Abstract: A camera system including a camera body and a camera accessory attachable to the camera body, such as an interchangeable back lid, an interchangeable lens, a flash device and so on, is disclosed. In the system, a plurality of circuits provided in plurality of camera accessories are controlled by a microcomputer provided in the camera body. Data is transmitted between the microcomputer and the circuits using a serial data bus and synchronizing clock line connected therebetween. The circuit to receive the data sent from the microcomputer, or the circuit which should send the data to the microcomputer are selected by the microcomputer through chip select lines provided between the microcomputer and each circuit.