Simatic CPU With Mpi Interface 6ES7314-1AG13-0AB0 6ES7 314-1AG13-0AB0 6ES7314-1AG13-OABO

Siemens 6ES7314-1AG13-0AB0 | SIMATIC S7-300 CPU 314 — 96KB Work Memory / MPI / Integrated 24V DC Supply / Micro Memory Card Required / Spare Part

CPU 314 — The Mid-Range S7-300 Workhorse

The CPU 314 occupies the productive middle of the SIMATIC S7-300 CPU range. Below it sit the entry-level CPU 312 and CPU 313 with smaller memory capacities for compact applications; above it are the higher-performance CPU 315 and 317 variants with larger memories and PROFIBUS DP interfaces. The CPU 314's 96KB work memory and MPI-only communication profile places it precisely where Siemens designed it: modular rack-based control systems of moderate complexity where the programme fits comfortably within 96KB and all network communication runs through the MPI interface — programming terminals, HMI connections, and inter-CPU data exchange.

Unlike the compact S7-300 CPUs (CPU 312C, CPU 313C, CPU 314C-2) that integrate onboard digital and analogue I/O channels directly into the CPU housing, the CPU 314 is a pure processing module. All I/O is handled by separate signal modules in the S7-300 rack. This is the standard modular architecture for mid-size machine control, process support panels, and utility automation systems where I/O count and type is defined by the installed signal modules, not by what is built into the CPU.

Key Specifications

MPI — The Interface That Defined S7-300 Engineering

MPI (Multi-Point Interface) is the CPU 314's communication connection to the outside world. At up to 12 Mbit/s and with support for up to 32 nodes per segment, MPI carries programming terminal (PG/PC) connections for STEP 7 programme upload/download, HMI panel (OP/TP) connections for operator screen data, and CPU-to-CPU data exchange (NetRead/NetWrite) between S7-300 CPUs in interconnected rack systems.

MPI is not PROFIBUS — it uses the same physical RS-485 hardware but a different protocol and a significantly shorter maximum cable length. For installations where field device communication requires PROFIBUS DP, the CPU 314's MPI-only configuration means a CP 342-5 communication processor must be added to the rack to provide DP master functionality. 

Installations designed around the CPU 314 either manage all field I/O through distributed rack expansion or through the rack's local S7-300 signal modules — the MPI-only design defines the application scope.

Integrated 24V DC Supply — No Separate PS 307 Required for the CPU

The integrated 24V DC supply on the CPU 314 connects directly to the 24V DC panel supply rail, independent of the PS 307 power supply module's AC-to-DC conversion. The CPU draws its operating power from 24V DC — the PS 307 is still needed for the rack bus voltage and field I/O module supply, but the CPU itself is powered directly from the 24V DC supply rather than through a separate connection from the PS 307's rail.

FAQ

Q1: What is the difference between CPU 314 and CPU 315-2 DP, and when should each be specified?

The CPU 314 has 96KB work memory and MPI-only communication — no PROFIBUS DP master. The CPU 315-2 DP has 128KB work memory and an integrated PROFIBUS DP master/slave interface in addition to MPI. Specify CPU 314 when the application fits within 96KB and all field I/O is through local rack modules or MPI-connected remote rack expansion. Specify CPU 315-2 DP (or higher) when a PROFIBUS DP master interface is required for distributed I/O or drive communication — the CPU 314 cannot serve as a DP master without a separate CP 342-5 communications module.

Q2: Is the CPU 314 a compact CPU with onboard I/O?

No. The CPU 314 is a pure rack processor — no onboard digital or analogue I/O channels. All I/O is provided by separate S7-300 signal modules (SM) installed in the rack alongside the CPU. The compact CPUs (CPU 314C-2 PN/DP, CPU 313C, etc.) integrate onboard I/O; the standard CPU 314 does not. The rack layout and all I/O addresses in the installed programme are based on the separate signal modules.

Q3: Can the Micro Memory Card from the failed CPU 314 be used directly in a replacement unit?

Yes — this is the standard programme recovery procedure. Power off the system, remove the MMC from the failed CPU, install it in the replacement CPU 314, restore power. The replacement CPU loads the programme from the MMC at startup without a programming terminal. Confirm the MMC is intact (no physical damage, no exposure to electrostatic discharge) before transferring. If the MMC was in the failed CPU during a hardware fault, verify the programme reads correctly after the first power-up.

Q4: How many nodes can the MPI network support with the CPU 314?

The MPI network supports up to 32 nodes, with addresses 0–31. Address 0 is typically reserved for the programming terminal, address 2 for the CPU. Connected HMI panels, other S7-300 CPUs on the same MPI segment, and programming devices each occupy one node address. Maximum cable length for MPI at 187.5 kbit/s is 50m per segment; at 12 Mbit/s the maximum is 50m without repeaters. For longer runs, RS-485 repeaters extend the reach.

Q5: Where is the 6ES7314-1AG13-0AB0 sourced?

As a Siemens spare part, through Siemens service channels and the well-established S7-300 aftermarket — industrial automation parts dealers and tested surplus suppliers. The CPU 314 in AG13 and adjacent revisions is one of the most widely deployed S7-300 CPUs globally; aftermarket availability is consistently good. Confirm the CPU 314 designation (not CPU 314C compact variant) from the installed unit's label before ordering. Transfer the Micro Memory Card from the original unit to the replacement.