C135 PCS 7 (PCS7)
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How to Configure Controller and I/O Hardware Diagnostics on the WinCC OS in PCS 7

How to Configure Controller and I/O Hardware Diagnostics on the WinCC OS in PCS 7

In SIMATIC PCS 7 V8.1, hardware-level diagnostic monitoring for controllers, fieldbus networks, and I/O modules on the WinCC OS is achieved natively through the PCS 7 Maintenance Station (MS Basic), which generates hierarchical asset faceplates automatically during compilation without requiring manual tag scripting. Alternatively, if individual status tags are needed for custom graphic mimics, engineers utilize the diagnostic outputs generated by the CFC Driver Wizard: CPU_DIAG for controller run/stop/fault status, Basis Library module drivers (such as MOD_D16, MOD_HA8) for module power and peripheral faults (QMODF, PERF), and technological channel drivers for signal quality (Bad).

Table of Contents

Hardware Diagnostic Paradigms: Maintenance Station vs Manual Tags

When engineering operator visualization in SIMATIC PCS 7 V8.1, plant engineers frequently seek to visualize the operational health of physical automation hardware on the WinCC OS:
* Detecting when an Automation Station (CPU) enters STOP mode, encounters a rack fault, or suffers a redundancy failure.
* Identifying power supply failures, missing auxiliary voltage, or pulled I/O modules on distributed ET 200M, ET 200iSP, or ET 200SP stations.
* Displaying real-time communication fault indicators on fieldbus networks (PROFIBUS-DP and PROFINET IO).

In legacy DCS systems, engineers were forced to manually poll system function blocks (SFC51 RDSYSST), decode hex status bytes in ladder logic, and map hundreds of internal HMI tags. In PCS 7, this manual approach is obsolete. The architecture provides two distinct methodologies:
1. Integrated Plant Asset Management (Maintenance Station): Standard Siemens automated diagnostic framework.
2. Standard Diagnostic Block Tag Mapping: Utilizing Driver Wizard block outputs for custom mimic diagrams.

Automatic Diagnostics via PCS 7 Maintenance Station Basic

The primary and Siemens-recommended method for hardware diagnostics on the OS is the PCS 7 Maintenance Station (MS Basic), which is included free of additional licensing in standard PCS 7 installations:

Automated Architecture

  • Driver Wizard Generation: During CFC compilation with 'Generate module drivers' selected, SIMATIC Manager automatically inserts diagnostic blocks (CPU_DIAG, RACK, MOD_, SUBNET) into system @Charts.
  • Report System Error (RSE): The compiler configures message blocks that automatically transmit timestamped alarms to WinCC whenever a hardware module is unplugged, loses power, or encounters a wire-break.
  • Diagnostic Screen Hierarchy: When OS Project Editor runs, it builds the Diagnostic View (@DiagnosticView.pdl). Operators can click the Maintenance button in the WinCC overview banner to view a visual plant topology showing green/yellow/red status indicators for every rack, power supply, and I/O card with integrated faceplates.

Extracting Discrete Hardware Diagnostic Tags for Custom Mimics

If an engineering specification specifically requires displaying custom hardware status icons directly on process overview mimics (e.g., a simplified graphic showing Rack 1 healthy, Rack 2 faulted):

Step 1: Controller-Level Status via CPU_DIAG

In the system @(1) chart generated by the Driver Wizard, locate the CPU_DIAG block:
* RUN: Output boolean indicating CPU is executing in RUN mode.
* STOP: Output boolean indicating CPU is entering STOP.
* EXTF: Output boolean indicating external fault (bus disruption, I/O rack missing).
* REDF: Output boolean indicating redundancy error in fault-tolerant H-systems.
* To expose to WinCC: Mark the desired outputs with the attribute S7_m_c := 'true' in CFC.

Step 2: Module-Level Status via MOD_ Driver Blocks

In the @Charts, locate the module driver blocks associated with the physical rack slots (e.g., MOD_D16, MOD_D32, MOD_HA8):
* QMODF (Module Fault): Asserts 1 when the module is removed, unpowered, or defective.
* PERF (Peripheral Fault): Asserts 1 when external channel power is missing or fieldbus communication to the ET 200 rack is severed.
* QUALITY: Outputs hex 16#80 when the module is healthy; drops to 16#00 on complete failure.

