Modbus-TCP Network Creation

Owned by Gary Cane
Last updated: Aug 25, 2011Version comment

The first step to adding a Modbus/TCP network to Design Pad is to create an Ethernet physical network. Go to the Workspace Network View and right click on the workspace name, selecting Add Network (Figure 9.92). Choose Ethernet as the physical layer and name the network (Figure 9.93). Click OK to save the network definition. Settings such as DHCP, IP address, etc. are to be set up as they would be for Modbus RTU. These settings will also be used in Modbus/TCP.



Figure 9.92. Add a Physical Network in the Network View



Figure 9.93. Ethernet Physical Layer Specification

To add a Modbus/TCP logical network to an Ethernet physical network, right click on the physical network and select Add logical network (Figure 9.94). In the window that follows (Figure 9.95), double click to select Modbus/TCP (and any other desired logical network) and name the logical network(s). Note that you can add additional logical networks of the same or different types by continuing to double click on the logical network(s) of choice. . Click OK to save the network definition(s).


Figure 9.94 Selecting Add Logical Network



Figure 9.95 Add the Logical Network to the Ethernet Physical Network



Figure 9.96. Completed Network Definitions


Next it's time to enable the Modbus/TCP protocol on the devices in the network. Do this by right clicking on each module in turn and selecting Module properties.(Figure 9.97) Left click on Modbus/TCP and check the box to enable the protocol (Figure 9.99). Repeat for each module. Press OK to save the settings.



Figure 9.97. Select Module Properties to...



Figure 9.99. Enable Modbus/TCP Protocol on the NIM-2


To assign a device to a logical Modbus/TCP network, right click on the device, select Assign network (Figure 9.100)and use the drop down box to select a physical Ethernet network and put a check next to the logical networks that the enabled protocols should attach to (in this case, click the Modbus/TCP network)(Figure 9.101).



Figure 9.100. Choose Assign Network



Figure 9.101. Select the Modbus/TCP Logical Network


The Modbus/TCP network has a Link Structure Library option which assigns the available structures for the broadcast and receiver operators. This is very similar to the EtherNet/IP implementation. Right click on the logical network name and choose Link Structure Libraries(Figure 9.102). The resulting dialog allows you to add filenames of the XML files which contain the desired structure definitions (Figure 9.103). Add a filename, click Apply and add more if desired. Click OK to save the links.

Note: Unlike EtherNet/IP, the use of structures is not required.  Further, structures should only be used when exchanging data between Fairmount Automation products.



Figure 9.102. Choose Link Structure Libraries



Figure 9.103. Choose the XML File Containing Structure Definitions



Figure 9.104. Structures Applied