PURPOSE: To prevent power from being wastefully consumed when the output terminal of a decoder circuit not being connected to memory is brought into contact with another output terminal, a pad, or a power source, etc., in an IC card provided with plural memory and the decoder circuit to select the memory.

CONSTITUTION: Three-state output buffers 3 are provided among the output terminals Y0'-Y7' of the decoder circuit 1 and among the output terminals CS1-CS8 of a decode IC 2, respectively. A decoder output control circuit 8 controls the operations of the three-state output buffers 3 based on signals inputted from input terminals D, E, and sets the output terminals CS5-CS8 not being connected to memory ICs 11-14 on the output terminals CS1-CS8 at high impedance states.