Monitoring IO Status in WinCC RT Advanced: Script Methods

Overview: IO Status Monitoring in WinCC Runtime Advanced

Engineers migrating from Citect SCADA to SIMATIC WinCC Runtime Advanced (WinCC RT Advanced) frequently ask whether an equivalent of the Citect tag monitoring table is available. Citect exposes a development-time "tag status" window that lists every I/O address, its current quality, and its live value, including forcing and override columns. WinCC RT Advanced, which runs on the SIMATIC Comfort Panels, Unified Comfort Panels, and WinCC RT Advanced PC runtime, has no native runtime tag table object with that layout. The closest developer aids are the TIA Portal project tree (engineering-only, not visible in runtime) and the HMI device toolbox, neither of which is reachable from an operator screen.

This reference documents the three practical workarounds that survive a TIA Portal compile and a panel restart:

1. Distributed I/O fields bound directly to PLC tags.
2. Archive tags with a logging cycle of 500 ms or 1 s and a runtime trend view.
3. A VB-script-driven status screen that polls an arbitrary tag list and writes results into a tabular I/O field array or a CSV text file.

The third method is the closest functional equivalent to the Citect tag table, and it is the recommended pattern when more than ten tags must be inspected in parallel. All three patterns are compatible with TIA Portal V17, V18, and V19 WinCC RT Advanced, with minor script-API differences called out below.

Architecture Constraints: Why a Native Tag Table Does Not Exist

WinCC RT Advanced is a panel-class runtime that targets resource-constrained ARM-based panels (TP700–TP2200 Comfort, MTP700–MTP2200 Unified). Unlike the server-class WinCC Runtime Professional, it does not expose a generic tag browser in runtime. The following architectural facts drive this:

• Tag database compiled into the runtime image. Only tags declared in the TIA Portal HMI tag table exist in the loaded runtime project. There is no runtime discovery of additional OPC or S7 addresses.
• No reflection API. The VB and C scripting engines in WinCC RT Advanced cannot enumerate tags by name pattern. Script code must reference each tag explicitly, or read from a configuration array declared in the script.
• No live forcing UI. Unlike Citect or WinCC Professional, RT Advanced has no Force/Modify dialog in runtime. Tag values can be written only through the configured authorization level (operator password or higher).
• Quality code is not displayed in the standard I/O field. The "Quality" property is exposed on the tag object in script but not as a configurable field on the standard I/O field. Script must read HmiRuntime.Tags(tagname).Quality manually.

These constraints are documented in the WinCC RT Advanced System Manual, section 5.3 "Tag management", and in the TIA Portal help topic "Differences between WinCC Runtime Advanced and WinCC Runtime Professional".

Method 1 — I/O Field Quick Reference (No Scripting)

The lowest-effort path is to drop one I/O field per tag onto a dedicated screen. This is suitable for screens of 1–20 tags; beyond that, layout and update load become cumbersome.

Step-by-step procedure

1. In the TIA Portal project tree, open the HMI device and create a new screen Screen_999_TagMonitor.
2. From the toolbox, drag an I/O field onto the screen.
3. In the properties pane, set Process value → Tag → the target PLC tag (e.g. "DB1.DBX0.0" or a configured HMI tag "Motor1_Run").
4. Configure the Display format (binary, decimal, hex) and Output mode (output only, input/output, input only).
5. Duplicate the I/O field for each tag and rename the label text beside it.
6. On the screen's Events tab, set Loaded → ActivateScreen to ensure refresh on entry.

Update rate: I/O fields update on tag change events with a minimum of 100 ms acquisition cycle configured on the connection. This is fast enough for status display but wasteful for 50+ tags.

Method 2 — Archive Tags and Trend View

When the requirement includes historical traceback (last 10 min, last 24 h), use archive tags with a 500 ms logging cycle and a runtime trend view. The trend view shows live data plus history, which is often what an engineer debugging a fault actually wants.

Configuration matrix

Method 3 — VB Script Tag Status Table (Recommended)

A scripted status table is the closest Citect-equivalent. The approach is to maintain a comma- or tab-separated list of tag names in a single HMI text tag, then have a periodic script iterate the list, read the value and quality, and push the formatted result into a multi-line I/O field. The pattern below works on TIA Portal V17+ with WinCC RT Advanced.

3.1 Declare the tag list

Create an HMI text tag TagList_1 (String, length 1024) holding one tag per line. Example content:

Motor1_Run
Motor1_Fault
Conveyor_Speed
Tank_Level
Valve_Open

3.2 Create the output text tag

Create TagStatus_Output (WString, length 4096) on the HMI. Bind it to a text view or a single multi-line I/O field configured as output-only.

3.3 Schedule a cyclic script

Create a function BuildTagStatusTable and call it on a 1 s scheduler:

1. Project tree → HMI device → "Schedules".
2. Add a schedule with trigger 1 second.
3. Event: When triggered → call BuildTagStatusTable.

