Engineering and diagnostics. Integrated in distributed I/O Within the framework of Totally Integrated Automation, the SIMATIC ET 200 I/O systems offer powerful, multi-stage diagnostic systems for errors occurring in the control system (system diagnostics). System errors are automatically recognized and result in programmable exception measures. Such system errors are also reported to the HMI system, where they are appropriately displayed. During commissioning and operation, the topology of the automation system with the ET 200 stations is offered as overview diagnostics. The module diagnostics provide additional information about the individual modules and comprises e.g. the short-circuit test for sensor supply and outputs. The diagnostics-capable modules can even monitor short-circuits and wire breaks differently, making it possible to react immediately to every irregularity and to every process event. Parameters can be easily assigned in STEP 7 to indicate whether the controller should respond to this and what the response should be. The system diagnostics functionalities of the SIMATIC ET200 I/O systems are rendered easy-to-use and user-friendly by the SIMATIC Maintenance Station. The modular ET 200 stations can be displayed in detail with their diagnostic status information, whereby the station, module and channel diagnostics are visualized.