Configuring WinCC HMI Language Switching with PLC Tag Bits

Overview: Mirroring WinCC Runtime Language in the PLC

Multilingual WinCC projects on Comfort Panels, WinCC Advanced Runtime, and WinCC Professional Runtime let the operator switch between languages through an HMI button configured with the ChangeLanguage system function. The PLC, however, does not automatically receive any notification of that change — yet many recipes, audit trails, alarm archives, and PLC-side messages need to know which operator locale is active to log localized actions or to switch between language-specific message classes.

This reference describes three reliable methods for synchronizing language state between the WinCC runtime and a SIMATIC S7-1200, S7-1500, S7-300, or S7-400 controller, and then walks through commissioning, verification, and fault diagnostics.

Prerequisites

Before configuring language tags, verify the following baseline:

Architecture: Bidirectional Language Tag Flow

Two distinct information paths can be configured. Both can coexist on the same panel.

Path A — HMI → PLC (status mirror)

The HMI detects the operator's language change through a button event or a tag-change handler, then writes a status bit (or the full LCID) into a configured PLC tag. The PLC reads this tag to know the current operator locale.

Path B — PLC → HMI (command channel)

A configured HMI connection area pointer named Language & Font carries an integer from the PLC that selects the active language index. The PLC writes the desired index and the runtime switches automatically without operator input.

Method 1 — Reading the Active Language with HMIRuntime.Language

The WinCC Runtime scripting object HMIRuntime exposes a read-only Language property that returns the locale identifier (LCID) of the currently active user interface language. This is the canonical method for HMI-internal logic that depends on language, such as branching in VBScript or triggering a SetBit to a PLC tag.

Typical Windows LCIDs encountered in Siemens projects:

Minimal VBScript reading the runtime language

Attach the following code to a button's Click event or to a tag's Change event:

' Returns the active runtime language LCID
Dim lngLCID
lngLCID = HMIRuntime.Language
SmartTags("HMI_Language_LCID") = lngLCID

Where HMI_Language_LCID is an INT tag connected to a PLC address (for example, DB100.DBW0 on an S7-1500) via the standard HMI tag list.

Method 2 — Driving the PLC Status Word from Button Events

When the operator changes language with an HMI button configured for the system function ChangeLanguage, that button accepts an unlimited number of additional events. Two of those events — SetBit and ResetBit — let you mirror the new language into one or more PLC bits without writing a single line of script.

Step-by-step configuration

1. In the WinCC project tree, locate the language button on the screen (typically the language toggle icon).
2. Open the button's Properties → Events.
3. Confirm that an existing event ChangeLanguage with a configured language parameter is present.
4. Add a new event: SetBit with PLC tag DB100.DBX0.0 (English status) when the language parameter is set to English (LCID 1033 or project index 0).
5. Add a new event: SetBit with PLC tag DB100.DBX0.1 (Italian status) when the language parameter is set to Italian (LCID 1040 or project index 2).
6. For each added SetBit, also add the corresponding ResetBit for the opposite language so the bits are mutually exclusive.

Resulting PLC tag layout (example for English / Italian)

Method 3 — Driving the WinCC Language from the PLC

WinCC Comfort and WinCC Advanced support a built-in connection area pointer named Language & Font. When this pointer is enabled and mapped to a PLC integer tag, the runtime polls that tag and changes the active language index whenever the value changes. This is the canonical answer to the follow-up question: "Can I set a bit in the PLC to select the language in the HMI?"

Configuration path

1. In the TIA Portal project tree, open HMI device → Connections.
2. Select the connection used for the target panel (e.g., "HMI_Connection_1").
3. In the Connection properties, enable the Language & Font area pointer.
4. Bind it to a PLC tag of type INT or WORD — recommended: DB100.DBW6 named PLC_Lang_Command.
5. Compile and download both the PLC and HMI projects.

PLC logic to drive the language

Write the desired project index to PLC_Lang_Command. WinCC reads the index on every cycle and selects the matching language:

S7-1500 Structured Text example (TIA Portal)

// Network 1: English command
IF "Cmd_Lang_EN" THEN
    "PLC_Lang_Command" := INT#0;
END_IF;

// Network 2: Italian command (overrides English if both set in same cycle)
IF "Cmd_Lang_IT" THEN
    "PLC_Lang_Command" := INT#2;
END_IF;

// Network 3: Optional sentinel for re-trigger (see Pattern B below)
IF "Cmd_Lang_Refresh" THEN
    "PLC_Lang_Command" := INT#99;
    "Cmd_Lang_Refresh" := FALSE;
END_IF;

Edge-detected behaviour

The pointer is change-driven: the runtime compares the polled value against the previous value and only switches if the integer changes. Toggling between two identical indices does not force a refresh. If a refresh is needed, write the target index, wait one acquisition cycle (default 1 s on Comfort Panels), then either clear the tag to a sentinel value (e.g., 99) or write the next desired value.

