1756-CN2RK | Allen-Bradley | Communication Module

The Allen-Bradley 1756-CN2RK, also cataloged as the 1756-CN2R Communication Module, operates as a dedicated hardware component for ControlNet network connectivity within ControlLogix system platforms.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Networks

The 1756-CN2RK implements deterministic ControlNet communications to manage time-critical data exchange between controllers and distributed I/O. The dual-channel interface facilitates redundant media configurations, ensuring continuous data flow upon single cable failure. The onboard processor supports up to 128 Logix connections, maintaining network integrity through scheduled bandwidth allocation and strict master-slave synchronization. Conformal coating provides physical resistance to airborne contaminants in harsh industrial environments, ensuring internal circuit board longevity.

Frequently Asked Questions

Q: Does the 1756-CN2RK support hot-swapping within the ControlLogix chassis?

A: Yes, the module is designed for Removal and Insertion Under Power (RIUP) in a ControlLogix chassis without disrupting the backplane bus communication or damaging the host controller.

Q: How is the 1756-CN2RK different from the standard 1756-CN2R?

A: The "K" suffix indicates that the module features conformal coating on its printed circuit board to provide enhanced protection against moisture, dust, and corrosive gases in specialized environmental conditions.

Field Installation Guidelines

1. Ensure the ControlLogix chassis is powered off before slot insertion, despite RIUP capabilities, to prevent potential backplane arcing.
2. Align the module with the chassis guide rails and push firmly until the top and bottom latching mechanisms click into place.
3. For redundant ControlNet configurations, connect the two separate cables to Channel A and Channel B to establish the physical loop.
4. Securely terminate the ControlNet coaxial cable using 75 Ohm BNC connectors; ensure the total cable length complies with the 5 Mbps data rate constraints.
5. Verify that the shield drain wire at the tap location is properly grounded to the cabinet common to minimize electromagnetic interference.