Product Overview

The 1756-RM is an enhanced redundancy module from Allen-Bradley, engineered as a cornerstone of Rockwell Automation’s ControlLogix platform for implementing high-availability controller redundancy solutions -5-6. As a dedicated module within the 1756 product series, the 1756-RM enables the creation of a redundant controller system comprising two identical ControlLogix chassis, each containing the same slot configuration, compatible modules, and critical redundancy firmware revisions -2. The primary function of the 1756-RM is to manage the connectivity and synchronization of two identical controllers, providing seamless system monitoring and automatic failover capabilities -5. The 1756-RM achieves this through a dedicated fiber-optic link, utilizing a single-mode LC connector and the 1756-RMCx redundancy cable to maintain constant communication between the controller pairs -5. With an operating temperature range of 0 to 60 degrees Celsius and power dissipation of 9 Watts, the 1756-RM is designed for robust industrial environments -2. The module features diagnostic LEDs including PRI, COM, and OK indicators, providing immediate visual feedback on system health and redundancy status -5. The 1756-RM is available in Series A and B revisions, with Series B delivering enhanced performance while maintaining backward compatibility within redundancy configurations -3-5. This module is exclusively compatible with the ControlLogix platform and is essential for applications where system downtime is unacceptable -5.

 

Technical Specifications

Parameter Name	Parameter Value
Product Model	1756-RM (Series A / B)
Manufacturer	Allen-Bradley / Rockwell Automation
Product Type	ControlLogix Enhanced Redundancy Module
Series	1756 ControlLogix
Redundancy Type	Hot-standby with automatic switchover
Compatibility	ControlLogix 5560, 5570, and 5580 controllers
Redundancy Cable	1756-RMCx (LC Fiber Optic Single Mode) -5
Communication Interface	LC Fiber Optic Single Mode Connector -5
Switchover Time	Typically <100 ms for seamless transition
Redundancy Speed	100 Mbps (with same series modules) -5
Backplane Current (1.2V DC)	4 mA -2-6
Backplane Current (5.1V DC)	1.2 A -2-6
Backplane Current (24V DC)	120 mA -2-6
Power Dissipation	9 W -2-6
Thermal Dissipation	31 BTU/hr -2-6
Mounting	Chassis-based, any slot (single-slot module) -2-5
Compatible Chassis	1756-A4, 1756-A7, 1756-A10, 1756-A13, 1756-A17 -5-6
Compatible Standard Power Supplies	1756-PA72, 1756-PA75, 1756-PB72, 1756-PB75 -5-6
Compatible Redundant Power Supplies	1756-PA75R, 1756-PB75R, 1756-PSCA2 -5-6
Operating Temperature	0 to 60°C (32 to 140°F) -2-6
Storage Temperature	-40 to 85°C (-40 to 185°F) -2-6
Certifications	CE, CSA, Ex, C-Tick, c-UL-us, FM, KC -2-6
IEC Temperature Code	T4 -2-6
Enclosure	Open Type -2
Weight	Approx. 0.29 kg (0.64 lbs) -2-6

 

 

Main Features and Advantages

Seamless redundancy for mission-critical control: The 1756-RM provides a comprehensive redundancy solution by managing two identical ControlLogix controllers in a hot-standby configuration -5. The module continuously synchronizes the secondary chassis with the primary, maintaining an exact operational state. In the event of a primary controller failure, the 1756-RM orchestrates an automatic switchover to the secondary chassis, achieving transition times of typically less than 100 ms to ensure uninterrupted process control -11. The 1756-RM utilizes a dedicated 100 Mbps fiber-optic link via the LC single-mode connector for high-speed data synchronization between the redundant chassis pairs -5.

Enhanced firmware and system compatibility: The 1756-RM supports multiple firmware revisions, including 3.002 for standard redundancy and enhanced versions for advanced redundancy systems -1-4. The 1756-RM is compatible with a wide range of ControlLogix controllers, including the 1756-L61, 1756-L62, 1756-L63, 1756-L64, 1756-L65, and the 5570 series processors -1-4. Recent firmware enhancements have improved the auto-qualification process, automatically stopping synchronization attempts after a chassis pair fails to synchronize, which significantly aids in troubleshooting by preventing event logs from being filled with repetitive failure events -10.

Simplified diagnostics and maintenance: The 1756-RM incorporates diagnostic LEDs including PRI, COM, and OK indicators that provide immediate visual status of system redundancy and module health -5. The module supports firmware upgrades through ControlFLASH software, with detailed procedures for upgrading both primary and secondary chassis -1. The 1756-RM also maintains synchronization logs that can be viewed through the RMCT tool, enabling rapid identification of synchronization issues and simplifying system maintenance -10.

Flexible chassis placement and compatibility: The 1756-RM is a single-slot module that can be installed in any available slot of the ControlLogix chassis -5. It is compatible with all 1756-A series chassis and supports both standard and redundant power supply configurations -5-6. The 1756-RM provides backward compatibility between Series A and B modules, although maximum operability at 100 Mbps is achieved when both modules are of the same series -5.