Resolving Missing Interlock Comments and Signal Descriptions on PCS 7 Faceplates

When signal descriptions or comments on interlock inputs ('In01', 'In02', etc.) fail to appear on WinCC APL Interlock faceplates ('Intlk02', 'Intlk04', 'Intlk08'), the cause is typically missing parameter comments in the CFC chart or uncompiled OS text references. To resolve this, open the CFC chart, double-click the interlock block input pins, and enter descriptive text in the 'Comment' field (or assign symbolic tag comments in the Symbol Table). Then, execute a full or changes-only OS compilation in SIMATIC Manager with 'Tags and messages' selected to transfer block texts into the WinCC Text Library.

Executive Summary

In process control visualization, APL Interlock faceplates are designed to provide operators with clear, descriptive explanations of process trip causes—such as 'High Discharge Pressure' or 'Lube Oil Low'—directly alongside bypass buttons and status LEDs. A frequent frustration during plant commissioning occurs when interlock faceplates open, but all input lines display generic placeholders like 'In01' or remain completely blank. This guide details the text propagation pipeline from CFC parameter comments into the WinCC Text Library and provides the step-by-step resolution workflow.

Architecture and Fundamental Mechanics

Interlock Text Propagation Architecture in PCS 7:

The Text Propagation Pipeline:
1. CFC Block Input Parameter Comment: The primary source for faceplate input text is the Comment attribute of the block parameter (e.g., Intlk04.In01.Comment).
2. Symbol Table Interconnection Comment: If the input pin is interconnected to a symbolic I/O tag (e.g., PIT_101_HH), CFC can inherit the comment from the Symbol Table.
3. OS Compilation (AS-to-OS Text Transfer): During OS compile, WinCC extracts block parameter comments and writes them into internal WinCC text references and the Text Library (TextDistributor).
Failure Mechanisms:
If the engineer interconnected a raw bit or left the parameter comment empty, WinCC displays the default pin identifier (In01).
If the OS was not compiled after editing comments in CFC, WinCC Runtime continues serving stale or empty strings from the local SQL database.

Step-by-Step Implementation Procedure

Step-by-Step Procedure to Populate Interlock Faceplate Comments:

Enter Descriptive Comments on the Interlock Block in CFC:
- Open the CFC chart containing the Intlk02 / Intlk04 / Intlk08 block.
- Right-click the input pin (e.g., In01) -> select Object Properties.
- In the Comment field, type the operator-facing text (e.g., High Tank Level LSH-101).
- Repeat for In02, In03, In04.
- Click OK.
Inherit Comments from Interconnections (Alternative):
- If interconnected to an upstream technological block or channel driver, right-click the pin -> select 'Interconnection to chart I/O' or verify that the connected signal has a valid Symbol Table comment.
Compile the OS Project:
- In SIMATIC Manager, select the OS -> right-click -> Compile.
- In the compile wizard, select Scope: Tags and messages -> Changes only (or 'Entire OS' if texts fail to update).
- Complete the compile wizard.
Verify in WinCC Text Library:
- Open WinCC Explorer -> open Text Library.
- Search for your interlock block name; confirm the descriptive comments appear under the active language column (e.g., English / German).
Test Runtime Faceplate:
- Open the interlock faceplate in WinCC Runtime; confirm each input line displays its full descriptive text.

Verification

To verify text display:
1. In WinCC Runtime, open the faceplate of the interlock block.
2. Verify that In01 through In04 display meaningful process descriptions rather than generic pin names.
3. Switch the runtime language (e.g., from English to German); verify that multi-lingual descriptions translate properly if dual languages were compiled.

Limitations and Operational Precautions

Operational precautions:
- Keep interlock parameter comments concise (<40 characters) so they fit comfortably on the standard APL faceplate dialog width without truncating.
- If editing texts directly inside the WinCC Text Library, subsequent OS compilations can overwrite manual edits unless changes are made in the source CFC charts.
- For multi-user engineering, ensure that chart changes are checked in before triggering the OS compile.

Engineer FAQ

Where do interlock faceplate comments come from in PCS 7?

From the 'Comment' property of the input pins (In01, In02, etc.) on the Interlock block in the CFC chart.

Why does my faceplate still say 'In01' after editing the comment in CFC?

Because the OS project has not been compiled after editing the CFC comment, or the compile scope excluded messages and texts.

Can interlock faceplate comments be multilingual?

Yes, by configuring multi-language project texts in SIMATIC Manager (Options -> Managing Multilingual Texts) and compiling into WinCC.

Does editing a parameter comment in CFC require a CPU STOP?

No. Parameter comments are documentation attributes; editing them only requires an OS compile, not a CPU stop or even an AS download.

Can interlock descriptions be pulled directly from the Symbol Table?

Yes, if the interlock input is directly interconnected to a symbolic I/O address, CFC can inherit the comment.

Technical References

Related Tags

Interlock Faceplate
Parameter Comments
OS Compile
Text Library
APL Interlock

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Resolving Missing Interlock Comments and Signal Descriptions on PCS 7 Faceplates