Siemens 6ES7315-1AF03-0AB0 Replacement for S7-300 CPU 315

Product Overview

Siemens 6ES7315-1AF03-0AB0 Replacement for S7-300 CPU 315: Smooth Transition & Legacy System Upgrade

The Siemens 6ES7315-1AF03-0AB0 is a CPU 315 central processing unit designed for the SIMATIC S7-300 programmable logic controller platform. As this model reaches end-of-life and spare stock becomes increasingly scarce on the open market, many plant engineers and maintenance teams are actively seeking verified replacement units or a structured upgrade path that preserves existing wiring, rack infrastructure, and STEP 7 program logic. TOPNLMS supplies tested, ready-to-ship units of the 6ES7315-1AF03-0AB0 to support both emergency breakdown replacements and planned modernization projects — with a 12-month warranty on every unit dispatched.

The CPU 315 occupies a single slot on the standard S7-300 DIN-rail mounting rack and communicates via the MPI (Multi-Point Interface) bus at up to 187.5 kbps. Its 48 KB work memory and 80 KB load memory make it well-suited for mid-complexity sequential and process control applications. When replacing a failed or obsolete unit, the physical form factor, backplane connector pinout, and MPI address assignment remain fully compatible with existing S7-300 racks — meaning no rewiring of the backplane bus connector or power supply rails is required.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful field replacement of the 6ES7315-1AF03-0AB0 rarely involves the CPU alone. In most S7-300 control cabinets, the CPU works in close coordination with a range of peripheral modules that must remain operational throughout the migration. The PS 307 power supply module (such as the 6ES7307-1BA01-0AA0) provides the regulated 24 VDC rail that powers both the CPU and the backplane bus — verifying its output voltage before inserting the replacement CPU is a standard commissioning step. Signal modules such as SM 321 digital input modules and SM 322 digital output modules connect to field devices via front connectors and remain fully reusable after a CPU swap, as their wiring and configuration data are stored independently of the CPU’s work memory.

For analog process signals, SM 331 analog input modules and SM 332 analog output modules retain their channel parameterization in the hardware configuration file (HW Config), which is re-downloaded to the new CPU via the MPI programming cable — typically a PC Adapter USB (6ES7972-0CB20-0XA0) or a compatible MPI/PPI cable. Engineers migrating from an older CPU 314 or a failed CPU 315 unit will find that the existing S7-300 UR2 rack and all installed I/O modules remain in place; only the CPU slot is exchanged.

Where the legacy system included a CP 343-1 Ethernet communication processor for PROFINET or Industrial Ethernet connectivity, this module continues to operate on its existing IP configuration after the CPU replacement, provided the new CPU is loaded with the same hardware configuration. Similarly, FM 350 counter modules or FM 355 PID control modules installed in the same rack retain their parameterization and do not require reconfiguration. If the control cabinet also houses an OP 7 or TP 177B HMI panel communicating over MPI, the panel’s MPI address and baud rate settings are unaffected by the CPU replacement — the HMI will reconnect automatically once the new CPU completes its startup cycle.

For sites planning a longer-term migration from S7-300 to the SIMATIC S7-1500 platform, the 6ES7315-1AF03-0AB0 serves as a reliable interim solution that keeps the line running while the new control architecture is engineered and validated offline. TOPNLMS can supply associated components including interface modules, terminal blocks, and bus connectors to support a complete rack rebuild or partial slot replacement.

Retrofit Guidance FAQ

Q: Do I need to rewire the field terminals when replacing the CPU?
No. The CPU 315 does not connect directly to field wiring. All field signals are wired to the front connectors of the SM-series I/O modules, which remain installed in the rack. Only the CPU module in Slot 2 is exchanged.

Q: How do I transfer the existing program to the new CPU?
Connect a PC running STEP 7 V5.x to the MPI port of the new CPU using a PC Adapter USB cable (6ES7972-0CB20-0XA0). Download the hardware configuration first, then download the program blocks (OBs, FBs, FCs, DBs) in the correct sequence. Ensure the CPU is in STOP mode during download.

Q: Is the MPI address preserved after replacement?
The MPI address is stored in the CPU’s non-volatile memory. After inserting the replacement unit, the MPI address defaults to 2. If your network uses a different address, set it via the PG/PC interface before going online, or use the hardware configuration download to restore the correct address.

Q: Will the replacement CPU fit in the existing S7-300 rack without mechanical modification?
Yes. The 6ES7315-1AF03-0AB0 uses the standard S7-300 module form factor and backplane bus connector. It installs in Slot 2 of any UR1 or UR2 rack without tools beyond a standard screwdriver for the module retaining screw.

Q: What is the power consumption of this CPU, and will my existing PS 307 support it?
The CPU 315 draws approximately 1.2 A from the 5 VDC backplane bus. The PS 307 2A (6ES7307-1BA01-0AA0) is sufficient for a typical rack configuration. For racks with a high density of I/O modules, verify the total current budget against the PS 307 5A or 10A variants.

Q: Can this CPU communicate with PROFIBUS DP slaves?
The 6ES7315-1AF03-0AB0 does not include an integrated PROFIBUS DP interface. For PROFIBUS DP master functionality, a CP 342-5 communication processor must be installed in an adjacent rack slot. If your existing system already uses a CP 342-5, it will continue to operate after the CPU replacement without reconfiguration.

Warranty Assurance

Every 6ES7315-1AF03-0AB0 unit shipped by TOPNLMS is covered by a 12-month warranty from the date of delivery. Prior to dispatch, each unit undergoes a functional power-on test and visual inspection to verify module integrity, connector condition, and firmware version. Units are packed in anti-static ESD bags with foam cushioning to prevent transit damage.

In the event of a warranty claim, TOPNLMS provides a replacement unit or full refund within the warranty period. Our technical support team is available to assist with installation queries, MPI configuration, and compatibility verification before and after purchase. Typical dispatch from our Xiamen warehouse is 1–3 business days for in-stock units, with DHL Express, FedEx International Priority, and sea freight options available depending on urgency and destination.

For bulk procurement, project-based quotations, or consignment stock arrangements, contact our sales team directly. We maintain buffer stock of common S7-300 CPU and I/O modules to support emergency breakdown scenarios with same-day or next-day dispatch where possible.