Using APL Blocks Manually in PCS 7: Resolving Missing Internal Tags (Memo, Lock Alarms, 'X' on Group Display)

When calling Siemens Advanced Process Library (APL) blocks (such as VlvMotL, MotL, VlvL) manually in custom charts or non-standard architectures and linking them to standard APL block icons via the Dynamic Wizard, visual defects—such as a dimmed memo icon, an open padlock, or an 'X' over the group display—occur because the AS-OS compiler has not generated the mandatory OS-internal structure tags. APL block icons rely on hidden WinCC internal tags: Tag.#TextPermanent and Tag.#StatusPermanent for operator memos, and Tag.#LockAlarms for alarm suppression. To resolve these display faults, ensure the AS block has attribute S7_m_c := 'true', compile the OS through standard Plant Hierarchy AS-OS compilation, or manually create the missing internal structure tags in WinCC Tag Management.

APL Block Icon Architecture and OS-Internal Structure Tags

In SIMATIC PCS 7, the Advanced Process Library (APL V8.1 through V9.1) integrates controller execution (AS) and operator visualization (OS) through standardized object-oriented models. When an APL block (such as VlvMotL FB1900 or MotL FB1850) is compiled via the standard AS-OS compilation wizard (Compile OS), the compiler generates two distinct sets of tags in WinCC:

AS Process Tags: External tags mapped directly to controller instance DB offsets (e.g. Motor01.FbkRun, Motor01.Open, Motor01.AutoAct).
OS-Internal Auxiliary Tags: Internal WinCC tags prefixed with # that manage HMI-exclusive features without consuming controller memory:
- #TextPermanent (Text tag 16-bit): Stores persistent operator electronic memo notes entered from faceplates.
- #StatusPermanent (DWORD): Bitmask indicating whether an active operator memo is stored (controls the memo icon).
- #LockAlarms (DWORD): Tracks alarm suppression and lock states for group display aggregation.

Root Causes of Dimmed Icons and 'X' Symbols on Group Displays

When an engineer calls APL blocks manually—or uses custom SCL/FBD chart implementations outside standard Plant Hierarchy conventions—and uses the WinCC Dynamic Wizard (Link a prototype to a structure) to connect block icons, three distinct visual errors emerge:

Dimmed Memo Icon: The memo notepad icon on the block icon header appears permanently dimmed or displays an interrogation mark. This occurs because internal tags #TextPermanent and #StatusPermanent do not exist in WinCC Tag Management.
'X' Over the Group Display: An 'X' rendered over the alarm group display indicator signifies that the block icon cannot resolve the alarm lock status word (#LockAlarms or LockAct). The icon flags that alarm suppression status is unknown.
Failed Local Mode Indication: If LocalLi signal changes in CFC but the faceplate remains in Manual, Feature.Bit24 (Local mode authorization) has not been configured in the block's feature word.

Comparison of APL Standard Generation vs Manual Tag Management

The following table compares standard AS-OS compilation with manual APL block icon binding:

Engineering WorkflowAS Tag GenerationOS-Internal Tags (#) Generated?Group Display 'X' RiskMemo System StatusStandard PCS 7 AS-OS CompileAutomatic via CFC compilerYES (Fully generated)Zero (Healthy status)100% FunctionalManual Dynamic Wizard BindingPartially boundNO (Missing internal tags)High ('X' displayed)Fails (Dimmed icon)Custom Chart-in-Chart (CFC)Automatic if S7_m_c = 'true'YES (if compiled via Plant View)LowFunctionalSCL Function Block CallManual structure definitionNO (unless authored in UDT)HighFailsTag Management Manual CreationManual tag entryYES (If created manually)ResolvedRestored to service

Step-by-Step Procedure to Resolve Missing Internal Tags

Follow this procedure to eliminate the 'X' symbol and restore full APL icon functionality:

Verify AS Block System Attributes in CFC:
- In the CFC Editor, open the chart containing the APL block (e.g. VlvMotL).
- Double-click the block to open Object Properties.
- Ensure the block has a valid name and that attribute Operator Control and Monitoring (OCM) is checked (S7_m_c := 'true').
Execute Standard AS-OS Compilation:
- The cleanest resolution is allowing PCS 7 to generate the tags natively.
- In SIMATIC Manager Plant View, right-click the OS project and select Compile.
- Select Entire OS with With memory reset.
- The compiler automatically instantiates the structure type and creates all #TextPermanent, #StatusPermanent, and #LockAlarms tags.
Alternative: Manually Creating Internal Tags in WinCC:
- If operating outside standard compilation, open WinCC Explorer -> Tag Management.
- Under Internal Tags, locate or create the structure tag group matching your block's tag prefix (e.g. VlvMotL_Unit1).
- Add the missing internal tags:
- Name: VlvMotL_Unit1.#TextPermanent | Data Type: Text tag 16-bit character set (Length: 256)
- Name: VlvMotL_Unit1.#StatusPermanent | Data Type: Unsigned 32-bit value
- Name: VlvMotL_Unit1.#LockAlarms | Data Type: Unsigned 32-bit value
Re-Link Block Icon in Graphics Designer:
- In Graphics Designer, select the block icon.
- Run the Dynamic Wizard Link a prototype to a structure or rename an existing link.
- Point the tag prefix to VlvMotL_Unit1 and confirm.

Verification

Verify block icon behavior in WinCC Runtime:
1. Start WinCC Runtime.
2. Inspect the valve block icon: verify that the 'X' over the group display is completely gone and alarm states reflect actual plant alarms.
3. Open the faceplate and click the Memo view (notepad icon). Enter a test memo note (e.g. 'Valve inspected') and click Save.
4. Confirm that the memo icon on the block icon header illuminates, indicating active memo storage.
5. In CFC, toggle LocalLi = 1; verify that the operating mode indicator updates from 'M' to 'L'.

Limitations and Operational Precautions

Manual Tag Vulnerability: Manually created internal tags in WinCC Tag Management can be deleted during a subsequent AS-OS compile with 'With memory reset' unless the block is natively part of the Plant Hierarchy. Always standardize on native Plant View compilation.
Memory Overhead: Attempting to bypass PCS 7 Multiproject compilation by calling APL blocks in raw S7 programs does not save controller RAM; APL block footprint is fixed in compiled firmware.
Small vs Large Block Types: To conserve CPU memory, use 'Small' block variants where available (e.g. MotS FB1910 and VlvS FB1911 instead of MotL/VlvL). Note that VlvMotL does not have an 'S' small variant.

Engineer FAQ

What does the 'X' over the group display mean on an APL block icon?

The 'X' indicates that the group display cannot determine the alarm suppression or lock state of the block, typically because the internal WinCC tag #LockAlarms or block status word is missing or unlinked.

Why did the memo function not work when I manually linked an APL icon?

The memo system requires two internal WinCC tags: <TagPrefix>.#TextPermanent (stores the message text) and <TagPrefix>.#StatusPermanent (tracks memo presence). These are only created automatically during a standard AS-OS compilation.

Is there a small 'S' variant for VlvMotL in APL?

No. While APL provides small variants for single-feedback drives (MotS FB1910) and two-way valves (VlvS FB1911), there is no small variant for motorized valves (VlvMotL FB1900).