Configured for Ethernet TCP/IP communication expansion in PLC-5 controller systems, the Allen-Bradley 1785-ENET (1785-ENET Ethernet Interface Module) provides direct network access through an RJ45 communication port and PLC-5 backplane connection.

Model Identification

The 1785-ENET is an Ethernet communication expansion module designed for installation in a 1771 PLC-5 chassis. It connects directly to the PLC-5 processor communication path and provides Ethernet TCP/IP connectivity for PLC-5 controllers.

Compatible module revisions vary by PLC-5 processor family. Series and revision compatibility should be verified against the installed PLC-5 processor firmware and chassis configuration before replacement.

Hardware Specifications

Ethernet Communication Architecture

The 1785-ENET uses PLC-5 backplane communication to exchange controller data through an Ethernet TCP/IP network. The module provides a single RJ45 Ethernet interface with automatic network speed detection between 10 Mbps and 100 Mbps.

Status indication is provided through front-panel LEDs:

• STAT indicator monitors Ethernet link activity and module status.
• 100M indicator identifies operation on a 100 Mbps Ethernet connection.
• 10M indicator identifies operation on a 10 Mbps Ethernet connection.

The module supports Ethernet communication expansion for Enhanced PLC-5 controllers, Ethernet PLC-5 controllers, and ControlNet PLC-5 controller configurations depending on series and revision.

PLC-5 Network Integration Features

Allen-Bradley PLC-5 systems use a backplane-based architecture where communication modules exchange data through the chassis bus. The 1785-ENET maintains compatibility with PLC-5 processor families through defined series and firmware revisions.

EtherNet/IP deterministic networks require proper configuration of addressing, communication parameters, and controller compatibility. Firmware flash compatibility must be confirmed when replacing modules with different series revisions.

The module supports PLC-5 network expansion without changing the existing processor instruction structure, allowing Ethernet communication access through the PLC-5 controller environment.

Ordering Information

• 1 x Allen-Bradley 1785-ENET Ethernet Interface Module
• 1 x Factory-installed communication interface assembly
• 1 x Compatible mounting hardware assembly if supplied with the module configuration
• Manuals, programming software, and external Ethernet cables are not included unless specifically listed

Field Installation Guidelines

Power and Chassis Preparation

• Disconnect power from the 1771 I/O chassis before installation.
• Confirm PLC-5 processor compatibility with the module series and revision.
• Inspect the backplane connector condition before mounting.

Communication Wiring

• Use shielded Ethernet cabling suitable for the industrial environment.
• Maintain separation between communication wiring and high-voltage power conductors.
• Connect the RJ45 port securely and verify link status indicators after startup.

Module Installation

• Align the module with the PLC-5 chassis slot connector.
• Secure the module using the appropriate mounting hardware.
• Restore system power and verify Ethernet communication activity.

Frequently Asked Questions

• Is the 1785-ENET compatible with all PLC-5 processors?

The module compatibility depends on the PLC-5 processor family and firmware revision. Verify series and revision requirements before installation.

• Does the 1785-ENET require external power?

No. The module receives operating power from the PLC-5 backplane at 5 VDC.

• What Ethernet communication protocol does the module support?

The module supports Ethernet TCP/IP communication through an 8-pin RJ45 connector.

• What Ethernet speed is supported by the 1785-ENET?

The module supports 10 Mbps and 100 Mbps Ethernet operation with auto-negotiation capability.

• Can the 1785-ENET be hot-swapped during operation?

Hot insertion is not specified. Power should be removed before removing or installing the communication module.

• What is the backplane current requirement?

The module requires approximately 1.0 A from the PLC-5 backplane at 5 VDC.

• Does the module provide PLC-5 processor communication expansion?

Yes. It provides Ethernet communication expansion through direct connection with PLC-5 controller systems.

• What installation factor affects Ethernet communication performance?

Proper grounding, cable routing, network configuration, and connector installation affect communication stability.