Siemens 6ES7315-2AH14-0AB0 — CPU 315-2 DP Spare Part Guide

By Abdullah Zahid
12 min read
Siemens 6ES7315-2AH14-0AB0 CPU 315-2 DP module for SIMATIC S7-300 rack-based industrial control systems

Siemens 6ES7315-2AH14-0AB0 — SIMATIC S7-300 CPU 315-2 DP, Central Processing Unit with MPI, Integrated Power Supply 24 V DC, Work Memory 256 KB, 2nd Interface DP

Controls engineers and procurement specialists searching for the Siemens 6ES7315-2AH14-0AB0 are typically at one of two points: verifying this is the correct spare part before committing to a purchase order, or confirming the CPU 315-2 DP fits a new or retrofit S7-300 application that requires PROFIBUS DP master capability without Ethernet. This module is the SIMATIC S7-300 CPU 315-2 DP — a compact central processing unit with 256 KB work memory, dual MPI and PROFIBUS DP interfaces, and an integrated 24 V DC power supply, running firmware V3.3 at hardware status 01.

If you have already confirmed this is the correct part, check current pricing and availability for the 6ES7315-2AH14-0AB0 at LeadTime.ca — ships worldwide.

Who Should Buy the 6ES7315-2AH14-0AB0 — and Who Shouldn't

This CPU is the right choice when your application sits clearly within the S7-300 mid-range control envelope and Ethernet connectivity is not a requirement. It is a strong fit when all of the following are true:

  • Your program scope fits within 256 KB work memory — adequate for approximately 70 percent of discrete manufacturing and process automation retrofit projects
  • The system uses PROFIBUS DP master communication to coordinate field devices and you do not require Ethernet or PROFINET
  • MPI is sufficient for programming and HMI supervisory communication at up to 187.5 kbit/s
  • Site power distribution is 24 V DC and the integrated supply eliminates the need for a separate power module
  • Your I/O architecture scales within 3 expansion units and up to 1,024 total inputs and outputs
  • You are replacing or maintaining an existing S7-300 rack and need a spare part with hardware status 01 and firmware V3.3

If your application requires Ethernet or PROFINET connectivity, the correct part is the 6ES7315-2EH14-0AB0 CPU 315-2 PN/DP with 384 KB memory. If program size exceeds 256 KB or faster cycle times are required, evaluate the CPU 317 or CPU 319 variants instead.

On this page:

What the 6ES7315-2AH14-0AB0 Actually Does in a Running System

The 6ES7315-2AH14-0AB0 is the SIMATIC S7-300 CPU 315-2 DP — the central processing unit that executes control logic, manages I/O data exchange, and coordinates communication across an S7-300 rack-based control system. It occupies the CPU slot in the S7-300 subrack and functions as the brain of the control architecture: scanning inputs, executing the program loaded into its 256 KB work memory, and writing outputs at the end of each scan cycle.

The defining characteristic of this variant is its dual interface configuration. The first interface is MPI, supporting both master and device roles at up to 187.5 kbit/s — the standard channel for STEP 7 programming connections, HMI communication, and S7 basic communication with up to 12 connections. The second interface is PROFIBUS DP, supporting both master and device modes, with isochronous operation via OB 61 and SYNC/FREEZE command support for time-synchronized control. This built-in PROFIBUS DP master eliminates the need for a separate CP communication module in most standard applications, which directly reduces cabinet footprint and component count.

The integrated 24 V DC power supply — rated at 850 mA with a no-load consumption of 150 mA — means the CPU draws directly from site 24 V DC distribution without requiring a separate Siemens PM power module. This is a meaningful distinction for OEMs and integrators designing compact panel layouts or replacing CPUs in existing enclosures with constrained rail space.

The SIMATIC S7-300 platform has maintained active support and spare part availability for over 20 years, and the 6ES7315-2AH14-0AB0 remains available through authorized channels as a spare part unit at hardware status 01 and firmware V3.3. For installed base maintenance, this continuity of availability is a practical operational advantage that reduces the risk of forced platform migration on a production timeline.

