What causes FANUC alarm 099?

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 099?

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 · 2-5 minutes

Alarm 099

Fanuc Alarm 099 - End of Tape/Rewind

Alarm 099 occurs when the CNC control detects an End of Tape (EOT) signal or rewind condition while attempting to read a program from external memory device, tape reader, or serial communication. This is typically caused by incomplete program data, missing M02/M30 program end code, communication buffer issues, or actual physical end of tape/file reached during DNC/drip feed operations.

FANUCProgram/G-codeBasic2-5 minutes

099

Fanuc Alarm 099 - End of Tape/Rewind

Rewind

Root Cause Summary

Alarm 099 occurs when the CNC control detects an End of Tape (EOT) signal or rewind condition while attempting to read a program from external memory device, tape reader, or serial communication. This is typically caused by incomplete program data, missing M02/M30 program end code, communication buffer issues, or actual physical end of tape/file reached during DNC/drip feed operations.

Safety

Program input complete

Causes and Fixes

1
Check the NC program in memory or being transferred for proper program end code. Verify program contains M02 (program end) or M30 (program end and rewind) as the final command before the % symbol.
2
Navigate to SYSTEM > PARAM and check parameter 020 (tape operation settings). Bit 0 controls TV check, bit 4 controls rewind code detection. Ensure settings match your input device type (RS-232, Ethernet, drip feed).
3
If using DNC/drip feed operation, verify parameter 0020 bit 6 (tape format) and parameter 0101 (input buffer size). Insufficient buffer or incorrect format can cause premature EOT detection.
4
Re-send or re-load the program ensuring complete file transfer. Check for communication errors in I/O channel diagnostics (SYSTEM > DIAGNOSIS > I/O screen, page to I/O LINK or SERIAL diagnostics).
Ensure program backup before modifying or re-transferring programs to prevent data loss

DIY Feasiblehigh confidence

Call a technician if:

·Parameter changes required beyond standard restart parameters
·Hardware mode switch replacement needed
·Persistent alarms after all troubleshooting steps

Prevention

Always allow 2-3 seconds between mode changes
Use proper sequence: AUTO > wait > MDI when switching from restart
Avoid rapid mode switching during program restart operations
Regularly verify restart parameter settings match OEM specifications

Common Mistakes

Switching modes too quickly after program search
Not pressing RESET to clear restart state
Attempting MDI moves while restart flags are still active
Ignoring mode indicator status during transitions

Related Alarms

010 011 020 098

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