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Heidenhain Controller
Servo/Axis · Intermediate · 30-120 minutes
HEIDENHAIN 320-0421 - PLC: error table missing
Alarm 320-0421 occurs when PLC modules 9085 or 9086 attempt to access an error table that doesn't exist or was corrupted. This typically happens when the PLC program references error handling routines but the corresponding error table wasn't properly compiled or was deleted after compilation.
320-0421
HEIDENHAIN 320-0421 - PLC: error table missing
PLC: error table missing
The PLC error table is missing or has no entries. This prevents proper error reporting from PLC error modules.
Root Cause Summary
Alarm 320-0421 occurs when PLC modules 9085 or 9086 attempt to access an error table that doesn't exist or was corrupted. This typically happens when the PLC program references error handling routines but the corresponding error table wasn't properly compiled or was deleted after compilation.
Safety
- Refer to Heidenhain service manual
- Ensure qualified technician performs repairs
Causes and Fixes
- 1
Access PLC Programming Environment
Press MOD key, select 'PLC' from menu, then select 'PLC Programming' to enter the programming environment.
- 2
Check Error Table Definition
Navigate to the error table section and verify that error definitions exist. Look for empty or missing error table entries.
Error tables should contain at least one entry if modules 9085/9086 are used in the program.
- 3
Compile PLC Program with Error Table
Select 'Compile' from PLC menu and ensure 'Include Error Table' option is checked before compilation.
Always backup existing PLC program before recompilation.
- 4
Verify Compilation Success
Check compilation log for errors and confirm error table was successfully included in the compiled program.
Call a technician if:
- ·PLC program source code is not available
- ·Multiple compilation attempts fail
- ·Suspected hardware memory issues
Prevention
- Always backup PLC programs before modifications
- Document error table entries and their purposes
- Use version control for PLC program changes
- Test error handling after any PLC modifications
Common Mistakes
- Deleting error table entries without removing corresponding module calls
- Compiling PLC without including error table
- Using undefined error numbers in modules 9085/9086
- Modifying error table after compilation without recompiling
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