Mitsubishi QJ71DN91 DeviceNet Master/Slave Module

The Mitsubishi QJ71DN91 is a high-performance DeviceNet master/slave communication module for the MELSEC Q Series programmable logic controller platform. Compliant with DeviceNet Specifications Release 2.0, this module enables seamless integration of DeviceNet networks into Q Series automation systems. It can operate as either a DeviceNet master node or a slave node, providing flexibility for various network architectures. The QJ71DN91 connects the MELSEC Q Series CPU to a wide range of DeviceNet-compatible devices including sensors, actuators, drives, and remote I/O blocks.

Technical Specifications

The QJ71DN91 module supports communication speeds of 125, 250, and 500 kbps (selectable). As a master node, it can communicate with up to 63 slave nodes. The module is equipped with a 5-pin open-style connector (using a 5.08 mm pitch terminal block) for DeviceNet network connection. Connection types for I/O communication include Polling, Bit Strobe, Change of State, and Cyclic, providing flexibility for different application requirements. The module also supports message communication (Explicit Messages) for reading and writing attribute data of slave nodes. Buffer memory is provided for temporary storage of parameter settings and I/O data, while flash ROM stores parameters for automatic loading on power-up. The QJ71DN91 occupies one I/O slot in the Q Series base unit and can be installed in any I/O slot. Power consumption is derived from the 5 V DC backplane. Operating temperature range is 0°C to 55°C. The module features LED indicators for network status, module status, and communication activity.

Key Features

• DeviceNet master/slave operation (compliant with Release 2.0)

• Communication speeds: 125, 250, 500 kbps

• Supports up to 63 slave nodes in master mode

• I/O communication connection types: Polling, Bit Strobe, Change of State, Cyclic

• Message communication via Explicit Messages

• Auto configuration for master function parameters

• Buffer memory for I/O data and parameter exchange

• Flash ROM for parameter storage and automatic loading

• Automatic refresh for data transfer to PLC CPU

• GX Configurator-DN utility for monitoring, testing, and parameter configuration

Operational Modes

The QJ71DN91 can be configured as a DeviceNet master or slave node. In master mode, it scans the network, reads inputs from slave devices, and writes outputs to slave devices. The module supports auto configuration functionality that detects slave nodes on the network and automatically creates master function parameters, significantly reducing programming effort. In slave mode, the module responds to communication requests from a DeviceNet master, allowing the Q Series PLC to appear as a node on an existing DeviceNet network. The module supports both I/O communication (cyclic data exchange for time-critical applications) and message communication (event-driven data requests). The I/O communication function is used for exchanging input/output data between the master and slave nodes, while the message communication function is used for reading or writing attribute data of slave nodes in response to a request message.

Configuration and Programming

The QJ71DN91 is configured using Mitsubishi GX Works2 or GX Developer programming software with the GX Configurator-DN utility package. The configuration software allows users to set network parameters including node address, baud rate, I/O data mapping, and connection types. Automatic refresh functionality automatically transfers data between the buffer memory and the programmable controller CPU, simplifying data exchange in the user program. The user program uses dedicated instructions for DeviceNet communication, enabling read/write access to slave device data. Buffer memory is used for temporarily storing parameter settings and I/O data. Parameters saved in buffer memory can be stored to flash ROM, and the module automatically loads these parameters when powered on.

Applications

Typical applications for the QJ71DN91 include connecting DeviceNet remote I/O blocks to a Q Series PLC, integrating DeviceNet-compatible drives and sensors into a control system, connecting barcode readers and RFID systems, implementing DeviceNet safety networks with safety I/O devices, and building distributed control systems with third-party DeviceNet equipment. The module is widely used in automotive assembly lines, material handling systems, packaging machinery, and food processing applications where DeviceNet is deployed.

Installation and Wiring

Install the QJ71DN91 into any I/O slot of a MELSEC Q Series base unit. The module requires a 5-pin open-style connector for DeviceNet network connection. DeviceNet wiring consists of two power lines (V+, V-), two communication lines (CAN_H, CAN_L), and a drain wire. The network must be properly terminated with 121 Ω resistors at both ends of the trunk line. The module includes terminating resistors in the package. Power for the DeviceNet network must be provided by an external 24 V DC power supply; the module does not supply power to the network. Set the node address using the rotary switches on the module front panel (0-63 for slave, 64-127 for master). Set the baud rate using DIP switches. The module's LED indicators provide visual confirmation of network status, module health, and communication activity.

Diagnostics and Maintenance

The QJ71DN92 provides diagnostic functions accessible through GX Configurator-DN. Users can monitor network status, check slave connection status, and view error logs. The module reports communication errors such as node address duplication, baud rate mismatch, and slave device timeouts. These errors are reflected in the module's LED status indicators and can be retrieved via the PLC's CPU buffer memory. The LED indicators provide quick visual diagnostics: green for normal operation, red for errors. Regular maintenance includes checking cable connections, verifying termination resistors, and monitoring for dust accumulation.

Environmental and Compliance

The QJ71DN31 is CE and RoHS compliant. Operating temperature: 0°C to 55°C. Storage temperature: -20°C to 70°C. Humidity: 10-90% non-condensing. The module is rated IP20 and must be installed in a control cabinet. It meets DeviceNet conformance standards, ensuring interoperability with certified DeviceNet devices.

Conclusion

The Mitsubishi QJ71DN91 DeviceNet master/slave module provides a flexible and reliable interface between MELSEC Q Series PLCs and DeviceNet networks. Its dual master/slave capability, support for multiple connection types, and comprehensive configuration tools make it a suitable choice for integrating DeviceNet devices into new or existing automation systems.