Siemens 6ES5946-3UR12 | SIMATIC S5-115U CPU 946 Processor

The Siemens 6ES5946-3UR12 delivers high-speed processing for advanced SIMATIC S5-115U systems. This CPU handles complex control tasks with expanded memory and faster execution times. You can program it using STEP 5 with all three available languages. It supports up to 1024 digital I/O points across multiple racks. Consequently, this unit suits demanding applications like injection molding and packaging lines.

Technical Specifications Overview

Parameter	Detailed Specification
Model	Siemens 6ES5946-3UR12
Category	SIMATIC S5-115U Central Processing Unit (CPU 946)
Processor Type	16-bit microcontroller (high-performance variant)
Program Memory	48 KB RAM (battery-backed, 32 KB usable)
Data Memory	24 KB (flags, timers, counters, data blocks)
Execution Speed	1.3 ms per 1K of statement list (STL)
Maximum I/O Points	1024 digital / 128 analog (with expansion)
Built-in Interfaces	AS511 (programming port, 5-pin DIN)
Operating Voltage	5V DC from backplane (typical 800 mA)
External Supply	24V DC (for I/O, not required for CPU alone)
Energy Storage	Replaceable lithium battery for RAM and clock
Battery Life	Approximately 1.5 years (CPU powered off)
Dimensions	250 mm x 25 mm x 130 mm (single-width)
Weight	0.54 kg (540 grams)
Indicators	5 LEDs (power, run, stop, battery, bus error)
Operating Temperature	0°C to 60°C

Functional Features and Processing Capabilities

The Siemens 6ES5946-3UR12 executes math operations and data handling with high efficiency. You can store up to 4000 function blocks within the 32 KB usable memory. The CPU includes 2048 internal flags, 256 timers, and 256 counters. Furthermore, it supports multiple interrupt sources for fast event responses.

This central processing unit features an integrated real-time clock with battery backup. The clock enables scheduled program execution and time-stamped alarms. Additionally, the processor handles remote I/O through interface modules like Siemens 6ES5312-5CA12. The hardware watchdog resets the system automatically during software lockups.

Installation and Configuration Steps

First, insert the Siemens 6ES5946-3UR12 into the first slot of your S5-115U rack. Next, connect a programming device to the AS511 port on the front panel. Then, verify the battery status using the front LED indicator. Finally, download your STEP 5 program through the serial interface.

You must replace the lithium battery every 18 months as preventive maintenance. The CPU loses all programs and data after complete battery discharge. Always place the CPU in STOP before removing it from the rack. Furthermore, back up your program to an EPROM memory card for permanent storage.

This central processing unit works perfectly for textile machinery and printing presses. It also controls metal forming equipment and assembly stations reliably. The Siemens 6ES5946-3UR12 supports all S5-115U I/O and communication modules. You can upgrade from a 942H without changing your existing I/O wiring.