Description
Key Technical Specifications
| Parameter | Value |
|---|---|
| Product Model | 1756-EN3TR |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Product Series | ControlLogix 1756 |
| Product Type | EtherNet/IP Communication Module |
| Communication Protocol | EtherNet/IP |
| Ethernet Ports | 2 × RJ45 copper ports |
| Communication Speed | 10/100 Mbps |
| TCP Connections | Up to 128 |
| CIP Connections | Up to 256 |
| Motion Support | Up to 128 axes |
| Mounting Type | ControlLogix chassis slot |
| Power Consumption | 1 A @ 5.1 VDC, 3 mA @ 24 VDC |
| Power Dissipation | 5.1 W |
| Operating Temperature | 0°C to 60°C |
| Ethernet Cable Type | Category 5 twisted pair |
| Isolation Voltage | 30 V continuous |
| Network Features | EtherNet/IP bridge, TCP/IP support, redundancy support |
Application Scenarios & Pain Points
A production line can lose communication long before anyone sees a hardware failure. One wrong IP address, an outdated firmware revision, or a damaged Ethernet cable can stop remote I/O updates and motion synchronization.
Typical applications:
- Automotive Manufacturing: Used for ControlLogix systems coordinating servo drives, robotic cells, and high-speed production equipment.
- Packaging Machinery: Supports communication between PLC processors, remote I/O adapters, and intelligent field devices.
- Process Plants: Provides Ethernet connectivity between ControlLogix controllers, operator interfaces, and distributed control equipment.
- Material Handling Systems: Used for conveyor systems requiring coordinated motion control and distributed I/O communication.
Field note: A manufacturing cell experienced intermittent Ethernet dropouts after years of stable operation. The controller program was unchanged, but the communication module had aging hardware and inconsistent network behavior. Replacing the 1756-EN3TR and reviewing the Ethernet configuration restored stable communication.
1756-EN3TR
Related Products
- Allen-Bradley 1756-EN2TR — Earlier ControlLogix dual-port EtherNet/IP module. Suitable for standard Ethernet communication but supports fewer motion axes than the EN3TR.
- Allen-Bradley 1756-EN4TR — Newer ControlLogix EtherNet/IP module with updated communication capacity and enhanced network functions.
- Allen-Bradley 1756-EN2T — Single-port EtherNet/IP communication module for ControlLogix systems where integrated switch capability is not required.
- Allen-Bradley 1756-EN2F — Fiber optic EtherNet/IP bridge module used in environments requiring longer-distance or electrically isolated communication links.
- Allen-Bradley 1756-L8x Series Controllers — ControlLogix processors commonly paired with EN3TR communication modules.
- Allen-Bradley 1756-A7 / 1756-A10 Chassis — ControlLogix rack platforms used for mounting the communication module.
- Allen-Bradley 1734-AENTR — POINT I/O dual-port EtherNet/IP adapter commonly connected through ControlLogix Ethernet networks.
- Allen-Bradley 1794-AENTR — FLEX I/O EtherNet/IP adapter used for distributed I/O architectures.
The Engineer’s Guide: Field Pitfalls to Avoid
⚠️ Firmware Revision Mismatch
A replacement EN3TR may communicate physically but fail with the existing Studio 5000 project if firmware requirements are different.
How to avoid: Verify module firmware revision, controller firmware, and Studio 5000 compatibility before installation.
⚠️ Duplicate IP Address Problems
EtherNet/IP networks are unforgiving when two devices share the same address.
How to avoid: Record the original IP configuration and verify DHCP/BOOTP settings before connecting the replacement module.
⚠️ Incorrect Network Topology Setup
The dual Ethernet ports can be used in different network designs. A wiring mistake may create communication loops or unexpected traffic behavior.
How to avoid: Match the original Ethernet layout and confirm switch configuration, VLAN settings, and cable routing.
Frequently Asked Questions (FAQ)
What is the main function of the Allen-Bradley 1756-EN3TR?
The 1756- is a ControlLogix EtherNet/IP communication module used to connect controllers with remote I/O, drives, HMIs, and motion devices.
Is the 1756- a PLC CPU?
No. It does not execute ladder logic or control programs. The module provides Ethernet communication functions for ControlLogix processors.
Can the 1756- replace a 1756-EN2TR?
In many applications it may replace an EN2TR, but compatibility must be verified. Check:
- Studio 5000 version
- Controller firmware
- Ethernet configuration
- Motion requirements
- Existing I/O tree setup
Does the 1756- support motion control?
Yes. The is designed for EtherNet/IP motion applications and supports up to 128 axes.
Why does the PLC show a communication fault after replacing the ?
Common causes include:
- Wrong IP address
- Incorrect module revision
- Missing I/O tree configuration
- Firmware mismatch
- Network switch configuration problems
What should be checked before purchasing a 1756-?
Recommended checks:
- Exact catalog number
- Module series and revision
- Existing ControlLogix chassis type
- Controller firmware
- Studio 5000 project backup
- Ethernet network design
Is a refurbished Allen-Bradley 1756- suitable for industrial service?
A tested refurbished unit can be suitable when it passes power-up checks, Ethernet communication testing, firmware verification, and integration testing with the target ControlLogix system.
