Configure the communication driver

This part of the tutorial shows how to select and configure a driver to communicate with an external I/O device.

1. In the Project Explorer, select the Comm tab.

2. Right-click the Drivers folder, and the select Add/Remove Drivers on the shortcut menu.

   The Communication Drivers dialog is displayed.

3. Highlight a driver in the Available drivers list, and then choose Select.

   For this tutorial, select MODBU.

   The driver is moved to the Selected drivers list.

   

4. Select OK.

   The Communication Drivers dialog is closed, and the driver is added to the Drivers folder in the Project Explorer.

5. In the Project Explorer, right-click the MODBU folder, and then select Settings on the shortcut menu.

   

   The Communication Settings dialog is displayed.

   

6. Configure the communication settings as needed for the target device. For this tutorial, you can accept the default settings.

   For more information about a specific driver, select Communication Drivers on the Help tab of the ribbon.

7. Click OK to close the dialog.

8. In the Project Explorer, right-click the MODBU folder and then select Insert on the shortcut menu.

   A new driver worksheet named MODBU001.drv is created and opened for editing.

9. Configure the worksheet header:

   1. In the Description box, type Tutorial Modbus.

      This setting is for documentation only; it does not affect the project during run time.

   2. In the Enable Read When Idle box, type 1.

      This setting is a trigger that takes a Boolean value. A value of 1 — either entered manually as above or evaluated from a tag/expression — forces your project to continue reading tag values from the target device even when there are no changes in value.

   3. In the Enable Write On Tag Change box, type 1.

      This setting is also a trigger. A value of 1 forces your project to write tag values to the target device only when those values change, rather than continuously. This improves runtime performance.

   4. In the Station box, type 1.

      This indicates the I/O device number to be accessed by this driver. Typically, the PLC is specified as Device #1.

   5. In the Header box, type 4X:0.

      Each driver has a specific format. The format for the MODBU driver is:

      register_type:initial_offset

   Register Type	Description
   0X	Coil Status
   1X	Input Status
   3X	Input Register
   4X	Holding Register
   ID	Unit ID Number

   

10. In the worksheet body, enter the tags and their associated device addresses — for each tag:

    1. In the Tag Name field, type the name of the project tag.

    2. In the Address field, type the value to be added to the header to form the complete device address.

    Tag Name	Address	Complete Device Address
    Level[1]	1	4X:1 (Holding Register 1)
    Level[2]	2	4X:2 (Holding Register 2)
    Level[3]	3	4X:3 (Holding Register 3)

    

11. Go to File, and then select Save.

12. When prompted to choose the driver sheet number, type 1 and then select OK.