Typical S7-300 System Architecture with the CPU 315-2 DP

The 6ES7315-2AH14-0AB0 sits at the top of the S7-300 rack, directly managing local I/O and acting as PROFIBUS DP master to distributed field devices. Here is where it fits in a typical deployment:

  • Engineering workstation running STEP 7 V5.5 SP1 or higher connects to the CPU via the MPI interface for program download, monitoring, and diagnostics
  • The CPU 315-2 DP occupies slot 2 of the S7-300 subrack, coordinating up to 3 expansion units of signal modules (digital and analog I/O) on the same rack
  • The PROFIBUS DP master interface connects to distributed I/O stations, drives, or remote I/O clusters across a shielded RS-485 network at variable baud rates
  • HMI panels connect via MPI or as PROFIBUS DP devices for operator visualization and control, within the 15-connection maximum for PG/OP communication
  • Up to 4 additional CP communication modules can extend DP master capability or add protocol bridging for applications where the single integrated DP master is insufficient

Industries and Control Scenarios Where This CPU Fits

Discrete manufacturing operations — injection molding lines, assembly machinery, machining centers — represent the core application space for the CPU 315-2 DP. Multi-zone production monitoring with local I/O banks and coordinated PROFIBUS DP device networks falls squarely within the 256 KB memory capacity and 1,024-point I/O envelope of this CPU.

Batch process control applications in food and beverage, adhesive and coating production, and pharmaceutical dispensing benefit from the CPU's isochronous mode support via OB 61. Synchronized timing across PROFIBUS DP slaves enables deterministic control of sequential process steps, which is a hard requirement in many batch applications.

Conveyor and sorting systems in material handling and logistics automation are a strong fit, particularly where the PROFIBUS DP master coordinates multiple variable-speed drives and distributed I/O nodes along a production line. PROFIBUS DP remains deployed in over 50 percent of discrete manufacturing environments globally, and this CPU integrates with that installed base without additional protocol bridge hardware.

Equipment OEM designers using the S7-300 as a standardized control platform across multiple machine variants benefit from the CPU's established form factor and the predictability of S7-300 rack compatibility. For machine retrofit projects — where the existing S7-300 infrastructure is already in place and only the CPU requires replacement — the 6ES7315-2AH14-0AB0 is a direct-fit spare part replacement.

Application Typical Deployment
Injection molding line control CPU manages zone monitoring, pressure feedback loops, and synchronized clamp/inject sequencing via PROFIBUS DP drives
Conveyor and sorting system MPI-based HMI supervision with PROFIBUS DP coordination of distributed I/O modules and servo drives along the line
Batch adhesive or coating process Isochronous mode via OB 61 for time-synchronized dispensing steps with equidistant PROFIBUS DP slave timing
S7-300 CPU spare part replacement Direct replacement into existing rack at hardware status 01, firmware V3.3 — no rack modification required
OEM machine control platform Standardized S7-300 rack design deployed across multiple machine units with STEP 7 program replication
Wastewater or HVAC auxiliary control PROFIBUS DP master to field instruments and actuators, MPI connection to supervisory SCADA terminal

Key Specifications: What Engineers Need to Make a Decision

Specification Value
Model / Part Number 6ES7315-2AH14-0AB0
Product Family SIMATIC S7-300 CPU 315-2 DP
Work Memory 256 KB
Supply Voltage (Rated) 24 V DC (range 19.2–28.8 V DC)
Current Consumption (Rated) 850 mA
Total Inputs / Outputs 1,024 inputs / 1,024 outputs (256 central each)
Interfaces MPI (master/device, 187.5 kbit/s max) + PROFIBUS DP (master/device)
Isochronous Mode Supported via OB 61 on PROFIBUS DP interface
Maximum Expansion Units 3
Operating Temperature 0–60 °C ambient
Dimensions (W x H x D) 40 mm x 125 mm x 130 mm
Firmware Version V3.3 (as of July 2025)

Full technical specifications are available on the product page at LeadTime.ca.

6ES7315-2AH14-0AB0 vs. 6ES7315-2EH14-0AB0 and Other CPU Variants

The most common ordering error with the CPU 315-2 family is confusing the 6ES7315-2AH14-0AB0 (MPI + PROFIBUS DP) with the 6ES7315-2EH14-0AB0 (Ethernet PROFINET + PROFIBUS DP). Both carry the CPU 315-2 designation and share identical rack form factor, but they serve fundamentally different network architectures.

Feature 6ES7315-2AH14-0AB0 6ES7315-2EH14-0AB0 CPU 317-2 DP
Primary Interface MPI (187.5 kbit/s max) Ethernet / PROFINET (12 Mbps) Ethernet
Secondary Interface PROFIBUS DP master/device PROFIBUS DP master/device PROFIBUS DP
Work Memory 256 KB 384 KB 512 KB+
Isochronous Mode Via DP interface (OB 61) Via DP interface Via DP interface
Integrated Power Supply 24 V DC integrated 24 V DC integrated 24 V DC integrated
Rack Compatibility S7-300 standard S7-300 standard S7-300 standard
Cost Positioning Mid-range, lower cost Higher (Ethernet premium) Higher (memory/speed premium)
Best For Legacy MPI/DP networks, cost-sensitive retrofits Systems requiring Ethernet/PROFINET High-memory or high-speed applications

If your architecture uses PROFIBUS DP master without an Ethernet requirement, the 6ES7315-2AH14-0AB0 is the cost-effective, correct choice — check current availability at LeadTime.ca.

