How to use system tags to determine if a device is connected


This post demonstrates how to use system tags to verify the connection status of an external device.

Software Version:

EasyBuilder Pro

Related Tutorials:

How to find and Reference “System Tags”


  1. Within the “Home” tab open the “System Parameters” to determine the “Device No.”:
    Note: The device no. of an external device can be read within the “Device” tab of the System Parameter Settings. Devices #1-3 will be assigned to COM port serial connections.

  2. Double-click a device driver to open the “Device Settings” menu to determine the “station no.”:

  3. After verifying the “Device no.” and “Station no.” select the “Address” icon within the “Project” tab to find status tags associated with the device no and station no. (SN):
    Note: Ensure that “System tags” is selected within the address dialog.

  4. The local address of a system tag that corresponds with the “Device no.” and “Station no.” of a device within your project can be used within an object directly as in the following example:


I have an HMI connected to a Modbus device and a remote HMI for this demonstration. The device status tags are mapped to Bit Lamps. The system tags used in this demonstration are:
Note: The HMI will not show when a device is disconnected if there are no tags read from the device.

  • LB-10100: device 4 status (ethernet), set on to retry connection
  1. Note: LB-10100 is being used because the system tag corresponds with the “Local Device” number within the project.

  2. I’ve addressed several “Bit Lamp” objects using the “System tag” search option available within the “Address” drop-down list:

  3. The following image depicts the “Bit Lamp” objects that I’ve placed for demonstration purposes:

  • The device status system tags are FALSE when the device is disconnected:

  • The device status system tags are TRUE when the device is connected:


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