Chapter 7
Counters
X Series User Manual
7-50
ni.com
Yo
u
can
u
se these defa
u
lts or select other so
u
rces and destinations for the
co
u
nter/timer signals in NI-DAQmx. Refer to
Connecting Counter Signals
in the
NI-DAQmx Help
or the
LabVIEW Help
for more information abo
u
t
how to connect yo
u
r signals for common co
u
nter meas
u
rements and
generations. X Series defa
u
lt PFI lines for co
u
nter f
u
nctions are listed in
X Series Physical Channels
in the
NI-DAQmx Help
or the
LabVIEW Help
.
Counter Triggering
Co
u
nters s
u
pport three different triggering actions:
•
Arm Start Trigger
—To begin any co
u
nter inp
u
t or o
u
tp
u
t f
u
nction,
yo
u
m
u
st first enable, or arm, the co
u
nter. Software can arm a co
u
nter
or config
u
re co
u
nters to be armed on a hardware signal. Software calls
this hardware signal the Arm Start Trigger. Internally, software ro
u
tes
the Arm Start Trigger to the Co
u
nter
n
HW Arm inp
u
t of the co
u
nter.
For co
u
nter o
u
tp
u
t operations, yo
u
can
u
se it in addition to the start and
pa
u
se triggers. For co
u
nter inp
u
t operations, yo
u
can
u
se the arm start
trigger to have start trigger-like behavior. The arm start trigger can be
u
sed for synchronizing m
u
ltiple co
u
nter inp
u
t and o
u
tp
u
t tasks.
When
u
sing an arm start trigger, the arm start trigger so
u
rce is ro
u
ted
to the Co
u
nter
n
HW Arm signal.
•
Start Trigger
—For co
u
nter o
u
tp
u
t operations, a start trigger can be
config
u
red to begin a finite or contin
u
o
u
s p
u
lse generation. Once a
contin
u
o
u
s generation has triggered, the p
u
lses contin
u
e to generate
u
ntil yo
u
stop the operation in software. For finite generations, the
specified n
u
mber of p
u
lses is generated and the generation stops
u
nless
yo
u
u
se the retriggerable attrib
u
te. When yo
u
u
se this attrib
u
te,
s
u
bseq
u
ent start triggers ca
u
se the generation to restart.
When
u
sing a start trigger, the start trigger so
u
rce is ro
u
ted to the
Co
u
nter
n
Gate signal inp
u
t of the co
u
nter.
Co
u
nter inp
u
t operations can
u
se the arm start trigger to have start
trigger-like behavior.
•
Pause Trigger
—Yo
u
can
u
se pa
u
se triggers in edge co
u
nting and
contin
u
o
u
s p
u
lse generation applications. For edge co
u
nting
acq
u
isitions, the co
u
nter stops co
u
nting edges while the external
trigger signal is low and res
u
mes when the signal goes high or vice
versa. For contin
u
o
u
s p
u
lse generations, the co
u
nter stops generating
p
u
lses while the external trigger signal is low and res
u
mes when the
signal goes high or vice versa.
When
u
sing a pa
u
se trigger, the pa
u
se trigger so
u
rce is ro
u
ted to the
Co
u
nter
n
Gate signal inp
u
t of the co
u
nter.
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