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Hi everyone


I'm fairly new at unitronics and I'm doing a project that calls for the use of two EX-RC1 connected by modbus.


I've been going through the webinars ( 

) and I'm still in the dark as to how I set up

the EX-RC's for my I/O expansions.


In my first RC I have the following I/O's :  #0: D16A3-RO16 #1:AO6X 2#: AO6X #3: AO6X #4:AI8  #5AI8

In the second RC I have four IO-PT400 modules


I've tried following the second youtube clip, using the EX-RC1 example file where I've added my I/O's, but I get an error when I try to export the Hardware config:


'Export failed (555)

You must define a minimum of one I/O, including its operand link, per module before you can export the configuration'


Can somebody point me in the right direction here?


Thanks :)

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  • 1 year later...
  • MVP 2023

You have to tell us the configuration of the modules connected to your RC1 for us to be of more help.  CANbus is basically a way to transfer blocks of integers between controllers.

For starters, look at Help->Examples->Version 900->Project Examples->Communications->UniCAN for CANbus between masters->V570_UniCAN 1.vlp.  It shows the basics in the ladder logic -  the PLC type doesn't matter at this level.

Give it a try and post your code with specific questions.

Joe T.

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  • 1 month later...

Hi Joe  thank you for willingness to help.

I am new and not an expert at all. This is  my second PLC from Unitronics I want to code. The first one was a great success. A stand alone one is not a problem with the I/O units connected and coding although I believe there is better ways than my way for coding did it work wonderfull.  

But now my second project is a Vision 130 with two EX-RC1 Units to it. The first EX-RC1 has a IO-RO16/IO-RO16/IO-RO16/IO-RO16/IO-PT400/IO-PT400/IO-PT400/IO/PT400 and the second IO-RO16/IO-RO16/IO/PT400/IO-AO6X     I sorted the communication out between my Vision controller and the two EX-RC1 units working fine right thru to all  my I/O units not a problem.  

My problem is how to send to the EX-RC1 a out put command for example to IO-R016  output 2-1  I need an example because can not get it sorted. I watched several u tube videos but can not get around it. Where must I do my main program must it be on the Vision and just send a message to the EX-RC1 not sure where to start. I also struggle with the struck command. Then how do I read the IO PT400  Thermo inputs back to the vision 130.  You will be able to see where I struggle with the coding.  My problem is not the screen display but the coding to and from the I/O s to the Vision 130. 

Thank you 


1 EX-RC 2 Paul 14-7-2018.vlp

1 EX-RC 3 Paul 14-7-2018.vlp

1 Main 1 Paul 14-7-2018.vlp

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  • MVP 2023


This is a really good example of a complex EX-RC1 application so I'm going to crank through it for the benefit of the forum.

Thank you for posting your code!

CANbus is a "sending" protocol - you don't read the PT400 inputs from the V130, you send them from the EX-RC1.  The same applies to digital inputs.

It's also not the easiest thing in the world to understand, but once you've done one it makes sense.  It's important that you map out your memory first, as described below:

Laying things out-

EX-RC ID #2-

No DI modules

IO-PT 4 modules not configured and mapped to local MIs - I configured them as DIN 100 RTDs and  mapped them to local MI 11..26.  Open up the hardware configuration on the RC1 to see what I did. 

So - RTD's located in MI 11..26 with be sent to ID #1 V130 MI 201..216.  I chose this address block because there's nothing existing around it.

Local O32 ..O95   - V130 outputs O8..O71     This will require four MIs to hold all these bits- V130 MI 20..23 -> RC1 #2 MI 40..43.   I didn't use MI 20 in RC1 because it was already mapped to temperature data.

EX-RC ID #4-  (make sure it really is ID #4 based on the DIP switches)

No DI modules

IO-PT 4 modules partially configured - I configured them as DIN 100 RTDs (alpha = .0385) and  mapped them to local MI 11..14. 

RTD's located in MI 11..26 with be sent to ID #1 V130 MI 221..224.

Local O32 ..O63   - V130 outputs O72..O103     This will require two MIs to hold all these bits- V130 MI 26..27 -> RC1 #4 MI 110..111.

IO-AO6 module - configured 0-10V to local MI 60..65.  The V130 will send  its own MI60..65 to these. 


This is a lot to get you head around, but take your time and make your own map of what registers and outputs in the V130 correspond to which I/O in the RC1s.  All your actual control code will be written in the V130.

And I may have made a mistake somewhere in here.  I wasn't able to test the configuration.  Let me know if it behaves.

Joe T.


1 EX-RC3Paul14-7-2018 JT.vlp

Main1Paul14-7-2018 JT.vlp

1 EX-RC2Paul14-7-2018 JT.vlp

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Hi Joe - Getting closer and closer to start my real project coding 

I down loaded the 1 EX-RC2Paul 14-7-2018  and 1 EX-RC3Paul 14-7-2018  direct to the units individually. They work fine. even the led's turn red on the IO-PT400'S because my RTD's is not connected yet.

EX-RC ID #4-  (make sure it really is ID #4 based on the DIP switches)  - Regarding this point my dip switches it is selected off off on off off off which is suppose to be #3 but when I check my connection the green fall on #4.  The dip switches for unit EX-RC ID  #2 is off on offoffoffoff  and then my Vison 130 ID #1. I would like it to be ID #1,ID#2,ID#3 but it is not working that way. I switched several dip switches to try sort this out. But at least when I test the communication it show green on ID #1,#2,#4 

With the two EX-RC1'S sorted -  I have to down load the Main 1Paul 14-7-2018 to the Vision 130 unit directly via canbus network 1  or directly but when I compile before burning it over to the controller  there is three errors and two warnings.  The one is sorted - you duplicated the one Unican send command but the other two errors is as follow: LDR 66 Main Module Out EX-RC1#2 net 3 Before Unican Send High Priority use -/\/of SB201 before new Priority -/\/of SB202 and then I have the same for #4.  with SB 208 I am not sure what this mean or how to correct it. 

I just want to ask can you just code for me one MI press button TEST out put activation to the EX-RC1 and do one RTD read coding to see how it must be done on the ladder.

I still have to work around the coding you send but need more time to see exactly what you did. Will provide feedback

Thank you so much Joe  well appreciated. 







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