Programming instructions

© National Instruments Corporation 28-1 LabVIEW Data Acquisition Basics Manual
28
Dividing Frequencies
Dividing TTL frequencies is useful if you want to use an internal timebase
and the frequency you need does not exist. You can divide an existing
internal frequency to get what you need. You can also divide the frequency
of an external TTL signal. Frequency division results in a pulse or pulse
train from a counter for every
N
cycles of an internal or external source.
Counters can only decrease (divide down) the frequency of the source
signal. The resulting frequency is equal to the input frequency divided
by
N
(timebase divisor).
N
must be an integer number greater than 1.
Performing frequency division on an internal signal is called a
down
counter
. Frequency division on an external signal is called a
signal divider
.
Figure 28-1 shows typical wiring for frequency division.
Figure 28-1.
Wiring Your Counters for Frequency Division
counter
your
device
your
device
your
device
gate
source
out
counter
your
device
gate
source
out
Frequency Division for a Signal Divider
Frequency Division for a Down Counter