FP-CTR-502 and cFP-CTR-502 14 ni.com
4. Set the Count Source of the prescaler counter to the clock on
which you want to base your pulse train. This can be the
external counter input or one of the [c]FP-CTR-502 internal
references.
5. Subtract 1 from the value that you want to divide the input
clock by, and set the terminal count of the prescaler counter to
the result. For example, a terminal count of 4 divides the input
clock by 5. If you use the 1 kHz reference as the prescaler count
source, this setting generates a 200 Hz clock for the pulse
counter.
To determine the frequency of the prescaler output, use the
following formula:
where fpre is the frequency of the prescaler counter output
fsrc is the count-input frequency for the prescaler counter
termpre is the terminal count value for the prescaler
counter
Step 2. Set Up the Pulse Counter
To set up the pulse counter, complete the following steps:
1. Set the Count Source of the pulse counter (the count-input
channel with the higher number) to Previous Channel so that
it uses the output from the prescaler counter.
Note If you are not using a prescaler counter, set the
Count Source to the clock on which you want to base
your pulse train.
2. Set the Read Reset Mode of the pulse counter to Don’t Reset
On Read and set the Gate Source to Always Enabled.
3. Subtract 1 from the value that you want to divide the count
input by and set the Terminal Count of the pulse counter to the
result.
The internal output from the pulse counter triggers the output
channel that you selected for the pulse train output.
f
pre
fsrc
termpre 1+
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