METHOD FOR MONITORING AN AUTOMATION SYSTEM

A method and a system for monitoring and determining preceding states of at least one terminal of an automation system are provided. The automation system includes one or more terminals (1, 2), each of which can assume two or more states and each of which outputs a monitoring message that depends on the two or more states, and a control unit (3) that reads in the monitoring message from the one or more terminals (1, 2). Each of the one or more terminals (1, 2) outputs another monitoring message only after it has received an acknowledgment signal (Q) from the control unit (3). In order to be able, even subsequently, to reconstruct at least some of the preceding state changes, the monitoring message contains, in addition to each state value, at least one additional component (S1_Z, S2_Z; S1_OV, S2_OV) whose value is changed during a transition of the state value and which is reset to an initial value when a monitoring message is output.