EXCHANGE NUMBER OVERLAPPED STATION DETECTING METHOD, EXCHANGE NUMBER OVERLAPPED STATION LINE REPEATING METHOD, EXCHANGE NUMBER OVERLAPPED STATION NUMBER MEASURING METHOD AND EXCHANGE NUMBER OVERLAPPED STATION LINE CANCELING METHOD FOR PROGRAMMABLE CONTROLLER

摘要

PURPOSE: To prevent malfunction caused by the exchange number overlap of the system and to improve the safety of a network system by transmitting a test message from each station so as to show whether the station equipped with the same exchange number as a present station exists or not. ;CONSTITUTION: At first, the gate of a line driver 1 at a master station is set active and a carrier is transmitted. Next, after the test message of the transmitting data of the master station is transmitted to two stations of slave stations, the master station sets the gate of the line driver 1 inactive and stops transmitting the carrier. The slave station judges whether the received data are the test message addressed to the present station or not and when those data are the test message addressed to the present station, response data are prepared. Afterwards, the gate of the line driver 1 is set active and the carrier is transmitted as transmission preparation processing. In the normal case when no competition carrier is detected by a carrier detecting circuit 3, the response data are transmitted to the master station.;COPYRIGHT: (C)1996,JPO