Chapter 8
Counters
8-28
ni.com
•
AI Reference Trigger (ai/ReferenceTrigger)
•
AI Start Trigger (ai/StartTrigger)
In addition, Co
u
nter 1 Internal O
u
tp
u
t, Co
u
nter 1 Gate, Co
u
nter 1 So
u
rce,
or Co
u
nter 0 Gate can be ro
u
ted to Co
u
nter 0 A
u
x. Co
u
nter 0 Internal
O
u
tp
u
t, Co
u
nter 0 Gate, Co
u
nter 0 So
u
rce, or Co
u
nter 1 Gate can be ro
u
ted
to Co
u
nter 1 A
u
x.
Some of these options may not be available in some driver software.
Counter
n
A, Counter
n
B, and Counter
n
Z Signals
Co
u
nter
n
B can control the direction of co
u
nting in edge co
u
nting
applications. Use the A, B, and Z inp
u
ts to each co
u
nter when meas
u
ring
q
u
adrat
u
re encoders or meas
u
ring two p
u
lse encoders.
Routing Signals to A, B, and Z Counter Inputs
Each co
u
nter has independent inp
u
t selectors for each of the A, B, and
Z inp
u
ts. Yo
u
can ro
u
te any inp
u
t PFI signal to each inp
u
t.
Counter
n
Up_Down Signal
Co
u
nter
n
Up_Down is another name for the Co
u
nter
n
B signal.
Counter
n
HW Arm Signal
The Co
u
nter
n
HW Arm signal enables a co
u
nter to begin an inp
u
t or o
u
tp
u
t
f
u
nction.
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. In some applications, s
u
ch as b
u
ffered semi-period
meas
u
rement, the co
u
nter begins co
u
nting when it is armed. In other
applications, s
u
ch as single p
u
lse-width meas
u
rement, the co
u
nter begins
waiting for the Gate signal when it is armed. Co
u
nter o
u
tp
u
t operations can
u
se the arm signal in addition to a start trigger.
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.
