National Instruments NI-VXI - Manual (Page 29)

Chapter 2 Introduction to the NI-VXI Functions
NI-VXI User Manual 2-10 © National Instruments Corporation
The busacc.h File
The busacc.h file defines constants and macros for use with the
high/low-level and slave memory access functions (see the Master
Memory Access and Slave Memory Access sections later in this
chapter). To make the code more readable,
busacc.h defines such
elements as memory space, privilege mode, and byte order as
constants, and it defines macros to combine these constants into the
necessary access parameters. Examine the header file for more
information on the available macros and constants. You can see these
tools in use by reviewing the example programs on memory accesses
that appear later in this chapter and also the example programs
included with your software.
The devinfo.h File
The devinfo.h file contains a data type that is used with the
GetDevInfo() function described in the System Configuration
Functions section in Chapter 3, Software Overview. The purpose of this
function is to return various information about the system.
GetDevInfo() can return the information either a piece at a time, or in
one large data structure. The header file devinfo.h contains the type
UserLAEntry , which defines the data structure that the function uses.
Refer to the header file for the exact definition of the data structure.
The Beginning and End of an NI-VXI Program
All NI-VXI programs must call InitVXIlibrary() to initialize the
driver before using any other functions. You must call
CloseVXIlibrary() before exiting from your program to free
resources associated with NI-VXI. The first function creates the
internal structure needed to make the NI-VXI interface operational.
When
InitVXIlibrary() completes its initialization procedures,
other functions can access information obtained by RESMAN , the
VXIbus Resource Manager, as well as use other NI-VXI features such
as interrupt handlers and windows for memory access. The second
function destroys this structure and frees the associated memory. All
programs using NI-VXI must call
InitVXIlibrary() before any
other NI-VXI function. In addition, your program should include a call
to
CloseVXIlibrary() before exiting.