Mitsubishi RJ71EIP91 EtherNet/IP Communication Module

The Mitsubishi RJ71EIP91 is a high-performance EtherNet/IP communication module for the MELSEC R series (and compatible with Q series systems). This module enables seamless integration of Mitsubishi PLCs into EtherNet/IP networks, allowing data exchange with Rockwell Automation PLCs, drives, HMIs, and other EtherNet/IP devices. The RJ71EIP91 supports both scanner (master) and adapter (slave) functions, providing flexible network configurations. It handles implicit (real-time I/O) and explicit (message) communications, with support for up to 32 connections and 256 I/O tags per connection. The module is equipped with two Ethernet ports (10/100 Mbps) with integrated switch, allowing daisy-chain wiring without external switches. The RJ71EIP91 is ideal for mixed-vendor automation systems where Mitsubishi PLCs need to communicate with Rockwell or other EtherNet/IP-compliant equipment.

Technical Specifications

The RJ71EIP91 module operates on 5 V DC (0.65 A) from the backplane. Ethernet ports: 2 × RJ45, 10BASE-T / 100BASE-TX, auto-MDI/MDIX. Communication functions: scanner (master) or adapter (slave) selectable. Number of connections (scanner mode): max 32 connections; total I/O points: up to 32,768 bytes. Number of connections (adapter mode): max 32 connections; total I/O points: up to 4,096 bytes. Supported classes: implicit messaging (class 1) and explicit messaging (class 3). Supported CIP objects: identity, message router, assembly, connection manager, and vendor-specific. The module can exchange data with up to 256 tags per connection (total 8192 tags). The integrated switch allows line or star topology with up to 10 modules daisy-chained. Dimensions: 27.8 mm (W) × 106 mm (H) × 110 mm (D). Weight: 0.22 kg. Operating temperature: 0°C to 55°C. Storage: -20°C to 75°C. Humidity: 10-90% non-condensing.

Key Features

• EtherNet/IP scanner (master) and adapter (slave) functions

• Two Ethernet ports with integrated switch for daisy-chain connection

• Supports implicit (real-time I/O) and explicit (message) communications

• Up to 32 connections in scanner mode

• Total I/O data up to 32 KB in scanner mode, 4 KB in adapter mode

• Automatic tag generation and EDS file import/export

• Compatible with Rockwell Automation Studio 5000 and RSNetWorx for EtherNet/IP

• Diagnostic functions: network status, link status, communication error logs

• Simple configuration using GX Works3 and RJ71EIP91 configuration tool

• Support for CIP safety (with additional safety CPU) – limited

Integration with Rockwell Automation Systems

The RJ71EIP91 is specifically designed to bridge Mitsubishi MELSEC R series PLCs into Rockwell Automation's EtherNet/IP environment. By configuring the module as an adapter (slave), the Mitsubishi CPU can appear as a virtual I/O chassis to a Rockwell CompactLogix or ControlLogix PLC. The Rockwell PLC can read and write tags (up to 256 tags) via implicit cyclic I/O connections. Conversely, when configured as a scanner, the RJ71EIP91 can control Rockwell PowerFlex drives or other EtherNet/IP devices directly from the Mitsubishi PLC. The module supports the import and export of EDS files, simplifying configuration in Rockwell's RSNetWorx for EtherNet/IP software. The integrated switch allows the module to be inserted into an existing EtherNet/IP ring or line topology without additional hardware.

Configuration and Programming

The RJ71EIP91 is configured using Mitsubishi GX Works3 software with the EtherNet/IP configuration tool (included). The user sets the module as scanner or adapter, assigns IP addresses, and defines the I/O tag mapping. For scanner mode, the user imports the EDS files of target devices, selects the I/O assemblies, and sets the packet intervals (RPI). The module automatically calculates the required connections. The tag data is automatically mapped to the MELSEC CPU's buffer memory, where it can be accessed with standard MOV and FROM/TO instructions. For adapter mode, the user creates a tag list (up to 256 tags) that the scanner device will read/write. The module's status can be monitored via dedicated special relay (SM) and special register (SD) areas.

Network Topology and Performance

The two Ethernet ports act as a built-in switch, allowing the module to be daisy-chained (line topology) without external switches. The maximum number of modules that can be daisy-chained is 10, but for higher reliability, a star topology with a central switch is recommended. The module supports CoS (Class of Service) packet prioritization and IGMP snooping for multicast filtering. The communication cycle time depends on the number of connections and RPI settings. For typical configurations (32 connections, RPI = 10 ms), the module can maintain cycle times of 10-20 ms. The module supports up to 32 simultaneous CIP connections; each connection can have its own RPI. The module also supports CIP sync (time synchronization) using IEEE 1588 (PTP) if the network infrastructure supports it.

Applications

The RJ71EIP91 is used in mixed-vendor automation systems where a Mitsubishi PLC needs to exchange data with Rockwell PLCs, drives (PowerFlex 525/755), HMIs (PanelView), or other EtherNet/IP devices. Typical applications include automotive assembly lines (where both Mitsubishi and Rockwell controllers coexist), material handling systems (integration of Mitsubishi PLC with Rockwell-controlled conveyors), packaging lines (combining Mitsubishi packaging machine with Rockwell overhead control), and process automation (data exchange between Rockwell DCS and Mitsubishi PLCs).

Installation and Wiring

The RJ71EIP91 mounts in any slot of a MELSEC R series rack (or Q series with adapter). Set the station number and IP address using the software (no physical switches). Connect the Ethernet cables to the RJ45 ports. For daisy-chain, connect from the module's Port 1 to the next device's Port 2. For star topology, connect each port to an Ethernet switch. Use shielded Cat5e or Cat6 cables for industrial environments. The module requires no external power; it draws power from the backplane. LED indicators: EIP (network status), MOD (module status), LINK (link status for each port). After installation, configure the module in GX Works3 and download the project.

Conclusion

The Mitsubishi RJ71EIP91 EtherNet/IP communication module provides a reliable, high-speed bridge between MELSEC R series PLCs and EtherNet/IP networks. Its scanner/adapter flexibility, dual Ethernet ports, and seamless integration with Rockwell Automation equipment make it an essential component for mixed-vendor industrial automation systems requiring CIP-based communication.