Configuring VBScript Timers in WinCC Flexible HMI Panels

Configuring VBScript Timers in WinCC Flexible HMI Panels

Siemens WinCC Flexible is the legacy HMI configuration environment that was used for SIMATIC panels prior to the TIA Portal-based WinCC Comfort/Advanced and WinCC Unified/Professional. Engineers still encounter brownfield installations running WinCC Flexible 2005, 2007, 2008, or 2008 SP3 on operator panels, and the question of which scripting language the runtime supports remains a frequent point of confusion. This reference explains the C-Script versus VBScript support matrix, shows working VBScript timer code, documents the affected runtime versions, and maps a migration path to the current RT Professional environment.

1. WinCC Flexible Overview and Scripting Architecture

WinCC Flexible configures the SIMATIC HMI panel families (K/TP 170/270/370, MP 270/370, OP 170/270/370, OP 73/77, TP 170/177/270/277/370, MP 177/277/377, Comfort Panels via early migrations, C7-635/636, and WinAC MP). Each panel runtime executes a stripped-down version of the configuration, and the available scripting engine depends on the runtime build rather than the configuration tool version.

Two scripting languages are relevant:

• C-Script — syntax-compatible subset of ANSI C, exposed as project functions and standard functions. Available on practically every WinCC Flexible panel runtime.
• VBScript (VBS) — Microsoft Visual Basic Scripting Edition 5.x, hosted through the Windows CE / Windows XP Embedded scripting engine. Available on a narrower subset of panel runtimes that bundle the VBS interpreter.

2. C-Script vs VBScript: Version and Panel Support Matrix

The original poster was using "WinCC 2005" (a WinCC Flexible build), and explicitly noted that the right-click context menu of the script editor did not show a "C Script" option. This is a strong indicator that the project was opened on a newer configuration host (or the project was migrated) and the panel target's runtime profile is the limiting factor — not the ES. The decision path is always: confirm the panel's runtime image supports VBS, then author VBS; otherwise use C-Script.

3. When VBScript Is the Right Choice on WinCC Flexible

VBScript offers tighter integration with HMI tag objects, simplified string handling, and direct use of the VBScript DateAdd, DateDiff, Timer, and FormatDateTime functions. For projects dominated by string formatting, recipe CSV import/export, logging rotation, and shift/time-of-day logic, VBS reduces the development effort substantially compared to C-Script, where the same string work must be done through sysstrcmp, sysstrncpy, and ASCII buffers.

C-Script still wins for:

• Bit-level work and high-frequency cyclic tasks (< 100 ms)
• Code that must run on basic OP/TP 170-class panels without VBS
• Code that depends on tightly-scoped local scope (C locals are stack-allocated; VBS uses Variant for everything)

4. VBScript Timer Implementation Reference

A "timer script" in WinCC Flexible parlance is a VBS or C function scheduled to execute on a fixed cycle. There is no explicit SetTimeout in the runtime API; instead, scheduling is performed through the scheduler and the function is invoked every N seconds. The pattern below shows a cyclic timer used to drive a 1-Hz status indicator and to roll a shift log tag.

4.1 Scheduler Configuration

In the WinCC Flexible project tree, navigate to Schedules > Schedules, create a new schedule, and attach the VBS function. The schedule interval must be a multiple of 100 ms; the smallest supported on most panels is 250 ms.

4.2 VBScript Tick Function

'------------------------------------------------------------------
' Function:   Tick_1s
' Trigger:    Schedule, 1 s cyclic
' Purpose:    Heartbeat, blink tag, and shift log rollover
'------------------------------------------------------------------
Sub Tick_1s()
    Dim hb          ' heartbeat pulse
    Dim blink       ' 0/1 toggle for IO field visibility
    Dim nowH, nowM, nowS
    Dim shiftTag

    ' Read HMI tags (Sm@rtClient / area pointers must be configured)
    hb    = HMIRuntime.Tags("HMI_Heartbeat").Read
    blink = HMIRuntime.Tags("HMI_Blink").Read

    ' Toggle blink at 0.5 Hz (every other call)
    If blink = 0 Then
        HMIRuntime.Tags("HMI_Blink").Write 1
    Else
        HMIRuntime.Tags("HMI_Blink").Write 0
    End If

    ' Drive heartbeat high then low; produces a 1-Hz pulse for PLC
    If (hb = 0) Then
        HMIRuntime.Tags("HMI_Heartbeat").Write 1
    Else
        HMIRuntime.Tags("HMI_Heartbeat").Write 0
    End If

    ' Shift rollover at 06:00:00 — log entry to recipe/text-tag
    nowH = Hour(Now)
    nowM = Minute(Now)
    nowS = Second(Now)

    If (nowH = 6) And (nowM = 0) And (nowS < 5) Then
        shiftTag = HMIRuntime.Tags("HMI_LastShiftLog").Read
        HMIRuntime.Tags("HMI_LastShiftLog").Write _
            FormatDateTime(Now, vbShortDate) & " 06:00 - shift change"
    End If
End Sub

Key runtime API elements used above:

• HMIRuntime.Tags("<Name>") — returns a tag object. Requires the tag to exist in the project tag table; otherwise a runtime error is thrown.
• .Read / .Write <value> — synchronous read/write.
• VBS built-in Now, Hour, Minute, Second, FormatDateTime.

