Patent ID: 6021356
Filing Date: 2000-02-01
Classification: G05B

Abstract:
A control system including a master programmable logic controller (PLC), a plurality of remote slave units (RSUs), and a communication cable for carrying out a data communication between the master PLC and the RSUs, wherein the master PLC comprises:an emergency data setting unit which enables a user to set a control data for use when the RSUs do not receive the control data from the master PLC, and wherein each of the plurality of RSUs comprises:an emergency output data storage unit for storing therein the emergency data determined by the emergency data setting unit;a normal output data storage unit for storing therein the control data normally received from the master PLC;an output data selection switch for enabling selection from among the emergency output data and the normal output data received from the master PLC, when the RSU does not receive the control data from the master PLC;a timer for generating a time out signal when the control data is not received from the master PLC for a predetermined amount of time; andan input/output controller for selectively outputting data selected from among the emergency output data stored in the emergency output data storage unit and the normal output data stored in the normal output data storage unit based on whether the time out signal is received from the timer.