National Instruments 622 Series User Manual

7-22 | ni.com
Chapter 7 Counters
Finite Pulse Train Generation
This function generates a train of pulses of predetermined duration. This counter operation
requires both counters. The first counter (for this example, Counter 0) generates a pulse of
desired width. The second counter, Counter 1, generates the pulse train, which is gated by the
pulse of the first counter. The routing is done internally. Figure 7-26 shows an example finite
pulse train timing diagram.
Figure 7-26. Finite Pulse Train Timing Diagram
Frequency Generation
You can generate a frequency by using a counter in pulse train generation mode or by using the
frequency generator circuit, as described in the Using the Frequency Generator section.
Using the Frequency Generator
The frequency generator can output a square wave at many different frequencies. The frequency
generator is independent of the two general-purpose 32-bit counter/timer modules on M Series
devices.
Figure 7-27 shows a block diagram of the frequency generator.
Figure 7-27. Frequency Generator Block Diagram
The frequency generator generates the Frequency Output signal. The Frequency Output signal
is the Frequency Output Timebase divided by a number you select from 1 to 16. The Frequency
Output Timebase can be either the 20 MHz Timebase divided by 2 or the 100 kHz Timebase.
The duty cycle of Frequency Output is 50% if the divider is either 1 or an even number. For an
odd divider, suppose the divider is set to D. In this case, Frequency Output is low for (D + 1)/2
cycles and high for (D - 1)/2 cycles of the Frequency Output Timebase.
Counter 0
(Paired Counter)
Counter 1
Generation
Complete
100 kHz Timebase
20 MHz Timebase
Frequency
Output
Timebase
FREQ OUT
Divisor
(1–16)
Frequency Generator
÷ 2

National Instruments 622 Series Specifications

General

Brand	National Instruments
Model	622 Series
Category	I/O Systems
Language	English