CPU With Mpi Interface 6ES7315-2AH14-0AB0 6ES7 315-2AH14-0AB0 6ES7315-2AH14-OABO

Siemens 6ES7315-2AH14-0AB0 | SIMATIC S7-300 CPU 315-2 DP — 256KB / MPI + PROFIBUS DP Master/Device / Isochronous Mode / FW V3.3 / Spare

Where CPU 315-2 DP Sits — Between Standard and High-End

The CPU 315-2 DP occupies the productive mid-upper range of the S7-300 CPU family. At 256KB, it offers twice the work memory of the CPU 314 (96KB), accommodating more complex programmes with larger data structures, more extensive alarm handling, and multiple machine function blocks — all within the same S7-300 rack architecture. It is not a high-end multi-interface CPU (that would be the CPU 317 or 319), but for the majority of industrial machine and process control applications that need PROFIBUS DP field device communication, it is the right-sized choice.

The defining feature is the second interface: an integrated PROFIBUS DP master/device port. As a DP master, the CPU 315-2 DP directly manages PROFIBUS IO stations (ET 200M, ET 200S, drives, transmitters) from the CPU without needing a separate CP 342-5 communications module. Isochronous mode on the DP interface synchronises the PLC scan cycle to the PROFIBUS DP bus cycle, enabling deterministic data acquisition for coordinated motion control and high-speed measurement applications.

Key Specifications

Application Scenarios

Machine tool and production cell control: The 256KB memory handles complex sequencing with multiple axes, tool management databases, and PLC-based recipe logic. The PROFIBUS DP master connects directly to remote I/O stations and drive controllers without consuming a rack slot on a CP module.

Distributed I/O over PROFIBUS: ET 200M and ET 200S remote stations at machine sections connect to the CPU 315-2 DP's DP port. Field wiring stays local to each machine section; only the PROFIBUS cable runs back to the CPU rack.

Coordinated motion with isochronous mode: For applications where sensor data must be acquired at a precisely defined phase of the machine cycle — press force measurement, conveyor synchronisation, positioning feedback — isochronous DP operation locks data acquisition to the bus cycle.

Maintenance spare for installed S7-300 systems: Many S7-300 installations built around CPU 315-2 DP remain in active production. Replacement preserving the same 256KB memory class, DP interface, and Micro Memory Card structure maintains the original system without STEP 7 programme modification.

FAQ

Q1: What is the difference between CPU 315-2 DP and CPU 315-2 PN/DP?

The CPU 315-2 DP provides MPI and PROFIBUS DP only — no integrated PROFINET. The CPU 315-2 PN/DP adds an integrated PROFINET interface as a third port alongside MPI and DP. For systems that communicate exclusively over PROFIBUS DP and MPI, the 315-2 DP is the appropriate choice. For systems that require both PROFIBUS DP and Ethernet/PROFINET from the CPU, specify the 315-2 PN/DP.

Q2: Can the Micro Memory Card from the failed CPU be reused in the replacement?

Yes — transferring the MMC is the standard programme recovery method. Remove the MMC from the failed CPU and install it in the replacement unit. The CPU loads the programme from the MMC at power-up without a STEP 7 connection. If the MMC is damaged or missing, the programme must be downloaded via MPI from a STEP 7 V5.x archive.

Q3: Is STEP 7 Classic or TIA Portal used for the CPU 315-2 DP?

STEP 7 Classic V5.x (STEP 7 Professional). TIA Portal does not support the S7-300 CPU 315-2 DP for programming. TIA Portal supports the S7-1500 and S7-1200 families; S7-300 systems require the classic STEP 7 environment.

Q4: What does isochronous mode provide on the PROFIBUS DP interface?

Isochronous mode locks the CPU's scan cycle to the PROFIBUS DP bus cycle in a phase-locked relationship. Input data is captured at a defined, reproducible phase of the bus cycle; output updates occur at another defined phase. For motion control and high-speed measurement where the timing of data acquisition relative to the machine cycle matters, this determinism eliminates the variable scan-to-bus phase jitter of asynchronous operation.

Q5: Where is the 6ES7315-2AH14-0AB0 sourced?

Through the established S7-300 aftermarket — Siemens service channels (while stock is available), industrial automation spare parts dealers, and tested surplus suppliers. The CPU 315-2 DP is one of the most widely deployed S7-300 CPUs globally; aftermarket availability is consistently good. Confirm the AH14 hardware revision from the installed unit's label and verify the MMC requirement before placing the order.