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Chapter 3 Software Overview

Building Block 2: Start

NI-DAQ has high-level and low-level start functions. The high-level start

functions are as follows:

• DAQ_Op

•

SCAN_Op

(MIO, AI, and DSA devices only)

•

Lab_ISCAN_Op

(DAQCard-500/700, 516 devices, LPM devices,

and Lab and 1200 devices only)

• DAQ_to_Disk

•

SCAN_to_Disk

(MIO, AI, and DSA devices only)

•

Lab_ISCAN_to_Disk

(DAQCard-500/700, 516 devices,

LPM devices, and Lab and 1200 devices only)

A high-level start call initiates data acquisition but does not return to the

function caller until the data acquisition is complete. For that reason, you

do not need the next building block, Checking, when you use high-level

start functions.

Figure 3-5.

Buffered Data Acquisition Application Building Block 2, Start

The major advantage of the high-level start functions is that they are simple.

A single call can produce a buffer full or a disk full of data. However, if

your application is acquiring data at a very slow rate or is acquiring a lot

of data, the high-level start functions might tie up the computer for a

significant amount of time. Therefore, NI-DAQ has some low-level

(or asynchronous) start functions that initiate data acquisition and return to

the calling program function caller immediately.

Yes

Streaming

to disk?

Scan Multiple

Channels?

DAQ_Op

Lab_ISCAN_Op SCAN_Op

Ye s