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Old July 31st, 2020, 12:15 PM   #1

andy_1983 is offline
Join Date: Mar 2018
Location: uk
Posts: 42
Mitsubishi Modbus


Iím using a QJ71MB91 modbus card in a Mitsubishi Q series PLC. Itís being used as a slave, and everythingís working fine aside from the error light.

When I unplug the modbus connection (port 1) the error light sometimes comes on when I reconnect. Itís a genuine error being caused. When I open the system monitor in GX Works 2, I can view the modbus card status and there is a button to reset the error, which works ok and the error LED goes out.

What Iíd like to do is the same error reset from the PLC code, that way it could be linked into a reset button on SCADA.

Anyone know if itís possible, and how to do it?

Thanks for any pointers....
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Old July 31st, 2020, 08:14 PM   #2
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AlfredoQuintero is offline
Join Date: Feb 2015
Location: Yokohama
Posts: 203

I had a look at the manual and it seems all the system functions are reserved, both on the MELSEC backplane "Y" or discrete output signals and the buffer of shared memory between the Melsec Q and the QJ71MB91Modbus module. I found the manual in the below link:

However, there is one functionality that may help you, but I do not have this module to test my hypothesis, but here it is:

Using the ZP.UINI it seems to be possible to change some operation parameters. So I wonder if you change the operation parameters to something different than what you need, then again back to what you need, you could correct the error lights that you need to disable.
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Old August 4th, 2020, 03:45 AM   #3

andy_1983 is offline
Join Date: Mar 2018
Location: uk
Posts: 42
Thanks for the advice. Iíll try and have a go at this in the next day or two.


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