2.1.2.4New Network of Modbus Devices

This will explain how to setup SimServe to act as a sophisticated network of Modbus slave devices. A schematic of the network is shown below:

To setup the simulation, follow the steps below.

1. Start with simulating network item 1 from the figure above. Network item 1 will be treated as a gateway — a device that converts from one communication protocol to another. In this case, we'll setup a gateway that converts Modbus TCP to Modbus RTU.

   1. Click on New Network Item in the network tree.

      

   2. Fill out the New Network Item form as described below and click Save.

      • Name — Enter any preferred name. For this example, we'll use NetworkItem01.
      • Network Item Type — Select Gateway.
      • Protocol — Select MBTCP-MBRTU.
      • IP Address — Enter the IP address of the real gateway. In this example, we'll use 172.31.41.70. Please note, the computer must also have IP address 172.31.41.70. Consult Windows documentation to add this IP address.
      • Port — Enter the TCP/IP port used for Modbus communication on the real gateway. In this example, we'll use 502. Most devices use port 502 by default.

      

2. Now we'll simulate network item 2. This network item is a device that uses the Modbus RTU protocol. We'll create the device underneath the NetworkItem01 gateway so that the Modbus master can communicate to it through the gateway using Modbus TCP.

   1. Expand NetworkItem01 in the network tree, and then click on New Network Item underneath NetworkItem01.

      

   2. Fill out the New Network Item form as described below and click Save.

      • Name — Enter any preferred name. For this example, we'll use NetworkItem02.
      • Slave Address — Enter the slave address that's used by the real device. For this example, we'll use 1.
      • Remaining Fields — Leave as default.

      

3. Repeat step 2 for network items 3 and 4. For network item 3, set the slave address to 2. For network item 4, set the slave address to 3. Upon completing this step, the network tree should appear as shown below:

   

4. Now we'll simulate network item 5. This network item is a device that uses the Modbus TCP protocol. We'll create the device in the root of the network tree so that the Modbus master can communicate directly to it, not through a gateway.

   1. Click on New Network Item in the root of the network tree.

      

   2. Fill out the New Network Item form as described below and click Save.

      • Name — Enter any preferred name. For this example, we'll use NetworkItem05.
      • Network Item Type — Select Device.
      • Protocol — Select MBTCP.
      • IP Address — Enter the IP address of the real device. In this example, we'll use 172.31.41.71. Please note, the computer must also have IP address 172.31.41.71. Consult Windows documentation to add this IP address.
      • Port — Enter the TCP/IP port used for Modbus communication on the real device. Most devices use port 502 by default.
      • Remaining Fields — Leave as default.

      

5. Repeat step 4 for network items 6 and 7. For network item 6, use IP address 172.31.41.72 and port 502. For network item 7, use IP address 172.31.41.73 and port 502. Upon completing this step, the network tree should appear as shown below:

   

6. Now we'll setup network item 8. This network item will be treated as a gateway that converts Modbus TCP to Modbus RTU, exactly the same as network item 1. Follow step 1 to create network item 8, but use IP address 172.31.41.74 and port 502. After creation of network item 8, the network tree should appear as shown below:

   

7. To simulate network items 9, 10, and 11, repeat step 2 but add the network items underneath network item 8. For network item 9, use slave address 1. For network item 10, use slave address 2. For network item 11, use slave address 3. Upon completing this step, the network tree should appear as shown below: