PROGRAMMABLE CONTROL DEVICE

PROBLEM TO BE SOLVED: To obtain a programmable control device capable of specifying a disconnection place when the disconnection occurs in a cable by which a master station and a plurality of slave stations are connected by multidrop wirings and immediately performing normal communication without notifying the slave stations that the disconnection has been restored. SOLUTION: A central control part 30a of a slave station shifts to a disconnection diagnosis mode when a normal system receiving part 18 for receiving a frame at a baud rate in a normal mode can not receive a frame to its own station within a disconnection diagnosis mode switching time, performs communication with the master station at a baud rate in the disconnection diagnosis mode lower than the baud rate in the normal mode by using a diagnosis system transmitting part 24 and a diagnosis system receiving part 28, and continuously performs receiving processing by the normal system receiving part 18. When the normal system receiving part 18 receives a frame, the central control part 30a shifts from the disconnection diagnosis mode to the normal mode and communicates with the master station by using the normal system receiving part 18 and a normal system transmitting part 14. COPYRIGHT: (C)2007,JPO&INPIT