4.3 C-Script Equivalent (for panels without VBS)

// Function: Tick_1s_C
// Trigger:  Schedule, 1 s cyclic
// Purpose:  Heartbeat for VBS-incapable panels (TP 170A, OP 77B)

#include "apdefap.h"
void Tick_1s_C(void)
{
    DWORD hb, blink;
    static int toggle = 0;

    hb    = GetTagWord("HMI_Heartbeat");
    blink = GetTagWord("HMI_Blink");

    blink = (blink == 0) ? 1 : 0;
    SetTagWord("HMI_Blink", (WORD)blink);

    hb = (hb == 0) ? 1 : 0;
    SetTagWord("HMI_Heartbeat", (WORD)hb);

    if (toggle == 0)
        toggle = 1;
    else
        toggle = 0;
}

The C-Script API uses GetTagXXX / SetTagXXX where XXX is Bit, Byte, Word, DWord, Char, Float, or Double. These calls are non-blocking and safe to invoke from a schedule.

5. Common Configuration Pitfalls

6. Diagnosing the Right-Click "C Script" Menu Issue

1. The function being edited was originally authored in VBS. C-Script and VBS are mutually exclusive per function; the function's Properties > General > Language field controls which menu options appear.
2. The ES host is WinCC Comfort/Advanced on TIA Portal. In TIA Portal, the script editor's language is selected when the function is created; the right-click context menu is replaced by a property sheet.
3. The target panel runtime was filtered by the configuration tool. The ES disables languages that are not in the panel's runtime profile.

To force a C-Script function, choose Scripts > New > C Function from the project tree — the language is locked at creation.

7. Migration Path to TIA Portal / RT Professional

WinCC Flexible ES is end-of-life and is not maintained for current hardware. For new panels or panel refreshes, projects should be migrated to TIA Portal WinCC Comfort/Advanced or to WinCC RT Professional. Migration tools in the TIA Portal import WinCC Flexible projects and convert:

• C-Script functions → C-Script functions (high fidelity, > 95% pass-through)
• VBScript functions → VBScript functions (90% pass-through; some COM objects must be re-mapped)
• Schedules → Schedules (cycle granularity preserved)
• Tag table → Tag table (PLC and HMI tag names retained)

For PC-based operator stations, RT Professional is the successor platform. Local VB scripts in RT Professional are authored under Project > Scripts > VB > Local and integrate with the system functions through the function list. Per Siemens documentation, the function list can be converted into a local script and edited inline. Reference: Integrating local VB scripts (RT Professional).

For panel-based Comfort targets, VBS remains a first-class language alongside C-Script. For Unified Comfort Panels (MTP/ET 200SP HMI), the script model is JavaScript (ECMAScript 5.1+) and existing VBS must be rewritten.

8. Verification Procedure After Authoring a VBScript Timer

1. Compile the project. Watch for warnings tagged "VBS function <name>: implicit Variant conversion" — these are usually benign but can mask logic errors in arithmetic.
2. Simulate with the WinCC Flexible runtime simulator. The simulator runs against the ES and exercises both VBS and C-Script.
3. Add a temporary HMIRuntime.Trace call (PC runtime only) or write a debug string to a visible text tag to confirm the schedule is firing at the correct cadence.
4. Deploy to the target panel. On the panel, navigate to Start Center > Control Panel > System > Information > Version and confirm the runtime image includes the VBS option. On a CE 5.0/6.0 panel, this is shown as a feature bit in the panel's .img.
5. Force a tag write from the PLC and confirm the script reacts within one scheduling cycle.

9. Field-Commissioning Checklist

• Confirm panel firmware revision >= the WinCC Flexible ES version's minimum. Mismatches cause silent feature loss, including VBS.
• Confirm PLC connection name in the HMI tags matches the configured connection; case-sensitive.
• For schedules firing below 250 ms, verify the panel CPU load in the diagnostic page; > 80% load will drop schedule ticks.
• Always provide a "manual override" tag so the schedule can be suspended during commissioning.
• Export the runtime trace to a USB stick or SD card and include it in the as-built documentation.

10. Frequently Asked Questions