Modbus is a serial communications protocol. Simple and robust, it has become a de facto standard communication protocol and is now a commonly available means of connecting industrial electronic devices. This chapter is an overview of the Modbus TCP functionality for RUT240 devices.
The information in this page is updated in accordance with the RUT2XX_R_00.01.12 firmware version.
Modbus TCP provides users with the possibility to set or get system parameters. The Modbus daemon acts as slave device. That means it accepts connections from a master (client) and sends out a response or sets some system related parameter in accordance with the given query.
The figure below is an example of the Modbus TCP window section and the table below provides information on the fields contained in that window:
Modbus parameters are held within registers. Each register contains 2 bytes of information. For simplification, the number of registers for storing numbers is 2 (4 bytes), while the number of registers for storing text information is 16 (32 bytes). The register numbers and corresponding system values are described in the table below:
* All received/sent data usage values are returned in kibibytes (KiB), which is an ISQ standard accepted by most major standard organizations.1 kibibyte (KiB) = 210 bytes = 1024 bytes1 mebibyte (MiB) = 210 kibibytes (KiB) = 220 bytes = 1 048 576 bytes
The Modbus daemon can also set some device parameters. These parameters and explanations on how to use them are described in the table below:
* All ON/OFF commands only accept 0 and 1 values, which represent the following:
A Modbus master device can request data from Modbus slaves. The Modbus TCP Master section is used to configure Modbus TCP slaves. To add a new slave, enter a custom name, slave’s ID, IP address and port and click the “Add” button:
You can create a maximum of 10 slave configurations.
The figure below is an example of the Slave device configuration and the table below provides information on the fields contained in that section:
A Modbus request is a way of obtaining data from Modbus slaves. The master sends a request to a slave specifying the function code to be performed. The slave then sends the requested data back to the Modbus master. You can create a maximum of 64 request configurations for each slave device.
The figure below is an example of the Requests configuration section and the table below provides information contained in the fields of that section:
The Modbus Data to Server function provides you with the possibility to set up senders that transfer data collected from Modbus slaves to remote servers. To add a new data sender, enter the server’s address, specify the data sending period and click the “Add” button:
When you add a new data sender, you will be redirected to its configuration window. The figure below is an example of that window and the table below provides information on the fields that it contains:
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