S7-1500 to WinCC Advanced: Connecting PLC Tags for HMI

Overview

When an S7-1500 PLC tag (typically a static or tag in a global data block, DB) cannot be selected from the drop-down list of an HMI object in TIA Portal WinCC Advanced, the cause is almost always that the HMI tag database on the operator interface side has not been synchronized with the PLC's symbol or tag list. WinCC Advanced does not browse the PLC's runtime memory at design time; it references a static copy of the tag definitions stored inside the HMI station's tag editor. Until the new setpoint, status word, or process variable is mirrored into the HMI tag table, the variable is invisible to faceplate configuration, pop-up screens, animations, scripts, and I/O field bindings.

This article documents the supported Siemens procedures for bringing S7-1500 tags into a WinCC Advanced project so that they can be selected as point-of-use references in faceplate interfaces, popup screens, and VBS/C actions on Comfort Panels and PC-based RT Advanced runtimes. Both automatic synchronization (HMI tag table → "Connect HMI tags to matching PLC tags") and manual entry are covered, along with the AS-OS engineering interface and the limits of WinCC Advanced's name-resolution mechanism.

Prerequisites

• Software: TIA Portal V14 SP1 or later. V15, V15.1, V16, V17, V18, V19, and V20 are all supported. Procedures below were validated against the SIMATIC WinCC Advanced V14 SP1 entry ID 109747174 documentation set; current builds follow the same menus.
• Controller: SIMATIC S7-1500, S7-1200, or ET 200SP CPU with a configured PROFINET or PROFIBUS HMI connection. S7-300/400 is also valid when an HMI connection is configured.
• Operator interface: Comfort Panel (TP, KP, TP700–TP2200, KP400–KP1500), or PC-based WinCC RT Advanced. Classic WinCC (WinCC Professional, WinCC flexible) is out of scope for the WinCC Advanced V14 SP1 procedure.
• PLC tag type: A defined symbol in the PLC program (global DB tag, input/output/in-memory tag, or shared DB) that is reachable via the HMI connection. Indirect (pointer-style) tag names are not browseable.
• HMI connection: An HMI connection between the PLC station and the HMI station in the project tree (Devices & Networks → Connections → HMI connection). Without an active HMI connection, "Connect HMI tags to PLC tags" cannot resolve the partner.

Background: Why the New Setpoint Is Missing

WinCC Advanced maintains its own point database, the HMI tag table, which is independent of the PLC's symbol table and data blocks. When you create a new setpoint tag in DB_Settings of the S7-1500, that tag exists only on the PLC side until you trigger a synchronization step. The WinCC Advanced faceplate, popup, and I/O field configuration dialogs use a pull-down populated exclusively by:

1. HMI tags created in the HMI station's tag table (default or user-defined tables).
2. HMI tags created automatically from PLC tags via the AS-OS engineering transfer.
3. For Comfort Panels and RT Advanced, internal system tags provided by the runtime.

Until one of those sources is updated, the new setpoint is invisible to any pick-list that uses the HMI connection's tag namespace. This is by design: HMI tags decouple the display layer from the controller, allowing different cycle times, scaling, limits, and acquisition modes on the operator interface side.

Step-by-Step: Connect HMI Tags to Matching PLC Tags

This is the supported one-click procedure shipped with WinCC Advanced V14 SP1 and later. It scans the HMI tag table and matches PLC tags by symbolic name, creating or updating HMI tag entries automatically.

1. Open the TIA Portal project containing both the S7-1500 station and the HMI station (Comfort Panel or PC RT Advanced).
2. In the project tree, expand the HMI station → "HMI tags" → the tag table that should receive the new tags (default table is "Default tag table").
3. Right-click the tag table (or a folder inside it) to open the context menu.
4. Select "Connect HMI tags to matching PLC tags". This option is documented in the WinCC Advanced V14 SP1 support entry.
5. TIA Portal performs a name-based match: any PLC tag with a symbolic name that already exists as an HMI tag of the same name is linked (its access path and connection are updated). PLC tags with no matching HMI tag are not created automatically — only existing pairs are reconciled.
6. For PLC tags that have no HMI counterpart, repeat the procedure using the "HMI tags" → "Add new tag" context menu, or use the AS-OS engineering transfer described below.

Method A: Manual Tag Creation in the HMI Tag Table

The most direct workaround, and the one Siemens documentation officially supports, is to create the HMI tag manually. This is appropriate when the new PLC tag is unique, has special HMI-side properties (scaling, limits, linear conversion, acquisition cycle), or when AS-OS engineering is disabled.

