Allen Bradley 1756-CNB ControlLogix ControlNet Communication Module

Product Description

The Allen Bradley 1756-CNB is a ControlLogix communication interface module designed for ControlNet networks. It provides a single-channel ControlNet connection with support for up to 64 connections and 99 nodes, ensuring reliable data exchange in distributed automation systems. Although discontinued by the manufacturer, it remains a key component for legacy ControlLogix installations, with the recommended engineering replacement being the 1756-CN2.

Technical Specifications

• Manufacturer: Allen Bradley

• Category: PLCs

• Product Line: ControlLogix

• Part Number: 1756-CNB

• Product Type: ControlNet Communication Module

• Weight: 0.26 kg (0.56 lbs)

• Ports: 1 ControlNet BNC, 1 NAP RJ45

• Transmission Rate: 5000 kbps

• Maximum Connections Supported: 64

• Logix Communication Connections Range: 40–48

• Maximum Number of Nodes: 99

• Slot Width: 1

• Power Dissipation: 5.1 W

• Thermal Dissipation: 17.4 BTU/hr

• Input Current: 970 mA @ 5.1 VDC, 1.7 mA @ 24 VDC

• Operating Temperature: 0–60 °C

• Storage Temperature: −40–85 °C

• Relative Humidity: 5–95% non-condensing

• Emissions Compliance: CISPR 11 Class A

• Vibration Resistance: 2 G @ 10–500 Hz

• Shock Resistance: 30 G operating, 50 G non-operating

• ESD Immunity: 6 kV contact, 8 kV air

• EFT/B Immunity: ±3 kV @ 5 kHz on ControlNet ports

• Conducted RF Immunity: 10 V rms, 1 kHz 80% AM, 150 kHz–80 MHz

• Radiated RF Immunity: 10 V/m (80–2000 MHz), 3 V/m (2000–2700 MHz)

• Surge Transient Immunity: ±2 kV line-earth (CM) on ControlNet ports

• Isolation Voltage: 30 V continuous, basic insulation (ControlNet to backplane)

• Enclosure Type: Open-style

• ControlNet Cable: 1786-RG6 quad shield RG6 coaxial

• NAP Cable: 1786-CP

• Module Location: Chassis-based, any slot

Application Scenarios

• Legacy ControlLogix systems requiring ControlNet communication

• Distributed control networks with multiple nodes and high reliability requirements

• Industrial automation environments needing robust EMI and surge protection

FAQ

Q: Is the 1756-CNB still available from the manufacturer?  A: No, it has been discontinued. The recommended replacement is the 1756-CN2.

Q: How many nodes can the module support?  A: Up to 99 nodes on a ControlNet network.

Q: What type of cables are required?  A: 1786-RG6 coaxial cable for ControlNet and 1786-CP for NAP connections.

Comparison with Similar Models

• 1756-CNB: Single-channel ControlNet communication, legacy module

• 1756-CN2: Engineering replacement, enhanced performance and reliability

• 1756-CNBR: Redundant ControlNet communication module for high-availability systems