Allen-Bradley 1756-CN2 ControlNet Communication Module

Configured for deterministic ControlNet data exchange in ControlLogix architectures, the Allen-Bradley 1756-CN2 (1756-CN2 ControlNet Communication Module) provides direct physical/electrical execution of scheduled network communication between controllers and distributed nodes through a dual-channel coaxial ControlNet interface.

Hardware Specifications

ControlNet Deterministic Communication Behavior

The 1756-CN2 operates on a scheduled ControlNet media access mechanism where backplane bus communication velocity is synchronized with network scan intervals. This deterministic model enforces time-slot allocation for each node, ensuring bounded latency during cyclic data exchange.

The dual BNC interface supports redundant media topology, where signal integrity is maintained through parallel coaxial paths. Channel arbitration is handled at the MAC layer, reducing contention and maintaining fixed-cycle execution across the ControlLogix chassis.

Protocol routing is managed through ControlLogix controller integration, while configuration via RSNetWorx for ControlNet defines network scheduling, node mapping, and connection ownership. Firmware flash compatibility is tied to Studio 5000 Logix Designer system revision alignment.

Frequently Asked Questions (FAQ)

Q: Does the 1756-CN2 support redundant media operation?
A: Yes. The module provides two BNC connectors for dual media paths, allowing redundant ControlNet operation when properly terminated and configured.

Q: What determines network determinism on ControlNet?
A: Determinism is enforced by scheduled time slots and network update intervals configured via RSNetWorx, not by raw data rate.

Q: Can the module operate without backplane communication?
A: No. The module requires ControlLogix backplane communication for configuration, routing, and controller-level integration.

Field Installation Guidelines

Install the module only into a compatible ControlLogix chassis slot with verified backplane power capacity. Ensure coaxial cabling is routed using approved ControlNet media with correct 75 ohm termination at network endpoints.

Maintain separation between ControlNet coaxial lines and high-voltage conductors to reduce electromagnetic coupling. Verify BNC connector locking integrity to avoid impedance discontinuities.

Network configuration must be completed using RSNetWorx before enabling scheduled communication. Do not introduce node changes without updating the network schedule.