Provided is a device capable of generating a new test pattern after the design stage with the area of a circuit that is not in use during normal operation reduced. The device includes a first circuit and a second circuit. The second circuit includes a plurality of third circuits, a plurality of fourth circuits, and a fifth circuit and has a function of generating a signal for testing operation of the first circuit and operating as part of the first circuit. The fourth circuits have a function of storing first data and second data. The fifth circuit has a function of writing the first data to the fourth circuits, writing the second data to the fourth circuits, and reading the second data from the fourth circuits. The first data is used to control the conduction between the third circuits. The second data is used for processing in the first circuit.