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FANUC Controller
System · Advanced · 30 minutes to several hours depending on cause
Fanuc Alarm 911 - SRAM PARITY: BYTE 1
Fanuc Alarm 911 SRAM PARITY BYTE 1 indicates a parity error in the first byte of the Static RAM module where critical system data, parameters, and programs are stored. This typically results from low or depleted backup battery voltage, corrupted SRAM module, or physical damage to the memory circuit on the main PCB.
911
Fanuc Alarm 911 - SRAM PARITY: BYTE 1
DRAM Parity
Fanuc program alarm 911: DRAM Parity. The part program contains an error or illegal condition that the Fanuc control cannot execute. Correct the program to clear this alarm.
Root Cause Summary
Fanuc Alarm 911 SRAM PARITY BYTE 1 indicates a parity error in the first byte of the Static RAM module where critical system data, parameters, and programs are stored. This typically results from low or depleted backup battery voltage, corrupted SRAM module, or physical damage to the memory circuit on the main PCB.
Safety
- Power down system completely and follow LOTO procedures before accessing internal components
- Handle CPU boards with proper ESD protection - use grounded wrist strap
- Verify all power supplies are off before disconnecting cables from CPU board
- Use proper ESD protection with grounded wrist strap when handling CPU boards
- Be aware of potential pinch points and sharp edges when working inside the CNC machine's electrical cabinet.
- If unfamiliar with electrical troubleshooting, consult a qualified technician to avoid electrical shock or further damage to the equipment.
- Ensure proper ventilation when using cleaning solvents like isopropyl alcohol.
- Watch for pinch points and sharp edges inside electrical cabinet
- Capacitors can hold a charge even after the power is disconnected. Discharge capacitors before handling the main CPU board.
- Be aware of the potential for hot surfaces, especially around heat sinks and power supplies.
- Watch for pinch points, sharp edges, and hot surfaces in electrical cabinet
Causes and Fixes
- 1
Check battery voltage at SYSTEM > MAINTENANCE > BATTERY screen. Voltage should read 3.0-3.6V for lithium batteries. If below 2.7V, immediate replacement is required.
Do not remove the old battery until the new battery is connected or all parameters and programs will be lost. Use hot-swap procedure with main power ON.
- 2
Physically measure battery voltage with multimeter at the battery connector on the main PCB (CPU board). Verify connector terminals are clean and making proper contact.
- 3
After battery replacement, clear the alarm and perform SRAM initialization: Set Parameter 0 (diagnostic parameter) bit 7 to 1, cycle power, then restore parameters from backup. Set Parameter 3202#0=1 to enable parameter write.
SRAM initialization erases all parameters, offsets, and programs. Ensure you have a complete backup before proceeding.
- 4
Verify alarm clears by cycling power (full power-down for 10 seconds). Check SYSTEM > ALARM > ALARM HISTORY to confirm no recurrence of alarm 911.
Call a technician if:
- ·Memory test shows multiple failing addresses
- ·Power supply voltages are unstable
- ·Alarm persists after battery and SRAM replacement
Prevention
- Replace backup battery every 2-3 years
- Maintain clean power supply with UPS protection
- Perform regular parameter backups
- Keep CNC cabinet properly sealed against dust and moisture
Common Mistakes
- Replacing battery with power off causing parameter loss
- Not checking power supply stability before replacing memory
- Ignoring previous low battery alarms
- Failing to backup parameters before troubleshooting
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Always verify with your machine manual or a certified technician before performing service procedures.