SIMATIC AX for TIA Portal Engineers

Why this guide exists

I am a controls engineer who has spent years in TIA Portal. When Siemens released SIMATIC AX, I did not want a marketing summary — I wanted to know what actually changes when you program a PLC from a text editor and a command line instead of a graphical engineering tool.

So I started working through it in public. Every article below is something I built, ran, or broke on my own machine, and where a thing did not work, I said so. That includes the parts where SIMATIC AX is clearly not finished yet.

If you already know TIA Portal, this guide is written for you. I explain each AX concept by pointing at the TIA Portal thing it replaces, because that is how I had to learn it myself.

Start here

If you are new to SIMATIC AX, these three answer the questions most TIA Portal engineers ask first.

• What Is the Future PLC Programming Tool of Siemens: Simatic AX or TIA Portal? — whether AX replaces TIA Portal, and what Siemens appears to be aiming at.
• SIMATIC AX Project Structure Explained for TIA Portal Engineers — a direct mapping from OBs, FBs, FCs, DBs and tag tables to their AX equivalents.
• Two Types of SIMATIC AX Projects — Full AX vs TIA Portal Hybrid — the choice you make at apax create, and why it matters later.

The tools and the workspace

• You Don’t Need AX Code IDE — SIMATIC AX Runs From Any VS Code Workspace
• The apax CLI in SIMATIC AX — Every Command Worth Knowing — create, install, build, test, dm, and the supporting commands, with honest notes on the rough edges.

The language and the type system

• Variables and the Type System in SIMATIC AX
• CLASS vs FUNCTION_BLOCK in SIMATIC AX — what each one is for, coming from an FB-only background.
• Namespaces in SIMATIC AX Explained for TIA Portal Engineers — what they are, and why TIA Portal has nothing like them.
• Error Handling in SIMATIC AX — TRY/CATCH from a TIA Portal Lens
• Siemens AX Libraries: Timers Are Packages, Not Magic Blocks

How the program actually runs

• Configuration, Tasks and Programs — The SIMATIC AX Scan Cycle
• Initialization Patterns in SIMATIC AX — Startup Task and ProgramCycle

Testing PLC code without a PLC

This is the part that changed how I think about controls work the most.

• Unit Testing in SIMATIC AX — I Proved My PLC Code Works Without a PLC — what unit testing is and why it matters for PLC code.
• How to Write Unit Tests in SIMATIC AX — A Step-by-Step Guide — the anatomy of a test file, and what to test versus what to leave for commissioning.

HMI — WinCC Unified Elements

• WinCC Unified Elements — Code-Based HMI for TIA Portal Engineers
• SIMATIC AX HMI Design — Siemens Just Filled the Biggest Gap
• TempController on a Real Screen — End-to-End AX + WinCC UE Demo

The tank control demo, start to finish

A complete worked example rather than isolated features. These are meant to be read in order.

1. Requirements and I/O Baseline — starting with a process description, not with code.
2. GitHub, TIA Selection Tool, and Hardware Configuration
3. Building the Software Skeleton — named UDTs, mapping functions, function block instances.
4. Tank Control Logic: From Empty Blocks to Tested Behavior — analog scaling, protected Manual and Automatic modes, and tests that prove the behaviour.
5. Does SIMATIC AX Already Support the S7-1200 G2 CPU 1214C? — hardware support package 4.8, and what compiled versus what did not.

If you came here from TIA Portal

Two companion guides written from the same starting point: TIA Portal, the platform I use for most customer work, and Codesys, the platform behind much of the non-Siemens PLC world.

Outside the PLC platforms, Custom Devices covers the electronics and operator interfaces I build myself when nothing off the shelf fits.

Working on something similar?

I am Yuriy Mosiyenko — I design and program industrial control systems, mostly Siemens, as a one-person practice based in Bedford, Nova Scotia, working with customers across Canada. If you have a controls project you cannot staff internally, tell me what you are building.