FANUC controls use a lithium battery (usually a BR-2/3A or BR-AGCF2W) to maintain SRAM contents while the main power is off. The SRAM holds CNC parameters, pitch error compensation, part programs, and tool offsets. The system ROM contains the boot software.
Here is the trap: If the battery voltage drops below 2.7V, the SRAM becomes unstable. On the next power cycle, the control attempts to validate the SRAM checksum. When it fails, the boot process can freeze at the "starting system software" screen because the control is unsure if it has a valid environment to load into.
To avoid seeing “Starting System Software” freeze again: fanuc starting system software please wait
Every 3 months, perform a full SRAM backup using one of these methods:
Store the backup on three different media (network drive, USB, paper printout). FANUC controls use a lithium battery (usually a
For a 0i-D or 31i-B with corrupt system software, you will need:
If you operate or maintain a FANUC CNC (Computer Numerical Control) machine or industrial robot, you have likely seen the stark, amber-on-black screen message: Every 3 months, perform a full SRAM backup
FANUC STARTING SYSTEM SOFTWARE PLEASE WAIT
This is not an error, but a critical state in the boot process. However, when it persists for an unusually long time (more than 5–10 minutes) or appears in a boot loop, it signals a fundamental issue with the controller’s software integrity, hardware, or data storage.
This piece explains what the system is doing during this phase, why delays happen, and how to diagnose them.