A coupler for an automation system for controlling a process, having a first interface for connection to a field bus for receiving a field bus message with process data of the process, a second interface for connection to a local bus for transmitting a local bus message, and a circuit implemented between the first interface and the second interface. The circuit has a non-clocked logic circuit comprising a number of hardware logic elements. The non-clocked logic circuit is equipped to change process data received through the first interface. The circuit is equipped to output the changed process data in the local bus message.