Beckhoff TwinCAT 3 ADS Error 6 after restart, what to check?
After a TwinCAT restart on our EtherCAT master, the HMI can't connect to the PLC. I'm getting an ADS Error 6. The route is definitely working, so what should I check first on the controller?
ADS Error 6 (0x6, ERR_TARGETPORTNOTFOUND) indicates that while the route to the target machine is functional, no ADS server is listening on the specific AMS port the client is trying to address. This often occurs after a TwinCAT restart or project download, or if the target is in CONFIG mode. It means the target machine responded, but nothing is registered on the AMS port.
Likely causes and checks
1Wrong AMS port in the client
- Points to it
- The client (HMI/SCADA) is configured to use an incorrect AMS port, such as a TwinCAT 2 port (e.g., 801) when the target is a TwinCAT 3 system with PLC runtime 1 (which typically uses port 851).
- Check
- Compare the AMS port configured in your client application with the actual ADS port of the PLC project running on the TwinCAT 3 target. For TwinCAT 3, PLC runtime 1 uses port 851, runtime 2 uses 852, and so on.
2No PLC project running on that port
- Points to it
- The target system might be in CONFIG mode, lack a boot project, or the PLC project was not started after activation, meaning no PLC program is actively listening on the expected port.
- Check
- Verify the TwinCAT state on the target system (ensure it's in RUN mode, not CONFIG). Confirm that the PLC project is loaded and actively running on the target system.
3ADS server not installed on the target
- Points to it
- If the error occurs on a non-PLC port (e.g., a port for an optional TwinCAT function), it could mean that the specific ADS server for that function is not installed or licensed on the target machine.
- Check
- If the issue is with a non-PLC port, check if the specific TwinCAT function is installed and licensed on the target. Also, verify that it is listed in the AMS port table on the target system.
Next check: First, I would verify the AMS port configuration in the HMI client to ensure it matches the TwinCAT 3 PLC runtime port (851 for runtime 1) on the target controller.
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