Mitsubishi FX Series PLC Data Communication Practical Manual

Mitsubishi FX Series PLC Data Communication Complete Guide: Practical Technical Analysis from N: N Network to Remote Maintenance

Mitsubishi Electric FX series programmable logic controllers (PLCs) occupy an important position in the field of industrial automation due to their flexibility and powerful communication capabilities. Its data communication function covers multiple network protocols and interface standards, which can meet various needs from simple device interconnection to complex remote monitoring. This article is based on the FX series PLC data communication manual, systematically sorting out its communication types, system configurations, parameter settings, and troubleshooting methods, providing engineers with a comprehensive and practical technical reference.

The FX series PLC supports multiple physical interfaces such as RS-232C, RS-485/RS-422, USB, and Ethernet, and provides various communication protocols including CC Link, N: N network, parallel link, computer link, inverter communication, non protocol communication, MODBUS communication, programming communication, and remote maintenance. Each communication method is designed for specific application scenarios, and engineers can flexibly choose based on system size, transmission distance, number of devices, and real-time requirements.

Analysis of Core Communication Types

1. N: N network

N: N Network is a small data link system that allows up to 8 FX series PLCs to automatically exchange data via RS-485 bus. This network supports three data link modes (mode 0, 1, 2), corresponding to different device point configurations:

Mode 0: 4-point device (D register) per station, only suitable for small PLCs such as FX0N and FX1S

Mode 1: 32 point devices (M relays) and 4-point devices per station

Mode 2: 64 point devices and 8-point devices per station (applicable to FX1N, FX2N, FX3 series)

N: The total extension distance of N network can reach 500 meters (when using 485ADP), and the communication baud rate is fixed at 38400bps. The master station completes configuration by setting special registers such as D8176 (station number), D8177 (number of slave stations), D8178 (refresh range), etc. The slave station only needs to set its own station number, and other parameters are automatically obtained from the master station.

2. Parallel linking

Parallel link is dedicated to high-speed data exchange between two PLCs of the same series, providing two options: regular mode and high-speed mode:

Normal mode: Transmission of 100 point devices and 10 point devices (FX0N/FX1S for 50 point M and 10 point D)

High speed mode: only transmits 2-point devices, but the link cycle is significantly shortened

In high-speed mode, the link time of FX3 series PLC is only "5ms+master station scanning cycle+slave station scanning cycle", which is suitable for situations with high real-time requirements. Parallel links are initiated through M8070 (master declaration) and M8071 (slave declaration), with M8162 used to switch high-speed mode.

3. Computer connection

The computer link adopts a dedicated protocol (format 1 or format 4), allowing the upper computer (or personal computer) to serve as the master station and connect up to 16 FX or A-series PLC slave stations. This communication supports two physical layers: RS-232C (1:1 connection, distance of 15 meters) and RS-485 (1: N connection, distance of 500 meters).

The core instructions for computer connectivity include:

BR/BW: Read/Write Bit Devices

WR/WW: Read/write word devices or 16 bit devices by word

QR/QW: Extended word read/write (applicable to FX3 series)

BT/WT: Random Test Write (bits/word)

RR/RS: Remote RUN/STOP Control

PC: Read PLC model code

GW: Global command (simultaneously controls all slave stations)

TT: Loop Test

The communication format is set through D8120 (ch1) or D8420 (ch2), including data length (7/8 bits), parity check (none/odd/even), stop bit (1/2 bits), baud rate (300~38400bps), and whether to add header/terminator/checksum. The station number is designated by D8121 (ch1) or D8421 (ch2).

4. Communication of frequency converter

The FX series PLC can communicate with Mitsubishi FR-E700, D700, A800, F800 and other series frequency converters through RS-485 to achieve operation monitoring, frequency setting, parameter reading and writing, and start stop control. For FX2N/FX2NC, use the EXTR instruction (K10~K13); For the FX3 series, more specialized IVCK, IVDR, IVRD, IVWR, IVBWR, and IVMC instructions are used.

The IVMC instruction (multifunctional inverter control) is particularly powerful, as it can simultaneously write operation commands and set frequencies in a single communication, and read the inverter status and output frequency, greatly improving communication efficiency. This instruction supports FX3S (V1.00 or above), FX3G/FX3GC (V1.40 or above), and FX3U/FX3UC (V2.70 or above).

The parameter settings for frequency converter communication include station number (Pr.117 or Pr.331), baud rate (Pr.118 or Pr.332), data format (Pr.119/Pr.333), parity check (Pr.120/Pr.334), etc. The operation mode of the frequency converter needs to be set to "network operation mode" (Pr.79=0 or Pr.340=1), and the communication timeout and retry times should be configured correctly.