Programming For Vxi - National Instruments VXI-MXI-Express Series User Manual

Chapter 3 Developing Your Application

Programming for VXI

Note The NI-VXI API development environment is not installed by default as part of
the NI-VXI installation. NI recommends using NI-VISA rather than NI-VXI for all new
VXI/VME applications. If you must develop an application using the older NI-VXI API,
run the NI-VXI installer and select the NI-VXI API Development option in the Feature
Selection screen. Be sure to review the
VXI-MXI-Express Series User Manual
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NI-VISA and the NI-VXI API are the two National Instruments
programming interfaces for accessing your VXI/VME instruments. With
NI-VXI 3.0 or later, NI-VISA is the native API for communicating with a
VXI or VME system, and NI recommends using it for all new applications.
Older programs that use the NI-VXI API now use the NI-VXI-to-NI-VISA
compatibility layer to communicate with the VXI devices. Using this layer,
older programs can run in NI-VXI 3.0 or later without being rewritten to
use the VISA interface.
NI-VISA is the National Instruments implementation of the VISA API as
the VXIplug&play standard defines. It provides a common interface to
many types of instruments (such as VXI, GPIB, PXI, Serial, TCP/IP, and
so on) and therefore is especially useful in situations where you are using
multiple types of instruments.
Both NI-VISA and the NI-VXI API include functions for register-level
access to VXI instruments and messaging capability to message-based
devices. You can also use either interface to service asynchronous events
such as triggers, signals, and interrupts, and also assert them. Compatibility
with the NI-VXI API is included for legacy applications only—
NI recommends that you write all new VXI/VME applications in VISA.
The best way to learn NI-VISA programming is by reviewing the example
programs your software includes. The examples directory contains working
VISA programs that illustrate many different types of applications. You can
find these examples in the Windows Start menu under Programs»
National Instruments»VISA»Examples.
If you are just getting started, you should learn how to access registers
with high-level calls and send messages with word-serial functions. The
NI-VISA examples for these tasks are
to the other examples as you try more advanced techniques. Consult the
NI-VISA online help for additional information about these topics.
3-6
NI-VXI API Notes section of this manual.
HighReg.c
and . Refer
RdWrt.c
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