Siemens 6ES5921-3WB13 Central Processing Unit for SIMATIC S5

The Siemens 6ES5921-3WB13 serves as the central processing unit for SIMATIC S5 PLCs. You can install this CPU into any standard S5 rack slot zero. It executes user logic and manages all system I/O data. This processor suits medium-scale automation applications reliably.

Technical Specifications and Hardware Architecture

This central processing unit measures 233 mm in height. Its width reaches 54 mm, and the depth equals 182 mm. The Siemens 6ES5921-3WB13 weighs approximately 0.95 kilograms. A single internal main PCB holds the microprocessor and memory circuits. The module includes one replaceable lithium battery for program retention. This battery preserves user logic and retentive data during power-off periods. One 48-pin edge connector interfaces directly with the S5 backplane. One 15-pin D-sub port provides programming device connectivity.

Memory Capacity and Processing Performance

The Siemens 6ES5921-3WB13 provides 48 KB of user program memory. It also includes 4 KB of retentive data storage. The module executes 1000 ladder logic instructions in just 2 milliseconds. Consequently, this speed handles complex control algorithms and fast sequencing tasks. The lithium battery offers two years of typical service life. A front-panel LED signals low battery voltage one month in advance. The CPU supports up to 512 local I/O points without expansion.

Programming and Diagnostic Features

You must insert this module into slot zero of the S5 rack. Transitioning to programming, use a Siemens PG programmer via the D-sub port. The module includes a three-position keyswitch for run, stop, and program modes. Four front LEDs show power, run, fault, and battery status clearly. A built-in watchdog timer resets the processor on software hangs. The operating temperature range spans from 0°C to 60°C reliably.