Patent ID: 8886786

Claim:
A method for plant monitoring a plurality of field devices connected with a fieldbus of process automation technology, with a process control unit and a plant monitoring unit, the method comprising the steps of: connecting the process control unit and the plant monitoring unit to the fieldbus; generating regular data traffic using the process control unit by cyclically sending output data to the individual field devices and receiving output data from the individual field devices; issuing telegrams of the regular data traffic; tapping by the plant monitoring unit the regular data traffic generated by the process control unit, examining by the plant monitoring unit the issued telegrams of the regular data traffic for information indicating a diagnostic event at one of the field devices; and requesting, when a telegram issued by a field device and detected by the plant monitoring unit, which telegram indicates a diagnostic event, by the plant monitoring unit via acyclic traffic further diagnostic information from such field device, wherein: acyclic data traffic occurs during a certain time interval which is available between two succeeding cycles of regular data traffic.