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Creating Multi-Bit Dynamic Status Logic for Custom Block Icons in PCS 7 Graphic Designer

Creating Multi-Bit Dynamic Status Logic for Custom Block Icons in PCS 7 Graphic Designer

In SIMATIC PCS 7 WinCC Graphic Designer, custom block icons should not evaluate multiple individual input tags across the network using complex boolean expressions in Dynamic Dialogs. Instead, follow the standard PCS 7 Advanced Process Library (APL) design pattern: pack binary input states into a structured DWORD status output (such as Status1 or Status2) within the S7 control block in CFC, and bind the block icon's visual elements to this DWORD using bit-masking in the Extended Status Display or Dynamic Dialog. This ensures high-speed graphic performance and full compatibility with the 'Create/update block icons' OS compilation wizard.

Table of Contents

Architecture of Dynamic State Visualization in PCS 7 Block Icons

In SIMATIC PCS 7, the Human-Machine Interface (HMI) visualizes field equipment through standardized Block Icons instantiated in WinCC Graphic Designer (.pdl process pictures). These block icons display real-time operational states, alarm conditions, interlocks, and operating modes for motors, valves, analog transmitters, and custom technological function blocks.

When designing custom block icons representing multi-input logic—such as displaying Circle 1 when In1 OR In2 is active, and displaying Circle 2 when In3 AND In4 are active—engineers must adhere to the PCS 7 graphical subsystem architecture:
* The OS Compilation Wizard: During OS Compilation, the Create/update block icons function parses CFC charts for blocks marked with S7_m_c := 'true' and instantiates block icons based on templates in @PCS7Typicals.pdl.
* Dynamic Property Binding: The wizard automatically binds the block icon's internal container properties (#tag, #type, #tag_parent) to the technological block tag name in the WinCC tag management database.
* Graphic Runtime Execution: In runtime, the Graphics Runtime subsystem (gcsrv.exe / pdlrt.exe) continuously polls the WinCC tag database. If graphic elements rely on ad-hoc network queries or inefficient scripting, runtime performance quickly degrades.

Why Individual Tag Boolean Expressions Cause Performance Degradation

A common design misstep is configuring Dynamic Dialogs or C/VBS scripts on graphic elements that directly reference multiple independent tag names across the network:
* Network and Tag Logging Overhead: Querying Tank1/Block1.In1, Tank1/Block1.In2, Tank1/Block1.In3, and Tank1/Block1.In4 as four separate WinCC tags forces the channel driver (Named Connections) to establish four cyclic read subscriptions for a single graphic icon. In a plant with hundreds of block icons, this quadruples the cyclic tag exchange volume.
* Loss of Template Automation: Hardcoding tag expressions like xxx/Block1.In1 || xxx/Block1.In2 breaks the automatic tag prefixing mechanism. When the block icon is duplicated across multiple process pictures via the OS compiler, the wizard cannot resolve generic #tag substitutions within arbitrary boolean expressions, resulting in broken tags (indicated by yellow exclamation marks or grayed displays in runtime).
* Asynchronous Jitter: Because separate tags may arrive in WinCC across different communication cycles, compound expressions like In3 && In4 can suffer from race conditions or transient flickering.

The APL Standard Pattern: DWORD Status Words and Bit-Masking

To achieve optimal performance and deterministic visualization, Siemens standardized the Status Word Pattern across all Advanced Process Library (APL) and Industry Library (IL) blocks:

  1. AS-Side Packing (SCL / CFC):
    The control block groups all internal digital statuses, mode flags, and input conditions into one or more 32-bit Double Words (e.g., Status1, Status2, Status3 of type DWORD). The block assigns each state to a dedicated bit position:
    * Bit 0: In1
    * Bit 1: In2
    * Bit 2: In3
    * Bit 3: In4
  2. WinCC Tag Optimization:
    Only the single Status1 tag is declared with the attribute S7_m_c := 'true'. The OS compilation wizard creates a single 32-bit tag in WinCC, reducing communication cycles by 75%.
  3. OS-Side Bit Mask Evaluation:
    The block icon evaluates the bits using bitwise masking:
    * Circle 1 Visibility: Evaluates (Status1 & 16#00000003) != 0 (True if Bit 0 OR Bit 1 is set).
    * Circle 2 Visibility: Evaluates (Status1 & 16#0000000C) == 16#0000000C (True if both Bit 2 AND Bit 3 are set).

