1756-CNBR Product datasheet 

1756-CNBR Functional Description

The 1756-CNBR ROCKWELL ControlLogix ControlNet Redundant Bridge Module is a high-performance ControlNet Bridge Redundancy module designed for robust industrial communication within ControlLogix systems. As an enhanced version of the 1756-CNB, this module features dual BNC ports to support redundant media connections, significantly improving network reliability compared to single-port versions. The Allen-Bradley 1756-CNBR efficiently manages both scheduled data coordination with Logix5550 controllers and unscheduled data bridging between ControlLogix backplanes and ControlNet networks. With capacity for 64 bidirectional connections and support for 99 network nodes, this module operates at the standard ControlNet speed of 5Mbps, making it ideal for demanding automation applications requiring deterministic communication. Its power requirements include 970mA at 5.1VDC and minimal 24VDC draw, ensuring efficient operation within ControlLogix chassis.

Designed for mission-critical applications, the Allen-Bradley 1756-CNBR ControlLogix Communication Module provides essential redundancy capabilities that prevent communication loss during network disruptions. The module's additional ControlNet port allows for redundant media implementation, a feature unavailable in standard CNB modules. This redundancy is particularly valuable in industrial environments where uninterrupted communication is crucial. It supports 40-48 logical communication connections per module and can buffer up to 20 unconnected messages, offering flexibility for complex control architectures. Its compatibility with various ControlLogix racks (including 1756-A4 through A17 series) and both standard/redundant power supplies makes it a versatile solution for distributed I/O implementations across different system configurations.

Installation of the Interface Module Allen-Bradley 1756-CNBR requires careful attention to network topology, particularly regarding tap drop cable orientation to prevent connection reversals that could disrupt communication. The module includes a Network Access Port (NAP) featuring an 8-pin RJ45 connector for local programming access. With power dissipation of 5.1 watts and thermal dissipation of 17.4 BTU/hr, the ControlLogix Communication Module Allen-Bradley 1756-CNBR is engineered for stable operation in industrial environments. Its quad-shield RG-6 coaxial cable connections ensure reliable data transmission while maintaining the deterministic characteristics essential for real-time control applications.

The 1756-CNBR ControlLogix ControlNet Interface Module represents a critical component in modern automation systems where network reliability and redundancy are paramount. Its ability to function both as a local communication module alongside ControlLogix processors and as a head module in distributed I/O racks provides system designers with flexible implementation options. The module's robust construction and advanced features make it particularly suitable for applications requiring high availability, such as continuous process industries or critical manufacturing operations. As part of Rockwell Automation's comprehensive ControlLogix ecosystem, the 1756-CNBR delivers the performance and reliability expected from industrial-grade communication solutions.