# Beckhoff TwinCAT 3 Runtime (XAR)

Controllers · `TwinCAT 3 XAR` · verification: source checked

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.

## Specification

| Property | Value |
|---|---|
| Kind | runtime |
| Series | TwinCAT 3 |

## Connected

- Alarm codes: [0x1000 RTERR_INTERNAL Real-Time Internal Error](https://machineschema.com/alarm/ads-0x1000.md), [0x1001 RTERR_BADTIMERPERIODS Invalid Timer Value](https://machineschema.com/alarm/ads-0x1001.md), [0x1002 RTERR_INVALIDTASKPTR Invalid Task Pointer](https://machineschema.com/alarm/ads-0x1002.md), [0x1003 RTERR_INVALIDSTACKPTR Invalid Stack Pointer](https://machineschema.com/alarm/ads-0x1003.md), [0x1004 RTERR_PRIOEXISTS Priority Already Assigned](https://machineschema.com/alarm/ads-0x1004.md), [0x1005 RTERR_NOMORETCB No More TCBs](https://machineschema.com/alarm/ads-0x1005.md), [0x1006 RTERR_NOMORESEMAS No More Semaphores](https://machineschema.com/alarm/ads-0x1006.md), [0x1007 RTERR_NOMOREQUEUES No More Queue Space](https://machineschema.com/alarm/ads-0x1007.md), [0x100E RTERR_EXTIRQNOTDEF External IRQ Not Defined](https://machineschema.com/alarm/ads-0x100e.md), [0x100F RTERR_EXTIRQINSTALLFAILED External IRQ Install Failed](https://machineschema.com/alarm/ads-0x100f.md), [0x1010 RTERR_IRQLNOTLESSOREQUAL Wrong Service Context](https://machineschema.com/alarm/ads-0x1010.md), [0x1018 RTERR_VMXDISABLED Intel VT-x Disabled](https://machineschema.com/alarm/ads-0x1018.md), [0x12 ERR_PORTDISABLED Port Disabled](https://machineschema.com/alarm/ads-0x12.md), [0x13 ERR_PORTALREADYCONNECTED Port Already Connected](https://machineschema.com/alarm/ads-0x13.md), [0x14 ERR_AMSSYNC_W32ERROR AMS Sync Win32 Error](https://machineschema.com/alarm/ads-0x14.md), [0x15 ERR_AMSSYNC_TIMEOUT AMS Sync Timeout](https://machineschema.com/alarm/ads-0x15.md), [0x17 ERR_AMSSYNC_NOINDEXINMAP No AMS Sync Index Map](https://machineschema.com/alarm/ads-0x17.md), [0x18 ERR_INVALIDAMSPORT Invalid AMS Port](https://machineschema.com/alarm/ads-0x18.md), [0x1A ERR_TCPSEND TCP Send Error](https://machineschema.com/alarm/ads-0x1a.md), [0x1B ERR_HOSTUNREACHABLE Host Unreachable](https://machineschema.com/alarm/ads-0x1b.md), [0x1C ERR_INVALIDAMSFRAGMENT Invalid AMS Fragment](https://machineschema.com/alarm/ads-0x1c.md), [0x1D ERR_TLSSEND TLS Send Error](https://machineschema.com/alarm/ads-0x1d.md), [0x1E ERR_ACCESSDENIED Access Denied](https://machineschema.com/alarm/ads-0x1e.md), [0x274D Connection refused](https://machineschema.com/alarm/ads-0x274d.md), [0x2751 No route to host](https://machineschema.com/alarm/ads-0x2751.md), [0x4 ERR_INSERTMAILBOX Mailbox Full](https://machineschema.com/alarm/ads-0x4.md), [0x5 ERR_WRONGRECEIVEHMSG Wrong HMSG](https://machineschema.com/alarm/ads-0x5.md), [0x500 ROUTERERR_NOLOCKEDMEMORY Router Locked Memory](https://machineschema.com/alarm/ads-0x500.md), [0x501 ROUTERERR_RESIZEMEMORY Router Memory Resize](https://machineschema.com/alarm/ads-0x501.md), [0x502 ROUTERERR_MAILBOXFULL Router Mailbox Full](https://machineschema.com/alarm/ads-0x502.md), [0x503 ROUTERERR_DEBUGBOXFULL Debug Mailbox Full](https://machineschema.com/alarm/ads-0x503.md), [0x504 ROUTERERR_UNKNOWNPORTTYPE Unknown Port Type](https://machineschema.com/alarm/ads-0x504.md), [0x505 ROUTERERR_NOTINITIALIZED Router Not Initialized](https://machineschema.com/alarm/ads-0x505.md), [0x507 ROUTERERR_NOTREGISTERED Port Not Registered](https://machineschema.com/alarm/ads-0x507.md), [0x508 ROUTERERR_NOMOREQUEUES No More Ports](https://machineschema.com/alarm/ads-0x508.md), [0x509 ROUTERERR_INVALIDPORT