Configuring Control Module Variants and Understanding XMLTRANSFER in SIMATIC PCS 7

To configure 'Variants' on a Control Module Type (CMT) in SIMATIC PCS 7, the CMT must reside within the project's Master Data Library (MDL, identified by a blue folder icon), not directly within an external or read-only library such as the Basic Process Control Modules (BPCM) Library (green icon). In the Master Data Library, open the CMT in CFC, access the Technological Editor, and right-click the CMT root under Technological I/Os to define and parameterize Variants. Regarding XMLTRANSFER: for standard PCS 7 internal engineering, the native Synchronize Editor is used; XMLTRANSFER is an add-on software program required specifically when exchanging CMT and Equipment Module Type (EMT) technological XML schemas with external engineering tools such as Plant Automation Accelerator (PAA), COMOS, or SIMIT.

Executive Summary

Control Module Technology (CMT) streamlines PCS 7 application design by enabling reusable technological types. A critical capability of CMTs is 'Variants'—the ability to define optional functional blocks and I/O configurations (e.g., reversing vs. single-speed drives, single vs. dual limit feedbacks) under a single master type definition. However, engineers frequently find the 'Variants' contextual menu option missing or greyed out when attempting to configure CMTs copied directly from the BPCM Library into an AS project. This restriction stems from the core PCS 7 architecture: technological types and their variants can only be authored in the Master Data Library. Furthermore, confusion often arises regarding the necessity of the XMLTRANSFER utility. This article clarifies the library mechanics required for variant creation and defines the exact application scope of XMLTRANSFER.

Architecture and Fundamental Mechanics

The architectural lifecycle of Control Module Types and Variants depends on strict library boundaries and schema synchronization:

Library Hierarchy and Write Permissions:
- External/Reference Libraries (Green Folder): Catalogs such as the BPCM Library or APL are read-only manufacturer standards. They provide pre-engineered starting blocks but prohibit technological schema modifications, including Variant creation.
- Master Data Library (Blue Folder): The central repository for a multi-project. All CMTs, Equipment Module Types (EMTs), and Equipment Phase Types (EPHTs) must reside here. Only within the Master Data Library does the Technological Editor unlock schema definition tools, allowing engineers to declare optional blocks, optional signals, and technological Variants.
- Target AS Projects: Plant Hierarchy instances (Control Modules, CMs) inherit their structure from the Master Data Library. When an instance is created, the engineer selects which defined Variant to activate.
Mechanics of CMT Variants: A Variant defines a subset of the CMT's total technological envelope. Blocks and interconnections inside the CMT can be designated as 'Optional'. When a specific Variant is assigned to an instantiated CM, optional blocks not belonging to that Variant are deactivated or omitted from compilation, optimizing controller memory and scan time without proliferating distinct library types.
Role of XMLTRANSFER vs. Synchronize Editor:
- Synchronize Editor: Integrated natively into SIMATIC PCS 7. Accessible via Plant View -> AS Project -> Plant Types -> Synchronize. It compares Master Data Library types directly with AS project instances using internal engineering database records. It does not require XML files or external utilities.
- XMLTRANSFER Utility: An independent Siemens engineering tool used to export and import technological definitions as standardized XML files. It is strictly required when integrating PCS 7 with external engineering tools—primarily Plant Automation Accelerator (PAA) and COMOS—or when generating automated simulation models for SIMIT. Engineers utilizing pure PCS 7 do not require XMLTRANSFER for CMT synchronization.

Step-by-Step Implementation Procedure

Configure Control Module Variants and execute type synchronization using the following procedure:

Copy CMT to Master Data Library:
- Open the source library (e.g., BPCM_Library) in SIMATIC Manager.
- Select the desired CMT (e.g., BPCM_MotL) under Templates -> Control Module Types.
- Right-click and copy the CMT.
- Open your project's Master Data Library (blue icon), navigate to Plant Types -> Control Module Types, and paste the CMT.
Configure Optional Elements and Variants:
- Open the pasted CMT in the Master Data Library using the CFC Editor.
- Open the Technological Editor (View -> Technological Views).
- In the Technological I/Os tree, right-click any optional sub-block (e.g., an auxiliary current monitoring block or run-time meter) and mark it as Optional.
- Right-click the root CMT node in the Technological I/O tree. The Variants option is now active and selectable.
- Select Variants -> Edit Variants. Click New to define variant names (e.g., Standard_Speed, Reversing_DuoLimit).
- For each variant, check or uncheck the optional blocks and signals to define their presence.
Synchronize Types to the Multi-Project:
- Switch to Plant View in SIMATIC Manager.
- Right-click the AS project or multi-project root and select Plant Types -> Synchronize.
- Verify that the Master Data Library is selected as the source. Click Synchronize.
Assign Variants to Plant Instances:
- In Plant View, instantiate the CMT into a plant hierarchy folder.
- Open the instantiated CM in CFC.
- In the Technological Editor, locate the Variant parameter and select the desired variant from the drop-down menu.
- The CFC automatically activates or suppresses the corresponding optional blocks.

Verification

Verify proper variant instantiation and synchronization:

Technological Editor Validation: Open the instantiated CM chart. In the Technological Editor, verify that the active Variant displays the expected enabled and disabled block subsets matching the Master Data Library specification.
CFC Compilation Check: Compile CFC charts. Confirm that suppressed optional blocks within inactive variants are excluded from the execution sequence and do not generate unassigned address warnings.
Process Object View Inspection: Open Process Object View -> Control Modules tab. Verify that the Variant column correctly lists assigned variant names for each plant tag across the facility.

Limitations and Operational Precautions

Variants cannot add blocks that do not already exist in the Master Data Library CMT definition; they can only include or exclude pre-defined optional blocks. If a completely different functional architecture is required, author a separate CMT. Furthermore, do not attempt to install or invoke XMLTRANSFER unless you are actively performing XML-based round-trip engineering with COMOS, Plant Automation Accelerator (PAA), or SIMIT, as native PCS 7 type synchronization is faster and self-contained.

Engineer FAQ

Why was the 'Variants' menu item disabled when I right-clicked the CMT?

The 'Variants' option is disabled if the CMT is opened directly from a read-only external library (green folder) or from an AS project chart folder. Variants can only be authored when the CMT is located within the Master Data Library (blue folder).

Do I need to install XMLTRANSFER if I only use SIMATIC PCS 7?

No. PCS 7 provides built-in synchronization via Plant Types -> Synchronize. XMLTRANSFER is an external exchange utility only required when exporting or importing technological structures to and from COMOS, PAA, or SIMIT.

What happens to field wiring if I switch an instantiated CM to a variant that excludes a channel driver?

If an instantiated CM is switched to a variant that excludes a channel driver block, any existing physical I/O interconnection to that excluded driver is severed upon synchronization. Ensure you verify signal assignments before changing variants on live units.

Can an Equipment Module Type (EMT) contain Control Module Types with variants?

Yes. EMTs encapsulate coordinated groups of CMTs and can incorporate CMTs configured with specific technological variants.

Can I create variants based purely on parameter values rather than optional blocks?

Yes. In addition to including or excluding blocks, Variants can define standard default parameter values (e.g., standard trip limits, ramp times) specific to that variant configuration.