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Access Diagnostics menu: HMI → Diagnostics → Servo/Drives. Verify the Profibus slave list and note which encoder/drive node addresses are present versus the alarm report indicating axis %1 encoder %2.

Do not modify parameters while drives are powered; ensure emergency stop is engaged.

Compare SDB-Type-2000 entries in the PLC project (accessed via STEP 7 or configurator) with the drive assignment in MD20050 (AXIS_IO_TYPE) and MD20210 (AXIS_IO_ASSIGNMENT) for the faulted axis. Confirm the slave address in SDB matches the configured slave number.

If the drive/encoder hardware is physically connected and powered, perform a Profibus network scan using the diagnostics tool (e.g., HMI Diagnostics → Network or STEP 7 slave detection). Re-download the SDB-Type-2000 to reflect active slaves.

Downloading SDB requires a soft reset (NC stop); cycle power after download completes.

Clear the alarm using the HMI reset button and attempt axis initialization. If alarm persists, verify drive firmware version matches the SDB entry compatibility (MD27000 series encoder type parameters).

Navigate to HMI → Diagnostics → System Information → Axis %1 Parameters. Record MD20050 (AXIS_IO_TYPE), MD20051 (AXIS_IO_RESPONSE_TIME), and MD20210 (AXIS_IO_ASSIGNMENT) values for the affected axis.

Cross-reference the encoder index from MD20210 against the SDB-Type-2000 slave table. If encoder %2 is out of range or points to a deleted/unconfigured slave, the assignment is invalid. Use the parameter editor to correct MD20210 to a valid encoder index (typically 1 or 2 for dual-encoder setups).

Editing MD20210 requires axis-specific knowledge; consult machine documentation for correct encoder assignment.

Verify MD27000 and MD27010 (encoder type and resolution) are defined for the encoder index in use. Missing or zero values in these parameters can cause the encoder to be unrecognized.

After correcting parameters, save to non-volatile memory (HMI → File → Save), then perform an NC cold start (power cycle or HMI reset). Re-initialize the axis and monitor the alarm status.

Check physical Profibus connectors (DB9 M12 or equivalent) on the affected drive and the interface module. Look for loose connectors, bent pins, or damaged cable shielding. Verify power supply to the encoder/drive module is active (LED indicators if available).

De-energize the system before inspecting connectors.

In HMI Diagnostics or STEP 7 Network Configuration, check the Profibus master status and per-slave diagnostics. Look for error codes such as 'device not responding' or 'short circuit' for the encoder slave node. Document the slave address and module type.

If a slave address conflict is suspected (two devices with the same address), use the Profibus configurator tool to audit the SDB-Type-2000. Reassign conflicting slave addresses, save the configuration, and download to the NCK.

Changing slave addresses requires re-commissioning of affected axes; coordinate with machine operator.