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Beckhoff TwinCAT 3 Runtime (XAR)

TwinCAT XAR is the real-time runtime environment of TwinCAT 3. It runs control applications on a target control computer and is installed separately from the TwinCAT 3 engineering environment (XAE). A reduced XAR-only setup is used for new installation or update of the runtime system on a control computer.

Source checked2/2 values · 2026-10-26Beckhoff AutomationRuntime

Specification

1 source
Kindruntime
SeriesTwinCAT 3

Study notes

  • XAR is installed as a separate setup; it contains only the components needed for the TwinCAT 3 runtime and is smaller than the full TwinCAT 3 installation.
  • The XAR-only setup is intended for new installation or update of the TwinCAT 3 runtime system on a target system.
  • TwinCAT 3.1 Build 4026 can install the runtime in kernel mode (XarMode KM), user mode (UM), or both (KMWithUM); user mode is for engineering and debugging without real-time behavior.
  • Only one TwinCAT Runtime System (XAR) may be active at a time; TcSwitchRuntime switches between TwinCAT 2 and TwinCAT 3 installations.
  • The XAR status is shown by a blue icon in configuration mode and a green icon in run mode in the Windows menu bar.
  • During a custom XAR installation, the runtime environments TwinCAT 3 PLC, TwinCAT 3 C++, and TwinCAT 3 MC can be selected; deselecting one prevents the corresponding module from running on that computer.
  • ADS (TwinCAT Automation Device Specification) is a medium-independent protocol for communication with or between TwinCAT components and is normally installed together with XAE or XAR.
  • TwinCAT 3 is installed by default in C:\TwinCAT\3.x (x = TwinCAT version number); changing the installation path is not recommended.

Safety

  • Installation and commissioning are intended only for trained specialists in control, automation and drive technology who are familiar with the applicable national standards.
  • Modifications to hardware or software configurations other than those described are not permitted and void the liability of Beckhoff Automation GmbH & Co. KG.
  • User mode runtime provides no real-time behavior and can execute a minimum cycle time of 1 ms, so timing can differ from real control systems.
  • Only one TwinCAT Runtime System (XAR) may be active at a time.
  • Flawless real-time behavior cannot be guaranteed when TwinCAT XAR is used on PCs from third-party providers.
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