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Platforms·7 min read·

CODESYS: the PLC platform you are probably already using

Hundreds of hardware brands run the same runtime underneath, which matters more than most engineers realise.

Short answer

CODESYS is an IEC 61131-3 development environment and runtime licensed by manufacturers rather than sold to end users, which is why it appears under other brand names. Roughly 500 hardware makers ship it, including ABB, WAGO, Festo, Lenze and Eaton, so a program written for one CODESYS device often ports to another with modest effort.

The five IEC 61131-3 languagesLDLadder Diagramgraphical, relay heritageFBDFunction Block Diagramgraphical, signal flowSFCSequential Function Chartsteps and transitionsSTStructured Texttextual, Pascal-likeILInstruction Listtextual, deprecatedOne standard, five notations. Most projects use two.

CODESYS is a development environment and a runtime for IEC 61131-3 programs. What makes it unusual is the business model: it is licensed to hardware manufacturers, who ship it under their own branding.

Why that matters

Around 500 manufacturers ship devices running the CODESYS runtime. ABB, WAGO, Festo, Lenze, Eaton, Beckhoff historically, and a long tail of smaller makers.

So an engineer who learns CODESYS has learned a substantial fraction of the non-Siemens, non-Rockwell market at once, and a program written for one device is closer to portable than it would be between the big two.

What actually ports

The language ports, because it is standard. Function blocks you wrote port. Structure ports.

What does not port is anything touching hardware: I/O configuration, vendor motion libraries, communication blocks, and the fieldbus setup. That is usually the majority of the commissioning time.

The phrase to be careful with is 'IEC 61131-3 compliant'. It means the language is standard. It does not mean two vendors' projects open in each other's tools.

PLCopen XML

CODESYS exports and imports PLCopen XML, which is the closest thing to a neutral interchange format the industry has. It carries a subset of what any given tool supports, so a round trip loses vendor-specific detail, but it carries the logic.

That subset is precisely why an interchange format is useful and why it is never a complete answer.

Common questions

Is CODESYS free?
The development environment is free to download and use. The runtime is licensed by the hardware manufacturer and is included in the price of the device, which is why you rarely buy CODESYS directly. Running the runtime on your own hardware, such as a Raspberry Pi, requires a separate licence.
Can I move a CODESYS program between brands?
Often, with work. The logic and the language are portable because they are standard, but I/O configuration, hardware-specific function blocks and motion libraries are not. Expect the program to move and the configuration to be redone.

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