Programming instructions

© National Instruments Corporation 13-1 LabVIEW Data Acquisition Basics Manual
13
Letting an Outside Source
Control Your Update Rate
Data acquisition (DAQ) devices use internal counters and timers to
determine the rate of data generation. However, you might encounter times
when you need to generate data in synch with other signals in your system.
For example, you might need to output data to a test circuit every time that
test circuit emits a pulse. In this case, internal counter/timers are inefficient
for your needs. You need to control the update rate with your own external
source of pulses.
Externally Controlling Your Update Clock
Chapter 12,
Letting an Outside Source Control Your Update Rate
,
mentions that for more control over your analog output applications, you
can use the Intermediate DAQ VIs. This chapter explains how to use these
Intermediate VIs to generate data using an external update clock.
The update clock controls the rate digital to analog conversions occur.
To control your data generation externally, you must supply this clock
signal to the appropriate pin on the I/O connector of your DAQ device.
The clock source you supply must be a TTL signal. Figure 13-1 shows the
Generate N Updates-ExtUpdateClk VI, located in
labview\examples\
daq\anlogout\anlogout.llb
, which applies this process.