PURPOSE: To improve the cost efficiency of the on-site system diagnosis of a built-in self test circuit by reducing the testing cost at the time of manufacturing the circuit by checking the monotonousness of the circuit and supplying a lamp voltage to an A/D input, and then, monitoring the output of the circuit by means of a state machine. CONSTITUTION: An integrated circuit 100 is provided with an A/D converter 101 incorporating a built-in self test(BIST) circuit. The BIST circuit checks a monotonous finite state automaton 14 and supplies a ramp voltage 102 to an A/D input. On the other hand, the BIST circuit monitors the output by means of state machines 104 and 105 so as to check whether all possible codes exist or not. The machines 104 and 105 check whether or not only the LSB of the output increases against individual output changes. At the end of tests, a counter confirms whether or not all possible codes are obtained. After a chip is packaged, boundary scanning tests are executed by actuating the BIST circuit and observing the results. COPYRIGHT: (C)1993,JPO