3.4 Script source (VB)

' BuildTagStatusTable
' TIA Portal V17/V18/V19 - WinCC RT Advanced
' Polls each tag in TagList_1 and appends a formatted row to TagStatus_Output.

Dim sList, arrLines, sLine, sResult
Dim i, idx, tagName, tagValue, tagQuality, sRow

On Error Resume Next

sList = SmartTags("TagList_1")
If Len(sList) = 0 Then
    SmartTags("TagStatus_Output") = "TagList_1 is empty."
    Exit Sub
End If

arrLines = Split(sList, vbLf)
sResult = "Tag" & vbTab & "Value" & vbTab & "Quality" & vbCrLf

For i = 0 To UBound(arrLines)
    tagName = Trim(arrLines(i))
    If Len(tagName) = 0 Then GoTo NextTag

    ' Read value
    tagValue = SmartTags(tagName)
    ' Read quality code (0=Good, 1=Bad, 2=Uncertain)
    tagQuality = SmartTags(tagName & ".Quality")
    Select Case tagQuality
        Case 0  sRow = "OK  "
        Case 1  sRow = "BAD "
        Case 2  sRow = "UNC "
        Case Else sRow = "?   "
    End Select

    sResult = sResult & tagName & vbTab & CStr(tagValue) & vbTab & sRow & vbCrLf

NextTag:
Next

SmartTags("TagStatus_Output") = sResult

If Err.Number <> 0 Then
    SmartTags("TagStatus_Output") = "Script error: " & Err.Description
    Err.Clear
End If

3.5 Performance and limits

Toolbox for HMI Projects — Reference Implementation

Siemens publishes a free "Toolbox for HMI Projects" (entry ID 106226404) on the Siemens Industry Online Support portal. The toolbox is a TIA Portal library containing ready-made HMI screens, faceplates, and VB scripts for common operations such as user administration, alarm filtering, and multi-tag status display. The status display faceplate in the toolbox implements essentially the pattern documented above (tag list → script → multi-line text field) and can be dropped into any project with a few mouse clicks.

What the toolbox provides

• Pre-built faceplate TagMonitor_FP with a configurable tag list property.
• VB script library TagMonitor_Scripts with safe wrappers for tag reads.
• Styles and color schemes consistent with the Comfort Panel WinCC Modern style.
• Compatible with TIA Portal V16, V17, V18, V19 (per the toolbox release notes).

To install: download the .zip from the Siemens Support entry, extract, and in TIA Portal choose Options → Global libraries → Open library and point to the extracted folder. Drag the faceplate from the library master copies onto your screen.

Building a Multi-Tag Status Screen (Worked Example)

The following example shows a complete screen setup that combines I/O fields (for the most-watched tags) with a script-driven text view (for the long tail of secondary tags).

Screen layout

Tag list maintenance

Keep TagList_1 in a separate recipe or a text file imported at startup. The recommended pattern is to bind a recipe with a single String element of length 1024 to TagList_1, allowing operators to switch between saved lists (e.g. Line1_Default, Line1_Debug, Line1_Commissioning) without re-engineering the script.

Configuration and Properties Reference

Tag properties used in the script

Scheduler limits by panel

Verification and Commissioning Checklist

1. Compile the project in TIA Portal. The output window must show zero errors and zero warnings related to the monitor screen.
2. Start the RT Advanced simulator from Online → Start runtime. Confirm the monitor screen loads without an error overlay.
3. Force a tag in the PLC simulator (PLCSIM) to a known value, then verify the same value appears in the I/O field and in the script text view.
4. Disconnect the S7 connection in PLCSIM. Confirm the Quality column shows "BAD" within two acquisition cycles (typically ≤ 2 s).
5. Reconnect and confirm "OK" is restored.
6. Watch the scheduler load in System information → Performance on the panel. CPU should remain below 60 %; higher values indicate the cycle is too short or the list too long.
7. Power-cycle the panel and confirm the tag list recipe and the monitor screen reload automatically.

Troubleshooting Matrix

Notes on Platform Differences

The patterns above are WinCC RT Advanced specific. The following platform-specific notes apply if the same monitor must be ported:

• WinCC Runtime Professional exposes a C# scripting API and a native tag table object (HMITagSet). The script approach is unnecessary there; use the Tag Table faceplate or the TAGSTATUS system function.
• WinCC Unified (V17+) uses JavaScript inside the runtime, not VB. The script above must be ported to HMIRuntime.Tags and Tags(tagname).QualityState. The conceptual pattern (tag list → loop → formatted output) is identical.
• WinCC flexible (legacy) on older panels (MP277, TP177B) uses VBScript with the same SmartTags object; the script above works unchanged.

For projects that must be supported on all three platforms, encapsulate the tag-reading function in a global module and use the platform's native binding. Avoid cross-platform code that mixes VB and C#.

FAQ