Expert Verdict: Honest Assessment for Controls and Procurement Teams

The 6ES7315-2AH14-0AB0 is a well-understood, reliable CPU for what it is: a mid-range S7-300 controller with PROFIBUS DP master capability, 256 KB of work memory, and an integrated 24 V DC supply that simplifies cabinet design. For retrofit and spare part applications on existing S7-300 infrastructure, this is the correct module. For OEM designers standardizing on the S7-300 platform for mid-sized discrete or batch process machines, the integrated DP master eliminates a CP module cost that adds up across a multi-unit production run. The 256 KB work memory is sufficient for approximately 70 percent of discrete manufacturing and process automation retrofit projects — a meaningful figure when evaluating whether a memory upgrade is actually necessary.

Where this CPU has real limits: if your application requires Ethernet or PROFINET connectivity for plant network integration, real-time data to SCADA over TCP/IP, or program sizes above 256 KB, this is not the right module. The 6ES7315-2EH14-0AB0 with 384 KB and a PROFINET interface is the direct upgrade path within the same physical form factor. If the application requires integrated safety functions, consider the CPU 315-2F. And if you are evaluating a full platform migration, the S7-1200 and S7-1500 families offer modern TIA Portal toolchains — but program conversion is a non-trivial engineering effort and does not fit every project timeline or budget.

From a procurement perspective, the S7-300 platform is mature and supply chain conditions for established SKUs like the 6ES7315-2AH14-0AB0 are generally more predictable than allocation-constrained newer modules. LeadTime.ca sources and stocks S7-300 CPUs for global distribution, with volume pricing available for integrators or OEMs ordering multiple units. If this matches your system requirements, view current stock and pricing for the 6ES7315-2AH14-0AB0 at LeadTime.ca.

For volume pricing or to confirm lead time before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

Wiring and Installation Overview

The 6ES7315-2AH14-0AB0 mounts in slot 2 of a standard S7-300 subrack via the backplane bus connector. Before installation, review the following:

  • Supply 24 V DC within the 19.2–28.8 V DC range to the CPU front connector; install a dedicated 2 A minimum fuse or circuit breaker in the supply line as recommended in the datasheet
  • Connect MPI and PROFIBUS DP cables using shielded RS-485 connectors; verify termination resistors are enabled only at the physical ends of each bus segment
  • Confirm that inrush current of 3.5 A typical at startup does not trip upstream protection — coordinate fuse characteristics accordingly with the I²t value of 1 A²·s
  • Verify that the 24 V DC return path is independent of control ground and that cable shields are grounded at both ends for PROFIBUS DP and MPI wiring runs
  • After physical installation, connect the STEP 7 programming terminal via MPI, confirm firmware version V3.3 is present, and perform a full program backup before any logic changes

What Engineers Get Wrong When Ordering This Part

The following checklist covers the most common specification and ordering errors associated with the 6ES7315-2AH14-0AB0. Verify each point before submitting a purchase order:

  1. Confirm exact model number 6ES7315-2AH14-0AB0 (not 6ES7315-2EH14-0AB0 Ethernet variant)
  2. Verify 256 KB work memory meets program size requirement (not 384 KB or higher)
  3. Confirm PROFIBUS DP master is needed (not PROFIBUS DP device-only mode)
  4. Check that MPI is sufficient for programming communication (not higher-speed networks)
  5. Ensure 24 V DC integrated power supply matches site distribution (not 120 V AC or 230 V AC requirement)
  6. Verify no integrated analog inputs/outputs are needed on CPU itself
  7. Confirm 3-slot expansion limit meets I/O scaling needs
  8. Check firmware version V3.3 compatibility with existing system software

If all eight checks pass, proceed to the product page at LeadTime.ca to confirm availability and request a quote. If any check raises a question, contact the LeadTime.ca team for pre-order technical validation before committing.

Frequently Asked Questions

Can the 6ES7315-2AH14-0AB0 be used as a drop-in replacement for an older CPU 315-2 DP in an existing S7-300 rack?

