistor selected by a decoder, and which has an output terminal that can be brought to a high impedance condition according to an input control signal, a first switch which is capable of selecting an output voltage of the first operational amplifier or an analog signal from an external terminal, and a comparator circuit for comparing the output voltage of the first operational amplifier with the analog signal.