The FANUC A02B-0259-C180 is a control PCB commonly referred to as the ASVU1 FSSB analog servo interface / I/O unit, designed for use in FANUC Series 16i, 18i, and 21i CNC controls. It provides the essential interface between the CNC main CPU and the servo amplifier system via FANUC Serial Servo Bus (FSSB), typically using fiber‑optic links for high‑speed, noise‑immune communication in demanding industrial environments. In many machine tools (including retrofits and OEM machines such as Amada and others), this board forms part of the I/O and servo interface section, allowing the control to handle axis commands, feedback, and related I/O signals for motion control.
This unit is installed in the CNC control rack as a dedicated servo/I-O interface board, and works together with the main CPU, I/O base units, and individual I/O modules. It is typically powered from the CNC backplane and designed for continuous operation in standard machine tool cabinets, with forced‑air cooling and typical ambient ranges used in CNC systems (around 0–45 °C, non‑condensing). Like many FANUC control PCBs, the A02B‑0259‑C180 is no longer produced new by the OEM, but is widely available as refurbished, tested, and exchange units from specialist CNC parts suppliers.
