An address control unit (114) stores write address (150) and write data (151) from a master (101) into a write address storage unit (110) and a write data storage unit (111), respectively, according to a write request to an external device (102) from the maser (101). The address control unit outputs a reception signal (155) to the master, writes the write data into the external device (102) specified by the write address. When the master (101) has stored the read address in a read-out address storage unit (112), the address control unit reads out data from the external device (102) specified by the read out address and stores it in a read-out data storage unit (113).