Documenting Technological I-O Variant Interconnections in SIMATIC PCS 7 Control Module Types (CMT)

In SIMATIC PCS 7 Control Module Types (CMT), multiple optional blocks can be interconnected to the same technological target input to define configuration variants (where only one optional block exists per instantiated control module). However, standard Chart Reference Data ('View > Block Interconnections') only parses graphical CFC connection lines and displays the single visually rendered connection, omitting dormant variant links. To comprehensively document and extract all technological I/O interconnections—including optional variant assignments—engineers must use the Technological Editor within the Master Data Library, export technological specifications via the Process Object View (POV) Technological I/Os tab, or utilize XML/CAEx exchange tools like SIMATIC PCS 7 Plant Automation Accelerator (PAA).

Control Module Types (CMT) and Optional Variant Concept

In SIMATIC PCS 7 (v8.0 and newer), the Control Module Type (CMT) architecture in the Master Data Library represents the modern object-oriented standard for process automation engineering, superseding legacy Process Tag Types (PTT). A key capability of CMT is the definition of Optional Blocks and Variants:
- A single CMT template can encompass multiple hardware or functional permutations (e.g., a standard motor with optional soft-starter, variable frequency drive, or reversing contactor).
- In the CMT template, block A.Out (standard contactor) and block B.Out (frequency drive) can both be routed to block C.In1 (interlock feedback) in the Technological I/Os definition view.
- When an engineer instantiates this CMT into the project plant hierarchy, selecting Variant 1 activates block A and deactivates block B. Selecting Variant 2 activates block B and deactivates block A.

In the Master Data Library template chart, both blocks A and B exist simultaneously. However, because CFC cannot draw two graphical wires to a single block input pin, CFC renders only the primary graphical line, while storing both potential interconnections in the underlying Technological I/O attribute table (Interconnection to...).

Understanding the Limitation of Chart Reference Data

The legacy Chart Reference Data tool (Options > Reference Data > Display) was engineered for standard Continuous Function Charts prior to the introduction of technological types.
- When selecting View > Block Interconnections, the parser evaluates the compiled CFC graphical database (pbase.db).
- It extracts strictly drawn graphical line connections.
- It completely ignores dormant technological variant definitions, optional block associations, and parameterized technological attributes that are managed by the Technological Editor.

Consequently, relying on Chart Reference Data for CMT documentation produces incomplete electrical and logical wiring schedules, creating significant validation and engineering audit risks.

Step-by-Step Procedure: Extracting Interconnections via Process Object View

The primary built-in method to export and document all technological I/O connections across CMT types and instances is the Process Object View (POV):

Step 1: Open Process Object View

In SIMATIC Manager, select View > Process Object View (or press Ctrl+Shift+P).
In the left hierarchy tree, expand the Master Data Library down to the Control Module Types catalog.

Step 2: Configure the Technological I/Os Table

In the right pane, switch to the Technological I/Os tab.
Right-click the table header, click Column Configuration, and enable:
- Control Module
- Technological I/O
- Block
- I/O
- Interconnection to
- Optional / Variant

Step 3: Filter and Review All Variant Assignments

In the filtered table, examine the rows corresponding to target inputs (e.g., Block C.In1).
Both variant connections (A.Out -> C.In1 and B.Out -> C.In1) are displayed explicitly along with their variant flags.

Step 4: Export to Excel / CSV

Select all table rows (Ctrl+A), copy (Ctrl+C), and paste directly into Microsoft Excel.
Alternatively, right-click and select Export to CSV... to generate formal engineering design records.

Technological I-O Documentation Matrix

The following table summarizes the capabilities of PCS 7 tools for documenting CMT interconnections:

Documentation ToolGraphical ConnectionsTechnological VariantsExport FormatAudit ReadinessChart Reference DataYes (Primary only)No (Completely omitted)Print / TextInsufficient for CMTProcess Object View (POV)YesYes (Full attribute data)CSV / Excel / ClipboardHigh (Standard DCS engineering)Technological EditorYesYes (Interactive view)Visual on-screenHigh (Detailed unit level)Plant Automation Accelerator (PAA)YesYes (Full lifecycle tracking)PDF Schematics / Excel / XMLFully Compliant (Enterprise standard)

Verification

To verify that all CMT variant interconnections are accurately documented and technically valid:
1. Type-Instance Synchronization Check: In the Master Data Library, select the CMT, right-click and choose Plant Types > Synchronize.... Confirm that all instantiated control modules show matching variant configurations without unresolved discrepancies.
2. Instance CFC Verification: Open an instantiated Control Module where Variant 2 was selected; verify in CFC that block B is active, block A is omitted, and the graphical connection B.Out -> C.In1 is rendered properly.
3. Compilation Check: Perform a test AS compilation (Changes only); confirm that no warnings or errors indicating 'Multiple inputs assigned' or 'Unresolved technological reference' appear in the compiler log.

Limitations and Operational Precautions

When managing CMT optional variants:
- Never attempt to manually wire two signals to the same block input pin directly inside standard CFC; multiple assignments are strictly valid only within the Technological Editor as conditional variants.
- Modifying a CMT technological interface requires synchronizing all instances across the plant hierarchy; always create a complete project archive before executing type-instance synchronization.
- Chart Reference Data remains useful for low-level memory allocation, but must never be used as the single source of truth for CMT technological signal audits.

Engineer FAQ

Can two active blocks drive the same input pin on an instantiated Control Module?

No. When a CMT is instantiated into a plant hierarchy, the engineer must select which variant applies. If two blocks attempt to write to the same input pin simultaneously during instantiation, the CFC compiler generates an error: 'Input is already interconnected'.

Where are CMT optional block definitions stored in the project database?

Optional block definitions are stored in the technological metadata catalog within the S7 program database (Technological Objects), accessible through the Technological Editor and the Process Object View.

Can I import technological interconnections back into PCS 7 from Excel?

Yes. Using the Process Object View, you can modify or define technological interconnections in Microsoft Excel and paste or import them back into the Process Object View table.