Siemens 6ES5921-3WB12 CPU | Central Processing Unit

The 6ES5921-3WB12 serves as a central processing unit for Siemens SIMATIC S5 PLC systems. This module executes user programs and manages all I/O data transfers. Its rectangular frame measures 232 millimeters in width. The module height reaches 210 millimeters exactly. Depth stays at 155 millimeters. You will find this unit weighs approximately 1.25 kilograms. Therefore, installation requires sliding the unit into a standard S5 rack slot. One front-panel serial port connects to programming software.

Physical Layout and Connectors

The front panel features a 2-line LCD display for system diagnostics. You will find eight push buttons for local configuration access. One RS-232 port supports connection to a programming terminal. A second RS-485 port handles communication with remote I/O networks. Three status LEDs indicate run, stop, and fault conditions.

Technical Specifications

Parameter	Specification
Module Width	232 mm
Module Height	210 mm
Module Depth	155 mm
Unit Weight	1.25 kg
Processor	16-bit @ 10 MHz
Program Memory	32 KB (STEP 5)
Data Memory	16 KB (retentive)
Scan Time	2.0 ms per 1K instructions
Communication Ports	RS-232, RS-485
Component Total	742 discrete parts
Internal Energy Storage	2200 µF capacitor bank
Backup Battery	Lithium (3.6V, 5 years)
Operating Temperature	0°C to +60°C

Internal Design and Energy Storage

The 6ES5921-3WB12 contains exactly 742 discrete components inside. A 2200 microfarad capacitor bank filters the main power supply input. This bank holds enough charge for 25 milliseconds after power loss. The 16-bit processor runs at 10 megahertz for reliable execution. A lithium battery retains data memory for up to five years. EPROM stores the user program without any battery backup required.

Operational Performance

This central processing unit executes STEP 5 logic from 32KB memory. It scans 1,000 instructions in approximately 2.0 milliseconds. Moreover, the unit handles up to 1024 digital I/O points system-wide. Two communication ports allow connection to HMIs and network adapters. The LCD display shows real-time system status and diagnostic messages. Eight buttons let you navigate menus without a programming computer. Consequently, you achieve dependable control for medium-sized automation projects. Siemens designed this CPU for SIMATIC S5 platform compatibility. Its robust construction suits demanding industrial environments.

In summary, the 6ES5921-3WB12 delivers reliable central processing performance. Use this CPU for factory automation or process control systems. It provides stable execution for legacy S5 installations. Order this central processing unit for your Siemens PLC system.