Allen-Bradley 1756-CN2RXT ControlLogix ControlNet Interface Module

Configured for deterministic ControlNet frame handling in ControlLogix chassis networks, the Allen-Bradley 1756-CN2RXT (1756-CN2RXT Interface Module) provides direct electrical execution of 5 Mbps ControlNet communication across redundant coaxial media paths within a Logix backplane environment. The module supports up to 99 nodes and manages up to 131 network connections with 128 Logix communication links via chassis-based scheduling.

Within the Rockwell Automation ControlLogix architecture, the module executes backplane-to-ControlNet data mapping using dual BNC interfaces and USB service access point for configuration-level communication handling.

Suffix Breakdown & Model Matrix

Single hardware configuration: 1756-CN2RXT ControlNet interface module. No additional functional suffix segmentation defined.

Hardware Specifications

ControlNet Dual Media Interface and Backplane Communication Behavior

The 1756-CN2RXT performs deterministic ControlNet scheduling at 5 Mbps using redundant coaxial media architecture. Dual BNC connectors provide parallel physical routing paths, while the backplane bus communication layer synchronizes Logix task execution with network transmission cycles.

USB access point enables configuration-level communication without interrupting ControlNet cyclic traffic. I/O density scaling is managed through ControlLogix chassis arbitration, allowing up to 128 Logix connections mapped into 131 total network links.

The module maintains fixed-cycle deterministic transmission timing, where frame propagation is aligned with controller scan execution and scheduled network windows.

Frequently Asked Questions (FAQ)

Q: Can the 1756-CN2RXT be hot-swapped in an active chassis?
A: Yes. The module supports hot insertion/removal. Network resynchronization is performed through ControlLogix backplane re-enumeration.

Q: What limits the maximum connection count?
A: The limit of 131 connections is constrained by ControlNet scheduling bandwidth and Logix backplane resource allocation.

Q: Does USB access interrupt ControlNet communication?
A: No. USB service access operates on a separate configuration channel and does not affect 5 Mbps ControlNet cyclic traffic.

Field Installation Guidelines

Install the module into any valid ControlLogix chassis slot ensuring full backplane connector engagement. ControlNet coaxial cables must maintain impedance matching and continuous shielding integrity across BNC connections.

Route ControlNet media separately from high-current power lines to reduce electromagnetic coupling. Shield termination should be implemented at a single-point ground reference to avoid loop currents across redundant media paths.

Verify firmware compatibility between chassis, controller, and communication module before commissioning to ensure deterministic scheduling alignment across backplane and network layers.