Siemens 6ES7315-2AH14-0AB0 CPU 315-2 DP

The Siemens 6ES7315-2AH14-0AB0 is a CPU 315-2 DP central processing unit for the SIMATIC S7-300 PLC family. This mid-range CPU combines high processing power with integrated PROFIBUS DP master/slave capability. It features 256 KB of work memory (RAM), a bit instruction execution time of 0.1 µs, and two communication interfaces: one MPI/DP (12 Mbit/s) and one DP (PROFIBUS) master/slave. The CPU is suitable for medium to large automation tasks such as process control, manufacturing lines, and material handling systems. It supports a wide range of S7-300 I/O modules and can be expanded with up to 32 modules. The integrated DP interface allows direct connection of distributed I/O (ET 200) and drives.

Technical Specifications

Work memory: 256 KB (RAM), load memory: 256 KB (RAM) expandable with MMC card (up to 8 MB). Bit execution: 0.1 µs, word execution: 0.2 µs, fixed-point arithmetic: 2 µs, floating-point: 3 µs. I/O capacity: 1024 digital inputs, 1024 digital outputs, 256 analog inputs, 256 analog outputs. Number of I/O modules: up to 32 (in main rack). MPI/DP interface: 12 Mbit/s (supports PG communication, S7 basic communication, etc.). DP master interface: PROFIBUS DP (12 Mbit/s), supports up to 124 slaves, DP-V1 slave also possible. Number of timers/counters: 256 each. Number of blocks: up to 1024 blocks (OBs, FBs, FCs, DBs). Dimensions: 130 mm × 40 mm × 120 mm. Weight: approx. 350 g. Power supply: 24V DC (20.4-28.8V), consumption 0.5 A. Operating temperature: 0°C to 60°C. Storage: -40°C to 70°C.

Key Features

• 256 KB work memory for complex applications

• 0.1 µs per bit instruction execution

• Integrated PROFIBUS DP master/slave (DP port)

• Second MPI/DP interface for programming and communication

• Supports up to 8 MMC card for program and data storage

• Real-time clock with battery backup (battery not included)

• Diagnostic LEDs for SF, BUSF, RUN, STOP

• Compatible with all S7-300 I/O modules

• Supports SIMATIC STEP 7 (TIA Portal) programming

Memory and Performance

The CPU 315-2 DP provides 256 KB of work memory, sufficient for medium-sized applications (approx. 30-50K lines of code). The load memory can be extended via a MMC (Micro Memory Card) up to 8 MB, which is mandatory for storing the user program (no internal Flash). The processing speed allows handling of high-speed processes and multiple communication tasks. The CPU supports up to 256 timers and 256 counters, and up to 1024 data blocks.

PROFIBUS DP Integration

The onboard DP interface can operate as a DP master (Class 1) to control up to 124 DP slaves (e.g., ET 200 I/O, drives, HMIs). It can also function as a DP slave, allowing the CPU to be part of another DP master system. The MPI/DP interface can be used either as MPI (multi-point interface) for programming and HMI communication, or as a second DP port (with reduced functionality). The PROFIBUS address is set via the CPU’s configuration software.

Programming and Software

The CPU is programmed with SIMATIC STEP 7 (versions up to V5.7) or TIA Portal (STEP 7 Professional V13 and higher). Languages: Ladder (LAD), Function Block (FBD), Statement List (STL), S7-GRAPH (Sequential Function Chart), and S7-SCL (Structured Text). The CPU supports all standard S7-300 functions, including PID control, high-speed counting, and motion control (with appropriate modules). Online debugging, variable monitoring, and diagnostic buffer are available via the MPI port.

Applications

The CPU 315-2 DP is widely used in automotive manufacturing lines, packaging machinery, chemical batch processes, and conveyor systems. Its DP master capability makes it ideal for distributed I/O architectures, reducing wiring costs. Typical applications include machine control with remote I/O stations, drive control via PROFIBUS, and supervisory control with an HMI connected via MPI.

Installation and Expansion

The CPU mounts on an S7-300 rack (U-type rail). Insert an MMC card into the CPU before use (MMC required for operation). Connect 24V DC power to the L+ and M terminals. Connect the PROFIBUS cable to the 9-pin D-sub connector (use proper terminating resistors). Expansion I/O modules can be added to the right of the CPU, up to 32 modules total. Power supply modules (PS) are usually placed to the left of the CPU. The CPU supports hot-swapping of MMC cards (with power off).

Maintenance and Diagnostics

The front panel LEDs indicate: SF (system fault), BUSF (bus fault), RUN, STOP. Use STEP 7 to read the diagnostic buffer for detailed error messages. The battery (order separately) backs up the real-time clock and retentive memory; replace every 2-3 years. The MMC card is non-volatile, no backup needed. The CPU can be reset to factory settings via the MRES switch on the front.

Environmental and Compliance

The CPU is CE, UL, and RoHS compliant. Operating temperature: 0-60°C. Storage: -40-70°C. Humidity: 5-95% non-condensing. Protection rating: IP20.

Conclusion

The Siemens 6ES7315-2AH14-0AB0 CPU 315-2 DP offers a balanced combination of processing power, memory, and PROFIBUS connectivity. It is a reliable choice for medium-sized automation projects requiring distributed I/O and high-speed logic.