Configured for ControlNet network bridging and data exchange in ControlLogix automation systems, the Allen-Bradley 1756-CNB (1756-CNB ControlLogix Communication Module) provides direct network interface execution between ControlLogix chassis components and ControlNet devices.

Model Configuration Details

The 1756-CNB is a ControlLogix bridge module designed for ControlNet communication. The module provides one ControlNet port and manages scheduled and unscheduled communication between Logix controllers, I/O devices, and network nodes.

Hardware Specifications

ControlNet Network Interface Characteristics

The 1756-CNB manages ControlNet communication traffic through the ControlLogix backplane interface. It transfers controller data, I/O information, and messaging packets between the ControlLogix processor and connected ControlNet nodes.

The ControlNet network operates with deterministic scheduling characteristics at a communication rate of 5 megabits/second. The module supports up to 99 network nodes and 64 communication connections according to the configured system architecture.

For ControlLogix applications, backplane communication performance depends on chassis configuration, processor loading, and installed communication modules. Proper firmware compatibility between the controller, bridge module, and network devices must be verified before system commissioning.

Ordering Information

The delivered package normally includes:

• 1 x Allen-Bradley 1756-CNB ControlLogix ControlNet Bridge Module
• 1 x ControlLogix chassis mounting interface
• 1 x Network connector interface
• 1 x Standard product documentation when supplied

Field Installation Guidelines

Chassis Installation

• Install the module into an available ControlLogix chassis slot.
• Confirm chassis power is removed before module insertion or removal.
• Verify keying position and slot alignment before installation.

ControlNet Wiring

• Connect the ControlNet cable using the correct network connector.
• Maintain separation between ControlNet communication cables and high-voltage power wiring.
• Follow ControlNet network termination requirements for the installed topology.

Grounding and Maintenance

• Confirm chassis grounding before applying system power.
• Inspect connectors for contamination or mechanical damage during maintenance.
• Verify node addressing and communication status after replacement.

Frequently Asked Questions

• What communication protocol does the 1756-CNB support?

The 1756-CNB is a ControlNet bridge module designed for communication between ControlLogix systems and ControlNet network devices.

• Can the 1756-CNB be installed while the chassis is powered?

Module installation should be performed with chassis power removed unless the system configuration specifically supports removal procedures.

• How many ControlNet nodes can this module support?

The module supports up to 99 ControlNet nodes within the configured network architecture.

• What is the ControlNet communication speed?

The module operates on ControlNet communication at a rate of 5 megabits/second.

• How many communication connections are supported?

The 1756-CNB supports up to 64 communication connections depending on system configuration.

• What power does the module consume from the chassis?

The module requires 970 mA at 5.1 VDC and 1.7 mA at 24 VDC according to the supplied specifications.

• Does firmware compatibility affect module operation?

Yes. The module firmware must be compatible with the ControlLogix controller and connected ControlNet devices.

• How should ControlNet cables be installed?

ControlNet cables should be routed separately from high-current wiring and installed according to network grounding and termination requirements.