Yes, the 6ES7315-2AH14-0AB0 at hardware status 01 and firmware V3.3 is designed as a spare part replacement for the S7-300 CPU 315-2 DP. It uses the standard S7-300 backplane bus connector and mounts in slot 2 of any standard S7-300 subrack. Verify that your existing STEP 7 project was developed with at least V5.2 SP1 with hardware update, and confirm the program fits within 256 KB work memory before downloading.

What is the difference between the 6ES7315-2AH14-0AB0 and the 6ES7315-2EH14-0AB0?

The 2AH variant provides MPI as its primary interface (187.5 kbit/s) and PROFIBUS DP as its second interface, with 256 KB work memory. The 2EH variant replaces MPI with a 12 Mbps Ethernet/PROFINET interface and increases work memory to 384 KB. If your system does not require Ethernet connectivity and operates on an MPI-based programming network, the 6ES7315-2AH14-0AB0 is the lower-cost, correct choice. If Ethernet or PROFINET integration is required, the 6ES7315-2EH14-0AB0 is the correct alternative.

Does the CPU 315-2 DP support isochronous mode for time-critical applications?

Yes. The 6ES7315-2AH14-0AB0 supports isochronous mode via OB 61 on the PROFIBUS DP interface. It also supports equidistant operation and SYNC/FREEZE commands for synchronized slave control. Isochronous mode is not available on the MPI interface of this CPU.

What STEP 7 software version is required to configure and program the 6ES7315-2AH14-0AB0?

The minimum requirement is STEP 7 V5.2 SP1 with the relevant hardware update applied. STEP 7 V5.5 SP1 or higher is supported natively and is the recommended version for full feature access. TIA Portal is not natively compatible with S7-300 CPUs without a migration tool — new program development for this module should use the STEP 7 Classic toolchain.

What happens if the 256 KB work memory is fully utilized during operation?

If the program and data blocks exceed available work memory, the CPU will enter STOP mode and generate a memory error diagnostic. Prevention requires estimating total program size — including organization blocks, function blocks, and data blocks — before download, with a recommended 20–30 percent margin. If program growth is anticipated, the CPU 315-2 PN/DP (6ES7315-2EH14-0AB0, 384 KB) or a CPU 317 variant should be evaluated.

Is the 6ES7315-2AH14-0AB0 still available as a spare part, and what are typical lead times?

The 6ES7315-2AH14-0AB0 is classified as a spare part unit (hardware status 01, firmware V3.3 as of July 2025). The S7-300 platform has maintained active support and spare part availability for over 20 years, and supply chain conditions for this SKU are generally more stable than allocation-constrained newer modules. For current stock status and lead time confirmation, check availability at LeadTime.ca or contact the team directly.

Why Order the 6ES7315-2AH14-0AB0 from LeadTime.ca

  • LeadTime.ca ships the 6ES7315-2AH14-0AB0 and other S7-300 modules worldwide — no regional sourcing restrictions
  • Volume pricing is available for integrators and OEMs ordering multiple CPU units for fleet deployments or stocking programs
  • Pre-order technical validation is available for procurement teams who need to confirm part fit before committing to a purchase order
  • Hard-to-find or long-lead S7-300 spare parts are a sourcing specialty — contact the team for parts not immediately visible in the online catalog
  • Fast response on quote requests for urgent maintenance and production-down situations

At-a-Glance Summary

  • Model: 6ES7315-2AH14-0AB0 — SIMATIC S7-300 CPU 315-2 DP, hardware status 01, firmware V3.3
  • Work memory: 256 KB — sufficient for approximately 70 percent of discrete manufacturing and process automation retrofit projects
  • Dual interfaces: MPI master/device at 187.5 kbit/s maximum, plus PROFIBUS DP master/device with isochronous mode via OB 61
  • Integrated 24 V DC power supply: 850 mA rated, 150 mA no-load — no separate power module required
  • I/O capacity: 1,024 total inputs and 1,024 total outputs (256 central each), up to 3 expansion units
  • External protection: minimum 2 A fuse or circuit breaker required; inrush current 3.5 A typical with I²t value of 1 A²·s
  • Operating temperature: 0–60 °C ambient; dimensions 40 mm x 125 mm x 130 mm, weight 290 g
  • Programming requirement: STEP 7 V5.2 SP1 with hardware update minimum; V5.5 SP1 or higher recommended
  • Ethernet alternative: 6ES7315-2EH14-0AB0 (384 KB, PROFINET) — different part number, verify before ordering
  • PROFIBUS DP remains deployed in over 50 percent of discrete manufacturing environments globally — this CPU integrates natively without protocol bridge hardware