MODBUS RTU Communication and program upload

[Jesus Flores]

Hi, today in our company we received an ultra filtration system that comes with a V1040 on it. We've never had worked with an unitronics system before and we are trying to communicate the plc via modbus rtu over rs485 to work with our network. 
We configured the com port of the plc to work with rs485 as it was factory configured to work with rs232 but we can't reach it on our system, it's just showing of offline status. 
In the ladders we had a special subroutine for modbus, including all the registers and status of the system, we are reaching these points but it doesn't work. I'll attach some screenshots of the COM and modbus configuration and the modbus registers that i'm trying to read and i'll appreciate any help if i'm doing something wrong. 

Also, if i modify the program i need to upload it all or there is an option to upload only the com configuration without stop the plc? Due to the critic status of the process i only have a few minutes to stop the plc so i'll appreciate any shortcut to work faster on the system. As i said we've never worked with this plc before so we don't know the   kind of responses of the system.

 

[Ausman]

HI Jesus,

8 hours ago, Jesus Flores said:

We configured the com port of the plc to work with rs485

So this means you have changed the dip switches inside the 1040 to make comms 485?  Find the install guide here: 

https://myzone-kza3sadj.netdna-ssl.com/wp-content/uploads/2015/12/V1040-T20B_INSTAL-GUIDE_11-10.pdf

and scoot down to page 6

cheers,

Aus

[Ausman]

Also, are you actually calling your subroutine?  With Visilogic you have to do this, and for first timers it is an easily missed thing.

Utils/Call/Call Subroutine.

Aus

[Jesus Flores]

2 hours ago, Ausman said:

HI Jesus,

So this means you have changed the dip switches inside the 1040 to make comms 485?  Find the install guide here: 

https://myzone-kza3sadj.netdna-ssl.com/wp-content/uploads/2015/12/V1040-T20B_INSTAL-GUIDE_11-10.pdf

and scoot down to page 6

cheers,

Aus

Yes i did that, and i'm also calling for the subroutine, i changed the configuration in the com init, do i have to upload the program to the plc again?

[Ausman]

OK. 

I'm assuming "MODBUS ADDRESS" in the initial config is not showing all that you have there.  Perhaps change it to direct with correct number at present until you get comms going ok.

Change your timeout in the init of 0.5sec to match your other timeout of 1 sec....I don't think this should make any difference but we are looking at stumbling blocks.

Re uploading (but uni call it downloading):   see my attached shot of the download varieties listed in help.  You need to do one of these operations at least.  I would also be doing a reset/initialise.

cheers,

Aus

 

[Davide]

Hello 

I am trying to set up a V350 as a slave of a master device that uses Modbus ASCII.  I understood that Visilogic does not handle Modbus ASCII. I want to get arround this by using a Modbus ASCII to Modbus RTU converter. However the master uses Modbus function code 22 (write multiple registers) and function code 23 (read, write multiple registers). Will the  V350 understand these commands once converted to RTU? I only find function code 16 highest command when using V350 as a master.  Does it understand command 22 and 23?

Thanks David 

[Ausman]

Damcos/David, I have moved your ask to be a new topic.  It is here:

cheers, Aus

[Davide]

HI Ausmann, I was able to solve that problem. As my RS485 master sends only one command to the slave I just implemented the appropriate answer with a FB. Now the PLC only understands the Modbus ASCII command 23 (read/write multiple registers). But as my master uses only this command and always asks for the same address to read and write, I just managed to programm an appropriate answer from the PLC.