Configuring Hardware Rack and Module Diagnostics in SIMATIC PCS 7 WinCC - Internal Diag Tags and Maintenance Station

In SIMATIC PCS 7, hardware rack and module diagnostic visualization (such as changing the color of an AS rack graphic based on fault state) relies on diagnostic driver blocks and system-generated internal tags. When compiling CFCs with 'Generate module drivers', the compiler creates diagnostic blocks (RACK, MOD_RACK, DP_DIAG) that evaluate rack fault states (QRACKF, STATUS). In classic PCS 7, internal tags named @Diag_<Station> are generated by the OS Project Editor and Lifebeat Monitoring. In modern PCS 7, this is superseded by the SIMATIC PCS 7 Maintenance Station (MS), which generates hierarchical diagnostic overview screens automatically.

Hardware Diagnostic Signal Flow: From Hardware Interruption to WinCC Tag

When a distributed I/O rack (ET 200M, ET 200SP HA) or central controller rack experiences a hardware fault (e.g., power supply failure, pulled module, or bus fault):
1. Hardware Interrupt: The interface module or peripheral triggers an interrupt line on the backplane.
2. Controller Processing: The CPU operating system intercepts the event and executes system organization blocks (OB82 for diagnostic interrupts, OB83 for pull/plug, OB86 for rack failure).
3. Driver Block Translation: Inside the OB, system driver blocks interrogate the diagnostic data record (e.g., via SFC51 RDSYSST) and update diagnostic output parameters.
4. AS-OS Compilation: WinCC reads these diagnostic outputs and maps them into internal status tags used to animate SCADA screens.

The Role of Generate Module Drivers and Diagnostic Driver Blocks

During CFC compilation, selecting Generate module drivers:
* The driver generator scans the hardware configuration (HW Config).
* It automatically places standard diagnostic blocks into system charts (prefixed with @):
* RACK / MOD_RACK: Monitors central and expansion racks (fault output QRACKF).
* MOD_CP: Monitors communication processors (e.g., CP 443-1, CP 341).
* DP_DIAG / OB_DIAG1: Monitors PROFIBUS DP and PROFINET remote I/O drops.
* If a newly added rack does not have an active diagnostic block, the driver generator was either not executed or the module's GSD/OM profile lacks driver support.

Generation of Internal Diagnostic Tags (@Diag and @MS) in WinCC

Why did the internal tag @Diag_xxx fail to generate after OS compilation?
* Classic Lifebeat Monitoring:
In legacy WinCC (v5.1 to v6.x), @Diag_ tags were created by the Lifebeat Monitoring wizard inside WinCC Explorer. The OS compiler does not create @Diag_ tags simply by compiling CFCs; the station had to be registered in the Lifebeat Monitoring table.
* Modern Maintenance Station (@MS):
In PCS 7 v7.x, v8.x, and v9.x, rack diagnostics are integrated into the PCS 7 Maintenance Station (MS Basic / MS Standard) (6ES7658-2CX58-0YB5):
* System tags follow the naming convention @MS_<StationName>_Status.
* The Plant Hierarchy automatically renders complete diagnostic faceplates for racks, modules, and field devices without manual tag creation.

Comparison Table: Classic Lifebeat Monitoring vs PCS 7 Maintenance Station

The table below compares diagnostic visualization methods in WinCC:

Feature / MetricClassic Lifebeat Monitoring (@Diag_)PCS 7 Maintenance Station (@MS_)System EraLegacy PCS 7 v5.x / v6.xModern PCS 7 v7.0 through v9.xTag Name Convention@Diag_<DeviceName>@MS_<PlantArea>_<Device>_StatusDiagnostic DepthStation communication alive / deadFull NAMUR NE 107 (Maintenance, Fault, Demand)Graphic GenerationStatic icon placed manuallyFully automated hierarchical overview screensDevice SupportRacks and network nodes onlyRacks, modules, HART sensors, PROFIBUS/PROFINETLicensing RequirementIncluded in Base WinCCMaintenance Station Basic (Free) / Standard (Licensed)

Step-by-Step Procedure to Implement Rack Diagnostic Graphics

Ensure Module Drivers are Generated:
In SIMATIC Manager, open any CFC chart. Click Charts -> Compile -> Changes only. Ensure the checkbox Generate module drivers is checked.
Assign Diagnostic Hierarchy in SIMATIC Manager:
* Open the Plant Hierarchy.
* Ensure the AS station has its diagnostic path mapped to a designated diagnostic folder.
Configure Maintenance Station / Lifebeat Monitoring:
* For Classic Systems: Open WinCC Explorer -> Lifebeat Monitoring. Add the new AS rack to the device list. Specify the device type and IP/MAC address. Click Update.
* For Modern Systems (PCS 7 v8.x): Open SIMATIC Manager -> Select the Multiproject root -> Click Options -> Plant Hierarchy -> Create/Update Diagnostics Screens.
Compile and Download OS:
Execute an OS compile. WinCC generates the internal @MS_ or @Diag_ status tags automatically.
Animate Graphic in Graphic Designer:
* Open your plant overview picture in Graphic Designer.
* Select the rack symbol. Open Properties -> Colors -> Background Color.
* Create a dynamic dialog or tag connection to the generated diagnostic tag (e.g., @MS_AS01_Rack0_Status).
* Map status values: 0 = Gray (Good), 1 = Yellow (Maintenance Demand), 2 = Red (Fault).

Verification

To verify rack diagnostic functionality:
1. Open the WinCC OS Runtime plant graphic. Confirm that the rack icon displays healthy green or gray.
2. Simulate a rack fault (e.g., unplug a redundant power supply or pull an I/O module in an ET 200M station).
3. Confirm that the rack symbol immediately changes color to red or yellow.
4. Verify that an audited hardware alarm appears in the WinCC Alarm Logging journal with the exact rack and slot location.

Limitations and Operational Precautions

Do Not Edit System Charts Manually: Diagnostic blocks generated in @ charts must never be manually altered or moved. Any manual changes will be silently overwritten during subsequent CFC compilations.
Driver Generator Errors: If a third-party non-Siemens module is inserted in HW Config, the driver generator may emit warnings and skip driver generation. Verify that third-party GSD files support standard diagnostic interrupts.
Licensing Disclaimer: Advanced Asset Management functions via SIMATIC PCS 7 Maintenance Station Standard (6ES7658-2CX58-0YB5) require validation against the applicable Siemens catalog and authorized distributor quotation.