Disabling OK Confirmation Buttons on APL Faceplates in SIMATIC PCS 7

To disable the mandatory OK confirmation step on SIMATIC PCS 7 Advanced Process Library (APL) faceplates, modify the WinCC internal tag @APLCommandExecutionSteps in WinCC Tag Management. Setting the start value of @APLCommandExecutionSteps to 2 enables direct two-step execution, where clicking an action or command button executes immediately without requiring an additional click on the OK confirmation button. Setting the value back to 3 restores three-step execution with mandatory OK confirmation. This change applies globally across all APL faceplates on the operator station and requires a runtime restart to take effect.

Understanding APL Command Execution Modes

SIMATIC PCS 7 Advanced Process Library (APL) faceplates provide standardized operator interaction models designed to prevent unintended process operations. By default, APL faceplates implement a three-step operational sequence: first, the operator opens the faceplate and selects a command or input field; second, the operator toggles the desired state or enters a setpoint; third, the operator must click the 'OK' confirmation button appearing below the control to transmit the command to the controller.

In high-tempo operational environments, repetitive operations on blocks such as OpDi01 (Digital Operator Input), OpAnL (Analog Operator Input), MotL (Motor), or VlvL (Valve) can cause operator fatigue when confirmation clicks are required for non-critical digital actions. PCS 7 APL provides a centralized system mechanism using the internal tag @APLCommandExecutionSteps to streamline command execution into a direct two-step workflow without altering the underlying controller logic or block interface structures.

Configuring @APLCommandExecutionSteps in WinCC Tag Management

The command execution behavior is governed by the internal WinCC tag @APLCommandExecutionSteps, which is automatically generated during OS compilation with APL block icons.

Open the target OS project in WinCC Explorer on the Engineering Station or Server.
In the navigation tree, open Tag Management.
Navigate to Internal Tags and select the tag group containing system and APL tags (typically under Internal Tags -> APL).
Locate the tag named @APLCommandExecutionSteps (Data type: Signed 16-bit value / Unsigned 16-bit value).
Open the tag properties and change the Start value from 3 to 2.
Save the Tag Management configuration.
If WinCC Runtime is currently active, deactivate and reactivate WinCC Runtime, or download the modified project from SIMATIC Manager if engineering in a multi-user environment.

Once active, clicking any command button (such as 'Start', 'Stop', 'Open', 'Close', or digital state selectors) immediately updates the binary command tag in the AS without waiting for an OK button click.

Command Step Operating Mode Comparison

The following table compares the operational modes and behaviors determined by the @APLCommandExecutionSteps tag:

Tag ValueOperational ModeExecution SequenceOperator ConfirmationTypical Application1Direct 1-Step (Restricted)Click icon/button -> Action firesNo faceplate confirmationHigh-urgency emergency stops or external pushbutton panels22-Step Direct ExecutionSelect command -> AS write executesSuppressed (No OK button required)Standard process operations, routine digital toggles, testing33-Step Confirmed ExecutionSelect command -> Click OK -> AS writeMandatory OK confirmation clickHigh-risk valves, hazardous chemical dosing, safety-critical drives4+ReservedFallback to mode 3 defaultEnforced confirmationFuture Siemens expansion

Per-Faceplate Customization and Safety Considerations

Setting @APLCommandExecutionSteps to 2 modifies the operational behavior across all APL faceplates rendered by that WinCC client or standalone station. If specific safety-critical drives or valves must retain the OK confirmation button while routine operator inputs like OpDi01 operate directly, you cannot use the global tag alone.

To implement selective confirmation behavior:
- Copy the standard faceplate view PDL (for example, @PG_OpDi01_Standard.pdl) from the default directory <OS_Project>\GraCS to a custom name, or modify the local instance script.
- In the faceplate view script, override the command step evaluation logic by hardcoding the step evaluation variable to 2 for OpDi01 while leaving the global tag at 3 for drive faceplates (@PG_MotL_Standard.pdl).
- Note that modifying standard Siemens APL PDLs directly in GraCS will cause changes to be overwritten if the OS Project Editor is executed with the option 'Update Picture Files' enabled. Always maintain backups of customized faceplate graphics.

Verification

To verify the operational configuration:
1. Open WinCC Runtime on the modified OS station.
2. Open an APL block faceplate, such as OpDi01 or MotL.
3. Click an operational command button (e.g., 'On' or 'Off').
4. Confirm that the command initiates immediately without rendering the blue/grey 'OK' button below the button group.
5. Verify in the CPU CFC chart online that the corresponding binary command input receives the pulse or state change.
6. Verify in the WinCC Alarm Logging list that the Operator Input Message (Bedienmeldung) is logged with the correct operator login name and timestamp.

Limitations and Operational Precautions

Global Station Scope: Changing @APLCommandExecutionSteps affects every APL faceplate on that specific OS Runtime station. In client-server architectures, internal tags must be configured on the OS Server or distributed to OS Clients depending on whether client-specific scripting is enabled.
Process Safety Risks: Suppressing confirmation eliminates an essential safety barrier against accidental touch-screen or mouse clicks. High-risk actuators (e.g., toxic gas valves or heavy conveyors) should maintain three-step confirmation.
OS Project Editor Overwrites: Custom faceplate script modifications stored in @PG_*.pdl files will be overwritten if the OS Project Editor is run without deselecting faceplate template updates.

Engineer FAQ

Can @APLCommandExecutionSteps be toggled dynamically at runtime?

Yes. Because @APLCommandExecutionSteps is an internal WinCC tag, an internal VBS or C script or an administrative toggle switch on an overview screen can change the tag value between 2 and 3 dynamically based on user authorization level.

Does changing this tag affect classic PCS 7 standard library faceplates?

No. The @APLCommandExecutionSteps tag is exclusively interpreted by SIMATIC PCS 7 Advanced Process Library (APL) faceplate scripts and OCX controls. Classic Standard Library faceplates use independent script mechanisms.

Why did the OK button reappear after running the OS Project Editor?

Running the OS Project Editor does not reset internal tag values, but if custom PDL scripts were modified to enforce two-step behavior, the OS Project Editor will restore the default factory PDLs unless protected.

Does setting the tag to 2 bypass user authorization levels?

No. The operator must still possess the required WinCC authorization level (e.g., Operation level 5 or 6). If the operator lacks authorization, the command buttons remain greyed out.