SIMATIC AX Meets TIA Portal V21
Code-Based PLC Programming with AI
Siemens is converging TIA Portal and SIMATIC AX into a unified code-based workflow. T-IA Connect bridges both worlds through the MCP protocol — giving you AI-powered PLC programming today, on any version.
The Evolution: From XML to Code
For years, TIA Portal stored PLC logic as proprietary SimaticML (XML). Editing blocks outside TIA meant wrestling with complex XML trees. SIMATIC AX changed this with a VS Code-based IDE and text-first approach — but it required leaving TIA Portal entirely.
With TIA Portal V21, Siemens introduces SIMATIC Source Documents (.s7dcl for code, .s7res for comments/i18n). This is the convergence point: TIA Portal now supports the same text-based format that SIMATIC AX pioneered. Code can be versioned with Git, diffed like normal source, and generated programmatically.
T-IA Connect has supported this transition from day one. Our MCP server already generates SCL code and injects it into TIA Portal through the Openness API — no XML manipulation required. With V21's Source Documents, this workflow becomes even more powerful.
What is SIMATIC AX?
SIMATIC AX is Siemens' next-generation PLC development environment built on VS Code. It brings modern software engineering practices to industrial automation: Git version control, unit testing (AxUnit), package management (apax), namespaces, OOP with classes and interfaces, and CI/CD pipelines.
While SIMATIC AX represents the future of Siemens PLC programming, most engineers still work in TIA Portal — and will for years to come. The question isn't 'AX or TIA Portal?' but rather 'How do I get the benefits of both?'
TIA Portal V21: The Bridge to Code-Based Workflows
Key changes that bring SIMATIC AX concepts into TIA Portal
Source Documents (.s7dcl)
Text-based representation of PLC blocks replacing XML. LAD uses wire#powerrail/Contact()/Coil() syntax, FBD uses direct assignment. Pragma headers define metadata (S7_Optimized, S7_PreferredLanguage, S7_Version).
Modular DLL Architecture
The monolithic Siemens.Engineering.dll is split into domain-specific assemblies: Base, Step7, Safety, WinCC, WinCCUnified, Startdrive. Each can be loaded independently.
Version Control Interface (VCI)
Native Git/SVN integration with workspaces, automatic .s7dcl synchronization, and visual diff inside TIA Portal. Finally, PLC code gets proper version control.
Named Value Types (NVT)
Real enum support with named values and automatic reference updates on rename. Proper refactoring comes to PLC programming.
ObjectIdentifierProvider
Persistent unique IDs for project objects. IDs survive project close/reopen and object moves. Enables O(1) object resolution instead of tree traversal.
AddIn Framework (89+ types)
10 new namespaces for TIA Portal add-ins: context menus, workflows, CAX import/export, safety compilation hooks, version control integration. T-IA Connect leverages this for deeper integration.
How T-IA Connect Bridges AX and TIA Portal
You don't have to choose between SIMATIC AX and TIA Portal. T-IA Connect's MCP server gives you the code-based, AI-powered workflow of AX while staying in TIA Portal.
Write PLC code in VS Code or Cursor with AI assistance, and T-IA Connect handles the injection into TIA Portal through the Openness API. Your AI sees your project context (UDTs, tags, existing blocks) and generates code that compiles on the first try.
VS Code + Any AI Model
Work in VS Code or Cursor with Claude, GPT, Llama, or any MCP-compatible model. Describe your automation logic in natural language, get compilable SCL code injected directly into TIA Portal.
V17 Through V21 Support
Unlike SIMATIC AX which requires the latest TIA version, T-IA Connect works with V17, V18, V19, V20, and V21. Modernize your workflow without upgrading your entire tool chain.
60+ MCP Tools
Create blocks, read UDTs, manage tags, compile, simulate with PLCSim, configure HMI screens — all through the open MCP protocol that any AI can use.
Git-Ready Workflows
Export block source code, track changes, and integrate with your existing CI/CD pipeline. With V21's VCI support, T-IA Connect can orchestrate full version-controlled automation projects.
SIMATIC AX vs TIA Portal + T-IA Connect
Two paths to modern PLC development — one requires a complete migration, the other works with your existing projects
| Capability | SIMATIC AX | TIA Portal + T-IA Connect |
|---|---|---|
| IDE | VS Code (built-in) | VS Code, Cursor, Windsurf + TIA Portal |
| AI Integration | Manual (no native AI) | Native MCP — any LLM with full project context |
| Version Control | Native Git | Via VCI (V21) or export/import workflows |
| Unit Testing | AxUnit (built-in) | PLCSim simulation via API |
| TIA Portal Versions | Latest only | V17, V18, V19, V20, V21 |
| Existing Projects | Migration required | Works with existing projects as-is |
| HMI / Drives / Safety | Limited scope | Full TIA Portal feature set via Openness |
| Offline AI | Not available | Ollama / vLLM with local models |
The Future is Code-Based — And It's Here Today
SIMATIC AX is Siemens' vision for the future of PLC programming. TIA Portal V21's Source Documents and VCI integration prove that Siemens is actively converging both platforms. In 3-5 years, the line between AX and TIA Portal will blur completely.
T-IA Connect lets you adopt this code-based, AI-assisted workflow today — without waiting for SIMATIC AX maturity, without migrating your projects, and without abandoning TIA Portal's full feature set. Start modern, stay compatible.
Frequently Asked Questions
Do I need SIMATIC AX to use T-IA Connect?
No. T-IA Connect works directly with TIA Portal (V17-V21) through the Openness API. You get the VS Code + AI workflow benefits without needing SIMATIC AX at all.
Will T-IA Connect support SIMATIC AX natively?
We are actively working on SIMATIC AX integration. The MCP protocol is tool-agnostic, so extending support to AX projects is a natural evolution. T-IA Connect V20/V21 already leverages the new Source Document format.
What are .s7dcl files?
SIMATIC Source Documents (.s7dcl) are the new text-based representation of PLC blocks introduced in TIA Portal V21. They contain the block interface and code in a human-readable format, replacing the old XML-based SimaticML. They can be versioned with Git and generated programmatically.
Can I use SIMATIC AX and TIA Portal on the same project?
Siemens is working on interoperability between AX and TIA Portal through the Source Document format. T-IA Connect's MCP server can work with both environments, making it the ideal bridge during the transition period.