Invalid Router Port](https://machineschema.com/alarm/ads-0x509.md), [0x50A ROUTERERR_NOTACTIVATED Router Not Active](https://machineschema.com/alarm/ads-0x50a.md), [0x50B ROUTERERR_FRAGMENTBOXFULL Fragment Mailbox Full](https://machineschema.com/alarm/ads-0x50b.md), [0x6 ERR_TARGETPORTNOTFOUND Target Port Not Found](https://machineschema.com/alarm/ads-0x6.md), [0x7 ERR_TARGETMACHINENOTFOUND Target Machine Not Found](https://machineschema.com/alarm/ads-0x7.md), [0x700 ADSERR_DEVICE_ERROR General Device Error](https://machineschema.com/alarm/ads-0x700.md), [0x701 ADSERR_DEVICE_SRVNOTSUPP Service Not Supported](https://machineschema.com/alarm/ads-0x701.md), [0x704 ADSERR_DEVICE_INVALIDACCESS Invalid Access](https://machineschema.com/alarm/ads-0x704.md), [0x707 ADSERR_DEVICE_NOTREADY Device Not Ready](https://machineschema.com/alarm/ads-0x707.md), [0x709 ADSERR_DEVICE_INVALIDCONTEXT Invalid Operating Context](https://machineschema.com/alarm/ads-0x709.md), [0x70A ADSERR_DEVICE_NOMEMORY Insufficient Memory](https://machineschema.com/alarm/ads-0x70a.md), [0x70D ADSERR_DEVICE_SYNTAX Syntax Error](https://machineschema.com/alarm/ads-0x70d.md), [0x70F ADSERR_DEVICE_EXISTS Object Already Exists](https://machineschema.com/alarm/ads-0x70f.md), [0x710 ADSERR_DEVICE_SYMBOLNOTFOUND Symbol Not Found](https://machineschema.com/alarm/ads-0x710.md), [0x712 ADSERR_DEVICE_INVALIDSTATE Device Invalid State](https://machineschema.com/alarm/ads-0x712.md), [0x714 ADSERR_DEVICE_NOTIFYHNDINVALID Invalid Notification Handle](https://machineschema.com/alarm/ads-0x714.md), [0x715 ADSERR_DEVICE_CLIENTUNKNOWN Client Not Registered](https://machineschema.com/alarm/ads-0x715.md), [0x716 ADSERR_DEVICE_NOMOREHDLS No More Handles](https://machineschema.com/alarm/ads-0x716.md), [0x717 ADSERR_DEVICE_INVALIDWATCHSIZE Notification Size Too Large](https://machineschema.com/alarm/ads-0x717.md), [0x718 ADSERR_DEVICE_NOTINIT Device Not Initialized](https://machineschema.com/alarm/ads-0x718.md), [0x71A ADSERR_DEVICE_NOINTERFACE Interface Query Failed](https://machineschema.com/alarm/ads-0x71a.md), [0x71B ADSERR_DEVICE_INVALIDINTERFACE Wrong Interface](https://machineschema.com/alarm/ads-0x71b.md), [0x71C ADSERR_DEVICE_INVALIDCLSID Invalid Class ID](https://machineschema.com/alarm/ads-0x71c.md), [0x71D ADSERR_DEVICE_INVALIDOBJID Invalid Object ID](https://machineschema.com/alarm/ads-0x71d.md), [0x71E ADSERR_DEVICE_PENDING Request Pending](https://machineschema.com/alarm/ads-0x71e.md), [0x71F ADSERR_DEVICE_ABORTED Request Aborted](https://machineschema.com/alarm/ads-0x71f.md), [0x721 ADSERR_DEVICE_INVALIDARRAYIDX Invalid Array Index](https://machineschema.com/alarm/ads-0x721.md), [0x722 ADSERR_DEVICE_SYMBOLNOTACTIVE Symbol Not Active](https://machineschema.com/alarm/ads-0x722.md), [0x724 ADSERR_DEVICE_LICENSENOTFOUND License Not Found](https://machineschema.com/alarm/ads-0x724.md), [0x725 ADSERR_DEVICE_LICENSEEXPIRED License Expired](https://machineschema.com/alarm/ads-0x725.md), [0x726 ADSERR_DEVICE_LICENSEEXCEEDED License Exceeded](https://machineschema.com/alarm/ads-0x726.md), [0x727 ADSERR_DEVICE_LICENSEINVALID Invalid License](https://machineschema.com/alarm/ads-0x727.md), [0x728 ADSERR_DEVICE_LICENSESYSTEMID Invalid License System ID](https://machineschema.com/alarm/ads-0x728.md), [0x729 ADSERR_DEVICE_LICENSENOTIMELIMIT License Not Time Limited](https://machineschema.com/alarm/ads-0x729.md), [0x72B ADSERR_DEVICE_LICENSETIMETOLONG License Period Too Long](https://machineschema.com/alarm/ads-0x72b.md), [0x72C ADSERR_DEVICE_EXCEPTION Startup