Understanding Chart-Based Runtime Group Management in SIMATIC PCS 7 - Folder Colors and Execution Organization

In SIMATIC PCS 7 V8.1 and later, the CFC editor introduces chart-based runtime group management, which alters how block execution sequences are visually represented and organized across runtime groups. When a CFC folder or runtime group icon changes color or fails to display the traditional blue folder icon, it indicates that the chart is operating under chart-oriented runtime group management rather than legacy task-oriented insertion. Under chart-based management, blocks belonging to a CFC are automatically bundled into chart-specific runtime groups within cyclic organization blocks (such as OB35), enabling the Selective Download feature for individual charts and preventing cross-chart sequence fragmentation.

Evolution of Runtime Group Management in CFC

Historically in SIMATIC PCS 7 (prior to V8.1), CFC blocks were inserted into runtime groups based strictly on task execution sequence. Whenever an engineer placed a new block into a Continuous Function Chart, the editor placed the block into the runtime group designated as the current insertion pointer within an execution OB (such as OB35 for 100ms cyclic tasks or OB1 for background cycles). If multiple charts contributed blocks to the same task without rigid organization, blocks from disparate charts became interleaved within common runtime groups. This legacy behavior made selective downloading impossible because changes to a single chart affected shared runtime groups across the entire AS.

Starting with PCS 7 V8.1 and continuing through V8.2 and V9.0, Siemens introduced 'Chart-based runtime group management' (Chart-Oriented Runtime Groups). Under this architecture, the engineering system automatically creates and maintains dedicated runtime groups linked specifically to individual CFCs. The folder icons and chart representations in the runtime editor adopt specialized color coding and visual flags to distinguish between charts managed via chart-oriented rules and those assigned manually to generic task groups.

Chart-Oriented vs Task-Oriented Runtime Groups

Understanding the architectural distinction between task-oriented and chart-oriented management is vital for maintaining predictable execution cycles and preventing CPU cycle overruns in process automation.

Architectural FeatureTask-Oriented Runtime Groups (Classic)Chart-Oriented Runtime Groups (V8.1+)Group OwnershipShared across multiple CFCs by cyclic OBDedicated to the specific parent CFCVisual RepresentationStandard blue runtime group folder iconChart-linked runtime group with chart iconSelective DownloadNot Supported (Full chart partition download only)Fully Supported for individual chartsBlock InsertionFollows manual insertion pointer in OBAutomatically grouped under chart hierarchyExecution ReorderingManual drag-and-drop within runtime groupGoverned by internal chart data flow rulesDe-allocation BehaviorDeleting chart leaves empty runtime groupsDeleting chart automatically purges runtime group

When chart-based runtime group management is enabled in the chart folder properties, creating a new CFC automatically generates runtime groups named after the chart within the target organization blocks. If a chart folder does not exhibit the anticipated blue folder icon, it signifies that the chart's blocks are either assigned to non-standard OB execution containers, managed under selective download tracking, or awaiting synchronization.

Configuration and Selective Download Workflow

To configure and maintain chart-oriented runtime groups in SIMATIC PCS 7, follow this engineering procedure:

Enable Chart-Oriented Group Management: In SIMATIC Manager, navigate to the component view, right-click the Charts folder of the S7 program, and select Object Properties. Under the Advanced or Runtime Groups tab, verify that Chart-oriented runtime group management is enabled.
Open the Runtime Editor: In the CFC Editor, open the runtime editor by selecting Options -> Edit Run Sequence (or pressing Ctrl+F5).
Inspect Chart Runtime Containers: Locate the target cyclic OB (e.g., OB35). Expand the tree to locate the dedicated runtime group corresponding to your chart name. Blocks placed within the chart are automatically contained within this group.
Manage OB Task Assignments: If specific blocks within the chart require different sampling times (e.g., a fast measurement in OB32 at 20ms and an alarm calculation in OB35 at 100ms), the chart creates distinct sub-groups within each respective OB, preserving chart traceability.
Execute Selective Download: When downloading changes to the automation system in RUN mode, select Target System -> Selective Download. The dialog identifies charts with modified runtime groups, allowing targeted compilation and transfer without disturbing unedited process units.

Verification

Execute the following validation checks to confirm proper runtime group organization and compiler behavior:

CFC Run Sequence Verification: Open the run sequence editor and verify that all blocks belonging to the CFC reside within the chart-named runtime group. Ensure that no orphan blocks reside outside the chart structure.
Chart Consistency Check: From the CFC editor, select Chart -> Check Consistency -> Entire Program. Confirm that no warnings or errors regarding fragmented runtime groups or invalid OB assignments appear.
Selective Download Test: In a test automation system or S7-PLCSIM, modify an internal parameter in the target chart. Select Selective Download and verify that the system downloads only the affected chart and its runtime group without initiating a broad program download.

Limitations and Operational Precautions

While chart-based runtime group management significantly enhances engineering efficiency and modularity, engineers must observe several operational constraints:

Mixing Management Modes: Transitioning an existing legacy project from task-oriented to chart-oriented management reorganizes runtime groups across all OBs. A full compilation and entire download in STOP mode is required if deep structural changes occur.
Execution Order Dependencies: When signals travel between charts, chart-based grouping executes blocks chart by chart. If inter-chart connections have tight timing requirements, ensure that the upstream chart executes before the downstream chart within the cyclic OB list to prevent one-cycle execution delays.
Library Upgrades: When importing older pre-V8.1 library typiclas, ensure that newly instantiated charts inherit the chart-based runtime group settings configured in the target chart folder.

Engineer FAQ

Why did my CFC folder icon change color after upgrading to PCS 7 V8.2?

PCS 7 V8.1 and V8.2 utilize differentiated visual indicators in the CFC run sequence editor to signify whether a chart uses chart-oriented runtime groups or traditional task insertion pointers. The color change confirms that the chart is registered under automated chart-based runtime group tracking for selective download.

Can I manually move blocks out of a chart-oriented runtime group?

No. In chart-oriented runtime group management, the relationship between the block and the chart's runtime group is strictly enforced. To move a block to a different task cycle (e.g., from OB35 to OB32), you change the block's task assignment, which automatically creates a corresponding chart group within the new OB.

Does chart-based runtime group management increase CPU cycle time?

The CPU execution overhead is negligible. The operating system executes blocks sequentially regardless of group grouping; however, organizing blocks strictly by chart can alter data flow order if cross-chart connections are not carefully sequenced within the cyclic task.