231-E033

Identify Affected FS Outputs

Check alarm parameters %4 and %5 to decode which specific FS outputs 64-127 are stuck high. Convert hex values to binary to identify individual output bits.

Use TNC calculator function (CALC key) to convert hex alarm parameters to binary for easier bit identification

Disconnect External Wiring

Power down system and disconnect all external wiring from the identified FS output terminals on the safety I/O modules.

Follow LOTO procedures - safety system must be completely de-energized before disconnecting FS outputs

Test Output Isolation

Power up control and check if alarm clears. If cleared, short circuit is in external wiring. If alarm persists, internal hardware fault exists.

Use TNC diagnostic screen MOD → Diagnosis → I/O to monitor FS output states in real-time

Measure Output Voltages

With outputs disconnected, measure voltage on affected FS output terminals. Should read 0V when output commanded off during watchdog test.

Use CAT III rated multimeter - FS outputs can carry significant current when shorted

Identify Safety Module Location

Access MOD → Machine → I/O Configuration to determine which physical safety I/O module handles the affected FS output range 64-127.

Note module position and part number - safety modules must be replaced with identical certified units

Check Module Status LEDs

Examine safety I/O module for fault indicators. Red ERROR LED or missing green RUN LED indicates module hardware failure.

Do not attempt to reseat safety modules while system is powered - can cause additional safety faults

Verify Module Communication

In TNC diagnostic screen, check communication status to the suspect safety module. Loss of communication confirms module failure.

Use MOD → Diagnosis → PLC → I/O Assignment to verify module addressing matches physical installation

Replace Safety Module

Power down completely, replace defective safety I/O module with identical certified unit, and restore safety configuration from backup.

Safety module replacement requires complete safety system validation and may need TÜV re-certification

Backup Current Configuration

Create complete backup via MOD → File Management → Backup/Restore before making any safety parameter changes.

Include safety signature files (.saf) in backup - these contain certified safety logic

Check Safety Parameter Integrity

Access MOD → Machine → Safety and verify all FS output assignments match documented machine configuration. Look for undefined or conflicting assignments.

Modifying safety parameters requires safety engineer authorization and may void certifications

Restore Safety Configuration

Load known-good safety configuration from backup or master copy. Ensure safety signature matches original certified version.

Compare safety checksums before and after restore to verify configuration integrity

Perform Safety Validation

Execute complete safety system validation including all FS output tests and emergency stop verification per machine documentation.

Machine cannot return to production until all safety functions are validated and documented

Access Watchdog Parameters

Navigate to MOD → Machine → Safety → Watchdog Settings and review timing parameters for FS output test cycles.

Document current settings before changes - watchdog timing affects entire safety system performance

Verify Timing Specifications

Compare current watchdog timing against machine manufacturer specifications and Heidenhain safety manual recommendations.

Incorrect watchdog timing can create safety hazards - only certified personnel should modify these parameters

Adjust Test Cycle Timing

Increase FS output test cycle duration to allow sufficient time for outputs 64-127 to properly reset during self-test sequence.

Typical FS output switching time is 10-50ms - allow 3x margin for reliable operation