Abstract: A method for signal transmission and reception by a bidirectional bus system in which plural devices performing the communication of a command and a request are interconnected over a bidirectional bus includes the steps of providing a frame of a transmission signal on the bidirectional bus the frame including an address field for designating addresses of communicating devices and a data field for designating the command or request to be transmitted, and inserting the discrimination information for discriminating between the command and the request at a pre-set position in the data field. The transmission signal including the discrimination information is transmitted over the bidirectional bus to other devices. A communication system employing such a bidirectional bus system is also provided.

Abstract: A communication protocol can communicate data among apparatus by a simple procedure efficiently. In an AV center (1) (D2B control unit (1a), for example, a communication mode thereof is set in the master transmission mode, and a packet of one frame is transmitted to a TV (2). In the TV 2 (D2B control unit (2a)), its communication mode is set in the slave reception mode. When a packet of one frame from the AV center (1) is received by the TV (2), a communication between the AV center (1) and the TV (2) is ended.