![background image](http://html1.mh-extra.com/html/national-instruments/usb-6210/usb-6210_user-manual_3656406123.webp)
Chapter 8
Counters
8-26
ni.com
Freq
u
ency O
u
tp
u
t can be ro
u
ted o
u
t to any o
u
tp
u
t PFI terminal. All PFI
terminals are set to high-impedance at start
u
p. The FREQ OUT signal also
can be ro
u
ted to DO Sample Clock and DI Sample Clock.
In software, program the freq
u
ency generator as yo
u
wo
u
ld program one of
the co
u
nters for p
u
lse train generation.
For information abo
u
t connecting co
u
nter signals, refer to the
section.
Frequency Division
The co
u
nters can generate a signal with a freq
u
ency that is a fraction of
an inp
u
t signal. This f
u
nction is eq
u
ivalent to contin
u
o
u
s p
u
lse train
generation.
For information abo
u
t connecting co
u
nter signals, refer to the
section.
Pulse Generation for ETS
In the eq
u
ivalent time sampling (ETS) application, the co
u
nter prod
u
ces a
p
u
lse on the o
u
tp
u
t a specified delay after an active edge on Gate. After
each active edge on Gate, the co
u
nter c
u
m
u
latively increments the delay
between the Gate and the p
u
lse on the o
u
tp
u
t by a specified amo
u
nt. Th
u
s,
the delay between the Gate and the p
u
lse prod
u
ced s
u
ccessively increases.
The increase in the delay val
u
e can be between 0 and 255. For instance, if
yo
u
specify the increment to be 10, the delay between the active Gate edge
and the p
u
lse on the o
u
tp
u
t increases by 10 every time a new p
u
lse is
generated.
S
u
ppose yo
u
program yo
u
r co
u
nter to generate p
u
lses with a delay of 100
and p
u
lse width of 200 each time it receives a trigger. F
u
rthermore, s
u
ppose
yo
u
specify the delay increment to be 10. On the first trigger, yo
u
r p
u
lse
delay is 100, on the second it is 110, on the third it is 120; the process
repeats in this manner
u
ntil the co
u
nter is disarmed. The co
u
nter ignores
any Gate edge that is received while the p
u
lse triggered by the previo
u
s
Gate edge is in progress.
The waveform th
u
s prod
u
ced at the co
u
nter’s o
u
tp
u
t can be
u
sed to provide
timing for
u
ndersampling applications where a digitizing system can
sample repetitive waveforms that are higher in freq
u
ency than the Nyq
u
ist