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ModBus TCP/IP Questions and Problems (VisiLogic, V1210, PLC Master)


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I did some tests, and yeah, It's the same on V570 as V700.

14 hours ago, kratmel said:

That is, an already open Socket should simply change the address without closing it. This is just a hypothesis, but if the IP address was only static here, I would understand the need for a constant switching process.

The Issue is not the Socket being Open, is that you need to connect the socket to a specific IP first to use Modbus OverTCP/IP.

If you connect to a Device 1, then use Modbus IP function for Device 1, then you try to use another Modbus Function to Device 2 (Using the stored IP for Device 2 on the MI and selecting the correct device) then the PLC still sends the Modbus requests to Device 1. I know that because I get a response status of 7. 

* Messages 6, 7, and 11mean that the master has found incompatible elements in the data sent between master and slave.

which makes sense because those requests don't make sense for Device 1. 

And based on my tests, to use connect function you should be disconnected first. already tried using connect without disconnecting first.  

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12 hours ago, kratmel said:

I searched the help a bit and found this (see the red box). Just what does that mean???

IP_red.jpg.a9aae301935e1840fafc6ca1a020013e.jpg

I also read that, and I also got confused about it.... however, I just tried and couldn't make it work.

It's even more confusing because it seems that for Modbus TCP/IP a socket connection must be stablished first ..maybe the broadcasting function works on UDP only?

 

but again... maybe I am doing something wrong, It is a shame that there is no example using Unitronics as a master to multiple slaves.

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  • MVP 2023

I've just asked support to get in on this topic as I think it is important.

As well, re the above, is this info below the above screenshots relevant? .........To me , it is.......

mbus.jpg.702d390de07ada8d5fcf2213c39b277e.jpg

As I don't use Modbus IP at all, my knowledge is limited.  But am following this topic with interest.

cheers, Aus

 

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3 hours ago, Ausman said:

I've just asked support to get in on this topic as I think it is important.

As well, re the above, is this info below the above screenshots relevant? .........To me , it is.......

mbus.jpg.702d390de07ada8d5fcf2213c39b277e.jpg

As I don't use Modbus IP at all, my knowledge is limited.  But am following this topic with interest.

cheers, Aus

 

I believe that that is to add the slaves to the protocol, and it means that you can't select a device which IP has not been added to the configuration FB first?

I can communicate without problems, but using the same socket for many devices requires closing the connection and connecting to the other IP before sending/receiving.

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Hi Fernando,

Please explain your task clearly, I will try to provide you with the right answers.

On 10/7/2023 at 3:43 AM, Fernando Castro said:

I believe that that is to add the slaves to the protocol, and it means that you can't select a device which IP has not been added to the configuration FB first?

I can communicate without problems, but using the same socket for many devices requires closing the connection and connecting to the other IP before sending/receiving.

 

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On 10/10/2023 at 1:09 AM, Ivgeny said:

Hi Fernando,

Please explain your task clearly, I will try to provide you with the right answers.

 

 It's a straightforward application: Use a Unitronics Vision PLC as Modbus TCP/IP Master, communicating with many slave devices at the same time (let's say minimum 2 maximum 4) with low latency, using only one single socket (All other sockets are being used for different applications).


One of the Modbus slaves was supposed to control a process variable linked to the output of a PID loop in the PLC.


BTW, at this point for me, it's only out of my curiosity, the company I worked for has filed for bankruptcy and I was laid off, so I cannot test anything, well... I guess I could (assuming I have some remote connection to the facility still enabled and all my test equipment is still on 😏) but of course that will be illegal. 😅

 

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