Exception handling

The communication between the RTCU device and I/O devices is fully automated, but in some cases the communication can be interrupted. For example if the device is unplugged from the net, or if the device and RTCU device configurations do not match. I/O exception handling is introduced to monitor the devices and report the changes of their status.

Exception handling is done by two VPL commands; ioWaitException(), which monitors the net and reports exceptions when the status of one or more devices change, and ioGetStatus() which will get the status of each device. Four possible exceptions are covered by the I/O exception handling:

•Device is operational and working correctly        .

•Device is unplugged or not responding.

•I/O configuration of the RTCU and the device do not match.

•The device is responding but the response cannot be understood.

Please refer to ioWaitException (Function) and ioGetStatus (Function) for detailed information on the functions.

Even if an exception occurs, the RTCU does not fault but continue to try and update the net. This allows a service technician to exchange a defect device without interrupting the net and the application running on the device. Since the application does not halt, it is possible to react when an exception occurs and for example send an SMS that includes a fault report.