Modbus RTU 2 registers at once


I have a question regards the RUT955. I want to connect a modbus rtu device to the RUT955, in the past I got some problems reading the data this because in all the devices i used there was no option to read 2 registers at once. (This is necessary to read data).

The image above is from the modbus rtu device. Is that possible?

I need to set al the values which are used in this screenshot.

Thanks in advanced!

Kind regards,

Dear Lukas

In Modbus RTU, reading two registers simultaneously in a single request is not natively supported. Each read operation typically focuses on a single register or a contiguous block.
To manage multiple requests, the master employs sequential polling. It sends requests to different slaves or diverse registers within the same slave in a sequential manner. The master waits for each response before proceeding to the next request. This means that reading two registers at a single time should not be possible

As an alternative, why don’t you try with Data to Server feature, here you can make sure all the Data that you require will be sent to your server, or any HTTP listener app like Hercules. Here all data could be seen within the set Interval


Best regards,

If i understand correct it is possible with the Data to Server feature that i can read 2 registers at once? It is really necessary for my modbus slave to read 2 at a time. Where can i configur it?

You should be able to read all registers at once, the device will pull the data and send it to your server
for config kindly refer into this

Forgive me, i think there is some misunderstanding from my side, If you are suggesting that the register Address 17 saves the data on two register count
configure it accordingly

Make sure that the data type is set according to the the RTU slave configuration.

Let me know if this is what you mean, sorry i was confused with Register Address

Best Regards

Yes, thats exactly what i want. No problem for the misunderstanding. Where can i set that up? Is it in modbus tab?

What do i need to fill in the Ip adress? It is just modbus RTU without some ip and ports

This will be coming under the Modbus Tab , , our device will act as a master and under Modbus Serial Client configuration in Instances, kindly add per the Modbus device specification

Specify the Serial Type(in my case RS232)

Add a new Instance

Add the register adress you want to add as a new instance

and you may edit the request configuration

should look something like this in your case

Make sure that the data type is set according to the the RTU slave configuration.

let me know if you run into any hiccups along the way
Best Regards

I don’t have the modbus serial client tab, i’m using the Rut955.
Do i need to install something?

I guess you are using an older Fw, kindly would you upgrade to latest Fw

What is the difference between modbus serial server and modbus serial client? Which one do i need to use to read the data from a slave?

The Modbus Serial Server is a device or software that provides data or services in response to requests, while the Modbus Serial Client is a device or software that initiates requests to obtain data or control devices. The client-server architecture is a fundamental concept in the Modbus protocol, allowing for efficient communication and control in industrial applications.

To read from a slave you need to configure the Modbus Serial Client

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