Patent ID: 7523239

Claim:
A bus communication system having a master unit and plural slave units connected to the master unit through a communication bus in a daisy chain connection, the system comprising: a switch device in each of the slave units for switching between connection and disconnection of communication that is established between one of the master unit and the slave unit on a preceding side of the daisy chain connection relative to the switch device and the slave unit on a subsequent side of the daisy chain connection relative to the switch device upon having an input of a switch signal outputted by the master unit; an ID acquisition device in each of the slave units for acquiring an ID upon having an ID acquisition signal outputted by the master unit on a condition that the switch device in the slave unit on the preceding side of the daisy chain connection is switched to connection of communication; and a trouble detection device in the master unit for detecting a trouble of the switch device, wherein the ID acquisition device outputs to the master unit an electric current response signal in response to the ID acquisition signal when the ID acquisition signal is inputted to the ID acquisition device, and the master unit detects the trouble of the switch device in the slave unit by using the trouble detection device based on the response signal outputted by the ID acquisition device.