Low-Level Access Functions; Local Resource Access Functions - National Instruments MXI VXI-PCI8026 Getting Started

Low-Level Access Functions

Local Resource Access Functions

Caution Use
memory that is reserved for your use only. Using any range of addresses that was not
returned from
computer to crash or behave incorrectly.
© National Instruments Corporation
The memory windows used to access the VXI/VMEbus are a limited
resource. You should follow the protocol of calling the
or
MapVXIAddress()
attempting to perform low-level VXI/VMEbus access with
/
viPeekX() viPokeX()
should always call the
function immediately after the accesses are complete so that you free up the
memory window for other applications.
The functions
viMapAddress()
for use with low-level access functions. It is strongly recommended that
you use the functions to access the memory instead of directly
dereferencing the pointer. Using these functions makes the NI-VXI/VISA
software more portable between platforms. Refer to the
Program for NI-VXI/VISA
on portability issues, and to your NI-VXI or NI-VISA software reference
manual for more information on low-level VXIbus or VMEbus access
functions.
By using
vxitedit
system memory on the motherboard or the onboard memory on the
PCI-MXI-2 with the VXI/VME system. Refer to the NI-VXI Text Utilities
Reference Manual for more information on setting these parameters.
Notice that sharing the system memory with the VXI/VME system does not
mean that the entire range of shared system memory is available to be used
for VXI/VME transfers. You need to be cautious in specifying the portion
of memory you want to share, as some areas are already used for other
purposes.
or
viMemAlloc() VXImemAlloc()
or
viMemAlloc() VXImemAlloc()
The onboard memory on your PCI-MXI-2, on the other hand, is entirely
available to you. You can obtain the VXI address of your onboard memory
using the
GetDevInfo()
you can access that memory using high-level or low-level VXI/VMEbus
access functions.
Chapter 7
function with Access Only mode first before
or /
VXIpeek() VXIpoke()
viUnmapAddress()
and
MapVXIAddress()
section later in this chapter for more information
, you can set up the PCI-MXI-2 to share either the
to allocate a buffer in the system
to receive data may cause your
function. When you have the VXI/VME address,
7-3
Using the NI-VXI/VISA Software
viMapAddress()
.Your application
or
UnMapVXIAddress()
return a pointer
Compiling Your C
VXI/VME-PCI8026 for Linux