Fanuc Om 900 Parameter — List Updated

This article provides a deep dive into the 900 parameter list for the Fanuc OM (Model A, B, C, and D). We will cover what these parameters are, why they trigger alarms, a line-by-line breakdown of alarms 900-999, how to recover lost parameters, and preventative maintenance strategies.

Some common FANUC OM 900 parameters include:

If you see , turn off the machine immediately. Replace the lithium battery on the master board (usually a BR-2/3A or BR-2/4A). If you continue to power cycle the machine with a dead battery, you will wipe the rest of the memory, turning a recoverable alarm into a total data loss. fanuc om 900 parameter list

No 900 parameter affects feedrate, backlash, or servo tuning. Those are in 100–800 range.

When your Fanuc OM displays "ALARM 900," it is not a parameter value; it is a diagnostic code. Here is the definitive list of 900-series alarms for the Fanuc OM control (Series 0 Model A/B/C). This article provides a deep dive into the

Each parameter is a . For example, parameter 910 bit 3 = 1 might enable Macro B.

The FANUC OM 900 parameter list is a critical component of the system's performance and capabilities. By understanding the types of parameters, configuration methods, and best practices for managing the parameter list, users can optimize their machining processes and achieve high-quality results. Whether you are a seasoned CNC professional or new to the FANUC OM 900, this comprehensive guide provides valuable insights and practical tips to help you unlock the full potential of your system. Replace the lithium battery on the master board

Option parameters are formatted as 8-bit binary strings (Bit 7 to Bit 0). Each individual bit acts as a toggle (1 for enabled, 0 for disabled) for a specific software feature.

| Alarm | Description | Most Common Cause | | :--- | :--- | :--- | | | ROM Parity Error (Main CPU) | Failed EPROM chip on the master PCB. Corrupted firmware. | | 901 | ROM Parity Error (Slave 1) | Failed EPROM on slave PCB or option board. | | 902 | ROM Parity Error (Slave 2) | Same as 901, but for secondary slave board. | | 903 | Software Revision Error | Incorrect EPROM version installed for the hardware. | | 904 | SERVO Module Error (ROM) | ROM checksum failure on the servo module. | | 905 | SERVO Module Error (RAM) | Servo RAM failure – usually a dead battery or bad chip. | | 906 | PMC (PLC) Ladder ROM Error | The ladder logic (PMC) EPROM is corrupt or incorrectly seated. | | 907 | PMC RAM Parity Error | Backup battery low caused loss of PMC parameters/timers. | | 908 | Option Parameter Error (Total) | The sum check of 900-series option params failed. (Most common after battery death). | | 909 | PMC Control Software Error | Ladder CPU failure or mismatched ladder firmware. | | 910 | DRAM Parity Error (Low byte) | Low-side dynamic RAM failure on main board. | | 911 | DRAM Parity Error (High byte) | High-side DRAM failure. (Alarm 910 & 911 often occur together). | | 912 | SRAM Parity Error (Tool offset memory) | Memory chip for offsets/tool data is bad. | | 913 | SRAM Parity Error (Work coordinate memory) | Memory for G54-G59, external offsets is corrupt. | | 914 | SRAM Parity Error (Macro variable memory) | Memory for #500+ custom macro variables is corrupt. | | 915 | SRAM Parity Error (Custom macro stack) | Corruption in macro call stack. | | 916 | SRAM Parity Error (Part program memory) | Memory corruption in the area storing your CNC part programs. | | 917 | SRAM Parity Error (Option parameter backup) | Backup area for 900 parameters is invalid. | | 918 | Battery voltage low (System RAM) | The lithium battery on the main board is dying (pre-alarm). | | 919 | Battery voltage low (PMC RAM) | The secondary battery (or separate battery) for ladder is low. | | 920 | Watchdog circuit error | CPU hardware hung; often requires master PCB replacement. | | 921 | Servo axis fault (overcurrent) | Related to drives, but sometimes flagged as a 900 series error. | | 922–929 | Axis-specific pulse coder errors | Feedback cable or encoder failure. | | 930 | CPU interrupt error | Severe hardware fault; board replacement likely needed. |