Resolving MP277 WinCC Demo Greyed-Out Buttons with WinAC MP

Problem: MP277 WinCC Demo Buttons Are Greyed Out

A SIMATIC MP277 8" Touch panel running WinCC Flexible Runtime with WinAC (Windows Automation Center) on board shows the bundled WinAC demo project with every control disabled. The screen background renders, but the start/stop and status buttons are not clickable. Hovering the mouse pointer over a button event (for example, the MRES button Click event) opens a WinCC Flexible editor tooltip that reads:

Warning: this device does not support this function

The same WinCC Flexible project compiles without warnings and downloads to the MP277 without errors. After upload, however, the runtime shows the warning tooltip on every event tied to a system function supplied by the WinAC demo. User-developed screens that call standard PLC tags and use basic system functions continue to work; only the WinAC-supplied controls fail.

This article documents the root cause, the corrective action, and the full verification procedure so that an integrator can repair the same fault on a MP277 or any other Multi Panel that ships with a WinAC demo image.

Environment and Component Identification

Before applying the fix, capture the exact hardware and software revision so that the same fix can be repeated and so that the related Siemens Support Entry 26729818 is the right one for the installed versions.

Root Cause Analysis: Why the Buttons Are Greyed Out

The "Warning: this device does not support this function" tooltip is emitted by the WinCC Flexible runtime when an event references a system function whose implementation is missing on the target device. In the WinAC demo project, the buttons call WinAC-specific system functions such as SetKeySwitch, StartWinAC, StopWinAC, GetWinACState, and MRES handler routines. These system functions are not part of the base WinCC Flexible runtime; they are added to the function catalog when the optional WinAC MP runtime is installed on the panel.

If WinAC MP V4.0 (or the WinAC MP option packaged with WinCC Flexible RT on the panel) is not installed, the function IDs are still serialized into the compiled project because the project was originally built on an engineering PC that did have WinAC MP installed. At runtime the panel cannot resolve those function IDs, so every button that references them is disabled and the editor-side tooltip is regenerated as the runtime stub.

The most common causes observed in the field are:

1. The MP277 was restored from a backup image that did not include the WinAC MP option set.
2. WinAC MP V4.0 was installed on the engineering PC but never transferred / re-installed on the panel after a ProSave restore or after a firmware / image update.
3. A newer service pack of WinCC Flexible RT (for example 2008 SP3) was flashed onto the panel and overwrote the previously-installed WinAC MP option.
4. ProSave's "Reset to factory settings" option was executed, which strips all optional runtimes.

Siemens Support Entry 26729818 documents the project components and option selection in chapters 3.1 and 3.2; the entry is the canonical reference for "what must be installed on the panel" before the demo functions resolve.

SetKeySwitch System Function Reference

The key corrective action on the engineering side is to replace the missing MRES event handler with the SetKeySwitch system function and to provide the MRES parameter. SetKeySwitch is a WinCC Flexible system function that simulates the position of the CPU's mode selector on a connected SIMATIC S7 station. When triggered on a button Click event, the panel writes the requested key-switch position to the S7 controller; the controller then behaves as if the physical selector had been turned to that position.

Solution Overview: Two-Step Fix

The fault is repaired by combining a panel-side install with an engineering-side reconfiguration. Both steps are required because the install restores the runtime function table on the panel, while the engineering change guarantees that any recompile does not reintroduce unsupported references.

1. Install WinAC MP V4.0 on the MP277 using ProSave so that the runtime function catalog is populated.
2. Re-author the demo button events using SetKeySwitch with explicit parameter values (for example MRES) and recompile the WinCC Flexible project.

Step-by-Step: Install WinAC MP V4.0 on the MP277

Prerequisites

• Administrator on the engineering PC running WinCC Flexible ES.
• WinCC Flexible 2008 (SP2 minimum recommended) installed on the engineering PC.
• WinAC MP V4.0 installation media (or the WinAC MP option installer available through the Siemens Automation License Manager / downloads portal).
• Ethernet cross-over cable or a managed switch connecting the engineering PC to the MP277 (PROFINET port X1).
• ProSave (bundled with WinCC Flexible) accessible from the engineering PC.
• The MP277 set to Transfer mode if transferring over MPI/PROFIBUS, or assigned an IP address if transferring over Ethernet.

