Industrial controllers are special purpose processing devices used for controlling (e.g., automated and semi-automated) industrial processes, machines, manufacturing equipment, plants, and the like. A typical controller executes a control program or routine in order to measure one or more process variables or inputs representative of the status of a controlled process and/or affect outputs associated with control of the process. A typical control routine can be created in a controller configuration environment that has various tools and interfaces whereby a developer can construct and implement a control strategy using industrial and conventional programming languages or graphical representations of control functionality.
Industrial controllers measure inputs and control outputs in a serial continuous manner. Inputs and outputs can be recorded in I/O memory. The input values can be asynchronously or synchronously read from the controlled process by one or more input modules and output values can be written directly to memory by a processor for subsequent communication to the process by specialized communications circuitry. An output module can interface directly with a controlled process by providing an output from memory to an actuator such as a motor, drive, valve, solenoid, and the like. During execution of the control routine, values of the inputs and outputs exchanged with the controlled process can pass through memory. Values of inputs in memory can be asynchronously or synchronously updated from the controlled process by dedicated and/or common scanning circuitry. The input values in a data table are updated and modified in real-time. Similarly, output control variables are calculated constantly.
Other areas of an enterprise system may wish to utilize the data measured by an industrial controller or keep a record of the output conditions. For instance, a database might be used to keep records of the values of certain inputs or outputs. This could be desired in situations where decisions affecting the overall manufacturing process are heavily influenced by a particular aspect of the industrial process. Enterprise Information Technology (IT) systems, such as database systems, are transactional in nature. As such, the data in the real-time controller environment is typically retrieved in scheduled batches at periodic intervals by complex custom systems.