PROBLEM TO BE SOLVED: To provide a duplicate address detecting method by which a slave or master can recognize the occurrence of duplicate address of a node, even in a field bus system employing a multi-drop wiring configuration.;SOLUTION: Each slave 20 is allowed to have random numbers, and the slave 20 returns a response with the random numbers in response to a status reading request ((1)) from a master unit 12 ((2)). Upon receiving the response, the master issues a status writing request added with the received random numbers ((3)). The slave compares the random numbers added to the status writing request with its own random numbers, and if the random numbers match with each other, the slave becomes a subscriber slave, and if the random numbers do not match, the slave recognizes that a duplicate address occurs and is brought into a standby state. The master recognizes the occurrence of a duplicate address by detecting a node in a standby state.;COPYRIGHT: (C)2004,JPO&NCIPI
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