Allen-Bradley 1756-CN2R/B ControlNet Communication Module

The Allen-Bradley 1756-CN2R/B is a high-performance ControlNet redundant bridge module engineered for the ControlLogix platform. As a Series B hardware revision, this communication interface facilitates deterministic data exchange between controllers, remote I/O, and field devices. By utilizing a dual-channel coaxial architecture, the module ensures robust network availability, effectively mitigating the risk of operational downtime caused by cable damage or signal degradation.

Features

• Redundant Media Support: Dual BNC coaxial ports provide automatic failover capabilities, allowing the network to maintain continuous operation if one cable path experiences a fault.
• High-Capacity Data Routing: Supports up to 131 parallel connections, including 128 dedicated Logix connections across a maximum of 99 network nodes.
• Optimized Performance: Operates at a consistent 5 Mbps deterministic throughput, suitable for time-critical industrial control applications.
• Integrated USB Interface: Includes a local USB port for convenient configuration and diagnostics.
• Standardized Infrastructure: Compatible with 1786-RG6 quad-shield coaxial cabling to ensure signal integrity in high-EMI environments.

Applications

This module is designed for demanding industrial environments requiring high-availability communication, such as process automation, manufacturing lines, and distributed control systems. It is commonly deployed in ControlLogix chassis to bridge communication between the controller and remote I/O or other intelligent field components.

Technical Specifications

Installation Guidelines

• Ensure the ControlLogix chassis is powered down before inserting or removing the module to prevent damage to the backplane pins.
• Seat the module firmly into a single slot of the 1756 series chassis; use the top and bottom connectors to secure it.
• Use only 1786-RG6 quad-shield coaxial cable for ControlNet connections to maintain network impedance and shielding standards.
• Maintain proper ventilation in the control cabinet; ensure the module is not obstructed by wiring or other components.
• Handle the module using ESD-safe practices to prevent static discharge damage to internal circuitry.

FAQ

Does this module support non-redundant configurations?

While the 1756-CN2R/B is specifically designed for redundant media applications, it can be utilized in non-redundant setups, though its primary advantage is the automatic failover capability provided by the dual BNC ports.

Is this module compatible with older Series A chassis?

The 1756-CN2R/B is compatible with standard ControlLogix chassis assemblies (1756-A4 through 1756-A17). Always verify your firmware revision in Studio 5000/RSLogix 5000 to ensure compatibility with your specific controller project.