Siemens 6ES7312-1AE14-0AB0 – SIMATIC S7-300 CPU 312 Central Processing Unit

The Siemens 6ES7312-1AE14-0AB0 is a SIMATIC S7-300 central processing unit. Specifically, this CPU 312 features an integrated MPI interface. It includes a built-in 24 V DC power supply. Furthermore, it provides 32 KB of integrated work memory. In addition, a Micro Memory Card (MMC) is required for program and data storage. Consequently, this compact CPU suits small to medium automation tasks requiring fast processing.

Ordering Configuration and Product Identification

• Product Type: CPU 312 Central Processing Unit.

• HW Functional Status: 01.

• Firmware Version: V3.3.

• Work Memory: 32 KB integrated (not expandable).

• Load Memory: MMC required (max. 8 MB).

• MMC Data Retention: Minimum 10 years after last programming.

• Backup: Maintenance-free via MMC (no battery required).

• Programming Package: STEP 7 V5.5 + SP1 or higher, or V5.2 + SP1 + HSP 218.

• Dimensions (W x H x D): 40 mm x 125 mm x 130 mm.

• Weight: Approximately 270 grams.

• Therefore, the Siemens 6ES7312-1AE14-0AB0 offers reliable memory retention without batteries.

Supply Voltage and Power Specifications

• Rated Supply Voltage (DC): 24 V.

• Permissible Range (Lower Limit): 19.2 V DC.

• Permissible Range (Upper Limit): 28.8 V DC.

• External Protection Recommendation: 2 A minimum.

• Mains Buffering (Stored Energy Time): 5 ms.

• Repeat Rate (Minimum): 1 second.

• Current Consumption (Rated Value): 650 mA.

• Current Consumption (No-load, typical): 140 mA.

• Inrush Current (typical): 3.5 A.

• I²t: 1 A²·s.

• Power Loss (typical): 4 W.

• Thus, the 6ES7312-1AE14-0AB0 operates reliably within standard industrial power ranges.

CPU Processing Times

• Bit Operations (typical): 0.1 µs.

• Word Operations (typical): 0.24 µs.

• Fixed Point Arithmetic (typical): 0.32 µs.

• Floating Point Arithmetic (typical): 1.1 µs.

• Command Set: Refer to instruction list.

• Nesting Levels: 8 per priority class.

• Additional Nesting in Error OB: 4.

• Consequently, the Siemens CPU 312 delivers fast processing for basic control tasks.

CPU Blocks and Memory

• Total Number of Blocks: 1,024 (DBs, FCs, FBs).

• Maximum DBs: 1,024 (Number range 1 to 16000).

• Maximum DB Size: 32 KB.

• Maximum FBs: 1,024 (Number range 0 to 7999).

• Maximum FB Size: 32 KB.

• Maximum FCs: 1,024 (Number range 0 to 7999).

• Maximum FC Size: 32 KB.

• Maximum OBs: See instruction list.

• Maximum OB Size: 32 KB.

• Free Cycle OBs: 1 (OB 1).

• Time Alarm OBs: 1 (OB 10).

• Delay Alarm OBs: 2 (OB 20, 21).

• Cyclic Interrupt OBs: 4 (OB 32, 33, 34, 35).

• Process Alarm OBs: 1 (OB 40).

• Startup OBs: 1 (OB 100).

• Asynchronous Error OBs: 4 (OB 80, 82, 85, 87).

• Synchronous Error OBs: 2 (OB 121, 122).

• Note: Loadable blocks may be reduced by the MMC used.

• Therefore, the 6ES7312-1AE14-0AB0 supports a wide range of block types for structured programming.

Counters, Timers, and Retentivity

• S7 Counters: 256 total.

• Retentivity: Adjustable (preset Z 0 to Z 7).

• Counting Range: 0 to 999.

• IEC Counters: Yes (SFB type, unlimited by RAM).

• S7 Timers: 256 total.

• Retentivity: Adjustable (preset no retentivity).

• Timer Range: 10 ms to 9,990 s.

• IEC Timers: Yes (SFB type, unlimited by RAM).

• Retentive Data Area (Max): 32 KB.

• Flag Size (Max): 256 bytes.

• Retentivity Preset: MB 0 to MB 15.

• Clock Memories: 8 (1 memory byte).

• Data Block Retentivity: Adjustable via non-retain property.

• Thus, the CPU 312 offers flexible retentivity options for critical data.

Address Area and I/O Specifications

• I/O Address Area (Inputs): 1,024 bytes.

• I/O Address Area (Outputs): 1,024 bytes.

• Process Image (Inputs): 1,024 bytes (adjustable).

• Process Image (Outputs): 1,024 bytes (adjustable).

• Default Process Image: 128 bytes each.

• Digital Channels (Inputs): 256 (central only).

• Digital Channels (Outputs): 256 (central only).

• Analog Channels (Inputs): 64 (central only).

• Analog Channels (Outputs): 64 (central only).

• Hardware Configuration: 1 rack maximum.

• Modules per Rack: 8 maximum.

• Expansion Units: 0 maximum.

• DP Masters (Integrated): 0.

• DP Masters (via CP): 4.

• Operable FMs: 8.

• Operable CPs (PtP): 8.

• Operable CPs (LAN): 4.

• Consequently, the 6ES7312-1AE14-0AB0 supports central I/O only.

MPI Interface and Communication

• Interface Type: Integrated RS 485 interface (MPI).

• Isolation: Not isolated.

• Max Output Current: 200 mA.

• Transmission Rate (Max): 187.5 kbit/s.

• Protocols Supported: MPI only.

