Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1756-CN2R |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Product Type | ControlNet Communication Interface Module |
| ControlNet Ports | 2 × BNC (redundant media support) |
| Transmission Rate | 5 Mbps |
| Maximum Nodes | 99 |
| Logix Communication Connections | 128 standard (131 total, 3 reserved for redundancy) |
| Backplane Current Draw | 1300 mA @ 5.1V DC; 3 mA @ 24V DC |
| Power Dissipation | 6.7 W |
| Thermal Dissipation | 22.9 BTU/hr |
| Isolation Voltage | 30V continuous (ControlNet to backplane) |
| Slot Width | 1 |
| Operating Temperature | 0 to 60 °C |
| Storage Temperature | -40 to 85 °C |
| Relative Humidity | 5 to 95% non-condensing |
| Vibration | 2 G @ 10–500 Hz |
| Shock (Operating) | 30 G |
| Certifications | CISPR 11 Class A; ESD, EFT/B, surge immunity rated |
| Weight | Approx. 0.293 kg |
Main Features and Advantages
Redundant Media Support for Critical Networks: The 1756-CN2R distinguishes itself from the standard 1756-CN2 by providing two ControlNet BNC ports, enabling connection to both the primary and redundant cable paths of a ControlNet network. In the event of a cable break or connector failure on one trunk line, the module maintains communication over the alternate path, preventing a single point of failure from disrupting I/O control or inter-controller data exchange . This redundancy capability is essential in continuous-process industries where network downtime translates directly into lost production.
High Connection Capacity for Complex Architectures: The 1756-CN2R supports 128 Logix communication connections for standard use, a substantial increase over the 64-connection limit of earlier ControlNet modules such as the 1756-CNB and 1756-CNBR . This expanded capacity allows the module to handle larger I/O configurations, more produced/consumed tag exchanges between controllers, and additional messaging connections without exhausting connection resources. For systems integrating multiple ControlLogix controllers and extensive distributed I/O, the 1756-CN2R provides headroom that reduces the need for additional communication modules.
Integrated USB Port for Local Access: The 1756-CN2R includes a USB 1.1 Type B port that provides local programming and diagnostic access without requiring a network connection . Maintenance personnel can connect a laptop directly to the module for firmware updates, configuration changes, or status checks, which is particularly useful during initial commissioning or when the ControlNet network is unavailable. The USB port is intended for temporary local use only, and cable length should not exceed three meters.
Compatibility with ControlLogix Redundancy Systems: The 1756-CN2R is designed to operate within ControlLogix redundant chassis configurations, where paired modules in primary and secondary chassis maintain synchronized communication with the ControlNet network . When a controller switchover occurs, the redundant communication path and paired module configuration help ensure that I/O and messaging continue without interruption. This capability makes the 1756-CN2R suitable for applications in power generation, water treatment, and other processes where controller availability is a primary design requirement.
