Interpreting Quality Codes and Resolving Shaded Attention Icons on WinCC I/O Fields in PCS 7 APL

In SIMATIC PCS 7 Advanced Process Library (APL), a shaded yellow 'Attention' (caution/wrench) icon appearing next to a valid value in a WinCC I/O field indicates that the connected tag has an abnormal Signal Status (Quality Code). Even though the process value updates correctly, a Quality Code of 16#60 (Simulated value active) or 16#78 (Substitute value active) triggers the icon via the 'Visualize Tag Status' property. To resolve it, disable simulation on the CFC block (SimOn = 0), restore healthy field I/O, or disable status visualization on the I/O field.

Architecture of Signal Status (Quality Code) in PCS 7 APL

In SIMATIC PCS 7 with the Advanced Process Library (APL), process variables are not passed as raw elementary data types (e.g., standard REAL or BOOL). Instead, they are encapsulated within structured data types:
* Struct_Analog: Contains Value (REAL) and ST (BYTE - Signal Status).
* Struct_Digital: Contains Value (BOOL) and ST (BYTE - Signal Status).

The Signal Status (ST) conforms to the international standard IEC 61158 and NAMUR NE 107. It continuously informs downstream technological blocks and the Operator Station of the validity, origin, and measurement health of the value.

In WinCC Graphics Designer, standard APL dynamic objects and customized I/O fields utilize the property Visualize Tag Status (under Miscellaneous / Properties). When this feature is active:
* If ST = 16#80 (Good), the I/O field renders cleanly with standard text.
* If ST = 16#60 (Simulated), the I/O field renders the value but overlays a shaded yellow attention/hand symbol, alerting operators that the value does not originate from a physical transmitter.
* If ST = 16#00 (Bad), the I/O field renders a red cross or warning indicator.

APL Signal Status (ST) Hexadecimal Quality Code Matrix

Understand how the byte value of ST drives the visual display in WinCC:

Quality Code (Hex)Quality ClassificationSub-Status / DescriptionWinCC I/O Field Visual IndicatorTechnological Impact16#80GoodOK - Normal operating stateNo icon; normal textNormal automatic processing16#60Good (Simulated)Simulation active on channel or technological blockShaded Yellow Attention / Hand IconPermissives evaluate simulated value; maintenance flag set16#78UncertainProcess-related; substitute value activeYellow Attention / Triangle IconInterlocks may trigger degraded response16#00BadNon-specific failure; sensor line breakRed Cross / Diagonal Slash IconValue frozen or substituted; alarms triggered16#28BadProcess-related; out of range (overflow)Red Cross / Overflow MarkerSafety interlocks evaluate bad quality

Quality standard note: Quality codes propagate automatically through upstream channel drivers to technological blocks.

Identifying the Cause of Quality Code 16#60 (Simulated Value)

When an I/O field linked to MonAnL.PV_Out#Value displays the shaded attention icon:

Inspect CFC Block in Online Test Mode:
* Open the CFC chart containing the MonAnL block.
* Switch to Test > Watch On.
* Locate the input parameter SimOn.
* If SimOn = TRUE, the block is currently ignoring field hardware and outputting the internal simulation value (SimPV_In), forcing PV_Out.ST = 16#60.
* Change SimOn to FALSE to restore live field processing.
Check Upstream Channel Driver (Pcs7AnIn / FbAnIn):
* Trace the interconnection of MonAnL.PV_In.
* If connected to an analog input driver block (e.g., Pcs7AnIn FB1869), check the driver's SimOn input.
* If simulation is active on the driver block, it outputs 16#60, which propagates transparently through MonAnL to WinCC.
Verify Force / Maintenance Overrides in WinCC Faceplate:
* In WinCC Runtime, open the faceplate for the block.
* Open the Maintenance View or Simulation View.
* If an operator activated simulation from the faceplate, click Reset Simulation to return to live measurement.

Configuring WinCC I/O Field 'Visualize Tag Status' Properties

If the I/O field is connected to an internal calculation or non-APL tag where the quality code is unmanaged or irrelevant:

Open Picture in Graphics Designer:
* Open the .pdl screen in WinCC Graphics Designer.
* Select the affected I/O field.
Modify Miscellaneous Properties:
* Open the Object Properties window.
* Under Properties, select the Miscellaneous group.
* Locate the property: Visualize Tag Status (Tag status anzeigen).
* Change the value from Yes to No.
Save and Activate:
* Save the picture. In WinCC Runtime, the shaded attention icon will be suppressed, displaying only the numeric value.

Verification

Verify quality code resolution:
1. In CFC, confirm that SimOn = FALSE on both Pcs7AnIn and MonAnL.
2. Confirm that PV_Out.ST displays 16#80 (Good) in CFC test mode.
3. Open WinCC Runtime: Confirm that the numeric process value displays clearly in the I/O field with zero shaded attention icons.
4. Temporarily activate simulation via the faceplate: Confirm that the shaded attention icon immediately reappears, proving dynamic status tracking is healthy.

Limitations and Operational Precautions

Never suppress 'Visualize Tag Status' on critical plant safety transmitters; operators must know whether a displayed value reflects live field conditions or simulated overrides.
Simulating an analog input on a channel driver overrides wire-break alarms; ensure physical transmitters are inspected before returning loops to service.
In redundant S7-400H systems, loss of one channel on a redundant analog input module drops the quality code to 16#68 or 16#78 (Degraded / Maintenance required).

Engineer FAQ

Why does the attention icon appear if the value is changing normally?

A value can change normally while being simulated (e.g., driven by a simulation ramp or manual slider in CFC). WinCC evaluates the 'ST' (Signal Status) byte, which flags 16#60 regardless of value dynamics.