Rockwell 1756-EN2TR Dual-Port Communication Module

1756：ControlLogix platform series

EN：Rockwell EtherNet/IP communication

2：Dual-port Ethernet

T：Twisted-pair copper interface

R：DLR (Device-Level Ring) support (core identifier)

Core Technical Specifications

⚠️Important: EN2TR only supports DLR ring redundancy. PRP dual-network and dual-IP hot-standby redundancy are NOT available. Two ports operate as an embedded switch, not two independent network adapters.

Primary Application Scenarios

1. EtherNet/IP remote I/O and distributed I/O (e.g. 1734-AENTR) for ControlLogix controllers
2. DLR ring architecture: assembly lines, packaging machinery, water treatment, material handling, auto network self-recovery upon single cable breakage
3. HMI & SCADA host communication; CIP-Motion servo motion network
4. Preferred upgrade replacement for legacy 1756-ENBT, delivering greatly improved performance

Series Selection & Comparison

Replacement Options

1. Direct drop-in replacement: 1756-EN2TR (Series-C). Keep consistent firmware revision; plug-and-play without program modification
2. Performance upgrade: 1756-EN4TR (Gigabit Ethernet, higher connection capacity, CIP security support)
3. Harsh environment variants: 1756-EN2TRXT wide-temperature; 1756-EN2TRK conformal coating

Hardware Installation & IP Configuration Guidelines

1. RIUP hot-swap supported; hot-swap forbidden in hazardous / explosive areas
2. IP configuration methods:

Module thumbwheel: setting static IP `192.168.1.xxx` via setting 1-254; position 999 enables BOOTP/DHCP assignment

Static IP assignment via BOOTP-DHCP tool; configure IP inside Studio5000 project and download

3. DLR ring wiring: Port1 connects upstream device, Port2 connects downstream device; close both ends to form a ring. At least one DLR Supervisor (ring manager) must exist in the ring. Ordinary non-managed switches cannot be inserted into DLR ring, which causes ring flapping and communication failure.
4. Cable requirement: minimum Cat5e shielded Ethernet cable

Common Troubleshooting

1. Ring convergence failure: Ordinary switches or multiple Supervisor nodes inside ring. Remove non-managed switches and retain exactly one Supervisor.
2. I/O glitch after cable break: DLR convergence time exceeds RPI request packet interval. Use PRP module (EN2TP) for motion-critical applications.
3. Duplicate IP alarm: Both ports connected to same switch network. One port for ring connection only; never plug both ports into common switch.
4. Electronic key error 160114: Firmware mismatch between project definition and physical hardware. Enable compatible-module setting or upgrade module firmware.

Key LED Indicators

OK: Module status; steady green = normal; flashing red = self-test; solid red = module fault

LNK/ACT: Port link & data activity indicator

NET: Network status

DLR: Device-Level Ring status

I can provide further materials upon request:

1. Minimal DLR ring configuration steps (Studio5000)
2. Index for official 1756-EN2TR Chinese manual
3. Inspection checklist for second-hand modules

1756-EN2TR Main Application Scenarios

Module positioning: Dual-port EtherNet/IP communication module for ControlLogix platform with DLR Device-Level Ring. Embedded switch shares one IP address; PRP dual-network redundancy is unsupported.

1. DLR Device-Level Ring (Core Advantage)

For field-level networks requiring self-recovery (<3 ms convergence) against single cable damage. Supports star, linear daisy-chain and closed DLR ring topologies.

Material handling & sorting lines; packaging & filling lines; automotive welding & assembly station networks

Remote I/O ring for water treatment, pump stations, tunnels and bridges; reduces switch count and cabling cost

Ring prerequisites: All ring nodes must be DLR-capable. Exactly one DLR Supervisor is required. Ordinary non-managed switches shall not be inserted.

2. Distributed Remote I/O Master Communication

Acts as backplane-mounted EtherNet/IP interface for ControlLogix, connecting remote I/O adapters such as 1734-AENTR and 1738-AENTR.

