Chapter 20 Network Configuration and Data Exchange Method 2 Select a PLC or a device on the device list, and then drag it to a position in the working area. The users can add a user-defined Modbus device to the working area. After the users select MODBUS Device on the device list, and add it to the working area in one of the two ways described below, the Custom Device window will appear. The users have to type a name in the Name box, select a number in the The number of ports from drop-down list box, with maximum of three ports and click OK . 20-15