Resolving Blank and Non-Rendering CFC Charts on Windows 7 in SIMATIC PCS 7 - Version Compatibility and ActiveX Registration

In SIMATIC PCS 7 (STEP 7 V5.5), CFC Editor opening with a completely blank, white, or gray canvas that fails to display chart blocks, signal lines, or sheet grids on Windows 7 (64-bit) indicates a software incompatibility or un-registered ActiveX graphics controls. Specifically, CFC V7.1 SP2 is not officially released for Windows 7 64-bit and fails to register its internal COM rendering server (s7cfcx.ocx). To resolve this, upgrade to an officially supported version (such as CFC V7.1 SP3 Upd1 or CFC V8.0), re-register the CFC OCX controls via an elevated command prompt, and ensure Windows display DPI scaling is set strictly to 100%.

CFC Editor Rendering Architecture and Windows 7 64-Bit Compatibility

The SIMATIC CFC Editor relies on an integrated COM/ActiveX visual canvas architecture:
* When an engineer opens a CFC chart in SIMATIC Manager, the application loads the core rendering engine via dynamic link libraries (s7cfca.dll) and ActiveX controls (s7cfcx.ocx, cfcx.ocx).
* Under 64-bit Windows operating systems (Windows 7 SP1 64-bit / Windows Server 2008 R2), 32-bit COM components must execute within the WOW64 (Windows 32-bit on Windows 64-bit) subsystem.
* If a legacy version of CFC (such as V7.1 SP2 or older) is installed on Windows 7 64-bit, its registration entries under SysWOW64 are invalid, preventing the graphical canvas from drawing chart sheets.

Root Causes of Blank Canvas and Chart Display Failures

The failure to render CFC charts stems from specific environment mismatches:
1. Operating System Incompatibility: CFC V7.1 SP2 was engineered for 32-bit Windows XP Professional. Official support for Windows 7 64-bit begins exclusively with CFC V7.1 SP3 Upd1 or PCS 7 V8.0.
2. Unregistered or Corrupted ActiveX Controls: System updates or antivirus interference can unregister s7cfcx.ocx. Without this control, the CFC window frame opens, but the internal document view remains empty.
3. High-DPI Display Scaling Conflicts: Windows display scaling set to 125% or 150% breaks the pixel coordinate calculation of legacy GDI controls in CFC, causing the canvas to render outside the visible viewport.

Remediation Procedure - Upgrading CFC and Re-Registering COM Server Components

Follow this procedure to restore full graphical rendering in the CFC Editor:

[Phase 1: Upgrade to Windows 7 Released CFC Version]
   │  • Verify current version: SIMATIC Manager -> Help -> About -> Display...
   │  • If version is CFC V7.1 SP2 or older:
   │      - Install CFC V7.1 SP3 (or PCS 7 V8.0) officially released for Windows 7 64-bit
   │      - Install latest update (e.g. CFC V7.1 SP3 Upd1 from SIOS)
   │
[Phase 2: Re-Register CFC ActiveX and COM Components]
   │  • Open Windows Command Prompt as Administrator (Run as Administrator)
   │  • Navigate to the STEP 7 binary directory:
   │      cd "C:\Program Files (x86)\Common Files\Siemens\Bin"
   │  • Execute registration commands:
   │      regsvr32 s7cfcx.ocx
   │      regsvr32 cfcx.ocx
   │  • Confirm dialog: "DllRegisterServer in s7cfcx.ocx succeeded"
   │
[Phase 3: Configure Windows Display and DPI Scaling]
   │  • Open: Control Panel -> Appearance and Personalization -> Display
   │  • Set text size to: "Smaller - 100% (default)" (Do not use 125% or 150%)
   │  • Right-click desktop -> Personalize -> Select "Windows 7 Basic" or standard Aero
   │  • Reboot the Engineering Station

CFC Version and Operating System Compatibility Matrix

Verify official manufacturer compatibility using the Siemens Compatibility Tool:

CFC Software VersionWindows XP (32-bit)Windows 7 SP1 (32-bit)Windows 7 SP1 (64-bit)Windows Server 2008 R2CFC V7.0 SP1ReleasedNot ReleasedNot ReleasedNot ReleasedCFC V7.1 SP2ReleasedCompatibleNot Released (Render Bugs)Not ReleasedCFC V7.1 SP3 Upd1ReleasedReleasedOfficially ReleasedReleasedCFC V8.0 SP1 / SP2Not ReleasedReleasedOfficially ReleasedReleasedCFC V8.2Not ReleasedReleasedOfficially ReleasedReleased

Verification

To confirm that the CFC Editor renders charts properly:
1. In SIMATIC Manager, navigate to the Charts folder in the AS project.
2. Double-click any complex CFC chart.
3. Confirm that the chart sheet grid (Sheet 1 to 6) renders immediately with full background line definition.
4. Verify that function blocks display all input/output pins, block headers, and live dynamic connections.
5. Switch to Test Mode online; confirm that online values update cyclically in yellow/green highlight bars.

Limitations and Operational Precautions

Never attempt to run mixed-version installations of STEP 7 and CFC (e.g. STEP 7 V5.5 SP4 with CFC V6.x). Such mismatched configurations lead to severe internal project database corruption during AS compilation. Always verify overall compatibility using the official Siemens Kompatibilitäts-Tool (Compatibility Tool) prior to deploying engineering software on newer Windows builds.

Engineer FAQ

Why did CFC install without warning if it wasn't compatible with Windows 7?

Older setup packages only checked major Windows NT kernel versions (NT 6.1) without distinguishing 32-bit from 64-bit WOW64 environments, allowing installation to finish despite binary incompatibility.

What happens if I cannot change my Windows display scaling to 100%?

Right-click s7cfcx.exe (or s7tgtopx.exe) -> Properties -> Compatibility tab -> check 'Disable display scaling on high DPI settings'.

Where is s7cfcx.ocx located on a 64-bit machine?

It is located in C:\Program Files (x86)\Common Files\Siemens\Bin\ or inside the STEP 7 installation directory C:\Program Files (x86)\Siemens\Step7\S7bin\.