Visualizing Signal Module Hardware Diagnostics in SIMATIC PCS 7: Maintenance Station Deployment

In SIMATIC PCS 7, automatically generated module diagnostic blocks (MOD_D1, MOD_D2, MOD_1) residing in system charts (@...) do not possess standard operator block icons or faceplates. Attempting to display them on regular process graphics is unsupported. To visualize the physical condition of I/O signal modules, interface modules, and field devices on the OS, engineers deploy the SIMATIC PCS 7 Maintenance Station (MS). The Maintenance Station automatically generates diagnostic screens directly from the hardware configuration, displaying rack overviews, channel faults, and NAMUR NE 107 diagnostic states.

Module Diagnostic Blocks (MOD_) and Why They Lack Standard Faceplates

When an engineer compiles CFC charts with Generate module drivers enabled, the PCS 7 Driver Generator inspects HW Config and creates internal diagnostic blocks:
* MOD_D1 / MOD_D2 (FB 94 / FB 95) – Monitoring digital and analog signal modules.
* MOD_1 (FB 91) – Monitoring compact modules and power supplies.
* RACK (FB 107) – Monitoring ET 200 interface modules and backplane bus rails.

Engineers frequently look for block icons in @PCS7Typicals.pdl to place on WinCC graphics to display module health, only to discover none exist.
* Why? The MOD_ family of blocks was never designed for direct graphical placement. They operate as internal diagnostic evaluators that process hardware interrupts (OB82), read system status lists (SSL), and feed status information into channel driver blocks (Pcs7AnIn, Pcs7DiIn).
* Standard process operator graphics (.pdl) are meant for technological devices (valves, motors, tanks), not hardware electronics.

The Architecture of the SIMATIC PCS 7 Maintenance Station

To provide dedicated, ergonomic visualization of physical hardware components without cluttering operator P&IDs, Siemens developed the SIMATIC PCS 7 Maintenance Station (MS):
* Operating as a dedicated OS Server/Client or integrated directly into standard OS Clients, the Maintenance Station acts as the plant's centralized Plant Asset Management (PAM) system.
* Automatic Screen Generation: The system evaluates STEP 7 HW Config and the Plant Hierarchy. During OS compile with MS options, the compiler automatically generates a dedicated Diagnostic Hierarchy:
- Top-level overview: Controllers, Fieldbuses, Distributed I/O, Network Switches, IPCs.
- Intermediate rack view: Graphical representation of the ET 200M / ET 200SP rack.
- Component view: Exact graphical representation of the signal module showing which specific channel has a wire break or short circuit.
* Standardized according to NAMUR NE 107 (Maintenance Required, Maintenance Demanded, Failure, Function Check).

Maintenance Station Editions: Basic, Standard, and PDM

Siemens provides the Maintenance Station in three scalable tiers:
1. Maintenance Station Basic (MS Basic):
- Zero Additional License Cost: Included with standard PCS 7 engineering and runtime licenses!
- Runs directly on existing WinCC OS Clients.
- Provides complete visual hardware diagnostics for all S7-400 controllers, ET 200 distributed I/O racks, signal modules, and SCALANCE switches.
2. Maintenance Station Standard (MS Standard):
- Requires dedicated MS Server/Client software licenses.
- Adds full maintenance cycle management: Work Orders, Maintenance Target Times, Maintenance Counter tracking, and integration with Enterprise Asset Management (EAM/CMMS) software (such as SAP PM or IBM Maximo).
3. Maintenance Station PDM:
- Integrates SIMATIC PDM, allowing technicians to open intelligent field device parameter screens (HART, PROFIBUS PA, Foundation Fieldbus) directly from the maintenance faceplate.

Hardware Diagnostic Visualization Strategy Matrix

The following matrix compares methods for visualizing hardware diagnostics in SIMATIC PCS 7:

Diagnostic MethodEngineering EffortLicense RequirementGranularity of DisplayNAMUR NE 107 SupportManual MOD_ Block LinksVery High (Custom scripts)Standard OS POsPrimitive (Bit values only)NoneMaintenance Station BasicLow (Fully automated generation)Included (Zero Extra Cost)Module, Rack, & Channel LevelFull Native SupportMaintenance Station StandardLow (Fully automated generation)Dedicated MS LicensesFull Plant Asset LifecycleFull Native SupportSTEP 7 HW Config OnlineZeroEngineering Station OnlyTechnical Diagnostic BufferNone

Step-by-Step Workflow to Deploy Maintenance Station Basic

Follow this procedure to enable Maintenance Station Basic on an existing PCS 7 system:
1. Configure Plant Hierarchy for Diagnostics:
- In SIMATIC Manager Plant View, select the root plant folder.
- Select Options -> Plant Hierarchy -> Settings....
- Ensure the plant hierarchy includes an assigned diagnostic area.
2. Assign Maintenance Station in HW Config:
- In SIMATIC Manager Component View, select your OS PC Station (e.g. OS_Server or single station).
- In Station Properties, select the Maintenance Station tab.
- Set the operating mode to MS Basic (Integrated).
- Select the target diagnostic picture hierarchy path.
3. Compile the Diagnostic Structure:
- In SIMATIC Manager, right-click the OS project and select Compile.
- In the Compile Wizard, ensure the option Diagnostic screens is checked.
- The compiler will parse HW Config and automatically construct all diagnostic pictures (@Diagnostic_...pdl), rack overviews, and module faceplates.
4. Download and Launch in Runtime:
- Download the OS project to the OS Server / Client.
- Activate WinCC Runtime.
- In the top-level overview navigation bar, click the Diagnostics icon (wrench symbol).
- Navigate through the plant tree to view real-time graphical representations of all signal modules.

Verification

Verify hardware diagnostic visualization in runtime:
1. Open WinCC Runtime on the OS Client.
2. Click the Diagnostics Overview button in the header bar.
3. Confirm that all Automation Stations, Plant Buses, and Distributed I/O racks display green healthy status symbols.
4. Click through to an ET 200M station: Confirm that each physical module is rendered with its correct slot number and order number (MLFB).
5. Simulate a Field Fault (e.g. disconnect a wire on an analog input module):
- Confirm that the module in the Maintenance Station screen immediately displays a red Failure symbol.
- Open the module faceplate: Confirm it highlights the exact channel number with text: Wire break.

Limitations and Operational Precautions

Generating Maintenance Station diagnostic screens creates hundreds of system .pdl graphics; ensure adequate disk space on the OS Server before initiating a full diagnostic compile.
In MS Basic, maintenance parameters (such as maintenance counter resets) cannot be saved permanently without an MS Standard license.
Ensure time synchronization is active across all controllers so that diagnostic interrupt timestamps in the Maintenance Station align with WinCC Alarm Logging.

Engineer FAQ

Does Maintenance Station Basic consume additional WinCC Process Object (PO) licenses?

No. Maintenance Station Basic is included free of licensing charges within standard PCS 7 OS packages, consuming zero additional Process Object licenses for generated diagnostic blocks.

Can Maintenance Station monitor network switches?

Yes. SCALANCE managed switches integrated into HW Config (via PROFINET IO or GSD) are automatically modeled in the Maintenance Station network overview with port-level link status.

Why did the Diagnostics button not appear in my WinCC header bar?

The Diagnostics button appears only if Diagnostic screens was selected during OS compilation and the OS Project Editor was executed with the standard PCS 7 navigation screen layouts.