Siemens 6ES5942-7UH11 | SIMATIC S5-115U CPU 942H

The Siemens 6ES5942-7UH11 serves as the core controller for SIMATIC S5-115U automation systems. This compact CPU handles both logic execution and communication tasks simultaneously. You can program it using standard STEP 5 software on a programming device. It supports up to 256 digital I/O points without requiring additional expansion racks. Consequently, this processor suits small to medium-sized machine control applications.

Technical Specifications Overview

Parameter	Detailed Specification
Model	Siemens 6ES5942-7UH11
Category	SIMATIC S5-115U CPU 942H (Central Processing Unit)
Processor Type	16-bit microcontroller (custom ASIC)
Program Memory	16 KB RAM (battery-backed)
Data Memory	8 KB (flags, timers, counters, registers)
Execution Speed	2 ms per 1K of statement list (STL)
Maximum I/O Points	256 digital + 64 analog
Built-in Interfaces	AS511 (programming port, 5-pin DIN)
Operating Voltage	5V DC from backplane (typical 650 mA)
External Supply	24V DC (for I/O, not required for CPU alone)
Energy Storage	Replaceable lithium battery for RAM retention
Battery Life	Approximately 1 year (with CPU powered off)
Dimensions	250 mm x 25 mm x 130 mm (single-width)
Weight	0.52 kg (520 grams)
Indicators	4 LEDs (power, run, stop, battery fault)
Operating Temperature	0°C to 60°C

Functional Features and Processing Capabilities

The Siemens 6ES5942-7UH11 executes statement list, ladder, and function block diagrams. You can store up to 2000 program steps within the 16 KB memory capacity. The CPU includes 256 internal flags, 128 timers, and 128 counters. Furthermore, it supports up to 64 KB of additional data blocks through memory submodules.

This central processing unit features an integrated real-time clock with battery backup. The clock allows time-stamped events and scheduled program executions. Additionally, the CPU provides hardware interrupt processing for high-speed events. The watchdog timer resets the system automatically during software lockups.

Installation and Configuration Steps

First, insert the Siemens 6ES5942-7UH11 into the first slot of your S5-115U rack. Next, connect a programming device to the AS511 port using the standard cable. Then, verify the battery status by checking the front panel LED indicators. Finally, download your STEP 5 program through the serial programming interface.

You must replace the lithium battery every year during scheduled maintenance. The CPU does not retain programs or data after complete battery discharge. Always place the CPU in STOP mode before removing it from the rack. Furthermore, back up your program to an EPROM or EEPROM memory card.

This central processing unit works perfectly for packaging machines and conveyor systems. It also controls small assembly stations and testing equipment reliably. The Siemens 6ES5942-7UH11 supports all standard S5 I/O and communication modules. You can upgrade to a larger CPU without changing your existing I/O wiring.