Using the VISA Interactive Control to Communicate with VXI/VME DevicesVISA comes with a utility called VISA Interactive Control (VISAIC) on platforms that support the Labwindows/CVI Run-Time Engine. This utility provides access to all of VISAs functionality interactively, in an easy-to-use graphical environment. It is a convenient starting point for program development and to learn about VISA. When VISAIC starts, it automatically finds all of the available resources in the system and lists the instrument descriptors for each resource in the starting screen. An example is shown in Figure 1 below.
VISAIC uses the Resource Manager output table to see what VXI resources are available in the system. VISAIC also tries to read a configuration register for each instrument to verify that the Resman table is correct. If one configuration register read fails, VISAIC provides a warning indicating that a resource is not present. Such a warning generally indicates that the Resource manager output table is out of date, and that you need to rerun the Resource Manager. The Soft Front Panels tab of the main VISAIC panel provides the option of launching the soft front panels of any VXIplug&play instrument drivers installed on the system. The NI I/O tab provides the option to launch the NI-VXI interactive utility VIC or the NI-488 interactive utility IBIC. This offers convenient links into the interactive utilities for the lower level drivers called by NI-VISA. Double-clicking on any instrument descriptor shown in the VISAIC starting window opens a session to that instrument. Opening a session to an instrument produces a window with a series of tabs for interactively running VISA commands. The exact appearance of these tabs depends on which compatibility mode VISAIC is in. To access the compatibility mode and other VISAIC preferences, select Edit » Preferences to bring up the window shown below in Figure 2.
The VISA implementations are slightly different in LabVIEW and LabWindows/CVIthese differences are reflected in the operation tabs shown when a session to a resource is opened. By default, the compatibility mode is set to Labwindows/CVI. You should change this setting to LabVIEW if you are using LabVIEW to program your VXI/VME instruments. After you change the preferences, the new preferences take effect for any session opened later. Figure 3 below illustrate an example of a session to a device at VXI logical address 1. Note that the instrument resource descriptor is included in the title bar of the session window.
Three main tabs appear in the resource interaction window. The Template tab contains all operations dealing with events, attributes, and locks. The Basic I/O tab contains the basic operations for Message-Based communication, while the Register I/O tab contains the basic operations for Register-Based communication. VISAIC is able to detect whether you are using a message based or register based device and will not display a Basic I/O tab for purely register based devices. |