Collect DI/DO, AI/AO signals for widely dispersed field points in large-scale plants

Direct upgrade substitute for legacy 1756-ENBT; no chassis or program modification, higher connection capacity and message performance.

3. CIP-Motion Motion Control Network

Supports up to 8-axis CIP-Motion servos, interfacing with Kinetix servos and PowerFlex variable-frequency drives.

Real-time servo control for packaging machines, material handling equipment and machine tools.

Note: When running CIP-Motion over DLR ring, properly tune RPI interval to avoid motion glitches triggered by ring convergence events.

4. HMI, SCADA & MES Data Exchange

Interfaces with PanelView HMI terminals, FactoryTalk SCADA hosts; upload production data to MES systems

Acquire data from VFDs, smart instruments and third-party EtherNet/IP devices

Maximum 256 CIP connections and 128 TCP connections support multi-device concurrent communication.

5. Industry-Specific Typical Deployments
6. Automotive manufacturing: Welding & paint shops, connecting robots, station I/O and VFDs via DLR ring per cell.
7. Food & beverage packaging: Filling, labelling and end-of-line packaging; daisy-chain / DLR wiring cuts field switch quantity.
8. Municipal water treatment: Waste-water & clean-water plants, pump-station remote-I/O rings with central SCADA supervision.
9. Warehouse & logistics: AS/RS automated warehouses, sortation conveyors for long-distance daisy-chain or DLR networking.

❌ Not-Recommended Use-Cases (Selection Pitfalls)

1. Dual-independent-IP / PRP true dual-link redundancy: Select 1756-EN2TP instead of EN2TR. EN2TR ports function as bridged switch ports rather than two independent NICs.
2. Gigabit requirement: EN2TR is 10/100 Mbps only; upgrade to 1756-EN4TR for gigabit speed.
3. Dual-network hot-standby for redundant controller systems: Not suitable; use two separate communication modules.

Network Topologies Supported by 1756-EN2TR

Hardware key fact: Dual ports implement internal Layer-2 switch, one shared IP with two MAC addresses; not two independent network interface cards.

✅ Three Supported Topologies

1. DLR Device-Level Ring (Core Feature)

Module can operate as a regular DLR ring node or be configured as DLR Supervisor (ring manager).

Wire Port1 to upstream device and Port2 to downstream device, close both ends to form closed ring.

Automatic self-healing when one cable fails; convergence time <3 ms.

Requirements: Every ring participant must support DLR. Only one Supervisor node allowed within ring. Non-managed switches must be excluded.

Use-case: Field-level redundant networking for conveyors, water-treatment and assembly lines.

2. Linear Daisy-Chain Topology

Port1 connects upstream device; Port2 daisy-chains next DLR-capable I/O device. Both ends remain open without ring closure.

Eliminates field switches by cascading devices sequentially and lowers hardware cost.

Drawback: Any intermediate cable failure takes down all downstream devices. No fault-tolerant recovery.

3. Star Topology

Use only one RJ45 port to connect to standard switch; leave second port unused.

Traditional widely-adopted EtherNet/IP topology for HMI, SCADA and remote-I/O connections.

⚠️Strict prohibition: Never plug both ports into the same ordinary switch. This creates Layer-2 loop, triggers duplicate-IP alarm and collapses network traffic.

❌ Unsupported Topologies (Selection Pitfalls)

1. PRP parallel dual-network redundancy: EN2TR does not implement PRP protocol. Choose 1756-EN2TP for physically separate redundant networks.
2. Separate sub-networks / dual-IP for two ports: Hardware limitation forces single shared IP; different sub-nets cannot be assigned per port.
3. Dual-NIC hot-standby for redundant controller pairs: Cannot realize true dual-network redundancy; deploy two discrete communication modules.

Topology Quick Reference Table

Supplement: Although CIP-Motion can run on DLR ring, cable break-triggered convergence may cause transient I/O or motion jitter. Star topology or PRP module is preferred for high-performance motion applications.