Mitsubishi Electric QJ71MT91 MELSEC Q Series Modbus/TCP Network Module

Description

Designed for seamless integration within MELSEC Q Series control architectures, the Mitsubishi Electric QJ71MT91 establishes reliable Ethernet-based communications by acting as a dedicated interface between high-performance PLCs and Modbus/TCP networks. This module allows MELSEC system processors to exchange data efficiently with third-party devices, instruments, and supervisory SCADA platforms over standard TCP/IP frameworks. Operating seamlessly in both master and slave capacities, it eliminates the need for expensive protocol converters or custom communication scripts in multi-vendor environments.

Key Features

• Dual functionality supports concurrent Master and Slave execution roles over the network.
• Built-in automatic communication utility simplifies data exchange without complex sequence ladder programming.
• High-density buffer memory provides robust storage capacity for 4k words of input and output data.
• Standard RJ45 physical layer interface supports industrial Ethernet architectures.
• Direct integration onto the MELSEC Q series baseplate, drawing power directly from the backplane system.

Applications

• Integration of multi-vendor PLC platforms (e.g., interfacing Modicon or Beckhoff controllers with MELSEC systems).
• Distributed SCADA and HMI network interfaces over enterprise-wide local area networks.
• Real-time telemetry and control of field instruments, power meters, and variable frequency drives over Modbus/TCP.

Technical Specifications

Empirical Engineering Insights

Alternative Models & Compatibility

The QJ71MT91 is a dedicated Modbus/TCP module that provides native TCP/IP encapsulation for Modbus protocols. When migrating older systems from serial Modbus (RTU/ASCII) architectures previously managed by the QJ71C24N module, the QJ71MT91 offers a modern Ethernet upgrade without necessitating significant redesign of the backplane. This module requires GX Works2 or GX Developer utility software for module parameter setup and configuration profile mapping.

Application Pitfalls & Engineering Notes

Engineering systems incorporating multiple network-heavy modules must carefully calculate backplane current consumption. The QJ71MT91 draws a substantial 0.52A from the 5VDC internal bus line. Always verify that your power supply module (e.g., Q61P, Q63P) can supply sufficient current to avoid unexplained system resets or communications interruptions during heavy packet routing phases.

Commissioning & Wiring Tips

To guarantee clean execution and isolate industrial data lines from electromagnetic noise, ensure all Ethernet cabling running from the RJ45 port of the module is category 5e/6 STP (Shielded Twisted Pair). Ensure the shield of the physical Ethernet line is correctly bonded to the control panel's ground point. If accessing the module through firewalls, keep standard Modbus/TCP port 502 open for bidirectional protocol traffic.

Installation Guidelines