The FANUC A20B-3900-0223 is a combined 32MB FROM and 1MB battery-backed SRAM memory module for selected FANUC CNC and robot controllers. It plugs into a compatible main board and provides system-software storage together with retained machine data.

The FROM section stores FANUC control software and related system files. The SRAM section is maintained by the controller battery and can contain parameters, programs, offsets and PMC information. Correct software and data restoration are essential when replacing the module.

A20B-3900-0223 Product Information

FROM and Battery-Backed SRAM Functions

A20B-3900-0223 combines two memory functions. FROM retains controller software without operating power, while SRAM provides writable storage retained by the controller battery. A low or disconnected battery can cause loss of SRAM contents even when the module is functional.

Compatibility and Data Requirements

Confirm the full A20B-3900-0223 label, host main-board number, controller series, software edition and memory capacity. Do not substitute A20B-3900-0224 or -0225 because they have different SRAM capacities. Although A20B-3900-0163 is the documented older 32MB/1MB specification, software and machine data must still match.

Testing and Replacement Notes

REACO CNC checks the label, contacts, physical condition, memory recognition, boot operation and SRAM integrity under an applicable test setup. Back up all controller data before removal. Replacement may require loading FANUC software and restoring parameters, programs, PMC data and machine-builder files. Qualified personnel should perform the work with power isolated and ESD protection.

Related resources: FANUC PCB and memory modules, FANUC CNC controls and FANUC CNC and robot repair services.