Allen-Bradley 1756-EN3TR ControlLogix Ethernet Communication Module

The Allen-Bradley 1756-EN3TR, also cataloged as the 1756-EN3TR Ethernet Communication Module, operates as a dedicated hardware component for Ethernet/IP data bridging and backplane-to-network packet routing within ControlLogix chassis architectures.

Configured for deterministic industrial Ethernet communication in ControlLogix platforms, the Allen-Bradley 1756-EN3TR (1756-EN3TR communication module) provides direct physical and protocol-level execution of Ethernet/IP frame handling through dual RJ45 interfaces and a USB service channel, enabling multi-topology network integration including Device Level Ring (DLR) and linear structures.

Suffix Breakdown & Model Matrix

No formal suffix segmentation is defined for 1756-EN3TR. The model identifier represents a fixed ControlLogix Ethernet communication module designation.

Hardware Specifications

Backplane Bus Communication Velocity & EtherNet/IP Deterministic Network Behavior

Within ControlLogix architectures, the 1756-EN3TR participates in high-speed backplane arbitration where cyclic data is mapped between CPU task scheduling and Ethernet/IP stack execution layers. The module maintains deterministic packet scheduling across dual-port switching logic, enabling ring redundancy via DLR topology without external switch dependency. I/O density scaling and connection handling are constrained by backplane bandwidth allocation (1 A at 5.1 VDC), where communication throughput is synchronized with chassis scan cycles and motion control task execution up to 128 axis coordination.

Frequently Asked Questions (FAQ)

Q: Can the 1756-EN3TR operate in Device Level Ring (DLR) mode without external switches?
A: Yes. DLR is internally supported through embedded ring logic, allowing fault-tolerant Ethernet topology without external switching hardware.

Q: What is the effect of backplane current loading on module communication performance?
A: The module draws 1 A at 5.1 VDC from the backplane. Excess chassis loading can affect available slot power but does not directly alter Ethernet throughput timing.

Q: Does the USB port affect Ethernet/IP communication cycles?
A: No. The USB interface operates at 12 Mbps as a service channel and is logically isolated from Ethernet/IP cyclic data processing.

Field Installation Guidelines

The module must be inserted into a powered-down 1756 chassis to ensure correct backplane connector engagement. Slot alignment must remain perpendicular to prevent pin shear across high-density backplane contacts. Ethernet cabling should maintain separation from high-noise power conductors to reduce induced jitter in RJ45 signaling lines. Shield termination should be referenced at a single enclosure ground point. USB service connections should be used only for configuration and diagnostics, not continuous runtime communication.