1. Open the HMI station → HMI tags → select the appropriate tag table.
2. Double-click "Add new tag" in the table editor, or right-click → "Add new tag".
3. Enter the symbolic name exactly as it appears in the PLC (case-sensitive). For DB tags, the symbolic name is the data block tag name, e.g. "setpoint" from DB_Settings, not the absolute path.
4. Set the Connection field to the HMI connection that targets the S7-1500.
5. Set the PLC tag field to the full path: {Data block}→{Tag name}, for example DB_Settings→setpoint. Use the browse button to navigate the PLC's symbol information.
6. Configure acquisition mode (cyclically, on demand, or on change) and update cycle (default 1 s is typical for setpoints).
7. Compile the HMI station. After successful compilation, the tag becomes selectable in the I/O field, faceplate interface, and popup configuration dialogs.

Method B: AS-OS Engineering (Automatic Transfer)

AS-OS engineering is the bulk mechanism for moving PLC tags into the HMI project. Unlike "Connect HMI tags to matching PLC tags", it can create new HMI tags that did not previously exist.

1. In the project tree, select the S7-1500 station.
2. Choose "Options → AS-OS Engineering" (or right-click the PLC station → "AS-OS Engineering").
3. In the dialog, select the target HMI station and the tag table(s) into which the PLC tags should be transferred.
4. Filter by tag type (inputs, outputs, DB tags, markers) and by DB number to limit the transfer scope.
5. Execute the transfer. TIA Portal creates an HMI tag for each selected PLC tag and links it via the configured HMI connection.
6. Recompile the HMI station and verify that the new setpoint appears in the HMI tag table.

AS-OS engineering is the recommended approach for greenfield projects where the PLC tag list is stable. It is also the only practical way to bring dozens or hundreds of PLC tags into WinCC Advanced in a single pass.

Method C: Linking from the Faceplate / Popup Configuration

When configuring a faceplate interface or popup screen property, the tag pick-list shows only HMI tags that already exist. The intended workflow is:

1. Create or synchronize the HMI tag first (Method A or B above).
2. Open the faceplate interface editor or the popup's I/O field properties.
3. Open the drop-down for the property that needs the setpoint. The newly added HMI tag is now in the list.
4. Select the tag and complete the property binding.

There is no inline "browse PLC" button inside the WinCC Advanced faceplate/popup configuration dialog at design time. The drop-down is a closed list of HMI tag names; if the tag is not there, you must add it via the tag table first.

Tag Property Mapping Reference

Verification

1. Compile check: Select the HMI station → Compile → Software (rebuild all). A clean compile confirms that the symbolic link between the HMI tag and the PLC tag is valid. Address-resolution errors here typically indicate a typo in the PLC tag path.
2. Tag simulation: In the HMI station's tag editor, right-click the new setpoint tag and select "Start/Stop Simulation". Enter a test value and observe the PLC tag value online (via watch table or PLC tag table in the S7-1500 project). If both update, the link is correct.
3. Faceplate / popup pick-list: Re-open the faceplate interface or popup screen configuration. The new setpoint must now be selectable in the drop-down.
4. Runtime test on Comfort Panel: Download the project to the panel. Use the HMI's service tools (or an I/O field bound to the new tag) to write the setpoint. Verify on the PLC side via TIA Portal's online view.
5. PLC tag table consistency check: In the HMI tag table, use "Go to PLC tag" (right-click → navigate) to confirm the HMI tag resolves to the expected PLC symbol. If navigation fails, the link is broken.

Troubleshooting Matrix

Performance and Design Notes

When scaling this approach to larger installations (several hundred PLC tags), consider these field-proven practices:

• Use multiple tag tables. Organize HMI tags into logical groups (per area, per unit) rather than one monolithic table. This keeps the faceplate/popup pick-lists focused and improves compile performance.
• Prefer symbolic access. Optimized S7-1500 data blocks with symbolic access deliver better diagnostics and avoid absolute-address drift across firmware updates. The HMI connection must use the S7-1500 symbolic mode, not legacy absolute addressing.
• Set acquisition mode deliberately. Setpoints should typically use "on demand" or "on change" so the panel is not reading them every cycle. Status flags should be "cyclic continuous" with a 500 ms–1 s update rate to balance CPU and bus load.
• Avoid creating runtime-only HMI tags for setpoints. Internal HMI tags are useful for faceplate logic, but the setpoint itself should be linked to the PLC so the value persists in the controller.
• Document tag naming conventions. Establish a project-wide prefix scheme (e.g. SP_ for setpoints, ST_ for statuses) so AS-OS engineering produces a clean HMI tag table that matches operator faceplate conventions.

Related Access Patterns

Once the tag is in the HMI table, VBS or C scripts in WinCC Advanced can read or write it through the runtime scripting interface (TIA Portal V20 documentation). Common calls include SmartTags("setpoint") in VBS and GetTagDouble/SetTagDouble in C. These runtime APIs only see HMI tags that exist in the project — which is why the design-time synchronization described above is the gating step.

FAQ