Cause

In the case of a PLC box that disposes of inputs and / or outputs the required value is missing at the Start address 1 of PLC card property and / or the Start address 2 of PLC card property.

Solution

1. Locate the PLC box in the schematic using the Go to (graphic) functionality that is provided by the popup menu of the Message management dialog.
2. Open the property dialog of the PLC box.
3. Bring the first tab to the front.
4. In the properties table fill in the value fields of the Start address 1 of PLC card and Start address 2 of PLC card properties in accordance with the following conditions:
   If the PLC box only has inputs, the value of the start address at the Start address 1 of PLC card property has to be entered.
   If the PLC box only has outputs, the value of the start address at the Start address 1 of PLC card or Start address 2 of PLC card property has to be entered.
   If the PLC box has inputs and outputs, a value for the respective start address has to be entered at both properties.
5. Click [OK].
6. Then start a new check run.