Step 3: Channel-Level Status via APL Channel Drivers

On standard technological charts, channel driver blocks (Pcs7DiIn, Pcs7AnIn) provide:
* Bad (QBAD): Indicates the specific I/O channel is invalid due to open wire, short circuit, or module failure.
* Interconnect Bad directly to technological faceplates or overview warning lamps.

Diagnostic Blocks and Output Parameter Reference Matrix

The following table outlines the diagnostic blocks generated by the Driver Wizard and their primary status outputs:

Block TypeHardware Component MonitoredOutput ParameterSignal State MeaningWinCC IntegrationCPU_DIAGS7-400 / CPU 410-5H ControllerEXTF1 = External system/bus faultEnable S7_m_c for HMI displayCPU_DIAGRedundant AS 410-5H StationREDF1 = Partner CPU down / uncoupledEnable S7_m_c for HMI displayRACK / DP_RACKET 200M / ET 200SP Interface ModuleQRACKF1 = Entire rack communication lostAutomatic Maintenance faceplateMOD_D16 / MOD_D32Digital Input/Output ModuleQMODF1 = Module missing, unpowered, faultedEnable S7_m_c or view in MSMOD_HA8HART Analog Input ModulePERF1 = Channel power supply faultEnable S7_m_c or view in MSPcs7AnIn / Pcs7DiInIndividual Process ChannelBad1 = Measurement invalid / failedBuilt-in APL block icon output

Leveraging native diagnostic outputs eliminates the need to develop custom diagnostic PLC logic.

Verification

To verify hardware diagnostic reporting in WinCC Runtime:
1. In WinCC Runtime, click the Maintenance / System Diagnostics button in the overview area.
2. Verify that the diagnostic tree displays all AS controllers, fieldbus segments, and ET 200 remote I/O stations in green (healthy) state.
3. Simulate a module fault in the field (e.g., unplug a test digital input card or trip its auxiliary 24V DC breaker).
4. Verify that:
* A high-priority system alarm appears immediately in the Alarm List: 'Module failure: Rack x, Slot y'.
* The Maintenance Station diagnostic icon turns red on the affected rack.
* On any custom process overview mimic, the interconnected QMODF or Bad tag asserts true, turning the warning indicator red.
5. Reinsert the module or restore power; confirm automatic clearing of alarms and indicators.

Limitations and Operational Precautions

  • Do not place custom user logic inside the system @Charts; if adding S7_m_c attributes to module drivers, remember that regenerating module drivers may overwrite manual chart modifications unless managed via Master Data Library templates.
  • Avoid manually polling SFC51 RDSYSST in cyclic OBs (e.g., OB35); acyclic system status requests consume significant CPU communication bandwidth and can increase cycle times.
  • For comprehensive diagnostic coverage including SCALANCE switches, IPC hardware, and PC clients, consider licensing PCS 7 Maintenance Station Standard rather than relying solely on MS Basic.
  • Ensure all I/O modules in HW Config have diagnostic interrupts enabled in their module properties to ensure fast event-driven alarming.

Engineer FAQ

What is the difference between PCS 7 Maintenance Station Basic and Standard?

MS Basic is included with PCS 7 and provides controller, fieldbus, and I/O module diagnostics. MS Standard requires an additional license and extends diagnostics to IPC hardware health, network switches via SNMP, HART field devices via PDM, and software licensing.

Why did the QMODF output not appear in WinCC Tag Management?

Driver blocks in @Charts do not have the S7_m_c attribute enabled on their outputs by default. To create WinCC tags, you must manually set S7_m_c := 'true' on the block output in CFC and compile the OS.

How does PCS 7 generate hardware failure alarms without user programming?

The CFC Driver Wizard automatically configures 'Report System Error' (RSE) data blocks (FB125/FB126 or internal Basis Library equivalents) that listen to operating system error OBs (OB82, OB83, OB85, OB86) and trigger ALARM_8P messages.

Technical References

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Related Tags

  • Maintenance_Station
  • Hardware_Diagnostics
  • Module_Drivers
  • QMODF
  • Report_System_Error
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