PURPOSE: To improve the non-defective rate of the titled device by providing flags which hold changeover information of an input data and an output data of a function unit for unit number's share required for the device playing the substantial function and allowing the flag to conduct changeover.

CONSTITUTION: When it is known that the k-th function unit 18 is defective, the 1st∼(k-1)th flags FLG(1)∼FLG(k-1) are brought into the 1st state to select an input at the right side of the corresponding input changeover circuit 18 thereby applying the input to function units F(1)∼F(k-1). Then the input at the left side of the corresponding output changeover circuit 19 is selected. The k-th∼n-th flags FLG(k)∼FLG(n) are brought into the 2nd state, the left side input of the corresponding input changeover circuit 18 is selected to apply the input to function units F(k+1)∼F(n+1), and the right side input of the corresponding output changeover circuit 19 is selected. The amount of the hardware is less and the range of defect relieve is wide.