CPU 312C with 8 integrated function blocks
The Siemens 6ES7312-5BF04-0AB0 is a CPU 312C for the S7-300 rack, packing 64 digital inputs and 64 digital outputs directly on the CPU — enough for a compact machine cell without a separate I/O rack. The FM 8 rating means it executes up to 8 function blocks (SFB type) in the firmware, which handles high-speed counting, frequency measurement, and pulse-width modulation without loading the user program scan.
Memory, programming, and network fit
Program memory is 256 bytes maximum for the command set (see instruction list for the full assembly). It programs in LAD, FBD, STL, SCL, GRAPH, and HiGraph via STEP 7 V5.5 + SP1 or higher (or V5.3 + SP2 with HSP 203). The CPU has one MPI port (RS 485) for programming and simple networking; PROFIBUS DP requires an external CP module (up to 4 CPs, 4 LAN CPs, 8 PtP CPs). PROFINET and PROFIsafe are not native — add a CP for Ethernet connectivity.
Panel fit and operating limits
The CPU measures 80 mm wide, 125 mm high, and 130 mm deep — it occupies one slot on the S7-300 DIN rail and leaves room for up to 8 additional modules in the rack (overall 6 modules maximum per the spec). Operating temperature range is 0 °C to 60 °C, so it sits in a ventilated enclosure without forced cooling for most factory-floor environments. The I2t rating of 0.7 A²·s is the thermal energy the internal 24 VDC supply can handle during a short-circuit event — relevant when sizing the external circuit protection.
No lifecycle status or successor is listed for this CPU 312C variant.