deny zaelani

FX3U Modbus RTU with FX-485-BD

7 posts in this topic

Hi Expert,

 

I've tried modbus communication with PLC FX3U and FX-485-BD. I've read some manual regarding modbus communication for FX3U. And also download FX ModbusRTU Master V100 and FX Modbus RTU Slave V100. My Question :

 

1. Can I use FX-485-BD for modbus communication and use it as ch1? As I check in modbus manual, FX-485-bd only for mitsu propitary not modbus? But I read in this forum it can be used

2. I tried this library unpack and open it, previous setting is for FX3G not FX3U, so when it change and compiled to FX3U and I always get error message "
" ERROR    FXModbusRTUMaster_PRG    Program compile    The number of word device (VAR range) points for Device/Label Automatic-Assign Setting fall short. (ModbusComm.ReceivedMessage)    F1035

I tried to find out how to rectify this error but can't find it? please suggest is there some missing setting or some miss program in library?

 

Regards.


DZ

 

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Hi Mr.Deny Zaelani,

   The Module FX3U-485-BD  Supports serial non procedure protocol and dedicated protocol for Mitsubishi communication devices like HMI.

To make a Modbus communication with Mitsubishi FX3U PLC you need to Have a FX3U Modbus Card.

This Card FX3U-485-BD will not support MODBUS

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14 hours ago, krishna k said:

This Card FX3U-485-BD will not support MODBUS

will not support programming instructions for Modbus comm, but can support programming implementation of Modbus protocol like non procedural.

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Hi Deny,

FX3U-485-BD  just support non-protocol to communicate with third party.

So, if you want to use Modbus-RTU to communicate via  FX3U-485-BD , you need understand frame of Modbus-RTU.

Modbus frame: Address || Function || Data || CRC

Noted that you need to calculate the CRC by yourself, I searched the CRC calculation online and fixed CRC value because I only use 1 RS2 instruction.

I have already checked the Modbus-RTU via  FX3U-485-BD , and it's work well.

If you need more information, contact to me via email minh89.automation@gmail.com.

I recommend you use the Modbus adapter FX3U-485ADP-MB (+FX3U-CNV-BD) to communicate Modbus-RTU easily.

FX3U-485-BD - Modbus RTU.pdf

Edited by minhpham
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thanks i sent mail for u.....i have plc fx3u and fx3u 485 bd modbus rtu   .i want connect plc fx3u to inveter ig5a ....but i canu...i used chanel 1   D8400   and test chanel 2 d8420...................but  i dont know  use chanel 1 or chanel 2 ..................please help me .....3days i try but no good ...

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As he said, the unit itself does not do Modbus RTU.  You need to write the communication in a string format and send it out.

Pretty sure they had a module for the left side bus that did offer Modbus, FX3U-485ADP-MB or something like that.

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@iraj2090 You need to create Modbus data communication manucally by use RS command for your own (need to calculate check sum) because FX3U-485BD does not support Modbus protocol but if you have FX3U-485ADP-MB you can use ADPRW command to communication with Modbus device.

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