23A-002F

Identify the affected device

Note the device name/number shown in the %2 parameter of the alarm message. Cross-reference this with the machine's wiring diagrams to locate the physical device and its connection point on the control cabinet.

Take a photo of the alarm screen showing the exact device identifier before resetting—this information disappears after acknowledgment.

Inspect physical connections

Power down the control, then inspect the specific device cable from the TNC X-port connectors (X116, X126) or PLC expansion connectors to the device. Check for damaged shielding, bent pins, cable strain at connectors, and proper cable gland tightness.

Always power down before disconnecting EnDat or bus connections to prevent damage to interface electronics.

Verify bus termination

For PROFIBUS or PROFINET devices, verify termination resistors are installed only at the physical ends of the bus segment. For EnDat devices, confirm the last encoder has termination enabled if using daisy-chain topology.

Use a multimeter to measure bus resistance with power off—PROFIBUS should read approximately 110 ohms between A and B lines when properly terminated.

Test with cable substitution

Replace the suspect cable with a known-good spare of identical type and length. For EnDat encoders, use only Heidenhain-approved cables with proper impedance. Power up and verify alarm clears.

If alarm clears immediately, the original cable likely has intermittent shielding breakdown or internal wire fracture invisible to visual inspection.

Access PLC configuration

Press MOD key → PLC → Configuration. Locate the device entry corresponding to the alarm %2 parameter and record the configured station address, device type, and communication parameters.

Compare current settings against the machine manufacturer's commissioning documentation—unauthorized parameter changes are a common cause after maintenance work.

Verify device physical address

Check the physical device for DIP switches, rotary address selectors, or software-configured station addresses. For encoders, verify the EnDat address matches the axis assignment in the control's encoder configuration.

EnDat encoder addresses are typically set via TNC setup during commissioning—access MOD → Axis Setup → Encoder to view expected versus actual addresses.

Check baud rate and protocol version

In MOD → PLC → Configuration, verify the communication speed (e.g., 1.5 Mbaud for PROFIBUS) matches the device capability. Ensure protocol version (EnDat 2.1, 2.2) is compatible between control and device firmware.

After TNC control software updates, occasionally device protocol parameters revert to defaults—always backup PLC configurations before software updates using MOD → System Files → Backup.

Perform device reset and re-initialization

Delete and re-add the device entry in the PLC configuration, forcing the control to perform a fresh device discovery and parameter negotiation. Save configuration and perform a full control reboot.

Deleting device entries will temporarily disable associated PLC functions—coordinate with machine operator to avoid disruption during production.

Perform device-level diagnostics

Access MOD → PLC → Status and select the affected device to view detailed communication statistics including error counters, telegram failures, and timeout events. High timeout counts indicate device-side problems.

Compare error statistics for the problem device against other devices on the same bus—isolated high error counts strongly suggest device hardware failure.