PURPOSE: To form a ring network, by providing a plurality of element chips on a semiconductor substrate, a going-out logic circuit and a coming-in logic circuit, an external control unit for controlling the element chips to form a chip row.

CONSTITUTION: Going-out logic circuits 31a to 37a and coming-in logic circuits 31b to 37b are amounted on element chips 210 to 216. While each element chip is put to a test, going-out logic circuits included in adjoining element chips are connected to each other, and coming-in logic circuits included in adjoining element chips are also connected to each other so that each one-dimensional chip row is formed. Moreover, in the last element chip the going-out logic circuit and the coming-in logic circuit are connected to form a ring network.