Product Overview

The Allen-Bradley 1747-L542 is a high-performance central processing unit for the SLC™ 500 modular hardware platform. As an SLC 5/04 processor, it is specifically engineered to provide faster execution speeds and more advanced networking capabilities than the 5/01, 5/02, or 5/03 series. This module features 32 KB of total user memory, split between 28K words for data/logic and 4K words for system overhead, supporting a maximum capacity of 4096 discrete I/O points.

Designed for slot 0 of a 1746 chassis, the 1747-L542 excels in medium-to-large scale automation tasks. It utilizes a high-speed logic engine capable of a typical program scan time of 0.9 ms per kiloword. Its standout feature is the integrated Data Highway Plus (DH+) port, which facilitates high-speed peer-to-peer communication and allows the controller to be easily integrated into plant-wide factory networks alongside PLC-5® and ControlLogix® systems.

Networking and Communication Interfaces

The 1747-L542 provides dual onboard communication channels, making it a versatile hub for both localized machine control and remote data acquisition.

• Channel 1 (DH+ Port): A dedicated 57.6 Kbps (or up to 230.4 Kbps) Data Highway Plus port for messaging between processors and high-speed HMI connectivity.

• Channel 0 (RS-232 Port): A versatile 9-pin D-shell port supporting DF1 Full-Duplex, DF1 Half-Duplex (Master/Slave), DH-485, and Modbus RTU (via logic) protocols. This port is commonly used for direct PC programming, SCADA interfacing, and connection to bar code readers or modems.

The processor also supports advanced math instructions, floating-point data types, and indirect addressing, providing the computational power required for complex PID loop control and sophisticated motion profiles.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Number: 1747-L542

• Controller Series: SLC 5/04

• User Memory: 32 KB (28K words for program/data)

• Max I/O Capacity: 4096 inputs and outputs

• Max Local Chassis Expansion: 3 Chassis (30 slots total)

• Typical Scan Time: 0.9 ms/Kword

• Backplane Current (5V DC): 1.0 A

• Backplane Current (24V DC): 0 mA

• Non-Volatile Storage: Optional Flash EPROM (1747-M11, M12)

• Battery Backup: 1747-BA (Lithium)

• Operating Temperature: 0°C to 60°C (32°F to 140°F)

• Weight: 0.9 kg

• Dimentions: 3.5x13x14.5cm

Reliability and Diagnostic Features

• Front Panel LEDs: Includes dedicated indicators for RUN, FAULT, BATT (low battery), FORCE, DH+, and RS-232 status for rapid onsite troubleshooting.

• Memory Protection: Utilizes a replaceable lithium battery to preserve the volatile RAM program during power loss, with optional Flash memory for permanent storage.

• Key-Switch Operation: Features a physical three-position keyswitch (RUN, REMOTE, PROG) to prevent unauthorized logic changes while the machine is in operation.

• Industrial Hardening: Designed to operate in high-vibration environments with a 30G operational shock rating, ensuring longevity in heavy manufacturing sectors.