• PG/OP Communication: Yes.

• Routing: No.

• Global Data Communication: Yes.

• S7 Basic Communication: Yes.

• S7 Communication (Server): Yes (configured on one side).

• S7 Communication (Client): No.

• PROFIBUS DP Master: No.

• PROFIBUS DP Slave: No.

• Point-to-Point Connection: No.

• PROFIsafe: No.

• Overall Connections: 6 total.

• PG Communication: 5 usable (1 reserved).

• OP Communication: 5 usable (1 reserved).

• S7 Basic Communication: 2 usable (0 reserved).

• S5 Compatible Communication: Via CP and loadable FC.

• Data Record Routing: No.

• Therefore, the CPU 312 provides basic MPI communication for programming and operator panels.

Clock and Operating Hours Counter

• Software Clock: Yes.

• Retentive and Synchronizable: No.

• Deviation per Day (Max): 10 seconds (typical 2 s).

• Clock Behavior after POWER-ON: Continues at the time it had when power was switched off.

• Operating Hours Counter: 1 total.

• Range of Values: 0 to 2^31 hours (via SFC 101).

• Granularity: 1 hour.

• Retentive: Yes (must be restarted at each restart).

• Clock Synchronization: Supported (to MPI master/slave, in AS master).

• Thus, the 6ES7312-1AE14-0AB0 includes basic timekeeping functions.

Diagnostic and Test Functions

• Diagnostic Buffer: Present (500 entries max).

• Powerfail-proof Entries: 100 (last 100 retained).

• Entries Readable in RUN: 499 max (adjustable 10 to 499).

• Service Data: Can be read out.

• Status Block: Yes (up to 2 simultaneously).

• Single Step: Yes.

• Breakpoints: 4.

• Status/Control Variables: Yes (inputs, outputs, memory bits, DB, timers, counters).

• Status Variables (Max): 30.

• Control Variables (Max): 14.

• Forcing: Yes (inputs and outputs, max. 10 variables).

• Process Diagnostic Messages: Yes.

• Simultaneously Active Alarm-S Blocks: 300 max.

• Login Stations for Message Functions: 6 (depending on connections).

• Consequently, the CPU 312 supports essential commissioning and diagnostic tools.

Know-How Protection

• User Program Protection: Password protection supported.

• Block Encryption: Yes (with S7 Block Privacy).

• Security Level: Protects intellectual property.

• Access Control: Prevents unauthorized program changes.

• Configuration: Set within STEP 7 programming software.

• Thus, the Siemens 6ES7312-1AE14-0AB0 offers basic protection for user programs.

Ambient Conditions and Installation

• Operating Temperature (Min): 0°C.

• Operating Temperature (Max): 60°C.

• Mounting: Standard S7-300 rail or DIN rail.

• Rack: 1 rack maximum.

• Modules per Rack: 8 maximum.

• Expansion Units: Not supported.

• Programming Languages: LAD, FBD, STL, SCL, GRAPH, HiGraph.

• Configuration Software: STEP 7 V5.2 SP1 or higher with HW update.

• Moreover, the 6ES7312-1AE14-0AB0 suits small control cabinets.

Installation Guide

First, verify that all power sources are completely disconnected. Then, mount the Siemens 6ES7312-1AE14-0AB0 on a standard S7-300 rail. The CPU occupies one slot in the rack. After that, insert the Micro Memory Card (MMC) into the slot on the front of the CPU. The MMC is required for program and data storage. Use an MMC up to 8 MB maximum. Then, connect the 24 V DC supply voltage to the integrated power supply. The permissible range is 19.2 V to 28.8 V DC. Use an external protection device rated at 2 A minimum. Then, connect the MPI network to the RS 485 interface (if needed). The transmission rate is up to 187.5 kbit/s. Then, apply power to the CPU. The CPU will perform a power-up sequence. For programming, use STEP 7 V5.5 + SP1 or higher. Alternatively, use V5.2 + SP1 with HSP 218. Download your program to the CPU. The program is stored on the MMC. Finally, test all I/O connections and communication paths. As a result, the Siemens 6ES7312-1AE14-0AB0 will provide reliable control.

Packaging List

• One Siemens 6ES7312-1AE14-0AB0 S7-300 CPU 312 unit

• One product identification label

• One installation and configuration guide

• MMC (purchased separately, required for operation)

Common FAQs

Q1: How much work memory does the Siemens 6ES7312-1AE14-0AB0 provide?
A: This CPU provides 32 KB of integrated work memory. Specifically, it is not expandable. Therefore, ensure your program fits within this memory limit before ordering.

Q2: What memory card is required for the 6ES7312-1AE14-0AB0?
A: A Micro Memory Card (MMC) is required for program and data storage. The MMC can be up to 8 MB maximum. Therefore, the CPU will not operate without an MMC installed.

Q3: What is the processing speed of the Siemens CPU 312?
A: Bit operations execute in 0.1 µs typical. Word operations execute in 0.24 µs typical. Fixed point arithmetic executes in 0.32 µs typical. Floating point arithmetic executes in 1.1 µs typical.

Q4: What communication interface does the 6ES7312-1AE14-0AB0 have?
A: This CPU has one integrated RS 485 interface (MPI). The transmission rate is up to 187.5 kbit/s. It supports PG/OP communication, global data communication, and S7 basic communication. However, routing is not supported.

Q5: Does the Siemens 6ES7312-1AE14-0AB0 support PROFIBUS DP?
A: No, this CPU does not support PROFIBUS DP master or slave. Specifically, it supports MPI only. Therefore, use a CP module if PROFIBUS DP is required for your application.