Mitsubishi QJ71E71 Connection Guide for UDP

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The QJ71E71 Ethernet module allows data access software, such as Fernhill SCADA, to monitor and control a Mitsubishi Q-Series PLC Device.

The information in this guide applies to a range of Mitsubishi Melsec Q-Series Ethernet modules:

QJ71E71-10010Base-T and 100Base-Tx

The rest of this article uses the name QJ71E71 to refer to any of the above modules.

This guide shows you how to set up a QJ71E71 Ethernet module to use MC Protocol over UDP.

Using the QJ71E71 Ethernet Module

To connect Fernhill SCADA to a QJ71E71 Ethernet module you will need to configure the QJ71E71 module to accept requests from Fernhill SCADA. As a minimum you will need to configure the Operational Settings of the module. The QJ71E71 Ethernet module is configured by writing values to the buffer memory of the module.

Recommended Operational Settings:

Setting Name Buffer Memory
Recommended Value
Communication Data Code 31 bit 1 0 - Binary
TCP Existence Confirmation 31 bit 4 1 - Use KeepAlive
Send frame setting 31 bit 5 0 - Ethernet V2.0
Allow controls in run mode 31 bit 6 1 - Enable
Initial Timing 31 bit 8 1 - Always wait for OPEN
IP Address 0 to 1 Your IP Address

By default the QJ71E71 Ethernet module opens UDP port 5000 (1388h). Without any further configuration to the module, Fernhill SCADA can communicate with the QJ71E71 Ethernet module using port 5000 (1388h).

If you want to use a different port, you will need to configure additional Open Settings. For communication with Fernhill SCADA, these settings are recommended:

Setting NameBuffer Memory
Recommended Value
Fixed buffer32 to 39 bit 01 - Receive
Existence confirmation32 to 39 bit 10 - No Confirm
Pairing open32 to 39 bit 70 - No pairs
Protocol32 to 39 bit 81 - UDP
Fixed buffer communication32 to 39 bit 90 - Procedure (MC)
Open system32 to 39 bits 14-1500 - Not applicable to UDP
Local station port no.40, 47, 54, 61, 68, 75, 82, 89Your Port Number
Destination IP address41-42, 48-49, 55-56, 62-63, 69-70, 76-77, 83-84, 90-914294967295 (FFFFFFFFh) -
Destination port no.43, 50, 57, 64, 71, 78, 85, 9265535 (FFFFh) - Any

You can configure the QJ71E71 Ethernet module directly from GX Developer, or using a PLC program. Both methods configure the QJ71E71 Ethernet module by writing to the buffer memory of the module.

Example configuration for setting up Connection 1 for Fernhill SCADA to access the PLC via port 21633 (5481h):

Buffer Memory
32501hReceive buffer, No confirm, No pairs, UDP, Procedure, Active Open
405481hPLC Port Number
41-42FFFFFFFFhFernhill SCADA IP Address (any)
43FFFFhFernhill SCADA Port Number (any)

For more information refer to the QJ71E71 User Manual.

Fernhill SCADA Configuration

The easiest way to configure Fernhill SCADA is to use the Mitsubishi Melsec UDP Autodetect Wizard. Based on the options you select the wizard will try different IP Addresses and Port numbers until the module is found. If a module is found you will be given an option to automatically create the correct configuration to communicate with the module.

Further Information

Mitsubishi Melsec UDP channel

To learn about Mitsubishi Melsec UDP communication channels.

Mitsubishi Melsec TCP Autodetect Wizard

To learn about automatically detecting Mitsubishi PLC Devices using TCP/IP.

Mitsubishi Melsec UDP Autodetect Wizard

To learn about automatically detecting Mitsubishi PLC Devices using UDP.

Mitsubishi Melsec Driver

For information about the Mitsubishi Melsec Driver.


For the meaning of terms used in Fernhill SCADA.