Compact CPU with integrated I/O for small control systems
The Siemens 6ES7312-5BE03-0AB0 is a SIMATIC S7-300 CPU 312C, a compact controller with 64 digital inputs and 64 digital outputs integrated on-board. With 8 KB work memory, it handles small to medium logic programs — enough for a packaging machine or a material-handling station where the I/O count stays under 64 each. The 80 mm width and 125 mm height fit a standard DIN-rail enclosure; depth is 130 mm including the front connector.
Engineering toolchain and program languages
Programming requires STEP 7 V5.3 SP2 with the corresponding hardware update — older versions of STEP 7 won't see this CPU in the device catalog. The CPU supports LAD, FBD, STL, SCL, and GRAPH, so the integrator can mix ladder logic for discrete control with structured text for data handling. The command set is listed in the instruction list; the CPU also supports HiGraph® for sequential function chart programming.
Communication and networking
The built-in MPI interface (RS 485) connects to the programming device and supports networking with other S7-300 stations. For Ethernet or PROFIBUS connectivity, the CPU works with CP modules: up to 4 CPs for LAN and 8 CPs for PtP connections. It can function as an MPI client or server, and as a PROFIBUS client via a CP and loadable FB. Routing is not supported, so the CPU cannot forward telegrams between subnets.
Data retention and restart behavior
The CPU has 6 KB of retentive memory, but the retentive data must be restarted at each restart — it is not maintained across power cycles unless explicitly re-initialized in the startup OB. The preset for retentive areas is "no retentivity" by default; the user adjusts retentive zones in the hardware configuration. Forcing of inputs and outputs is supported, useful during commissioning to override field signals without rewiring.
The 6ES7312-5BE03-0AB0 is an active-production part in the SIMATIC S7-300 family.