| 摘要 |
PURPOSE:To detect a slave station in which abnormality occurs by sending a general polling signal having bits of all slave stations periodically from a master station, and confirming a signal returned from the slave station. CONSTITUTION:The master station 1 sends out the general polling signal 3 to monitor plural slave stations 21-2n comprehensively. The last terminating station 2n sends out a polling bit corresponding to the one of its own station out of the signals 3 to the slave station 2n-1 nearer next to the master station 1 without inverting when no state change occurs in its own station. Similarly, the slave station 21 inverts the polling bit corresponding to the slave station 23 when the state change occurs in its own station, and sends it to the master station without inverting when no state change occurs. The master station 1 checks the polling bits of the slave stations 21-2n from received signals 3, and judges that no state change occurs when none of bits are inverted. |
