Mitsubishi QJ71C24N-R2 MELSEC-Q 2‑Channel RS‑232 Serial Communication Module

Mitsubishi Electric MELSEC-Q series serial communication module with two independent RS‑232 channels (CH1 and CH2). Supports full‑duplex and half‑duplex communication, asynchronous start‑stop synchronization, and multiple protocols: MC protocol (MELSEC communication protocol), non‑procedural protocol, bidirectional protocol, and predefined protocol (function version B required). Baud rates up to 230.4 kbps (CH1 only, total of two interfaces ≤ 230.4 kbps). Enables connection of Q series PLCs to external devices such as personal computers, HMIs, barcode readers, measuring instruments, modems, and printers. Remote password function prevents unauthorized access via modem. Up to 128 predefined protocols can be stored in a single module. Capable of high‑speed, large‑volume communication up to 960 words (MC protocol). RS‑232 transmission distance up to 15 m.

Applications:

• Factory automation serial communication between Q series PLC and PCs / HMIs

• Barcode reader and measuring instrument data acquisition

• Modem connection for remote programming and monitoring

• Printer interface for alarm logging and report generation

• Legacy system replacement for QD51 intelligent communication modules

Technical Specifications:

Core Specifications

• Communication protocol: MC protocol, non‑procedural protocol, bidirectional protocol, predefined protocol

• Synchronization method: Start‑stop synchronization (asynchronous)

• Transmission speeds: 50, 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, 115200, 230400 bps

• 230400 bps available for CH1 only (not available for CH2)

• Total transmission speed of two interfaces ≤ 230400 bps (when communication data monitoring function used: ≤ 115200 bps)

• Data format: Start bit 1; Data bits 7 / 8; Parity bit even / odd / none; Stop bits 1 / 2

• Transmission distance (RS‑232): max. 15 m

• Error detection: Parity check (selectable odd/even), sum check code

Physical Specifications

• Number of channels: 2 (CH1, CH2)

• Interface type: RS‑232‑compliant (D‑Sub 9‑pin male, screw‑type)

• Transmission control: DTR/DSR (ER/DR) control, RS/CS control, CD (DCD) signal control, DC1/DC3 (Xon/Xoff) control, DC2/DC4 control

• Line configuration: 1:1 connection

• Number of occupied I/O points: 32 points (I/O assignment: Intelligent 32 points)

• Internal current consumption (5 V DC): 0.26 A

• External dimensions (H × W × D): 98 mm × 27.4 mm × 90 mm

• Weight: 0.20 kg

• Mounting: Backplane / rack mounting (Q series main base unit or extension base unit)

• Protection rating: IP2X

• Operating temperature: 0 °C … 55 °C

• Storage temperature: –20 °C … 75 °C

Advanced Specifications:

• Flash ROM write endurance: max. 100,000 writes to the same area

• Predefined protocol storage: up to 128 protocols per module (function version B, serial number first five digits ≥ 11062)

• Modem function: supports public network modems (CH1 RS‑232, remote password protection)

• Maximum data transfer (MC protocol): up to 960 words read/write from QCPU device memory

• MELSOFT connection: programming and maintenance via RS‑232 serial communication

• Access cycle (MC protocol): processes one request during END processing of the CPU module

• Access cycle (non‑procedural / bidirectional): sends each time a send request is issued, can receive at any time

System Integration:

• This serial communication module belongs to the Mitsubishi Electric MELSEC‑Q series.

• Installs into any MELSEC‑Q series main base unit (Q3□B, Q5□B, Q6□B series) or extension base unit slot.

• Compatible with Q series CPU modules (Q00J, Q00, Q01, Qn, QnH, QnPH, QnPRH, QnU series).

• Supports programming, monitoring, and data communication using GX Works2 / GX Developer software.

• For predefined protocol configuration, GX Works2 version with predefined protocol support and module function version B are required.

• Remote password function: prevents illegal access to Q series PLCs via modem line.

• For detailed wiring, connector pinout (D‑Sub 9‑pin male), and parameter settings (switches CH1/CH2), refer to the MELSEC‑Q/L Serial Communication Module User's Manual.

Standards & Compliance:
Refer to manufacturer official documentation for detailed certification and compliance information (CE, UL/cUL).

Related Products:

• QJ71C24N – 1× RS‑232 + 1× RS‑422/485, same housing

• QJ71C24N-R4 – 2× RS‑422/485 channels

• QJ71E71-100 – Ethernet interface module for Q series

• QJ71MT91 – MODBUS/TCP interface module

• GX Works2 – Engineering software for configuration and programming