CPU 315-2 DP with technology functions
The Siemens 6ES7315-6TH13-0AB0 is a SIMATIC S7-300 CPU 315-2 DP, an SFB-type processor built for applications requiring integrated technology functions — high-speed cam switch signals, for example, or motion sequences that need deterministic cycle times without a separate motion controller. It carries an FM 8 rating, meaning the firmware and hardware are configured for eight technology channels or function modules, depending on the specific application block loaded. The 244-byte input and 244-byte output process image handles distributed I/O on PROFIBUS DP without overrunning the cycle budget. Programming is supported in CFC, FBD, LAD, SCL, STL, GRAPH, and HiGraph — essentially the full TIA Portal language set, minus S7-SCL for some legacy blocks. The CPU requires STEP 7 V5.2 SP1 or higher with the S7 Technology option package installed.
I/O and communication profile
The CPU has one integrated RS 485 interface for PROFIBUS DP. It can act as a DP master (class 1) or as a DP slave via a loadable FB. No MPI port is present on this variant — all multi-point communication goes through the DP interface or an external CP. For expanded connectivity, the CPU supports up to 2 CPs for DP, 10 CPs for LAN (PROFINET or Industrial Ethernet), and 8 CPs for PtP serial links. Routing is not supported, so any cross-network data exchange must be handled at the application layer. The process image is 244 bytes each for inputs and outputs, with a total of 16 slots (overall) for modules. Forcing is supported, which is useful during commissioning to override process values without modifying the logic.
Lifecycle and sourcing posture
The I2t rating of 1 A²·s is the thermal energy the internal bus can handle during a short-circuit event — useful for sizing the external 24 VDC power supply and ensuring the backplane fuse coordinates downstream.
Environmental and compliance
Rated for 0 °C to 60 °C operating ambient, which covers most control-cabinet environments without active cooling. Dimensions are 160 mm wide, 125 mm high, 130 mm deep — standard S7-300 single-width format, fitting the standard DIN-rail mounting rail. The RS 485 interface is isolated, which helps avoid ground-loop issues when the DP cable runs across cabinets or through junction boxes. No PROFIsafe capability is present — if functional safety over PROFIBUS is required, a different CPU or a safety-rated CP would be needed.