Tag Configuration Reference

VBScript Reference Library

The following snippets cover the three most common patterns. All scripts are valid for WinCC Comfort/Advanced V15.1 to V19 and WinCC Professional V16 to V19.

Pattern A — Write LCID to PLC on every change

' Attach to the "Change" event of the screen's language button
Sub OnClick(ByVal Item)
    Dim sLang
    sLang = HMIRuntime.Language
    SmartTags("HMI_Language_LCID") = sLang

    ' Optional: decode and set discrete bits
    Select Case sLang
        Case 1033, 2057
            SmartTags("HMI_Lang_EN") = True
            SmartTags("HMI_Lang_IT") = False
        Case 1040
            SmartTags("HMI_Lang_EN") = False
            SmartTags("HMI_Lang_IT") = True
        Case Else
            SmartTags("HMI_Lang_EN") = False
            SmartTags("HMI_Lang_IT") = False
    End Select
End Sub

Pattern B — Force a refresh of the Language & Font pointer

' Use when re-applying the same language after configuration
Sub OnClick(ByVal Item)
    Dim iCurrent
    iCurrent = SmartTags("PLC_Lang_Command")

    ' Pulse a sentinel value to force edge detection
    SmartTags("PLC_Lang_Command") = 99
    HMIRuntime.Trace "Sentinel written - runtime will re-evaluate on next poll"
    SmartTags("PLC_Lang_Command") = iCurrent
End Sub

Pattern C — Subscribe to HMIRuntime events for centralized handling

Available on WinCC Professional and Unified Comfort Panels (V17+). Use the OnLanguageChanged event:

' Global module or screen-level event
Sub OnLanguageChanged(ByVal newLanguage)
    SmartTags("HMI_Language_LCID") = newLanguage
End Sub

For more scripting details consult the VBScript Reference for WinCC Comfort/Advanced manual.

Commissioning and Verification

1. Compile the TIA Portal project. Resolve all warnings — HMI area pointer mismatches appear as warnings of category "HMI Tag Consistency".
2. Download to the PLC first, then to the HMI. Reboot the panel if the firmware version changed.
3. Open the configured language button. Toggle English ↔ Italian three times.
4. Monitor DB100.DBX0.0 and DB100.DBX0.1 online in the PLC. They must toggle mutually exclusive.
5. Verify DB100.DBW2 (LCID mirror) holds 1033 for English and 1040 for Italian.
6. For Method 3, force PLC_Lang_Command to 0, 1, 2 from the PLC watch table. Confirm the HMI language changes within one acquisition cycle.
7. Open the HMI's diagnostic page (Control Panel → System Information → Runtime Diagnostics) and verify no pointer errors are reported under "Area pointers".
8. Test power-cycle behaviour. After a warm restart, the HMI typically defaults to project index 0 unless you bind the Language & Font pointer to a retentive PLC tag.
9. Test operator rights. Log in as a restricted user; confirm the language change button is greyed out and no PLC bit fires.
10. Capture a screenshot of the HMI audit trail (if WinCC Logging is licensed) showing both languages were selected during commissioning.

Troubleshooting Matrix

Field-Proven Best Practices

• Always combine the bit-status mirror (Path A) with the LCID mirror in the PLC so downstream logic has both a quick boolean test and a precise identifier.
• Keep the language pointer under PLC control only on startup or via a dedicated engineering screen. Letting the operator control the language from the PLC defeats the purpose of multilingual HMI.
• Document the project language index order in the PLC source comments. Index assignments shift whenever the engineer reorders the language list, which silently breaks PLC-driven selection.
• For Unified Comfort Panels, prefer the new Languages global object over VBScript-legacy calls. The legacy HMIRuntime.Language still works in compatibility mode but is deprecated.
• Add a status tag HMI_Lang_Unknown that fires if the runtime reports an LCID not present in the project. It catches translation gaps early during FAT.
• When deploying to multiple panels, give each panel its own PLC DB block for language state. A single shared DB requires tag multiplexing that is brittle on slow PROFINET links.
• Use TIA Portal's Cross-reference tool to confirm every language change button has its Set/Reset events bound — missing events cause silent failures during SAT.

Frequently Asked Questions

For authoritative details on area pointer configuration see the WinCC Comfort/Advanced Communication manual and the VBScript for WinCC reference. For Unified scripting refer to the Unified Comfort Panel programming manual.