Procedure

1. On the MP277, open Control Panel > OP > Transfer and confirm the target IP. Default address space is 192.168.0.x/24; many MP277 panels default to 192.168.0.2.
2. On the engineering PC, launch ProSave (Start > Siemens Automation > ProSave).
3. In ProSave, set Device type = MP277 Touch 8"/10", Connection = Ethernet, and enter the panel's IP. Test the connection with Status.
4. Open the Options tab in ProSave and click Install/Remove Options.
5. Select WinAC MP V4.0 from the option list, point ProSave to the WinAC MP installation source, and confirm.
6. Wait for the option transfer to complete. The panel reboots automatically.
7. After reboot, open Control Panel > OP > System > Installed Options on the panel and verify that WinAC MP V4.0 is listed with status Installed.
8. Optionally, re-install the WinCC Flexible Runtime image that matches your engineering project version if the image was wiped by the option installer.

Step-by-Step: Re-author the Demo Button Events

Open the Demo Project

1. Launch WinCC Flexible ES.
2. Open the WinAC demo project (File > Open > Samples > WinAC > demo). The project ships with the WinAC installation under ...\WinAC\Samples\WinCCFlex\demo.
3. Switch to the screen editor and open the screen that contains the start/stop, status, and MRES buttons.

Replace the Unsupported Event

1. Select the MRES button.
2. In the Properties dialog, open the Events tab and select the Click event row.
3. From the function catalog, navigate to System functions > PLC operations > Key switch and choose SetKeySwitch.
4. In the parameter list, pick the constant MRES from the dropdown. Do not type the string manually; pick from the catalog so the compiler validates the spelling against the project locale.
5. Repeat for any other button whose event was previously bound to an unsupported function: STOP → SetKeySwitch(STOP), RUN → SetKeySwitch(RUN), RUN-P → SetKeySwitch(RUN-P).
6. For Start/Stop WinAC, use the WinAC-specific functions StartWinAC and StopWinAC from the catalog. If those are still greyed out after install, repeat Step 6 of the previous section to confirm WinAC MP is registered.

Recompile and Transfer

1. Project > Compiler > Compile (Full rebuild).
2. Resolve any warnings about unknown system functions - the absence of warnings confirms that every function called by the project is available in the target image.
3. Transfer > Transfer to target device > Ethernet. Choose Overwrite all to ensure the recompiled project replaces the prior one on the panel.
4. When the transfer completes, the panel reboots into the new runtime.

Verification and Commissioning Tests

After the install and recompile, execute the following checks to confirm that the fault is resolved and that the demo behaves correctly.

Related System Functions and Key Switch Positions

SetKeySwitch is one of several system functions that the WinAC demo project uses. Knowing the related functions helps when migrating the demo to a different panel or extending it.

Compatibility Matrix: MP 277 / MP 377 and WinAC MP

Troubleshooting Matrix

Field-Proven Caveats and Edge Cases

Image-version mismatch. Even when WinAC MP V4.0 is installed on the panel, the WinCC Flexible Runtime version on the panel must match (or be binary-compatible with) the version used to compile the project on the engineering PC. A project compiled with WinCC Flexible 2008 SP3 deployed onto a panel running the 2007 SP3 image will throw "Function not supported" warnings at runtime for functions introduced in 2008. Always align the panel image with the engineering version.

ProSave Option store vs. Image store. ProSave writes options into a separate partition on the panel. Performing a "Reset to factory settings" wipes the option store. Operators frequently confuse "Restart" (which preserves options) with "Reset to factory" (which wipes them). Document the difference in the operator-facing SOP.

Authorization. SetKeySwitch with the MRES parameter issues a memory reset. By default, the S7 CPU requires the user to be logged in with sufficient authorization for "Memory reset". Confirm the WinCC Flexible project supplies a valid password for the CPU protection level; otherwise, the call returns a permission error and the buttons appear to do nothing.

Remanent data. MRES clears all non-retentive work memory and forces a cold restart. Always warn operations before binding MRES to a panel button. For a soft "reset to initial state" use case, prefer a user-defined function that writes the initial values from a data block rather than the system function SetKeySwitch(MRES).

Sequence of install. Install WinCC Flexible Runtime first, then WinAC MP V4.0. Installing WinAC MP before the base RT produces a fragmented option store on some MP 277 panels and the option is not detected on reboot.

Migration Path: MP 277 to Comfort Panel

The MP 277 is in the phase-out / migration lifecycle as of the Siemens Component Lifecycle Manager. New installations should consider migrating to a TP900 / TP1200 Comfort Panel with a separate S7-1500 PLC. The migration changes the runtime model fundamentally: Comfort Panels cannot host WinAC MP at all, so the WinAC-specific system functions in the demo must be removed and replaced with direct PLC tag manipulation against an external S7-1500. The SetKeySwitch call is not available on Comfort Panels; the equivalent on a Comfort Panel is a tag write to the S7-1500 mode selector tag or a protected operation from TIA Portal.

Frequently Asked Questions