C135 PCS 7 (PCS7)
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·Publicada en C135 PCS 7 (PCS7)

Managing and Renaming CFC Runtime Groups in SIMATIC PCS 7 Execution Sequences

Managing and Renaming CFC Runtime Groups in SIMATIC PCS 7 Execution Sequences

In SIMATIC PCS 7 CFC, manually renaming runtime groups in the Run Sequence editor (Edit > Run Sequence) is 100% safe for CPU execution and will not disrupt program logic or cause runtime faults, because the S7-400 operating system executes blocks based on internal machine block numbers rather than textual group names. When CFC charts are copied, runtime groups automatically append suffixes like (1). Renaming them to meaningful identifiers (matching the new chart name) restores engineering clarity. However, manual renaming permanently severs automatic name synchronization between the CFC chart and the runtime group for future chart renames.

Table of Contents

Executive Summary

Continuous Function Chart (CFC) programming in SIMATIC PCS 7 abstracts complex machine execution into modular graphical charts. Under the hood, every block placed in a CFC chart must be scheduled for execution within specific Organization Blocks (OBs), such as startup OB100 and cyclic interrupt OB35 (100 ms). To manage this execution, PCS 7 automatically groups blocks belonging to the same chart into Runtime Groups. During rapid engineering phases, automation engineers routinely duplicate standardized equipment charts (e.g. copying solenoid valve chart SOV122 twenty times in Process Object View to create SOV135 through SOV155). However, inspecting the Run Sequence reveals that the copied runtime groups retain confusing names such as SOV122(1) or SOV122(2). Engineers frequently hesitate to rename these groups, fearing broken AS-OS compilation or CPU download faults. This technical guide clarifies the execution mechanics and confirms the safety of renaming runtime groups.

CFC Runtime Groups and Controller Execution Sequence Architecture

Runtime Groups serve as organizational containers within the controller's task scheduler:

  • OB Execution Hierarchy: Organization Blocks (e.g. OB35) execute runtime groups sequentially from top to bottom.
  • Internal Block Ordering: Inside each runtime group, technological blocks (VlvL, Pcs7DiIn, Pcs7DiOu) execute in a defined order to minimize signal transport delays (e.g. inputs read first, control logic executed second, outputs written last).
  • Dynamic Group Control: Runtime groups can be conditionally enabled or disabled via logic connections to their EN input, allowing entire functional units to be bypassed during specific operational modes.

Why Copying Charts Generates Generic Suffixes like SOV122(1)

When a CFC chart is copied and renamed in SIMATIC Manager:

  • If a chart contains blocks distributed across multiple runtime groups (or contains startup blocks in OB100 and cyclic blocks in OB35), the CFC copy engine avoids making assumptions about user intent.
  • To prevent naming collisions in the target OB, CFC creates a new runtime group appending an incremental numeric index (1).
  • Renaming the chart afterwards does not retroactively rename the group once multiple blocks exist.

Safety and Operational Impact of Renaming Runtime Groups

Renaming runtime groups is completely safe:

  • Execution Indifference: The S7-400 CPU compiles runtime groups into MC7 execution lists calling standard block numbers (e.g. CALL FB1899, DB500). The textual name of the runtime group exists exclusively in the offline engineering database.
  • Zero AS-OS Impact: WinCC tag compilation and block icon generation are linked to the CFC chart name and Plant Hierarchy path, completely independent of the runtime group name.
  • The Only Tradeoff: Once a runtime group name is manually edited, CFC severs the dynamic link that would have automatically renamed the group if the chart name changes in the future.

Runtime Group Synchronization Behavior Matrix

The following table compares runtime group management operations and their system impacts:

Engineering ActionImpact on CPU ExecutionImpact on WinCC OSRequires CPU STOP?Engineering TradeoffManually Rename GroupZero Impact (100% Safe)Zero ImpactNo (Delta Compile)Restores project clarity; severs auto-rename.Move Group Between OBsAlters execution cycle (e.g. 100ms->500ms)Zero ImpactNo (Delta Compile)Modifies block execution frequency.Reorder Blocks Inside GroupEliminates 1-cycle dead timeZero ImpactNo (Delta Compile)Optimizes closed-loop response.Delete Runtime GroupDeletes block execution callsAlarms go into faultNo (Delta Compile)Blocks cease executing in AS.

Step-by-Step Procedure to Rename and Organize Runtime Groups

Method: Renaming Groups in the CFC Run Sequence Editor

  1. Open any CFC chart in the target S7 program.
  2. In the CFC Editor menu, select Edit > Run Sequence (or click the Run Sequence toolbar icon).
  3. In the left navigation pane, expand the target cyclic interrupt OB (e.g. OB35).
  4. Locate the runtime group displaying the generic name (e.g. SOV122(1)).
  5. Right-click the runtime group and select Object Properties (or press Alt + Enter).
  6. In the Name field, enter the desired name matching the actual chart (e.g. SOV135).
  7. Add an optional engineering comment (e.g. 'Solenoid valve control for Tank 102').
  8. Click OK.
  9. Repeat for the corresponding runtime group located in OB100 (Startup).
  10. Close the Run Sequence editor.
  11. Execute Chart > Compile > Changes Only and download changes to the AS in RUN.

Verification

To verify runtime group naming and execution:

  1. CFC Compile Check: Execute a delta compilation. Confirm that compilation completes with 0 errors.
  2. Online Delta Download: Download changes to the AS controller in RUN. Confirm that the download finishes bumplessly without CPU STOP.
  3. Process Functionality Audit: In CFC Test Mode, verify that the renamed blocks continue executing cyclically, processing inputs and updating outputs normally.

Limitations and Operational Precautions

  • Do Not Scramble Block Order: When organizing runtime groups, maintain proper signal flow ordering: input channel drivers must execute before control blocks, and control blocks before output drivers.
  • Runtime Group Sizing: Keep runtime groups modular; assigning too many blocks (e.g. > 100) to a single giant runtime group impairs execution scheduling.
  • Copy/Move Customization: Under Options > Customize > Copy/Move, reviewing the setting 'Interconnection to runtime groups' allows pre-configuring how runtime groups are handled during chart duplication.

Engineer FAQ

Does renaming a runtime group force a full compile of the entire program?

No. Renaming a runtime group is an offline metadata change that compiles in seconds via 'Changes Only'.

Can two runtime groups share the exact same name?

Within the same OB, runtime group names must be unique; identical names are permitted across different OBs (e.g. OB35 and OB100).

Why are there runtime groups in OB100 as well as OB35?

OB100 executes once during CPU startup to initialize block parameters; cyclic processing occurs continuously in OB35.

Technical References

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  • https://industrialautomation.net/search?query=cfc-editor
  • https://industrialautomation.net/search?query=run-sequence
  • https://industrialautomation.net/search?query=engineering-workflow
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