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4-7
Figure 4-3 shows an example of low-to-high transitions of the input signal. High-to-low
transitions work similarly.
Assume that an input terminal has been low for a long time. The input terminal then changes
from low to high, but glitches several times. When the filter clock has sampled the signal high
on consecutive rising edges, the low-to-high transition is propagated to the rest of the circuit.
Figure 4-3.
Filter Example
Getting Started with DI Applications in Software
You can use the cDAQ chassis in the following digital input applications:
•
Single-point acquisition
•
Finite acquisition
•
Continuous acquisition
For more information about programming digital input applications and triggers in software,
refer to the
NI-DAQmx Help
or the
LabVIEW Help
for more information.
Change Detection Event
The Change Detection Event is the signal generated when a change on the rising or falling edge
lines is detected by the change detection task.
Routing Change Detection Event to an Output Terminal
You can route ChangeDetectionEvent to any output PFI terminal.
Change Detection Acquisition
You can configure lines on parallel digital modules to detect rising or falling edges. When one
or more of these lines sees the edge specified for that line, the cDAQ chassis samples all the lines
in the task. The rising and falling edge lines do not necessarily have to be in the task.
Change detection acquisitions can be buffered or nonbuffered:
•
Nonbuffered Change Detection Acquisition
—In a nonbuffered acquisition, data is
transferred from the cDAQ chassis directly to a PC buffer.
•
Buffered Change Detection Acquisition
—A buffer is a temporary storage in computer
memory for acquired samples. In a buffered acquisition, data is stored in the cDAQ chassis
onboard FIFO then transferred to a PC buffer. Buffered acquisitions typically allow for
much faster transfer rates than nonbuffered acquisitions because data accumulates and is
transferred in blocks, rather than one sample at a time.
Digit
a
l Inp
u
t P0.
x
Filter Clock
Filtered Inp
u
t
1
1
2
1
1
2
1
