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Chapter 1
Introduction
1-4
©
National Instruments Corporation
NI-DAQ has both high-level DAQ I/O functions for maximum ease of use
and low-level data acquisition I/O functions for maximum flexibility and
performance. Examples of high-level functions are streaming data to disk
or acquiring a certain number of data points. An example of a low-level
function is writing directly to registers on the data acquisition device.
NI-DAQ does not sacrifice the performance of National Instruments data
acquisition devices because it lets multiple devices operate at their peak
performance—up to 500 kS/s on ISA computers and up to 1 MS/s on
EISA computers.
NI-DAQ includes a Buffer and Data Manager that uses sophisticated
techniques for handling and managing data acquisition buffers so that you
can simultaneously acquire and process data. NI-DAQ functions for the
DAQCard-DIO-24 can transfer data using interrupts or software polling.
With the NI-DAQ Resource Manager, you can simultaneously use several
functions and several DAQ devices. The Resource Manager prevents
multiple-device contention over DMA channels, interrupt levels, and
RTSI channels.
NI-DAQ can send event-driven messages to DOS, Windows, or Windows
NT applications whenever a user-specified event occurs. Thus, polling is
eliminated and you can develop event-driven data acquisition applications.
An example of an NI-DAQ user event is when a specified digital I/O pattern
is matched.
NI-DAQ also internally addresses many of the complex issues between the
computer and the DAQ hardware such as programming the PC interrupt
and DMA controllers. NI-DAQ maintains a consistent software interface
among its different versions so that you can change platforms with minimal
modifications to your code.
Figure 1-1 illustrates the relationship between NI-DAQ and LabVIEW and
LabWindows. You can see that the data acquisition parts of LabVIEW and
LabWindows are functionally equivalent to the NI-DAQ software.