Tutorial: Building a Simple Project The Communication Settings dialog is displayed. Communication Settings dialog for MODBU driver 6. Configure the communication settings as needed for the target device. For this tutorial, accept the default settings. Note: For more information about a specific driver, click 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 click Insert on the shortcut menu. A new driver worksheet named MODBU001.drv is created and opened for editing. 9. Configure the worksheet header: a) In the Description box, type Tutorial Modbus .
This setting is for documentation only; it does not affect the project during run time. b) 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. c) 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 saves system resources and improves performance during rutime.
d) 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. e) In the Header box, type 4X:0 . You must use a driver-specific format. The format for the MODBU driver is: register_type : initial_offset Page 75 Register Type Description 0X Coil Status 1X Input Status 3X Input Register