235-0045

Power down and inspect connectors

Switch off main power and disconnect 24VDC supply. Remove and inspect all X116 and X126 HSCI connectors at the NC unit, PLC module, and any inverter modules. Look for bent pins, corrosion, or contamination.

Always disconnect power before handling internal control connectors to prevent damage to HSCI communication boards.

Reseat all HSCI cables

Firmly reseat each HSCI cable connection, ensuring you hear or feel the locking mechanism engage. Verify cable strain relief is properly installed to prevent vibration-induced disconnection.

Mark each cable position before removal with tape labels to ensure correct reconnection sequence on the HSCI bus chain.

Inspect cable routing

Check that HSCI cables are routed away from servo motor cables, spindle power lines, and switching power supplies. Maintain minimum 100mm separation from high-voltage/high-current conductors.

HSCI cables should be the short, specific Heidenhain-supplied shielded cables with proper EMC ferrite cores intact.

Test with known-good cable

If available, substitute a known-good HSCI cable (Heidenhain part number specific to your control generation) and retest to eliminate cable as the failure point.

Identify failing node via MOD diagnostics

Power on and enter MOD mode (hold MOD key during startup if alarm prevents normal boot). Navigate to System Information → Communication Status → HSCI Bus Overview. Note which node number shows 'Not Ready' or 'Timeout' status.

The HSCI node address is typically labeled on the physical module - cross-reference the failed node number with physical module positions.

Isolate suspect module

Power down completely. Disconnect the HSCI cable from the suspect module (temporarily bypassing it in the chain if possible, or removing it if it's the last device). Re-establish proper 120-ohm termination at the new end point.

The HSCI bus requires proper termination at the last device - do not leave the bus unterminated or you will create new communication errors.

Power on and verify alarm clears

With suspect module isolated, power up the control. If error 235-0045 clears, the isolated module's HSCI interface has failed and the module requires replacement.

Document the failing module's serial number and position for replacement ordering - Heidenhain modules are often control-generation specific.

Replace failed module

Install replacement PLC or inverter module with matching part number. Reconnect to HSCI chain in the original position. Module may require configuration transfer via Heidenhain TNCremo software depending on module type.

Locate termination point

Identify the last physical device on the HSCI chain by following cables from the NC unit through PLC and any inverter modules. The termination resistor is typically a small jumper or switch on the last module.

Common termination locations: PLC module has a switch labeled 'TERM ON/OFF' or small jumper block near the HSCI connector. Check your specific module documentation.

Verify termination settings

Ensure the termination switch or jumper is set to ON/enabled at the last device ONLY. All intermediate devices must have termination set to OFF. The NC unit typically has internal termination for its end if it's first in chain.

Never enable termination on multiple devices - this creates impedance mismatch and will cause communication failures.

Measure termination resistance

With power OFF and HSCI cables disconnected at the last module, use a multimeter to measure resistance across the HSCI signal pair (typically pins marked HSCI+ and HSCI-). Should read approximately 120 ohms if termination is properly enabled.