1756-CNB Allen-Bradley ControlLogix ControlNet Bridge

Technical Specifications

Product Overview

The Allen-Bradley 1756-CNB is a premium ControlLogix ControlNet Bridge Module engineered by Rockwell Automation to provide high-speed deterministic communication across industrial automation networks. Weighing a lightweight 0.26 kg, this network interface links the ControlLogix controller to a ControlNet network infrastructure. It occupies a single chassis slot and supports a reliable 5 Mbps transmission rate, facilitating rapid implicit I/O messaging and explicit data exchange for up to 99 nodes and 64 simultaneous system connections.

Core Technical Advantages

• Deterministic I/O Telemetry: Uses the reliable ControlNet protocol to ensure critical time-slice scheduling and repeatable data updates across remote I/O chassis.
• Scalable Architecture Capacity: Capable of managing complex network topologies with native support for up to 99 physical node addresses and 64 logical messaging connections.
• Optimized Thermal Performance: Engineered for dense industrial enclosures, featuring a low 5.1 Watt power consumption and a thermal dissipation rating of 17.4 BTU/hr.
• Seamless Chassis Integration: Easily inserts into any available slot of a standard 1756 ControlLogix chassis, drawing its operating power (970 mA @ 5.1V DC) directly from the backplane for this compact 0.26 kg unit.

Installation Guide

Ensure the ControlLogix chassis power supply is turned off before slot assignment. Align the 1756-CNB circuit board with the top and bottom chassis guides of the selected single-slot location, sliding the 0.26 kg module firmly inward until the retention tabs lock safely. Connect the standard ControlNet BNC coax media taps to the front panel interface. Apply system backplane power and verify that the onboard alphanumeric LED indicators display a healthy, active network status without communication line errors.

Technical FAQs

Q1: What is the maximum data transmission throughput supported by the 1756-CNB module?
A1: The module operates at a fixed, high-speed ControlNet communication rate of 5 Mbps, providing deterministic network scheduling for critical process instrumentation.

Q2: How many individual network connections can a single bridge unit handle?
A2: A single 1756-CNB module supports a maximum connection limit of 64 discrete backplane or network routing pathways simultaneously.

Q3: What is the physical weight of this communication card and does it require an independent external power supply?
A3: The module has a net weight of approximately 0.26 kg (0.57 lbs). It does not require an independent power line, as it is fully powered directly from the standard ControlLogix 1756 chassis backplane (drawing 970 mA at 5.1 V DC and 1.7 mA at 24 V DC).