The data source input screen opens, in which you can select the MODBUS data source as “Type” as the first step.
However, if you first assign a name to the data source and this contains the word “modbus“, “MODBUS” is already preselected as the data source type. (This works with all data source types)
Once this has been done, the data source-specific settings of the MODBUS data source are automatically adjusted.
MODBUS specific
Role: From the MODBUS data source there are 2 variations. The MODBUS master and the MODBUS slave. The master is the client and the slave is the server, with the master sending commands to the slave.
Create MODBUS master data sources
MODBUS Master Specific
Connection type
- TCP
Connection via a network in direct communication.
- RTU
Runs via a Com port, and the data is transmitted in RTU format.
All settings here must be taken from the specifications of the counterpart.
- RTU over TCP
Runs via TCPIP, and the data is transmitted in RTU format.
All settings here must be taken from the specifications of the counterpart.
- ASCII
Runs via a Com port and the data is transmitted in Ascii format.
All settings here must be taken from the specifications of the counterpart.
- UDP
Network connection without guarantee that it will be received.
Connection details
Both the IP address of the server (slave) and the port of the slave are specified here.
Advanced settings
- Address offset
The value entered here is added to the base address as an offset.
- Byte sequence
Also stored in the slave and ensures data exchange. The order in which the bytes are transmitted can be set here.
Either in the normal order(AB_CD_BigEndian), or backwards(DC_BA_LittleEndian).
- Slave ID
Enter the slave ID that is set for the slave.
- Register mode
Defines the register size that is set for the slave.
- Summarize data sources
The ability to combine data sources is essential for RTU and ASCII if there are several devices on the same bus.
Otherwise, it is not possible to use multiple data sources from the same bus. We therefore recommend that you do not change this setting.
- PDU limitation
Defines the register size that is set for the slave.
After entering the relevant information for the connection, click on “Add” or on “Save” after editing an already created data source.
The MODBUS master data source is created and subsequently displayed in the data source overview.
Created data sources can be edited or deleted again. You can do this using the corresponding buttons.
You also have the option of displaying all internal data sources. This works by activating the “Show internal data sources” checkbox.
Create MODBUS slave data sources
MODBUS slave specific
Connection type
- TCP
Connection via a network in direct communication.
- RTU
Runs via a Com port, and the data is transmitted in RTU format.
All settings here must be taken from the specifications of the counterpart.
- RTU over TCP
Runs via TCPIP, and the data is transmitted in RTU format.
All settings here must be taken from the specifications of the counterpart.
- ASCII
Runs via a Com port and the data is transmitted in Ascii format.
All settings here must be taken from the specifications of the counterpart.
- UDP
Network connection without guarantee that it will be received.
Connection details
- Port
502 is the standard port here.
Advanced settings
- Address offset
The value entered here is added to the base address as an offset.
- Byte sequence
Also stored in the slave and ensures data exchange. The order in which the bytes are transmitted can be set here.
Either in the normal order(AB_CD_BigEndian), or backwards(DC_BA_LittleEndian).
- Slave ID
Assign an ID to the MODBUS slave data source to be created.
- Register mode
Defines the register size that is set for the slave.
- Merging data sources
The ability to merge data sources is essential for RTU and ASCII when multiple devices are on the same bus. Otherwise, there is no way to use multiple data sources from the same bus. We therefore recommend that you do not change this setting.
The offset within an array or data structure object is an integer that indicates the distance (displacement) between the beginning of the object and a given element or point, presumably within the same object.
After entering the relevant information for the connection, click on “Add” or on “Save” after editing an already created data source.
The MODBUS slave data source is created and subsequently displayed in the data source overview.
Created data sources can be edited or deleted again. You can do this using the corresponding buttons. You also have the option of displaying all internal data sources. This works by activating the “Show internal data sources” checkbox.
In the following you can Variables for the MODBUS slave data source data source.
Combine MODBUS data sources
This option allows you to combine several data sources that were created individually in the editor into one data source on the server side.
This option is particularly important if several RTU/ASCII data sources with the same COM port but different slave IDs are created.
As each COM port can only be opened once, these data sources must be combined on the server side.
This procedure only has internal effects. The external behavior remains unchanged.
The “Combine data sources” option is only available for TCPIP/UDP data sources. This is because merging is only optional for these types. This property has a global effect on all TCPIP/UDP MODBUS data sources that have identical settings except for the slave ID.
If merging is activated, data sources that have identical settings(except for the slave ID) are combined into one unit.
This means that only one connection to the data source is established. If this option is deactivated, a separate connection is established for each data source.
