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How to communicate with Mitsubishi 485( fx2 series)

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If possible, show me an example of communication with the fx2n series through 485 media.


One important information: All blocks in toolbox have ? simbol for explain funtion block .But COM:Serial don't have a help in help glossary . My doubt is if this block have a internal checksum or is necessary put together inside the message?



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What PLC are you using?

Have you setup the RS485 Communications in the hardware configuration?    Com - PLC Communications-Physical-Serial Com

       and then   Com- PLC Communications-Protocols - Modbus    

      Who is Master?   Slave?

Mitsubishi supports  Modbus, Have you set up the protocol in it?     Master or Slave?

Download the UniStream Example programs  from the download section -just below the UniLogic download.

Under Communications there are a couple of RS485 Examples  to help guide you. - General - Not Mitsubishi Specific.


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I use fx2 series, it not have a modbus, because it is legacy system in site my client.  I see examples , but not help me.

After , i discovered in message composer having a checksum , optional and there was information about this resource in help . 


I feel like a blind man walking on the street with a walking stick looking for information. kkkkk...


Thanks in advance for try help me.

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  • MVP 2023

This is not a trivial task.  And yes, the Help is currently a little light on the COM blocks.

You'll need to define exactly what data it is in the Mitsubishi you want.  Who will be the master - Visilogic or the Mitsubishi?

You'll need to get very familiar with this document:

FX Communication Protocol

It looks like in the Mitsubishi you can set D8120 to turn off the checksum.  Look at  chapter 6 of the manual.

Get a USB->485 converter and develop the strings you'll need using a terminal program- I like this one: Bray's Terminal

This is a much easier and faster way to figure out protocol strings.

Once you've got the strings you need, you can start to configure your COM:Protocol blocks.  Send a request to support@unitronics.com for direct help on this.


Joe T. 


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