126-0113

Access PLC programming environment

Press MOD key, navigate to PLC PROGRAMMING MODE. Enter PLC password (typically machine-builder or service-level). Select EDIT PLC PROGRAM to access the PLC source code.

Only authorized personnel should modify PLC programs. Incorrect changes can affect machine safety systems.

Search for shutdown output assignments

Use the SEARCH function in the PLC editor to find all instances of the output marker shown in the alarm text (typically ESTOPM, M4700, or similar safety marker). Document each location where this output is assigned.

Use 'Search All Files' function to scan both the main plc.plt and all included module files in one operation.

Identify duplicate assignments

Review each found instance and determine which is the primary/correct assignment (usually in the main safety logic section) and which are duplicates. Check modification dates and comments to understand when duplicates were introduced.

Machine manufacturer's original code is typically in lower-numbered module files or marked with manufacturer comments.

Remove duplicate definitions

Delete or comment out the duplicate assignments, retaining only the primary shutdown output definition. Ensure the remaining assignment is in the appropriate safety logic section with proper interlocks.

Never remove all instances. Exactly one shutdown output assignment must remain for proper safety function.

Compile and verify PLC program

Select COMPILE PLC PROGRAM from the PLC menu. Verify compilation completes with 0 ERRORS. Review any warnings to ensure they are acceptable. Save the modified program.

Create a backup of the working PLC program to the TNC:PLC directory with a dated filename before testing.

Test shutdown functionality

Exit PLC programming mode and restart the control. Verify emergency stop and safety shutdown functions operate correctly. Test all E-STOP buttons and safety interlocks per machine safety checklist.

Full safety system validation is required after any PLC changes affecting shutdown logic.

Identify protected PLC modules

In PLC programming mode, review the module list. Protected or encrypted modules are typically marked with a lock icon or designated as READ-ONLY. These contain manufacturer safety logic.

Protected modules often have names like SAFETY.PLC, MACHINE.PLC, or manufacturer-specific identifiers (e.g., DMG_SAFE.PLC).

Review manufacturer documentation

Consult the machine PLC documentation (typically provided by machine builder) to identify which output markers and ranges are reserved for manufacturer use and must not be modified in user programs.

Modifying reserved safety outputs may void machine safety certification and warranties.

Locate conflicting user code

Search user-created PLC sections (typically in USER.PLC or custom module files) for assignments to the conflicting shutdown output. Compare against the reserved marker list from manufacturer documentation.

User code is typically in higher-numbered modules or files with names indicating customization (CUSTOM.PLC, USER_MACRO.PLC).

Relocate or remove user logic

If user code requires shutdown control, use a different, non-reserved output marker and coordinate with manufacturer-defined inputs. Remove direct assignments to protected shutdown outputs. Alternatively, use PLC function calls if manufacturer provides API for safety integration.

Use intermediate markers (M flags) to interface between user logic and manufacturer safety logic without direct output conflicts.

Recompile and validate

Compile the modified PLC program and verify alarm 126-0113 no longer appears. Test that both user functionality and manufacturer safety systems operate as intended without conflicts.

Coordinate with machine manufacturer if safety logic modifications are required for custom applications.

Review recent PLC modifications

Check the PLC program modification history or timestamps. Identify recently edited sections by checking file dates in TNC:\PLC directory or reviewing PLC edit logs if available.

Use Windows file properties or TNC file manager to sort PLC module files by modification date to quickly identify recent changes.