Beckhoff TwinCAT 3: EtherCAT slave stuck in PREOP with AL Status 0x0024, why?
I'm commissioning a new EtherCAT slave on my machine, and it's getting stuck in PREOP mode with an AL Status 0x0024. The TwinCAT 3 runtime is the EtherCAT master. What should I check first?
An EtherCAT slave reporting AL Status 0x0024 indicates an invalid input mapping, meaning the process data configuration (PDOs) in the TwinCAT 3 project does not match what the slave expects. This typically occurs during the transition from PREOP to SAFEOP. The issue often stems from incorrect PDO selection, a mismatch between physical and configured modules, or conflicting startup entries.
Likely causes and checks
1PDO selection not supported by device or revision
- Points to it
- The PDO assignment configured in the project (0x1C13) might not be supported by the specific device or its firmware revision. This is common after changing PDOs or replacing a device with a different revision.
- Check
- Compare the PDO assignment (0x1C13) in your TwinCAT 3 project with the device's ESI file and its documentation for the specific revision.
2Bus coupler / modular device module mismatch
- Points to it
- If you are using a bus coupler or a modular device, the physically connected modules might differ from what is configured in the TwinCAT 3 project. This leads to a discrepancy in the expected input mapping.
- Check
- Perform an online scan to compare the physically connected modules with the configured ones in your TwinCAT 3 project.
3Conflicting Startup (CoE) list entries
- Points to it
- Custom entries in the Startup tab of the TwinCAT 3 project might be writing a conflicting input mapping to the slave, even if the Process Data tab appears correct.
- Check
- Review the Startup tab in your TwinCAT 3 project for any entries related to 0x1A0x (input PDOs) or 0x1C13 (PDO assignment).
Next check: Start by comparing the PDO assignment (0x1C13) in your TwinCAT 3 project with the device's ESI file and its documentation to ensure the selected PDOs are supported by your specific device and revision.
Related questions
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