What causes FANUC alarm 100?

Part program contains an illegal or malformed command related to the alarm condition. Missing required address word or parameter value in the program block. Programmed value is out of the allowable range. Conflict between active modal codes and the commanded function. Post-processor configuration mismatch for this Fanuc series.

How do I fix FANUC alarm 100?

1. Note the block number shown in the alarm screen and locate that block in the program. 2. Review the command in that block against the Fanuc programming manual. 3. Check for missing words, incorrect values, or conflicting G-code combinations. 4. Verify the program is post-processed for the correct Fanuc series. 5. Correct the program and dry-run at low speed before resuming machining.

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FANUC Controller

Program/G-code · Basic · 15-30 minutes

Alarm 100

Fanuc Alarm 100 - Data Parity Error

Fanuc Alarm 100 indicates a parity error detected during program data transfer from external media (tape reader, DNC system, USB, RS-232) or internal CNC memory. The CNC detects corrupted data bits that fail the parity check algorithm, preventing program execution to avoid machining errors. This is typically caused by communication errors, physical media damage, incorrect interface settings, or electrical noise.

FANUCProgram/G-codeBasic15-30 minutes

100

Fanuc Alarm 100 - Data Parity Error

Parity Alarm

Root Cause Summary

Fanuc Alarm 100 indicates a parity error detected during program data transfer from external media (tape reader, DNC system, USB, RS-232) or internal CNC memory. The CNC detects corrupted data bits that fail the parity check algorithm, preventing program execution to avoid machining errors. This is typically caused by communication errors, physical media damage, incorrect interface settings, or electrical noise.

Safety

Data may be corrupt

Causes and Fixes

1
Navigate to SYSTEM > PARAM and verify Parameter 0020 (I/O channel selection), 0101/0102 (input/output baud rate - typically 4800, 9600, or 19200), 0103 (stop bit - usually 1 or 2), and 0104 (parity setting - 0=none, 1=odd, 2=even). Compare with external device settings.
2
Check Parameter 0000 bit 0 (enable parameter write) is set to 1 if parameter changes are needed. Ensure exact match between CNC and DNC/computer communication settings. Most common: 9600 baud, 2 stop bits, even parity.
Setting Parameter 0000 bit 0 to 1 allows parameter modification. Return to 0 after changes to protect parameters.
3
Inspect RS-232 cable for damage, proper shielding, and secure DB-9 or DB-25 connector attachment. Replace with shielded cable, maximum 15 meters (50 feet) length. Verify proper null-modem configuration if required.
4
Test data transfer at lower baud rate (4800) to eliminate noise-related errors. Navigate to SYSTEM > DIAGNOSIS > I/O and monitor diagnostic 0300-0303 (serial communication status) during transfer for error flags.

DIY Feasiblehigh confidence

Call a technician if:

·Parameters repeatedly fail to activate after restart
·System fails to boot after power cycle
·Critical servo or spindle parameters involved

Prevention

Always plan parameter changes during scheduled downtime
Document all parameter changes before implementation
Verify parameter requirements before modification

Common Mistakes

Ignoring restart requirements
Changing multiple parameter groups simultaneously
Not backing up settings before restart

Related Alarms

FANUC 101 FANUC 102 FANUC 400

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