Configuring Extended Status Display vs Dynamic Dialog Bit Masks

WinCC provides two proven mechanisms to evaluate bit-masked DWORD tags on block icons:

  • Extended Status Display (ExtendedStatusDisplay):
    This is the native APL graphic object. It allows the engineer to define multiple bit patterns (masks) directly in its configuration table. Each matching mask displays a specific SVG/EMF graphic or icon index. It delivers the highest rendering performance with zero script compilation overhead.
  • Dynamic Dialog with Bit Expression:
    On the graphic element (e.g., a circle or polygon), open Properties > Display > Visible, right-click the dynamic light bulb, and select Dynamic Dialog:
  • Set Data Type to Bit.
  • Select the dynamic tag: . followed by the status tag name (e.g., .Status1). The leading dot tells WinCC to prepend the block icon's #tag prefix automatically.
  • Define the bit mask: Check the specific bit or evaluate the numeric expression using C bitwise operators (&, |).
  • Assign colors or visibility states (Yes/No) corresponding to the evaluated states.

Comparison of Dynamic Visualization Techniques in WinCC

The following table compares the different dynamic visualization methods for custom block icons:

CriterionMulti-Tag Dynamic DialogC / VBS Script TriggerExtended Status DisplayDWORD Dynamic Dialog Bit MaskCyclic Tag Count4+ tags per icon4+ tags per icon1 DWORD tag per icon1 DWORD tag per iconCommunication LoadHigh (multiple cyclic reads)High (script queue overhead)Minimal (single packed tag)Minimal (single packed tag)OS Wizard CompatibleNo (breaks tag prefixing)Difficult (requires GetTagChar)Fully native APL standardFully native standardExecution PerformanceModeratePoor (can choke script queue)Maximum (native C++ renderer)High (compiled internal logic)Engineering EffortLow for one icon; unscalableHigh (complex scripting)Low (declarative table)Low (standard bit selection)Recommended DeploymentSimple isolated test graphicsAvoid on block iconsHighly recommended for APLRecommended for custom blocks

Step-by-Step Implementation of Custom Multi-Bit Dynamic Icons

Follow these steps to create an automated, high-performance custom block icon:

  1. Pack Bits in the S7 Control Block (SCL):
    In the S7-SCL block code, define Status1 : DWORD; under VAR_OUTPUT with { S7_m_c := 'true' }.
    Pack the logic inside the execution block:
    scl Status1 := 16#00000000; IF In1 THEN Status1 := Status1 OR 16#00000001; END_IF; IF In2 THEN Status1 := Status1 OR 16#00000002; END_IF; IF In3 THEN Status1 := Status1 OR 16#00000004; END_IF; IF In4 THEN Status1 := Status1 OR 16#00000008; END_IF;
  2. Compile S7 Block and Transfer to CFC:
    Compile the SCL code, instantiate the block in a CFC chart, and verify that the block's Create block icon property is enabled.
  3. Create the Template Icon in @PCS7Typicals.pdl:
    * Open @PCS7Typicals.pdl in WinCC Graphic Designer.
    * Group the visual elements (the two circles and background border) into a Custom Object.
    * In User Objects > Edit User Object, expose the properties type (e.g., @MYBLOCK/1), tag, and servername.
  4. Configure Dynamics for Circle 1 (OR Logic):
    * Select Circle 1 inside the custom object.
    * Under Properties > Miscellaneous > Visible, open Dynamic Dialog.
    * Tag: .Status1.
    * Expression: (.Status1 & 3) > 0.
    * Result: If True -> Yes, If False -> No.
  5. Configure Dynamics for Circle 2 (AND Logic):
    * Select Circle 2 inside the custom object.
    * Under Properties > Miscellaneous > Visible, open Dynamic Dialog.
    * Tag: .Status1.
    * Expression: (.Status1 & 12) == 12.
    * Result: If True -> Yes, If False -> No.
  6. Compile OS:
    Execute Compile OS with "Create/update block icons" selected. The wizard instantiates the block icon in target pictures and automatically connects .Status1 to the specific instance tag.

