Appendix
A.2 Evaluation of the operator control elements
Mobile Panel 177 (WinCC flexible)
A-10 Operating Instructions (Compact), Edition 07/2005
A.2.3.2 Basic procedure
Introduction
You can use WinCC flexible system functions to evaluate the operator control elements of
the HMI device or to control the LEDs of the softkeys and of the illuminated pushbutton.
Direction pulses of the handwheel and the switch state of the softkeys, key-operated switch,
or illuminated pushbutton are then transferred via tags to the PLC.
Consistent data
If tags with process interface are assigned directly to the operator control elements, this may,
for example, result in inconsistent values of the operator control elements between operator
control element, HMI device and PLC.
1. The HMI device is connected directly to the terminal box.
2. The HMI device starts.
3. The values of the operator control elements are determined and entered in the tags in the
HMI device.
4. Communication between the HMI device and PLC is established.
5. After communication has been established, the old values of the tags are transferred from
the PLC into the tags of the HMI device.
6. Not until a change has been carried out to an operator control element, is the valid value
written into the tag of the HMI device and transferred to the PLC.
Procedure
In order to ensure consistent values for the operator control elements, proceed as follows
when configuring in WinCC flexible:
1. Specify the connection to the PLC in the "Connections" editor. Activate the "Coordination"
area pointer to ensure that the live bit is available to the PLC side.
2. Create three tags in the "Tag" editor.
– Internal tag: "Status_Control_Element"
– External tag: "Auxiliary_Tag"
– External tag: "Control_Element_PLC"
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