Locating and Monitoring SFC Type Instances in Continuous Function Chart (CFC)

In SIMATIC PCS 7, an SFC Type located in Component View (Komponentensicht) is merely an abstract function block template and cannot be monitored online directly. To monitor the active execution steps of an SFC Type in a running controller or SIMIT simulation, you must locate its instantiated block inside a Continuous Function Chart (CFC). To find where the SFC Type is placed, check its assigned FB number in its object properties, open Chart Reference Data (Plan-Referenzdaten) in CFC, select 'Block Types' (Bausteintypen), sort by S7-Name (FB number), and double-click the instance to open the CFC chart and monitor the SFC instance.

Architecture: SFC Types vs SFC Instances in SIMATIC PCS 7

In SIMATIC PCS 7, Sequential Function Charts operate under two programming models:

SFC Chart (Plan): A standalone sequential chart that compiles directly into an executable sequence for a single specific application.
SFC Type (Typ): An object-oriented, reusable state machine template. When an engineer creates an SFC Type, the compiler generates a standard Function Block (FB) with defined inputs, outputs, characteristics, and setpoints.

To execute an SFC Type in the controller, an engineer must drag the generated FB from the block catalog into a CFC chart. This creates an SFC Instance, which allocates runtime instance memory in an associated instance Data Block (DB).

Why SFC Types Cannot Be Monitored in Component View

The Component View (Komponentensicht) of SIMATIC Manager organizes project assets by hardware and software objects. Double-clicking an SFC Type in Component View opens the SFC Type Editor, which is exclusively an offline template authoring environment.

Because a single SFC Type template may be instantiated dozens of times across multiple distillation columns or reactors, the template itself possesses no live controller memory. Online monitoring (Test > Watch / Beobachten) is strictly permitted only on specific, instantiated SFC blocks inside CFC charts.

Method 1: Locating SFC Instances via Chart Reference Data

Follow this systematic method to trace any SFC Type instance:

Identify the Assigned FB Number:
- In Component View, navigate to the AS Chart folder (Pläne).
- Right-click the target SFC Type and select Object Properties.
- On the General tab, note the assigned FB Number (e.g., FB 1050).
Open Chart Reference Data (Plan-Referenzdaten):
- Open any CFC chart in the project.
- From the top menu, select Options > Chart Reference Data (or click the yellow cross icon Ctrl+R).
Filter by Block Types:
- In the reference data window, select View > Block Types (Bausteintypen).
- Click the column header S7-Name to sort numerically; scroll to find your FB number (e.g. FB 1050).
- The list displays every CFC chart, hierarchy folder, and block instance name where the SFC Type is placed.
Jump to Instance: Double-click the desired entry; the CFC editor opens automatically and selects the block.

Method 2: Locating SFC Instances via Technological Plant View

If the project is engineered using the Plant Hierarchy (Technologische Sicht):

Navigate through the plant folders representing equipment units (e.g., Distillation_Plant > Column_01 > Phase_Heating).
Open the CFC charts residing within that equipment folder.
Look for block instances displaying the SFC symbol icon in their header.

Opening and Monitoring the Running SFC Instance Online

Once the block is located in CFC:

Right-click the block header of the SFC instance in the CFC chart.
Select Open (or double-click the block body).
The SFC Instance window opens, displaying the specific step sequence, active timers, and transition flags.
Click the Test Mode (Glasses icon / Test > Watch) on the toolbar to monitor live step transitions in real time.

Comparison of SFC Types vs SFC Instances

The table below contrasts the characteristics of SFC Types versus SFC Instances:

| Characteristic | SFC Type (Template) | SFC Instance (Runtime Object) |
|---|---|---|---|
| Storage Location | Component View (Chart folder) | CFC Chart (Plant Hierarchy) |
| Underlying S7 Object | Function Block (FB Type) | Placed FB with Instance DB |
| Execution Capability | Cannot run independently | Executes cyclically in OB3x |
| Online Monitoring | Not possible (Template only) | Full live step and timer monitoring |
| Modification Scope | Changes affect all instances | Modifies parameters of this instance only |
| WinCC Faceplate | Generates @pg_@sfc_type template | Opens specific instance faceplate |

Verification

Verify live monitoring of the SFC instance:

Open the SFC instance window from CFC.
Switch the view to Online (Test > Watch).
Verify that the active step is highlighted with a green background.
Trigger a step advance condition in SIMIT or the controller; confirm that the active step transitions smoothly to the next step.
Confirm that step elapsed times (T_Step) increment dynamically.

Limitations and Operational Precautions

Observe the following safeguards when working with SFC Types:

Template Compilation Impact: Modifying an SFC Type in Component View and compiling changes updates the interface of ALL placed instances across the entire plant, requiring a delta download to the CPU.
Multiple Instances: Always verify which specific instance you are monitoring if a plant has multiple identical distillation columns.
SIMIT Interconnection: Ensure SIMIT simulation models write to the process image inputs mapped to the SFC instance parameters.

Engineer FAQ

Why can't I click the 'Watch' (glasses) icon on an SFC Type in Component View?

An SFC Type in Component View is an abstract type template, not an executing controller instance. You must open the specific SFC instance placed inside a CFC chart to monitor live controller memory.

Can I edit steps and transitions directly on an SFC instance in CFC?

No. The step and transition topology of an SFC Type instance is locked to the master template. To modify the sequence logic, you must edit the SFC Type master in Component View and recompile.