A method is disclosed by which B.times.n bits, including dummy bits and address data bits in the stated order are transmitted to a storage unit in series, B bits of transmission data is then transmitted to the storage unit in series, and the transmission data are written in the storage unit. The B.times.n bits including the dummy bits, a number of which dummy bits is smaller by one, address data bits and one dummy bit in the stated order are transmitted in series. A signal is given by a storage unit in response to the data transmitted to the storage unit, and a group of B bits of the signal is processed as data read from the storage unit after a last bit of a group of B bits of the signal indicates address reception completion.