Siemens 6FC5357-0BB21-0AE0 NCU Processor Profibus DP MPI Bus I

Siemens 6FC5357-0BB21-0AE0 is the SINUMERIK 840D/DE NCU 572.2 Processor Module, the central Numeric Control Unit (NCU) that acts as the brain of SINUMERIK 840D CNC systems. This processor board provides the CPU for NC and PLC tasks with NC memory of 0.5 MB and 96 KB of PLC memory, and is shipped without system software memory. It is prepared for PROFIBUS DP communication, enabling DP-network connectivity to external I/O, drives, and other devices within a machine-tool environment. The 572.2 variant is documented in Siemens and aftermarket listings as a direct replacement or spare part for 840D/DE configurations, making it suitable for repair, retrofit, or upgrade of compatible machines that require a robust, compact NCU processor. Typical applications include CNC milling and turning centers using the SINUMERIK 840D control architecture, where the NCU handles motion control, CNC logic, and PLC sequencing while integrating with DP-based I/O networks for sensors, actuators, and field devices.