Allen-Bradley 1756-CN2RXT ControlLogix ControlNet Interface Module

Configured for ControlNet communication in ControlLogix networks, the Allen-Bradley 1756-CN2RXT (1756-CN2RXT Interface Module) provides direct physical/electrical execution. This hardware unit manages 128 Logix communication connections and enables high-speed data exchange at a 5 Mbps ControlNet rate, serving as a dedicated interface for nodes across the ControlNet link.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Networks

The 1756-CN2RXT module utilizes the ControlLogix backplane bus to synchronize data packets, requiring precise bus communication velocity for deterministic network performance. As part of the XT (extended temperature) product line, the module is engineered for environmental robustness; however, I/O density scaling within the ControlNet segment remains subject to the node count limits (max 99 nodes). Users must ensure firmware flash compatibility across all ControlNet nodes to avoid time-slot allocation errors and maintain deterministic timing synchronization.

Frequently Asked Questions

Q: Does this module support redundant media?

A: Yes, the 1756-CN2RXT includes redundant media ports to support dual-cable ControlNet configurations, facilitating uninterrupted communication in the event of a single-cable failure.

Q: Is this module compatible with standard (non-XT) ControlLogix chassis?

A: Yes, the 1756-CN2RXT is physically and electrically compatible with all standard ControlLogix chassis. It can be installed in any available chassis slot.

Field Installation Guidelines

• Chassis Installation: The module can be seated in any chassis slot. Ensure the module is fully inserted and the latching mechanism is engaged to establish a secure backplane connection.
• Cable Termination: Use RG-6 quad-shield coaxial cable for ControlNet connections. Ensure that all taps are properly terminated with a 75 Ohm resistor to prevent signal reflections that induce jitter.
• Grounding: The ControlNet media must be grounded at a single point per segment to avoid ground loops. Ensure the module chassis is bonded to the common equipment ground to provide a robust reference for shielding.
• Thermal Environment: While rated for operation up to 70 deg C, maintain adequate convective airflow around the module. In high-density chassis configurations, avoid placing high-heat-generating modules directly adjacent to the 1756-CN2RXT where possible.