The QJ71PB92D is Mitsubishi Electric’s PROFIBUS-DP slave module for the MELSEC-Q programmable controller series, enabling a MELSEC-Q controller to operate as a PROFIBUS-DP intelligent slave device — allowing it to be controlled by any Class 1 PROFIBUS-DP master from any manufacturer, including Siemens SIMATIC S7, ABB AC500, Schneider Electric Modicon, or any other PLC platform acting as the PROFIBUS network master. As the slave counterpart to the QJ71PB92V master module, the QJ71PB92D provides the critical interoperability capability required when a MELSEC-Q system must be integrated into an existing PROFIBUS infrastructure managed by a non-Mitsubishi master controller, or when a MELSEC-Q subsystem controller must report data to a higher-level supervisory PLC. In stock at Atlantech Drives. Request your quote within 24-48 hours with worldwide shipping and 12-month warranty.
What Is the QJ71PB92D?
The QJ71PB92D is a MELSEC-Q series intelligent communication module implementing PROFIBUS-DP protocol at the DP slave level, compliant with IEC 61158 and EN 50170 PROFIBUS-DP V0 and V1 standards. As a DP slave, the QJ71PB92D receives output data from the PROFIBUS master and makes it available in the module’s buffer memory for the MELSEC-Q CPU to read, while simultaneously making MELSEC-Q data available in the buffer memory for the master to read as input data — enabling bidirectional data exchange between the Mitsubishi CPU and the PROFIBUS master in each bus cycle. The module provides a GSD file (Generic Station Description) for import into the PROFIBUS master’s configuration tool, defining the module’s I/O data structure, supported baud rates, and device identification information. Maximum I/O data per exchange is 244 bytes input and 244 bytes output, consistent with the PROFIBUS-DP standard slave data limit.
Key Technical Specifications
- Model: QJ71PB92D
- Protocol: PROFIBUS-DP (IEC 61158 / EN 50170)
- Operating Mode: DP Slave (V0 and V1)
- Transmission Speed: 9.6 kbps to 12 Mbps (auto-detected from master)
- Maximum Input Data (master reads from MELSEC-Q): 244 bytes
- Maximum Output Data (master writes to MELSEC-Q): 244 bytes
- Station Address Range: 1 to 125 (set via rotary switches on module)
- Bus Connector: 9-pin D-Sub female (RS-485)
- GSD File: Provided by Mitsubishi for master configuration
- Current Consumption (5 VDC internal bus): 0.55 A
- Operating Temperature: 0°C to 55°C
- Compatible CPUs: All MELSEC-Q series CPU modules
- Weight: Approx. 0.22 kg
Typical Industrial Applications
The QJ71PB92D is most commonly deployed in hierarchical control architectures where a Siemens or other brand PLC acts as the plant-level supervisor and multiple MELSEC-Q subsystem controllers handle local machine control. In automotive paint shop automation, a Siemens SIMATIC S7-400 plant controller manages the overall production flow and communicates setpoints, recipe parameters, and production commands to MELSEC-Q controllers at individual spray booths via PROFIBUS — each MELSEC-Q booth controller uses a QJ71PB92D to receive these commands from the Siemens master and reports production status back. In water treatment facilities where the SCADA system uses a Schneider Modicon PROFIBUS master for field device communication, MELSEC-Q pump station controllers with QJ71PB92D modules integrate seamlessly into the existing PROFIBUS infrastructure without requiring the SCADA system or fieldbus architecture to be modified. Pharmaceutical clean room environmental monitoring systems use the QJ71PB92D to connect MELSEC-Q environmental controllers to a centralised Siemens building automation PROFIBUS network, enabling unified monitoring of temperature, humidity, and pressure from both process automation and building management systems on the same network infrastructure.
Installation Advice
The QJ71PB92D’s PROFIBUS station address is set using two rotary hex switches on the front of the module, accessible without removing the module from the base unit — set the station address before installing the module and before applying power, as the station address is read only at power-up and changes take effect only after a power cycle. Verify that the assigned station address does not conflict with any other device on the PROFIBUS segment, including the master station — duplicate station addresses cause the affected slave to fail to initialise and generate a bus conflict. For the PROFIBUS cable connection, use the 9-pin D-Sub connector with integrated bus termination resistance — enable the termination resistor (typically a DIP switch or sliding switch on the connector housing) if the QJ71PB92D is at one physical end of the PROFIBUS cable, and disable it if the module is in the middle of the bus. Unterminated bus ends cause signal reflections that degrade communication reliability, particularly at 12 Mbps where signal rise times are most critical. After connecting the module to the PROFIBUS network and powering up, verify the module’s DATA_EXCHANGE LED indicator is illuminated — this confirms that the PROFIBUS master has successfully initialised the QJ71PB92D as a slave and cyclic data exchange is active.
Frequently Asked Questions
Q: Can the QJ71PB92D operate on the same PROFIBUS segment as the QJ71PB92V master module?
A: Yes, but not simultaneously controlling each other. The QJ71PB92V (master) and QJ71PB92D (slave) can be installed in different MELSEC-Q base units on the same PROFIBUS segment — the QJ71PB92V acts as master managing other slaves, and the QJ71PB92D acts as slave responding to a different master on the same segment. However, a QJ71PB92V master in one MELSEC-Q system cannot directly communicate with a QJ71PB92D slave in another MELSEC-Q system on the same segment without proper GSD-based configuration in GX Configurator-DP.
Q: What happens to the QJ71PB92D output data (data received from the PROFIBUS master) if the PROFIBUS master enters STOP mode or communication is interrupted?
A: When the PROFIBUS master enters STOP mode or cyclic communication is interrupted, the QJ71PB92D transitions to the CLEAR state and the output data (master-to-slave data) is cleared to zero. The module sets a communication error flag in the buffer memory, which the MELSEC-Q CPU ladder program can monitor to detect master communication loss and implement appropriate safe-state logic for the controlled process.
Q: Does the QJ71PB92D support DPV1 acyclic communication for parameter access from the master?
A: Yes. The QJ71PB92D supports DP V1 acyclic communication, allowing the PROFIBUS master to read and write specific parameter data records to the QJ71PB92D’s buffer memory outside of the normal cyclic data exchange. This enables the master to access extended diagnostic information, configuration parameters, and event data from the MELSEC-Q system on demand without dedicating cyclic I/O bytes to these values.
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