Chapter 4
Analog Input
©
National Instruments
4-57
X Series User Manual
AI Hold Complete Event Signal
The AI Hold Complete Event (ai/HoldCompleteEvent) signal
generates a p
u
lse after each A/D conversion begins. Yo
u
can ro
u
te AI Hold
Complete Event o
u
t to any PFI <0..15>, RTSI <0..7>, or PXIe-DSTARC
terminal.
The polarity of AI Hold Complete Event is software-selectable, b
u
t is
typically config
u
red so that a low-to-high leading edge can clock external
AI m
u
ltiplexers indicating when the inp
u
t signal has been sampled and can
be removed.
AI Start Trigger Signal
Use the AI Start Trigger (ai/StartTrigger) signal to begin a meas
u
rement
acq
u
isition. A meas
u
rement acq
u
isition consists of one or more samples.
If yo
u
do not
u
se triggers, begin a meas
u
rement with a software command.
Once the acq
u
isition begins, config
u
re the acq
u
isition to stop:
•
When a certain n
u
mber of points are sampled (in finite mode)
•
After a hardware reference trigger (in finite mode)
•
With a software command (in contin
u
o
u
s mode)
An acq
u
isition that
u
ses a start trigger (b
u
t not a reference trigger) is
sometimes referred to as a posttriggered acq
u
isition.
Retriggerable Analog Input
The AI Start Trigger can also be config
u
red to be retriggerable. The timing
engine will generate the sample and convert clocks for the config
u
red
acq
u
isition in response to each p
u
lse on an AI Start Trigger signal.
The timing engine ignores the AI Start Trigger signal while the clock
generation is in progress. After the clock generation is finished, the co
u
nter
waits for another Start Trigger to begin another clock generation.
Fig
u
re 4-31 shows a retriggerable analog inp
u
t with three AI channels and
fo
u
r samples per trigger.
Figure 4-31.
Simultaneous MIO X Series Retriggerable Analog Input
AI
S
t
a
rt Trigger
AI
Sa
mple Clock
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com