NI-XNET I/O Names in LabVIEW

LabVIEW I/O names (also known as refnum tags) are provided for various object classes within NI-XNET. I/O names provide user interface features for easy configuration.

Note NI-XNET I/O names are relevant to programming with LabVIEW only.

You can use an I/O name as a control, indicator, or constant:

  • Control (or indicator)—Use an I/O name control to select a specific instance on the front panel. NI-XNET I/O name controls are in the front panel Modern » I/O » XNET controls palette.

    Typically, you use I/O name controls to select an instance during configuration, and the instance is used at run time.

    As an alternative, you also can use I/O name controls to select an instance at run time. This applies when the VI always is running for the end user, and the VI uses distinct stages for configuration and I/O.

    You can build a standalone application (executable) that contains NI-XNET I/O name controls on its front panel. While running in an executable, the I/O name drop-down menu is supported, but the right-click menu is not operational.

  • Constant—Use an I/O name constant to select a specific instance on the block diagram. NI-XNET I/O name constants are in the block diagram Measurement I/O » XNET palette. You can access I/O name constants only during configuration, prior to running the VI.

    • If you are using LabVIEW Real-Time (RT), you can right-click the RT target within a LabVIEW project and select the Connect menu item. Doing so connects to the RT target over TCP/IP, which in turn enables the user interface of NI-XNET I/O names to operate remotely. For protocols that support databases, you can select names from the databases on the RT target and menu items to manage database deployments.

    At run time, the VIs use I/O names to access features for the selected instance. The I/O name has two simultaneous LabVIEW types:

  • String—When you wire the I/O name to a LabVIEW string, the string contains the selected instance name. Use this string to store the I/O name is a portable form, such as a text file.You can wire a LabVIEW string directly to an I/O name.
  • Refnum—At run time, the I/O name contains a numeric reference to the instance for use with NI-XNET property nodes and VIs. The property node for the I/O name provides access to its configuration. The VIs provide methods for the instance, such as to change state (start/stop), or access data (read/write).

    • There are multiple classes of NI-XNET I/O names, each with their own individual I/O names. The PXIe-8520 supports the following I/O name class(es).