The QJ71DN91 is Mitsubishi Electric’s DeviceNet master/slave communication module for the MELSEC-Q programmable controller series, enabling MELSEC-Q controllers to communicate with DeviceNet-compatible field devices — including Allen-Bradley drives, sensors, valve manifolds, and I/O blocks — on the industry-standard DeviceNet (CIP) network used extensively in North American discrete manufacturing, automotive assembly, and material handling applications. Supporting both Class 1 master operation (managing cyclic I/O with up to 63 slave devices) and Group 2 slave operation (responding to another master’s polling), the QJ71DN91 provides the cross-vendor interoperability required for MELSEC-Q integration into DeviceNet-based facilities, and is particularly valuable for manufacturers operating mixed Mitsubishi/Rockwell Automation environments where DeviceNet is the established field device network. Available now at Atlantech Drives with worldwide express delivery and 12-month warranty — complete our quote form for pricing and availability.
What Is the QJ71DN91?
The QJ71DN91 is a MELSEC-Q series intelligent communication module implementing DeviceNet — the CIP (Common Industrial Protocol) based field-level network standardised by ODVA (Open DeviceNet Vendor Association) and widely used in North American industrial automation for connecting PLCs to field devices. As a Class 1 master, the QJ71DN91 manages polled I/O communication with up to 63 DeviceNet slave devices in a single network, reading input data from sensors and drives and writing output data to actuators and drives within a configurable network scan cycle. As a Group 2 slave, the QJ71DN91 allows another PLC or scanner (such as an Allen-Bradley ControlLogix with a 1756-DNB scanner module) to read and write MELSEC-Q data as if it were a standard DeviceNet I/O device. The module uses the DeviceNet physical layer (ISO 11898 CAN bus, 125/250/500 kbps) with the standard 5-pin open-style or micro-style DeviceNet connector. Network configuration is performed using Mitsubishi’s GX Configurator-DN software tool, which imports Electronic Data Sheet (EDS) files from slave device manufacturers to define each slave’s I/O data structure.
Key Technical Specifications
- Model: QJ71DN91
- Protocol: DeviceNet (CIP, ODVA standard)
- Operating Modes: Class 1 Master and Group 2 Slave (selectable)
- Transmission Speed: 125 kbps, 250 kbps, 500 kbps (configurable)
- Maximum Slaves (Master Mode): 63
- Maximum Input Data (Master Mode): 2,048 bytes total across all slaves
- Maximum Output Data (Master Mode): 2,048 bytes total across all slaves
- Maximum Cable Length: 500 m at 125 kbps; 250 m at 250 kbps; 100 m at 500 kbps (trunk line)
- Bus Connector: 5-pin open-style DeviceNet connector (V+, V-, CAN_H, CAN_L, Shield)
- Node Address: 0 to 63 (set via rotary switches)
- Current Consumption (5 VDC internal bus): 0.60 A
- Operating Temperature: 0°C to 55°C
- Compatible CPUs: All MELSEC-Q series CPU modules
- Weight: Approx. 0.25 kg
Compatibility & System Integration
The QJ71DN91 is compatible with all DeviceNet-compliant field devices from any ODVA member manufacturer. Allen-Bradley PowerFlex drives (520, 525, 700 series) equipped with the 22-COMM-D DeviceNet adapter are directly compatible with the QJ71DN91 as slaves, enabling MELSEC-Q speed and torque control of Allen-Bradley drives via DeviceNet — a configuration common in facilities where the drive infrastructure is Allen-Bradley but the machine PLC has been upgraded to MELSEC-Q. Rockwell Automation 1734 POINT I/O modules with 1734-ADN DeviceNet adapter and 1791DS DeviceNet Safety I/O modules are also compatible as slaves, providing MELSEC-Q access to distributed I/O in Allen-Bradley-wired panels. For installations where a Rockwell Automation ControlLogix with 1756-DNB scanner module acts as the DeviceNet master, the QJ71DN91 configured as a Group 2 slave allows the ControlLogix to read MELSEC-Q data and write setpoints directly without requiring a separate communication interface — the MELSEC-Q appears to the ControlLogix as a standard DeviceNet I/O device. Banner, Balluff, Pepperl+Fuchs, and other major sensor manufacturers’ DeviceNet-enabled sensors and multiplexers are all compatible with the QJ71DN91 master, provided their EDS file is imported into GX Configurator-DN for network configuration.
Maintenance Tips
DeviceNet physical layer maintenance is critical for long-term network reliability — the 5-wire DeviceNet cable carries both communication signals and 24 VDC bus power on the same cable, and degradation of any conductor affects both power supply to bus-powered devices and communication signal integrity simultaneously. Inspect DeviceNet trunk and drop cable connectors annually for corrosion, particularly in environments with high humidity, wash-down exposure, or chemical atmospheres — DeviceNet open-style connectors with screw terminals are susceptible to terminal corrosion that increases contact resistance and causes intermittent communication errors. Verify the DeviceNet bus power voltage at the far end of the trunk line annually — the 24 VDC bus power should remain above 21.6 VDC at the most distant powered device under full load; voltage below 21.6 VDC causes bus-powered devices to drop off the network. Check that the network termination resistors (121 Ω, 1%) are installed at both ends of the trunk line and that no additional termination resistors have been inserted at intermediate points — incorrect termination is the most common cause of DeviceNet communication errors in older installations where network modifications have been made without updating the termination configuration. The QJ71DN91’s node status LEDs (NS: Network Status, MS: Module Status) provide quick visual confirmation of network health — NS solid green indicates normal operation, NS flashing green indicates the module is online but not connected to all configured slaves, and NS red indicates a critical communication fault requiring investigation via GX Works2 buffer memory diagnostics.
Frequently Asked Questions
Q: Can the QJ71DN91 communicate with Allen-Bradley PowerFlex 700 drives configured for DeviceNet speed control?
A: Yes. The PowerFlex 700 drive with a 22-COMM-D DeviceNet communications adapter is fully compatible with the QJ71DN91 as a DeviceNet slave. The PowerFlex 700 EDS file must be imported into GX Configurator-DN to define the drive’s I/O assembly instances (typically Assembly 20 for basic speed/direction control and Assembly 21 for extended control with status feedback). The QJ71DN91 writes the speed reference and control word to the drive’s output assembly and reads the drive’s actual speed, status word, and fault code from the input assembly, all within the DeviceNet network scan cycle.
Q: What is the difference between the QJ71DN91 in master mode versus slave mode, and can both modes be active simultaneously?
A: In master mode, the QJ71DN91 manages cyclic I/O with up to 63 slave devices, acting as the network controller. In Group 2 slave mode, the module responds to polling from another master, making MELSEC-Q data available as a DeviceNet I/O node. The QJ71DN91 can only operate in one mode at a time — master or slave — not simultaneously in both. The operating mode is configured in GX Configurator-DN’s network parameter settings and cannot be changed while the module is online.
Q: How many QJ71DN91 modules can be installed in a single MELSEC-Q base unit?
A: Multiple QJ71DN91 modules can be installed in the same MELSEC-Q base unit, each managing an independent DeviceNet network. The practical limit is the number of available peripheral slots in the base unit. Each QJ71DN91 module manages its own independent DeviceNet network — installing two QJ71DN91 modules allows the MELSEC-Q CPU to simultaneously master two separate DeviceNet networks, useful for systems where DeviceNet slave count exceeds the 63-slave limit of a single network, or where network segmentation is required for safety or performance reasons.
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