Allen-Bradley 1756-CNB ControlLogix ControlNet Communication Module

Overview

The 1756-CNB (1756-CNB) is a high-performance communication bridge specifically designed for the ControlLogix® platform. It facilitates deterministic, high-speed data transfer between a controller and remote I/O devices or other controllers across a ControlNet™ network. This module serves as a critical link in industrial architectures requiring scheduled data delivery and hardware redundancy. By occupying a single slot in any 1756 chassis, it provides the backbone for coordinated motion, complex drive control, and distributed process automation.

Detailed Technical Specifications

• Network Interface: ControlNet Bridge

• Transmission Rate: 5 Mbps fixed

• Node Capacity: Supports up to 99 nodes per network

• Logical Connections: 64 maximum connections

• Backplane Current (5.1V DC): 970 mA

• Backplane Current (24V DC): 1.7 mA

• Total Power Dissipation: 5.1 Watts

• Thermal Output: 17.4 BTU per hour

• Chassis Slot Width: 1 (Single Slot)

• Configuration Interface: RSNetWorx for ControlNet

• Diagnostic Indicators: Status LEDs for module health and network activity

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

• Storage Temperature: -40 to 85 °C (-40 to 185 °F)

• Relative Humidity: 5 to 95% non-condensing

Operational Capabilities

The 1756-CNB (1756-CNB) allows for seamless bridging between networks without the need for additional programming. It supports the producer/consumer model, which optimizes network bandwidth by allowing multiple nodes to consume the same data simultaneously. This module is essential for applications where timing is critical, such as high-speed bottling lines or synchronized axis control, ensuring that control data arrives at its destination with minimal jitter.

Engineering FAQ

• Does the 1756-CNB support redundant media?The 1756-CNB (1756-CNB) features two BNC connectors for redundant coaxial cable connections. This ensures that if one cable path is severed, the module continues to communicate via the secondary path without system interruption.

• How do I set the node address for this module?The node address (01–99) is manually selected using the two rotary switches located on the side of the module before installation into the chassis.

• What is the difference between the 1756-CNB and 1756-CN2?While both are ControlNet bridges, the 1756-CNB (1756-CNB) is the standard performance version. The 1756-CN2 series offers significantly higher connection capacities and faster CPU processing for larger, more complex I/O trees.