Interpreting Strikethrough Items in Symbol Selection Dialog in SIMATIC PCS 7 V9.0

In SIMATIC PCS 7 V9.0, strikethrough text appearing in the symbol selection window when interconnecting process signals to CFC channel drivers is a known graphical rendering bug in STEP 7 V5.6. The strikethrough formatting is purely visual and does not indicate an invalid, deleted, or reserved signal address. The underlying symbol definitions, hardware addresses, and data types in the Symbol Table remain completely functional and valid. Selecting the strikethrough symbol successfully establishes the interconnection without compiler errors. Siemens resolved this user-interface anomaly in STEP 7 V5.6 Update 3, which is included in SIMATIC PCS 7 V9.0 SP1.

Root Cause of Strikethrough Symbols in STEP 7 V5.6 / PCS 7 V9.0

During the engineering of SIMATIC PCS 7 V9.0 Continuous Function Charts (CFC), opening the symbol browser dialog to interconnect an I/O signal (such as IW 512 or Q 4.0) to an Advanced Process Library (APL) channel driver block (Pcs7AnIn, Pcs7DiIn, Pcs7DiOu) may display table entries rendered entirely in strikethrough typography.

In traditional programming environments, strikethrough font denotes deprecated routines, deleted variables, or disabled hardware addresses. However, in SIMATIC PCS 7 V9.0 (which incorporates STEP 7 V5.6 base release through Update 2), this behavior is caused by a graphical drawing glitch within the Win32 Common Controls list-view component under Windows 10 and Windows Server 2016. When the symbol selection dialog queries hardware-assigned peripheral inputs and outputs, a font rendering flag (LF_STRIKEOUT) is inadvertently applied to the text buffer.

Technical Validity of Strikethrough Interconnections in CFC

Engineers encountering this visual defect often hesitate to proceed, fearing corrupted hardware configurations or data type mismatches. Diagnostic analysis reveals that the underlying database remains fully intact:

Diagnostic DimensionObserved ConditionUnderlying RealitySystem ImpactGUI Text DisplaySymbol name and address strikethroughFont rendering bug in STEP 7 V5.6 UI list controlZero impact on database recordsSymbol Table IntegritySYMLIST records in SIMATIC ManagerSymbol names, addresses, and data types validData integrity 100% verifiedCFC InterconnectionDriver block input (e.g., PV_In) linkedBlock parameter binds to absolute peripheral addressNormal signal scaling and quality processingCFC CompilationCompilation of charts as programCompiler resolves address via S7 symbol dictionaryCompiles with 0 Errors and 0 Warnings

Because the CFC compiler queries the binary database rather than the graphical UI state, the strikethrough text does not impair signal flow, module driver generation, or runtime diagnostics.

Workarounds and Permanent Resolution via Software Updates

Depending on project constraints and release timelines, engineers can choose between immediate operational workarounds and permanent software updates:

Proceed with Normal Selection (Immediate Workaround): Highlight the required strikethrough symbol in the dialog and click OK (or press Enter). The connection binds cleanly to the channel driver block input.
Direct Text Entry in CFC (Alternative Workaround): Rather than opening the symbol browser dialog, click directly on the input pin of the channel driver block, type the exact symbolic name or absolute address (IW 512), and press Enter. CFC automatically resolves the symbol against the Symbol Table without displaying the dialog.
Apply STEP 7 V5.6 Update 3 (Direct Patch): For standalone PCS 7 V9.0 installations, download and install STEP 7 V5.6 Upd3 (or higher) from Siemens Industry Online Support (SIOS). The update replaces the flawed UI drawing libraries and restores standard font rendering.
Upgrade to SIMATIC PCS 7 V9.0 SP1 (Comprehensive Resolution): Upgrade the Engineering Station to SIMATIC PCS 7 V9.0 SP1. SP1 natively integrates STEP 7 V5.6 SP1 / Upd3, permanently eliminating the rendering anomaly across all multiproject tools.

Verification

Verify that the strikethrough symbol interconnection functions properly through these checks:

CFC Connection Inspection: Examine the connection line on the CFC sheet. Confirm that the green symbolic name and absolute address appear adjacent to the block input pin without error markers.
CFC Program Compilation: Execute Chart -> Compile -> Chart as Program -> Changes Only. Verify compilation logs confirm that module drivers (MOD_*, OB_BEGIN, OB_END) are correctly generated and that zero address errors exist.
Online Signal Monitoring: Download the program changes to the AS controller. Switch CFC to Test Mode (Debug -> Test Mode). Verify that the channel driver PV_In or PV_Out reads the live field transmitter value with signal quality status 16#80 (Good).

Limitations and Operational Precautions

When addressing symbol display behavior in PCS 7 V9.0, observe these technical boundaries:

Distinguish UI Bugs from Real Address Conflicts: Do not assume all unexpected symbol behaviors are cosmetic. If a symbol appears in red text with a yellow warning triangle in the Symbol Table itself, a genuine syntax error, duplicate address, or overlapping byte boundary exists and must be corrected in HW Config.
Engineering Station Version Uniformity: In multi-engineering environments with multiple Engineering Stations sharing a central Multiproject, ensure all engineering PCs have the identical STEP 7 update level installed to prevent project database version mismatches.
Software Update Qualification: Prior to installing STEP 7 V5.6 Update 3 or PCS 7 V9.0 SP1 on an active engineering system, verify compatibility of all installed optional packages (e.g., S7 F Systems, CEMAT, APF) using the Siemens Compatibility Tool.

Engineer FAQ

Does selecting a strikethrough symbol cause runtime driver errors in the CPU?

No. The strikethrough appearance is strictly a graphical font drawing anomaly in the STEP 7 V5.6 dialog. The compiled S7 machine code contains the exact peripheral address and executes identically in the controller.

Can I disable strikethrough rendering via a Windows registry setting?

No. The font style flag is hard-coded within the Win32 list control implementation of the STEP 7 V5.6 UI component. Only the official Siemens patch (Update 3 or PCS 7 V9.0 SP1) resolves the code defect.

Why did this bug only appear in PCS 7 V9.0 and not in PCS 7 V8.2?

PCS 7 V8.2 utilized STEP 7 V5.5 SP4, which used older 32-bit common control libraries under Windows 7. STEP 7 V5.6 was recompiled with updated Microsoft toolchains for Windows 10 / Server 2016 compatibility, which introduced this list rendering regression.