Configuring the WinCC Extended Status Display for SIMATIC PCS 7 APL Blocks - Mapping CFC Status Words to Bit Indexes

In SIMATIC PCS 7 Advanced Process Library (APL) block icons, the WinCC Extended Status Display (ESD) does not map CFC status DWORD outputs 1-to-1 to its internal status word slots. Instead, the ESD is a combinatorial decoding engine that accepts up to four input status words and generates binary state indexes based on configured bit conditions. In standard APL motor blocks like MotL, the block icon connects CFC output 'Status2' (which holds run, stop, starting, and stopping bits 20-23) to the ESD's 'Status1' input property. Consequently, configuring 'from status word 1' inside the ESD configuration dialog evaluates the bits of CFC Status2.

The Architecture of the WinCC Extended Status Display (ESD)

The Extended Status Display is a core WinCC graphic object widely employed across SIMATIC PCS 7 APL block icons and faceplates to achieve multi-state dynamic visualization without writing complex C-scripts or VBScripts.
- Underlying Principle: The ESD evaluates up to four 32-bit double words (DWORDs) assigned to its input properties (Status1, Status2, Status3, Status4).
- Bit Selection: For each active status word, the engineer configures specific bit positions to evaluate.
- Index Generation: The object calculates a numerical index ($0, 1, 2, \dots, N-1$) representing the exact binary combination of the selected bits:
$$\text{Total State Indexes} = 2^k$$
where $k$ is the total number of evaluated bits across all enabled status words.
- Image Association: Each resulting index is assigned a distinct Enhanced Metafile (.emf) or bitmap graphic from the project GraCS library.

CFC Status Word Bit Allocation vs ESD Internal Status Words

A frequent source of engineering confusion arises from the naming convention between the CFC function block and the WinCC Customized Object:
1. The CFC Block Perspective (APL MotL FB 1850):
- Status1: Collects operating modes (Auto, Manual, Local, Out of Service), interlock states, and simulation flags.
- Status2: Collects physical actuator states:
* Bit 20: Stopped
* Bit 21: Stopping
* Bit 22: Starting
* Bit 23: Running
- Status3: Collects interlock bypasses and detailed permission signals.
- Status4: Collects auxiliary states and customized user bits.
2. The WinCC Block Icon Perspective (@MotL/1):
- The block icon is a Customized Object containing an internal ESD object named Symbol1.
- The developer who designed the APL block icon linked the block icon's external property Status directly to CFC Status2.
- Internally, this property is wired to Symbol1.Status1.
- Therefore, inside the ESD configuration dialog, selecting from status word 1 does NOT query CFC Status1; it queries the DWORD connected to the ESD's first input slot, which is CFC Status2.

Combinatorial Truth Tables and State Index Generation

To understand how the ESD generates indexes for animation, consider evaluating two bits from status word 1:

Two-Bit Configuration:
- Configure Bit 20 (Stopped) and Bit 23 (Running).
- This creates $2^2 = 4$ discrete states:
- Index 0: Bit 20 = 0 AND Bit 23 = 0 (Undefined / Transition) $\rightarrow$ Assign apl_bi_MotL_err.emf
- Index 1: Bit 20 = 1 AND Bit 23 = 0 (Stopped) $\rightarrow$ Assign apl_bi_MotL_off.emf
- Index 2: Bit 20 = 0 AND Bit 23 = 1 (Running) $\rightarrow$ Assign apl_bi_MotL_on.emf
- Index 3: Bit 20 = 1 AND Bit 23 = 1 (Fault / Inconsistent) $\rightarrow$ Assign apl_bi_MotL_err.emf
Multi-Status Word Combinations:
- The ESD can evaluate Bit 23 (Running) from Status Word 1 (CFC Status2) and Bit 0 (Automatic Mode) from Status Word 2 (CFC Status1).
- This yields 4 indexes allowing distinct graphics for: Manual Stopped, Auto Stopped, Manual Running, and Auto Running.
Alarm Group Value Integration:
- By enabling the Use group value for display checkbox in the ESD properties, the object expands its state table to incorporate alarm acknowledgment states (Unacknowledged Alarm, Acknowledged Alarm) directly into the index hierarchy.

APL MotL Status2 Bit Allocation and ESD Index Mapping Table

The following table details the mapping of CFC MotL.Status2 bits to the Extended Status Display runtime indexes:

Evaluated Bit in Status Word 1CFC Signal OriginBinary StateGenerated ESD IndexVisual State in WinCC RuntimeAssigned Graphic FileBit 20MotL.Status2.Bit201 (others 0)Index 1Motor Stopped (Idle)apl_bi_MotL_off.emfBit 21MotL.Status2.Bit211 (others 0)Index 2Motor Stopping (Transition)apl_bi_MotL_off_down.emfBit 22MotL.Status2.Bit221 (others 0)Index 4Motor Starting (Transition)apl_bi_MotL_on_up.emfBit 23MotL.Status2.Bit231 (others 0)Index 8Motor Running (Nominal)apl_bi_MotL_on.emfNone ActiveAll zero0 (all)Index 0Invalid / No Feedbackapl_bi_MotL_err.emfMultiple ActiveConflicting feedbackMultiple 1sComposite IndexSensor Contradiction / Faultapl_bi_MotL_err.emf

Verification

To verify Extended Status Display bit mapping in WinCC:
1. Open the CFC chart containing the motor block in test mode and force the motor into Stopped mode (FbkRun = 0, Run = 0). Verify in CFC that Status2 has bit 20 = TRUE.
2. Open WinCC Runtime and verify the motor block icon displays the stopped graphic (apl_bi_MotL_off.emf).
3. Start the motor and observe the transition:
- When Run = 1 and feedback is pending, bit 22 activates, triggering Index 4 (apl_bi_MotL_on_up.emf).
- When FbkRun = 1 confirms running status, bit 23 activates, triggering Index 8 (apl_bi_MotL_on.emf).
4. If an unexpected image appears, open the ESD configuration dialog in Graphics Designer, verify the bit assignments under Status Word 1, and cross-check the assigned image against the active index in the Assign Pictures grid.

Limitations and Operational Precautions

When configuring the WinCC Extended Status Display:
1. Maximum Bit Limit: Do not select more than 6 to 8 total bits across all status words. Every additional bit doubles the index count ($2^8 = 256$ indexes), making manual graphic assignment error-prone and increasing memory consumption.
2. Property Naming Mismatch: Always check the Customized Object's internal property mapping. An external property labeled Status1 on the block icon wrapper may be mapped to Status2 on the internal ESD object.
3. Runtime Restarts: Modifying picture assignments inside an existing ESD instance sometimes requires stopping and restarting WinCC Runtime to clear GDI image caches.

Engineer FAQ

Why does the ESD show 'from status word 1' when my CFC motor status is in Status2?

Because the block icon's Customized Object links CFC tag 'Status2' to the ESD's internal 'Status1' property slot. The ESD numbers its slots 1 to 4 regardless of what external CFC tag name is connected to them.

How many distinct status words can a single Extended Status Display evaluate?

The Extended Status Display supports up to 4 independent 32-bit DWORD status words simultaneously.

Can the Extended Status Display evaluate negative numbers or floating-point values?

No. The ESD evaluates DWORD bit patterns exclusively. It cannot perform threshold comparisons (> or <) on REAL or INTEGER values. For analog range indicators, use the standard Bar Graph or Extended Analog Status Display.

What does the 'Use group value for display' option do in the ESD?

It superimposes the collective alarm state (e.g., unacknowledged alarm flashing, acknowledged alarm steady) from an associated Group Display object onto the status display indexes, multiplying the available states.