23A-001D

Check HSCI Device Count

Navigate to MOD function → System Info → Hardware Info to verify the number of HSCI devices connected and compare against TNC capacity limits.

Most TNC systems support maximum 8-12 HSCI devices depending on model

Review Machine Parameter MP7440

Check MP7440 (HSCI bus cycle time) in Setup → Machine Parameters. Increase value from default 125µs to 250µs or 500µs to reduce bus load.

Backup machine parameters before making changes

Analyze HSCI Traffic

Use PLC program to monitor HSCI communication status via system variables and identify devices with excessive communication frequency.

Redistribute HSCI Load

Consider moving non-critical devices to separate communication interfaces or reducing update rates for position displays and auxiliary encoders.

Identify Problem Device

Note the device ID (%3) and serial number (%4) from alarm message, then locate corresponding device in Setup → Touch Probe → Probe Configuration or encoder settings.

Cross-reference device serial number with physical labels on encoders/probes

Inspect HSCI Cable Integrity

Visually inspect HSCI cable for damage, proper shielding connection, and correct 9-pin D-sub connector pinout. Check for bent pins or corrosion.

Power down system before disconnecting HSCI cables

Test Cable Continuity

Use multimeter to verify continuity on HSCI cable pins 1-9, paying special attention to data lines (pins 2,3) and power supply (pins 4,5).

Replace or Reterminate Cable

Replace damaged cable with genuine HEIDENHAIN HSCI cable or reterminate connectors ensuring proper shield connection and pin assignments.

Verify Device Power Supply

Check voltage at HSCI connector pins 4(+5V) and 5(GND) should read 5.0V ±0.25V. Also verify current consumption is within device specifications.

Typical HSCI devices draw 100-400mA at 5V

Test Device Communication

Navigate to Setup → Encoder Configuration and attempt to read device information. Check if device responds to EnDat commands or position requests.

Review Device Error Memory

Access encoder diagnostics through MOD function → Encoder Test to read internal error memory and identify specific device faults.

Perform Device Reset

Execute encoder reset procedure via Setup menu or replace device if internal diagnostics indicate hardware failure.

Check System Error Log

Navigate to MOD function → Error Messages → System Log to review historical HSCI-related errors and identify patterns affecting multiple devices.

Verify HSCI Interface Status

Check machine parameter MP7441 (HSCI interface status) and system variables for HSCI hardware state indicators.

Test with Known Good Device

Connect a verified working HSCI device to isolate whether the issue is with the TNC interface or specific connected devices.

Only use HEIDENHAIN-certified HSCI devices for testing

Contact HEIDENHAIN Service

If multiple devices fail communication tests, document error patterns and contact HEIDENHAIN service for TNC interface card replacement.

Verify HSCI Timeout Settings

Check MP7442 (HSCI timeout value) in Setup → Machine Parameters. Default should be 1000ms; increase if dealing with slow-responding devices.

Review Device Address Configuration

Ensure each HSCI device has unique address assignment in encoder configuration and no conflicts exist between device IDs.

Restore Default HSCI Parameters

Reset HSCI-related machine parameters (MP7440-MP7449) to factory defaults and reconfigure devices systematically.

Document current parameter values before resetting