Mitsubishi QJ71C24N Communication Module | Industrial Spare Part

The Mitsubishi Electric QJ71C24N is a dual-channel serial communication module designed for MELSEC-Q Series programmable logic controller platforms. Providing independent RS-232 and RS-422/485 interfaces, this intelligent function module enables connectivity between MELSEC-Q CPU systems and industrial serial peripherals, including barcode readers, RFID scanners, digital scales, temperature controllers, and external operator panels.

Key Technical Specifications

• Product Model: QJ71C24N (Standard Dual-Interface Model)
• Module Classification: MELSEC-Q Series Intelligent Function Module (Serial Communication)
• Interface Configuration: 2 independent communication channels:
  • Channel 1 (CH1): RS-232 interface (standard 9-pin D-sub male connector)
  • Channel 2 (CH2): RS-422 / RS-485 interface (2-piece detachable terminal block)
• Transmission Speed (Baud Rate):
  • CH1 (RS-232): 300 to 230,400 bps
  • CH2 (RS-422/485): 300 to 115,200 bps (Note: 230,400 bps is strictly unsupported on CH2)
  • Combined Transmission Speed: The total simultaneous transmission speed across CH1 and CH2 must not exceed 230,400 bps. When the communication data monitoring function is enabled, the combined limit is 115,200 bps per manufacturer performance specifications.
• Communication Protocols: MC Protocol (Format 1 through Format 4), Non-procedure protocol (bidirectional ASCII/binary data streaming), Bidirectional protocol
• Synchronization Method: Asynchronous communication
• Transmission Distance: Up to 15 m for CH1 (RS-232); up to 1200 m total overall cable distance for CH2 (RS-422/485)
• Internal Current Consumption (5V DC): 0.31 A (standalone module base consumption)
• I/O Occupied Points: 32 points (Intelligent function module, assigned as 32 I/O points in base unit configuration)
• Mounting Location: MELSEC-Q main base unit or extension base unit (Q3xB, Q6xB)
• Engineering Software: Configurable via GX Developer and GX Works2 serial communication parameter utilities

Channel Architecture & Hardware Differentiation

The standard QJ71C24N combines one RS-232 port with one RS-422/485 port on a single-slot module. System engineers must differentiate this standard configuration from variant models in the same family: the QJ71C24N-R2 (equipped with two RS-232 ports) and the QJ71C24N-R4 (equipped with two RS-422/485 ports). Channel 1 uses standard D-sub pin assignments supporting optional hardware flow control signals (RTS/CTS, DTR/DSR) where required by external device wiring. Channel 2 features a detachable 2-piece terminal block designed for multi-drop RS-422/485 topologies with external terminating resistor configurations. Dedicated buffer memory and specialized instructions (such as G.OUTPUT and G.INPUT) permit communication without complex ladder protocol programming.

Migration & Engineering Considerations

For prospective plant modernization toward the MELSEC iQ-R Series, the referenced migration model is the RJ71C24 (or RJ71C24-R2 / RJ71C24-R4 depending on interface requirements) per the MELSEC-Q Series to MELSEC iQ-R Series Migration Guide [L(NA)08510ENG-H]. Note that iQ-R modules require iQ-R base units and CPUs and cannot be mounted onto MELSEC-Q backplanes. For replacement of existing units in running machines, engineers should verify hardware function version, existing wiring terminations, and software buffer memory assignments prior to commissioning.

Procurement & Technical RFQ

NORTHLINK supports industrial automation spare-parts sourcing for maintenance and engineering applications. Because serial communication modules are managed under an RFQ workflow, stock status, delivery lead times, and formal pricing are confirmed upon application review. Please submit an inquiry detailing required channel configuration, delivery timeline, destination, and any specific hardware version requirements for a formal quotation.