Product Overview
The 1756-CN2R is a high-availability ControlNet redundant bridge module manufactured by Allen-Bradley, a brand of Rockwell Automation, and designed for the ControlLogix 1756 programmable automation controller (PAC) platform. As a dual-channel communication module, the 1756-CN2R provides the ControlLogix system with two independent ControlNet network interfaces that can be configured for redundant media operation, ensuring that critical network communication remains active even if one network path fails. This redundancy capability makes the 1756-CN2R an essential component in high-availability and safety-critical applications where network downtime is simply not acceptable.
The core function of the 1756-CN2R is to serve as a bridge between the ControlLogix backplane and one or two ControlNet networks, enabling the controller to communicate with ControlNet-enabled devices such as remote I/O racks, drives, operator interfaces, and peer controllers. In standard (non-redundant) mode, the module provides two independent ControlNet ports that can each connect to a separate network, effectively doubling the available ControlNet bandwidth and device capacity. In redundant mode, the two ports operate as primary and secondary paths on the same network, with automatic failover occurring in the event of a cable break, connector failure, or other network fault. This seamless transition ensures that communication is never lost, even during a network failure.
Positioned as a premium networking solution within the ControlLogix ecosystem, the 1756-CN2R is widely used in applications where network reliability is paramount. Its support for ControlNet’s deterministic, high-speed communication protocol combined with redundant media capability makes it particularly valuable in process industries, continuous manufacturing, and safety systems where even a momentary loss of communication can result in product loss, equipment damage, or unsafe conditions. With its robust construction, comprehensive diagnostics, and seamless integration with Studio 5000 Logix Designer software, the 1756-CN2R delivers the network resilience and engineering flexibility that demanding high-availability applications require.
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1756- |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Type | ControlNet Redundant Bridge Module |
| Platform | ControlLogix 1756 PAC |
| Network Protocol | ControlNet (CIP-based, redundant media capable) |
| Number of Ports | 2 (Channel A and Channel B, both BNC) |
| Data Transfer Rate | 5 Mbps |
| Redundancy Modes | Redundant media, Single network (dual independent) |
| Network Media | RG-6 coaxial cable (per port) |
| Network Topology | Bus with trunk and drop cables |
| Maximum Nodes per Network | 99 |
| Maximum Cable Length | 1,000 m (3,280 ft) per segment |
| Backplane Current Draw | 1.2 A @ 5.1V DC, 0.5 A @ 24V DC |
| Power Dissipation, Max | 7.0 W |
| Isolation (network to backplane) | 500V AC continuous |
| Operating Temperature | 0°C to 60°C (32°F to 140°F) |
| Storage Temperature | -40°C to 85°C (-40°F to 185°F) |
| Certifications | CE, UL, cULus, CSA, TÜV, ATEX, IECEx, RoHS |
| Dimensions (W x H x D) | 5.7 x 6.65 x 5.8 in (145 x 169 x 145 mm) |
