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.
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.
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.