Corrected from:
Controller c300 V3.18
Controller 3200C V3.18
Panel Controller p300 V3.18
Panel Controller p500 V3.18
Response of the new version:
The digital outputs are set to the value '0' if the PLC is stopped due to an exception error and it is defined in the PLC settings of the PLC project that the digital outputs are to be set to their default value when the PLC is stopped.
What happens?
In the PLC settings of the PLC project it is defined that the digital outputs are to be set to their default value (to the value '0') at PLC-Stop. Nevertheless, the digital outputs retain their value if the PLC is stopped due to an exception error.
When does this behaviour occur?
The behavior can occur if PLC processing is stopped by an exception error and the bus cycle task and the task in which the process image is calculated are different.
Which products are affected?
Controller c300 as of V3.8
Controller 3200C as of V3.0
Panel Controller p300 V3.8 and higher
Panel controller p500 V3.3 and higher
Short-term measures:
Make sure that the bus cycle task and the task that calculates the process image match. The process image is always calculated in the bus cycle task if the 'Update variables' field in the 'I/O image' tab of the device or in the 'PLC settings' tab of the controller (device) is set to 'Enabled 2 (always in bus cycle task)'.
Check in the 'Task setup' tab of the controller (device) in the PLC project in which task the process image of the digital outputs is calculated.
Evaluation/recommendations:
In PLC Designer, the behaviour of the digital outputs when the PLC is stopped is set so that they are set to their default value (value '0'). If an exception error occurs, such as a task overflow, it is possible that digital outputs are not reset to the default value. An applicative solution is described under Short-term measures.
Automatic Translation
