1756-CN2RXT | Allen Bradley | ControlNet Redundant Interface Module

Allen‑Bradley 1756‑CN2RXT ControlNet Redundant Interface Module

Configured for redundant ControlNet communication in ControlLogix XT platforms, the Allen‑Bradley 1756‑CN2RXT (1756‑CN2RXT interface module) provides direct physical execution of coaxial network signaling, dual‑channel redundancy, and deterministic data exchange across ControlNet segments.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Network Considerations

Although the 1756‑CN2RXT is dedicated to ControlNet, its redundant dual‑channel architecture supports deterministic behavior similar to EtherNet/IP and Profinet systems. The module’s fixed 5 Mbps coaxial signaling and CRC‑validated frames reduce jitter and timing drift when operating alongside high‑density I/O or mixed‑protocol networks. Firmware flash compatibility across ControlLogix XT chassis ensures stable synchronization during redundancy switchover events.

Frequently Asked Questions

Q: Can the 1756‑CN2RXT be hot‑swapped in a powered ControlLogix chassis? A: Yes. ControlLogix supports module insertion/removal under power, but network behavior may momentarily re‑establish link states.

Q: Does redundancy require both ControlNet channels to be wired? A: Yes. Channel A and Channel B must be fully connected for proper 2‑channel redundant operation.

Q: Does the USB port affect ControlNet timing? A: No. The USB interface is used only for configuration and does not participate in network scheduling.

Field Installation Guidelines

• Maintain correct torque on BNC connectors to ensure stable 75 ohm impedance.
• Route coaxial cable away from high‑energy conductors to reduce induced noise.
• Verify proper seating in the ControlLogix backplane before energizing.
• Ensure conformal‑coated XT modules are installed in environments requiring moisture or corrosion resistance.
• Avoid sharp bends in coaxial cable to preserve signal integrity.