Verification

Verify correct dynamic behavior using the following steps:
1. In CFC, open the chart in Test Mode and force In1 = 1 and In2 = 0. Confirm in WinCC Runtime that Circle 1 becomes visible while Circle 2 remains hidden.
2. In CFC, force In3 = 1 and In4 = 0. Confirm that Circle 2 remains hidden. Then force In4 = 1; confirm Circle 2 immediately displays.
3. Open WinCC Channel Diagnosis (WinCCChannelDiagnosis.exe) and verify that only a single cyclic request exists for Status1, confirming zero communication bloat.
4. Check the APIDiag / WinCC system diagnostics console (diagnose.log) to confirm there are no tag evaluation errors or unresolved tag prefixes.

Limitations and Operational Precautions

  • Leading Dot in Tag Names: In the block icon's Dynamic Dialog, the tag name must always begin with a period (e.g., .Status1). Omitting the leading period prevents the WinCC Picture Tree Manager and block icon wizard from prepending the parent tag name.
  • Editing Master Templates: Always edit @PCS7Typicals.pdl or a custom typicals file (e.g., @PCS7Typicals_Custom.pdl). Never manually modify generated icons directly on target process screens, as running "Create/update block icons" will overwrite manual changes.
  • Tag Type Consistency: Ensure the variable type in CFC matches WinCC Tag Management exactly (S7 DWORD maps to WinCC 32-bit unsigned value). Mismatched sign interpretation can corrupt high-order bit masking (Bit 31).
  • Commercial Accuracy: Standard WinCC Runtime and Engineering packages (6AV6381-2BM07-5AX0 or 6ES7658-2CX58-0YB5) must be licensed appropriately based on total OS process objects and archive tags. Validate with an authorized Siemens distributor quotation.

Engineer FAQ

Can I use C-scripts inside the block icon to evaluate the dynamic logic?

While C-actions can evaluate bit states, using scripts inside block icons is strongly discouraged by Siemens. If a screen contains 50 block icons, 50 cyclic C-scripts execute simultaneously, placing severe load on the WinCC script processing queue and causing visible UI lag. Dynamic Dialogs and Extended Status Displays execute compiled C++ code inside the graphics engine, offering drastically superior performance.

What happens if I need to evaluate more than 32 binary conditions?

Standard PCS 7 blocks create multiple status words (Status1, Status2, Status3, Status4). For example, APL motor blocks use Status1 for operating states, Status2 for interlocks, and Status3 for monitoring flags.

Why does my block icon lose its dynamic connections after recompiling the OS?

If you manually drew the icon directly in the process picture rather than instantiating it from @PCS7Typicals.pdl, the OS compilation wizard replaces the block icon with the template from @PCS7Typicals.pdl, wiping out your local edits. All custom designs must be saved inside @PCS7Typicals.pdl.

Does packing variables into a DWORD in S7-400 CPU consume more memory?

No. Packing 32 booleans into a single DWORD consumes exactly 4 bytes of data block memory and generates 1 WinCC tag. Storing 32 individual booleans with OS attributes consumes significantly more memory and creates 32 separate WinCC tags, which inflates tag licensing and communication buffers.

Technical References

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Related Tags

  • WinCC Graphic Designer
  • Block Icons
  • APL
  • Status Word
  • Dynamic Dialog
  • PCS 7 HMI
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