Exception](https://machineschema.com/alarm/ads-0x72c.md), [0x72D ADSERR_DEVICE_LICENSEDUPLICATED Duplicate License Read](https://machineschema.com/alarm/ads-0x72d.md), [0x72E ADSERR_DEVICE_SIGNATUREINVALID Invalid Signature](https://machineschema.com/alarm/ads-0x72e.md), [0x72F ADSERR_DEVICE_CERTIFICATEINVALID Invalid Certificate](https://machineschema.com/alarm/ads-0x72f.md), [0x730 ADSERR_DEVICE_LICENSEOEMNOTFOUND OEM Public Key Missing](https://machineschema.com/alarm/ads-0x730.md), [0x731 ADSERR_DEVICE_LICENSERESTRICTED License Restricted](https://machineschema.com/alarm/ads-0x731.md), [0x732 ADSERR_DEVICE_LICENSEDEMODENIED Demo License Denied](https://machineschema.com/alarm/ads-0x732.md), [0x733 ADSERR_DEVICE_INVALIDFNCID Invalid Function ID](https://machineschema.com/alarm/ads-0x733.md), [0x734 ADSERR_DEVICE_OUTOFRANGE Outside Valid Range](https://machineschema.com/alarm/ads-0x734.md), [0x735 ADSERR_DEVICE_INVALIDALIGNMENT Invalid Alignment](https://machineschema.com/alarm/ads-0x735.md), [0x736 ADSERR_DEVICE_LICENSEPLATFORM Invalid Platform Level](https://machineschema.com/alarm/ads-0x736.md), [0x737 ADSERR_DEVICE_FORWARD_PL Forward to Passive Level](https://machineschema.com/alarm/ads-0x737.md), [0x738 ADSERR_DEVICE_FORWARD_DL Forward to Dispatch Level](https://machineschema.com/alarm/ads-0x738.md), [0x739 ADSERR_DEVICE_FORWARD_RT Forward to Real Time](https://machineschema.com/alarm/ads-0x739.md), [0x740 ADSERR_CLIENT_ERROR Client Error](https://machineschema.com/alarm/ads-0x740.md), [0x741 ADSERR_CLIENT_INVALIDPARM Client Invalid Parameter](https://machineschema.com/alarm/ads-0x741.md), [0x742 ADSERR_CLIENT_LISTEMPTY Polling List Empty](https://machineschema.com/alarm/ads-0x742.md), [0x743 ADSERR_CLIENT_VARUSED Variable Connection In Use](https://machineschema.com/alarm/ads-0x743.md), [0x744 ADSERR_CLIENT_DUPLINVOKEID Duplicate Invoke ID](https://machineschema.com/alarm/ads-0x744.md), [0x745 ADSERR_CLIENT_SYNCTIMEOUT ADS Sync Timeout](https://machineschema.com/alarm/ads-0x745.md), [0x746 ADSERR_CLIENT_W32ERROR Client Win32 Error](https://machineschema.com/alarm/ads-0x746.md), [0x747 ADSERR_CLIENT_TIMEOUTINVALID Invalid Client Timeout](https://machineschema.com/alarm/ads-0x747.md), [0x748 ADSERR_CLIENT_PORTNOTOPEN Port Not Open](https://machineschema.com/alarm/ads-0x748.md), [0x749 ADSERR_CLIENT_NOAMSADDR No AMS Address](https://machineschema.com/alarm/ads-0x749.md), [0x750 ADSERR_CLIENT_SYNCINTERNAL Ads Sync Internal Error](https://machineschema.com/alarm/ads-0x750.md), [0x751 ADSERR_CLIENT_ADDHASH Hash Table Overflow](https://machineschema.com/alarm/ads-0x751.md), [0x752 ADSERR_CLIENT_REMOVEHASH Key Not Found](https://machineschema.com/alarm/ads-0x752.md), [0x753 ADSERR_CLIENT_NOMORESYM No Symbols Cached](https://machineschema.com/alarm/ads-0x753.md), [0x755 ADSERR_CLIENT_SYNCPORTLOCKED Sync Port Locked](https://machineschema.com/alarm/ads-0x755.md), [0x8 ERR_UNKNOWNCMDID Unknown Command ID](https://machineschema.com/alarm/ads-0x8.md), [0xB ERR_UNKNOWNAMSCMD Unknown AMS Command](https://machineschema.com/alarm/ads-0xb.md), [0xD ERR_PORTNOTCONNECTED Port Not Connected](https://machineschema.com/alarm/ads-0xd.md)
- Manufacturer: [Beckhoff Automation](https://machineschema.com/manufacturer/beckhoff.md)

## 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.

## 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.

## Sources

1. [TC3 Installation EN](https://download.beckhoff.com/download/document/automation/twincat3/TC3_Installation_EN.pdf) (accessed 2026-10-26)

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