Allen-Bradley 1756-EN2TR ControlLogix EtherNet/IP Dual Port Communication Module

Product Insights

The 1756-EN2TR (1756EN2TR) is a high-performance, dual-port EtherNet/IP communication module engineered for the Rockwell Automation ControlLogix platform. This module is indispensable for industrial sectors such as oil and gas refining, power generation, and automotive manufacturing, where network uptime is non-negotiable. By supporting Device Level Ring (DLR) topology, the 1756-EN2TR provides hardware-layer redundancy that prevents system failure in the event of a single cable break. Its ability to manage high-speed I/O data and explicit messaging simultaneously makes it the backbone of modern distributed control systems, significantly reducing unplanned downtime and enhancing plant-wide data transparency.

Network Architecture & Capabilities

The 1756-EN2TR utilizes standard EtherNet/IP protocols to bridge the gap between high-level information systems and floor-level industrial assets.

• Dual-Port Functionality: Unlike single-port modules, the dual RJ45 ports allow for flexible topologies, including linear and DLR, eliminating the need for external Ethernet switches in many configurations.

• High Connection Capacity: Supporting up to 256 CIP connections and 128 TCP connections, this module handles dense I/O traffic and peer-to-peer interlocking with ease.

• Message Bridging: It facilitates seamless bridging of CIP unconnected messages (128 via backplane and 128 via Ethernet), ensuring that diagnostic and configuration data flow without bottlenecking real-time control traffic.

• Ruggedized Security: The module features 30V continuous isolation and is type-tested at 980V AC to ensure electrical noise on the factory floor does not migrate to the ControlLogix backplane.

Hardware Specifications

Technical Knowledge Base

Does the 1756-EN2TR support Ring Redundancy without an external switch?

Yes. The module features integrated switching technology that specifically supports Device Level Ring (DLR) topology. This allows the module to be part of a resilient ring network where the hardware manages path recovery automatically.

What is the difference between the 1756-EN2T and the 1756-EN2TR?

The "R" suffix in 1756-EN2TR stands for Redundancy/Ring. While the 1756-EN2T has only one Ethernet port, the 1756-EN2TR has two ports and supports DLR and linear topologies directly.

Can this module be used in hazardous locations?

The module is rated with North American Temp Code T4A and ATEX/IECEx Temp Code T4, making it suitable for specific hazardous environments when installed in a properly rated enclosure.

Engineering & Installation Guide

• DLR Implementation: When configuring a Device Level Ring, ensure that at least one node (typically a programmable controller or a specialized switch) is configured as the Ring Supervisor. While the 1756-EN2TR is DLR-capable, the ring will not function as a redundant path without an active supervisor.

• Cabling Requirements: Use Category 5e (or higher) shielded twisted-pair (STP) cabling in high-interference environments to maintain 100 Mbps speeds. Ensure the drain wire is properly grounded at the chassis to mitigate EFT (Electrically Fast Transient) issues on the Ethernet ports.

• Thermal Management: In high-density chassis where multiple 1756-EN2TR modules are used, maintain a minimum of 2 inches of clearance above and below the chassis. The module dissipates 17.4 BTU/h, and stagnant air can lead to thermal throttling or premature component aging.

• USB Port Usage: The front-facing USB port is intended for temporary local configuration and programming only. It is not designed for permanent connection or industrial networking.