6ES7314-1AF10-0AB0 SIMATIC S7-300 CPU 314
The Siemens SIMATIC S7-300 CPU 314, part number 6ES7314-1AF10-0AB0, is a mid-range central processing unit belonging to the S7-300 programmable logic controller family. This CPU is designed for medium-complexity automation tasks and serves as the core processing element in S7-300 modular PLC configurations. It is manufactured by Siemens and is part of the well-established SIMATIC S7-300 series, which has been widely deployed across industrial automation environments worldwide.
The CPU 314 (6ES7314-1AF10-0AB0) features 96 KB of work memory and supports both binary and floating-point arithmetic operations. It communicates via the integrated MPI (Multi-Point Interface) port, enabling connection to programming devices, HMI panels, and other S7-300 or S7-400 CPUs. The unit supports PROFIBUS-DP when used with appropriate communication modules, and it is programmable using STEP 7 software via the MPI interface. The CPU includes an integrated 24 V DC power supply for sensor/actuator supply and supports a micro memory card (MMC) for program storage and data retention without a battery.
The SIMATIC S7-300 CPU 314 is commonly used in manufacturing automation, machine tool control, conveyor systems, and process automation applications. Its modular design allows integration with a wide range of S7-300 signal modules, function modules, and communication processors, making it suitable for applications requiring flexible I/O expansion. Industries such as automotive, food and beverage, chemical processing, and packaging rely on this CPU for reliable and deterministic control tasks.
Technical Specifications
| Work Memory | 96 KB |
|---|---|
| Load Memory | Micro Memory Card (MMC), up to 8 MB |
| Processing Speed (Binary Operations) | 0.1 ms / 1000 instructions |
| Communication Interface | MPI (Multi-Point Interface) |
| MPI Data Rate | 187.5 kbit/s to 12 Mbit/s |
| Input/Operating Voltage | 24 V DC |
| Power Consumption | 2.5 W (from backplane bus) |
| Number of Timers | 256 |
| Number of Counters | 256 |
| Digital I/O (integrated) | None (via expansion modules) |
| Operating Temperature | 0 °C to +60 °C |
| Storage Temperature | -40 °C to +70 °C |
| Relative Humidity | 10% to 95% (non-condensing) |
| Dimensions (W x H x D) | 40 mm x 125 mm x 130 mm |
| Mounting | DIN rail (35 mm) |
| Certifications | CE, UL, cULus, ATEX |
Common System Event Codes
- Fault Code 1
- STOP caused by user program error or illegal instruction encountered during execution.
Connect programming device via MPI, read diagnostic buffer in STEP 7, identify the offending network block, and correct the program logic. - Fault Code 2
- STOP caused by a time error — the cycle time watchdog was exceeded.
Increase the maximum cycle time in the CPU properties via STEP 7, or optimize the user program to reduce scan cycle time. - Fault Code 3
- I/O access error — the CPU attempted to access a module that is not present or not responding.
Check physical seating of all S7-300 modules on the rail, verify module configuration in STEP 7 hardware configuration matches the actual hardware, and replace any faulty modules. - Fault Code 4
- STOP due to a programming error — block not found or called block does not exist in load memory.
Verify all called function blocks (FBs), function calls (FCs), and data blocks (DBs) are downloaded to the CPU. Re-download the complete program from STEP 7. - Fault Code 5
- Battery/memory card fault — program retention may be lost due to missing or faulty micro memory card.
Insert a valid Siemens Micro Memory Card (MMC) into the CPU slot. Perform a memory reset (MRES) and re-download the program. - Fault Code 6
- Configuration error — hardware configuration downloaded to CPU does not match the actual installed modules.
Open STEP 7 HW Config, verify that the configured modules match the physically installed modules in type, order number, and slot position, then recompile and download the configuration. - Fault Code 7
- MPI communication error — loss of communication between CPU and programming device or HMI.
Check MPI cable connections and terminating resistors. Verify MPI address settings are unique on the network. Confirm baud rate settings match across all connected devices.
Frequently Asked Questions
What programming software is required for the 6ES7314-1AF10-0AB0?
This CPU is programmed using Siemens STEP 7 (version 5.x or higher) via the MPI interface. TIA Portal does not natively support S7-300 CPUs of this generation without the STEP 7 Professional package.
Does the CPU 314 (6ES7314-1AF10-0AB0) require a battery for program retention?
No, this CPU uses a Siemens Micro Memory Card (MMC) for non-volatile program and data storage, eliminating the need for a backup battery for program retention. However, retentive data areas are maintained by the MMC.
What is the maximum number of S7-300 modules that can be connected to this CPU?
The S7-300 system supports up to 8 modules per rack, and up to 4 racks can be connected using expansion interface modules (IM 360/361), allowing a maximum of 32 signal modules in total.
Does this CPU support PROFIBUS-DP communication?
The 6ES7314-1AF10-0AB0 does not have an integrated PROFIBUS-DP interface. PROFIBUS-DP connectivity can be added by installing a CP 342-5 communication processor module in the same rack.
What is the cycle time for the CPU 314?
The CPU 314 processes 1000 binary instructions in 0.1 ms. The actual cycle time depends on program complexity and I/O configuration, and the maximum watchdog cycle time is configurable in STEP 7 CPU properties.
Troubleshooting
CPU remains in STOP mode after power-up and will not transition to RUN
Check the diagnostic buffer in STEP 7 (accessible via PLC > Module Information > Diagnostic Buffer) to identify the specific stop cause. Verify the mode selector switch on the CPU is set to RUN or RUN-P.
Resolve the fault indicated in the diagnostic buffer, which may include re-downloading the user program, correcting hardware configuration mismatches, or inserting a valid Micro Memory Card. Perform a memory reset (MRES) if necessary before re-downloading.
CPU cannot be reached via MPI from the programming device
Verify the MPI cable is correctly connected and that bus termination resistors are enabled on the first and last devices on the MPI segment. Check that the MPI address of the CPU (default address 2) does not conflict with other devices.
Ensure the PC adapter or MPI interface card is configured to the correct baud rate (typically 187.5 kbit/s for S7-300). Replace the MPI cable if damaged. Reset MPI address conflicts by connecting devices one at a time.
SF (System Fault) LED is lit red on the CPU
The SF LED indicates a hardware or software fault. Access the diagnostic buffer via STEP 7 to read the specific event entries. Common causes include I/O module faults, configuration mismatches, or program errors.
Address the specific fault identified in the diagnostic buffer. Replace faulty I/O modules, correct hardware configuration in STEP 7 HW Config, or fix program errors and re-download. Perform a CPU restart after resolving the fault.
Program data is lost after power cycle
Check whether a Micro Memory Card is properly inserted in the CPU card slot. Inspect the MMC for physical damage. Verify that the program was saved to the MMC and not only to RAM.
Insert a compatible Siemens MMC, perform a memory reset (MRES), and re-download the complete program and hardware configuration from STEP 7. Ensure the download completes without errors before cycling power.
I/O modules are not responding or showing BF (Bus Fault) LED
Inspect the physical seating of the affected module in the rack. Check the backplane bus connector for bent pins or damage. Verify the module order number matches what is configured in STEP 7 HW Config.
Re-seat the module firmly in the rack. If the BF LED persists, swap the module with a known-good unit to confirm hardware failure. Update the STEP 7 hardware configuration if the replacement module has a different order number.
| Condition | Repair, Used, Refurbished, New in box (sealed) |
|---|
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