Compact CPU with integrated I/O and multi-language support
The Siemens 6ES7313-5BG04-0AB0 is a CPU 313C from the SIMATIC S7-300 family, a compact PLC that integrates 24 digital inputs and 16 digital outputs on the module itself, plus analog inputs for voltage and current. It supports programming in CFC, FBD, LAD, SCL, STL, GRAPH, and HiGraph, giving the controls integrator flexibility to match the team's preferred language for each routine. The FM 8 value indicates the number of function blocks available for motion or counting tasks — a parameter that governs how many high-speed channels can run without an external module.
I/O capacity and signal conditioning
The CPU handles up to 253 inputs and 250 outputs in total across the S7-300 rack, with the ability to force I/O states for commissioning. Analog inputs accept ±10 V / 100 kΩ and 0 to 10 V / 100 kΩ, plus current signals at ±20 mA / 100 Ω, 0 to 20 mA / 100 Ω, and 4 to 20 mA / 100 Ω. The Pt 100 support means direct connection of RTD temperature probes without an external signal conditioner — saves a terminal block and a channel on the analog module.
Communication and networking
Built-in MPI and RS 485 interfaces allow the CPU to talk to operator panels, drives, and other S7-300 CPUs without a separate CP. For Ethernet or PROFIBUS connectivity, the CPU supports up to 4 CPs via the backplane, up to 6 CPs for LAN, and up to 8 CPs for PtP (point-to-point) serial links. It can act as an OPC UA server or client via a CP and loadable function blocks — useful for pulling data into a SCADA or MES layer without a gateway appliance.
Programming environment and toolchain
The CPU is programmed with STEP 7 V5.5 + SP1 or higher, or STEP 7 V5.3 + SP2 or higher with HSP 203. It supports retentive data areas (must be restarted at each restart), and the variables that can be retained include inputs, outputs, memory bits, DBs, times, and counters. The I²t rating of 0.7 A²·s is the thermal energy limit for the internal DC bus — relevant when sizing an external 24 VDC power supply for the backplane.
Physical dimensions and environmental limits
The I/O is not isolated from the backplane, so field wiring shares a common reference with the CPU logic — plan accordingly for ground loops in mixed-voltage panels.
The Siemens 6ES7313-5BG04-0AB0 is an established product in the S7-300 line. No lifecycle status or successor is recorded for this order code. The 3RT2536-1AP00, 3RT2535-1AB00, and 3RT2535-1AD00 are contactors, not PLCs, and do not functionally replace this CPU.