126-0115

Access PLC programming environment

Press MOD key, enter password if required, select 'PLC' and then 'EDIT'. Open the file SYS_PLC.P which contains the main PLC program and system marker definitions.

Always create a backup copy of the PLC program before making any modifications using the PLC SAVE function.

Locate switch-off output definition

Search for 'NC_POWER_OFF' or 'NC_SWITCH_OFF' using the PLC search function. This marker should be defined and assigned to a physical output or internal marker consistent with your machine configuration.

Common assignments are M4000-M4999 range for system functions. Check your machine manufacturer's PLC documentation for the specific marker number.

Verify correct marker syntax

Ensure the marker definition follows correct Heidenhain PLC syntax: the output must be properly declared (e.g., 'M4010 = NC_POWER_OFF') and the logic must set this marker appropriately for shutdown conditions.

Improper configuration of shutdown logic can prevent emergency stop functions from working correctly.

Compile and test PLC program

Select 'PLC COMPILE' from the PLC menu to compile the program. Check for compilation errors. If successful, exit PLC mode and cycle power to the control to reload the PLC program.

Review the PLC compilation report for warnings or errors that might indicate other related issues.

Search for duplicate marker usage

In PLC EDIT mode, use the search function to find all instances of the marker number assigned to switch-off functions. Document each occurrence and its context within the PLC program.

Use 'SEARCH ALL' function to generate a list of all occurrences rather than searching one-by-one.

Identify conflicting assignments

Review each instance to determine if the marker is assigned to multiple outputs or functions. Look for the same marker number used in different module files (SYS_PLC.P, USER_PLC.P, etc.).

Never assign the same output marker to both NC control functions and machine-specific outputs simultaneously.

Reassign conflicting markers

Modify the PLC program to use unique markers for each function. Assign a different, unused marker to one of the conflicting functions, ensuring all references are updated throughout the PLC code.

Maintain a marker allocation table to track which markers are assigned to which functions, preventing future conflicts.

Recompile and verify

Compile the corrected PLC program and verify no compilation errors occur. Test the switch-off function in a controlled manner to ensure proper operation.

Always test emergency shutdown functions after PLC modifications to ensure safety systems remain functional.

Check PLC file integrity

Navigate to PLC FILE MANAGEMENT and verify that all PLC program files (SYS_PLC.P, USER_PLC.P, and associated module files) show correct file sizes and dates. Compare with backup copies if available.

After any TNC software update, always verify PLC files were correctly migrated by comparing file checksums or dates.

Force complete PLC recompilation

Delete the compiled PLC object files (typically .OBJ or .BIN files in the PLC directory) to force a fresh compilation. Then select 'PLC COMPILE ALL' to rebuild all PLC modules from source code.

Ensure you have valid source code backups before deleting compiled files, as compilation errors may prevent the PLC from running.

Restore from known-good backup

If compilation errors persist, restore the PLC program from a known-good backup. Use TNC:\PLC\BACKUP directory or external backup media. After restoration, compile the PLC program completely.

Heidenhain controls typically store automatic PLC backups in the system backup directory—check TNC:\system\backup for timestamped copies.