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Technical Notes
Modbus TCP VIM - Master/Slave Communications Setup
By Adisa Shaljani
Product: IOD-4101 - Modbus TCP/IP Master Driver (General Modbus TCP/IP Communications)

This technical note describes the Modbus TCP VIM's ability to act as a master or slave device, and explains how to configure the Modbus TCP VIM as a master or slave.

VIMNet Explorer Configuration of Master VIM

In the VIMNet Explorer the user needs to add the master ModbusTCP VIM placeholder. The user can choose the IP address and subnet mask per his/her network requirements.

The next step is to commission the VIM placeholder to a real physical VIM card.

The following step is to add a SLAVE VIM device with the device address and IP address. The IP address needs to match the configured slave VIM’s IP address.

The next step is to upload the configuration to the master VIM. Right-click on the Master_VIM placeholder and select "VIM Configuration Upload" as shown below:

VIMNet Explorer Configuration of Slave VIM

In the VIMNet Explorer the user needs to add the ModbusTCP VIM placeholder for the Slave VIM. The user can choose the IP address and subnet mask per his/her network requirements.

The next step is to commission the VIM placeholder to a real physical VIM card.

The following step is to add a SLAVE VIM device with the device address and IP address. The IP address needs to match the configured slave VIM’s IP address.

The next step is to upload the configuration to the slave VIM. Right-click on the Slave_VIM placeholder and select "VIM Configuration Upload" as shown below:

DeltaV Configuration of Master VIM

The DeltaV configuration of datasets is very simple. It starts by Auto-sensing for new IO cards.

Once the 4 Programmable Serial cards are inserted, the IO needs to be downloaded.

In order to start the configuring devices the user needs to choose the card and expand it to see the ports. Right-click on Port1 and go to "Properties." Check the checkbox to enable this port as shown below:

Click on the Advanced tab. The following dialog will appear:

In this dialog, leave the default selection as the Master mode. Then configure retry count, message timeout and transmit delay according to your application. The serial parameters on the Communications tab are not used for the VIM communications.

Next step is to right-click on the Port and select "Add Serial Device." It opens the following dialog box, where the user needs to specify the device address and description. Then click "OK."

Next, the user needs to configure datasets in the Serial Device. To add a new dataset, right-click on the Serial Device and select "New Dataset."The following dialog will appear:

In "master" mode, the user can select the direction. It’s optional but the user can also add the dataset description to make the configuration more readable.

On the DeltaV tab the user will select the DeltaV data type.

On the PLC tab the user will select the device data type, starting address (offset), and number of values. In example below, the device data type is 3 or Holding Registers.

The special data tab is not used unless the Floating Point data type is used. In that case, the user needs to configure 1 in special data 2.

In another example we have configured a coil dataset.

On the DeltaV tab the user needs to select the DeltaV data type.

On the PLC tab the user needs to enter the device data type that is equivalent to coils. The starting address is the offset of the full address, and the number of values is desired number of values for this dataset.

The special data tab is not used for the VIM slave communications except when the data type used is floating point with the status.

Floating Point Dataset

DeltaV Configuration of Slave VIM

The DeltaV configuration of the datasets is very simple. It starts by Auto-sensing for new IO.

Once the 4 Programmable Serial cards are inserted, the IO needs to be downloaded.

In order to start configuring devices the user needs to choose the card and expand it to see ports.

Right-click on Port1 and go to "Properties." Check the checkbox to enable this port as shown below.

Click on the "Advanced" tab. The following dialog will appear:

In this dialog, the user needs to select the "Slave" mode. Select the transmit delay. Click "OK." The rest of messaging parameters are not available. The parameters under the Communications tab are not used for the VIM communications.

Next step is to right-click on the Port and Add Serial Device. It opens the following dialog box, where the user needs to specify the device address and description. Then click "OK."

Next, the user needs to configure datasets in the Serial Device. To add a new dataset, right-click on the Serial Device and select "New Dataset." The following dialog will appear:

In the slave mode the data direction is not significant. It’s optional but the user can add the dataset description to make the configuration more readable.

On the DeltaV tab the user will select the DeltaV data type.

On the PLC tab user will select the device data type, starting address (offset), and number of values. In example below, the device data type is 3 or Holding Registers.

The special data tab is not used unless the Floating Point data type is used. In that case, the user needs to configure 1 in special data 2.

In another example we have configured a coil dataset.

On the DeltaV tab the user needs to select the DeltaV data type.

On the PLC tab the user needs to enter the device data type that is equivalent to coils. The starting address is the offset of the full address, and number of values is desired number of values for this dataset.

The special data tab is not used for unless the data type selected is "Floating Point with Status."

Below is the example of the DeltaV configuration for the Floating Point Slave Dataset:

In the following dialog box, the user needs to specify a value of 1 in special data 2 field. It sends the message to the master that data in the slave is in the Floating Point format and vice versa.

The following screen capture shows the VIMNet Diagnostics with the master and slave VIM:

Summary

As the technical note details the ModbusTCP VIM allows the users to configure the VIM as slave or master device, or both at once. The configuration parameter changes are minimal and very simple to implement.