Chapter 6 Digital I/O
X Series User Manual 6-16 ni.com
Digital Output Triggering
Digital output supports two different triggering actions:
• Start trigger
•Pause trigger
An analog or digital trigger can initiate these actions. All X Series devices
support digital triggering, but some do not support analog triggering. To
find your device’s triggering options, refer to the specifications document
for your device. Refer to the DO Start Trigger Signal and DO Pause
Trigger Signal sections for more information about these triggering
actions.
Digital Waveform Generation
You can generate digital waveforms on the Port 0 DIO lines. The DO
waveform generation FIFO stores the digital samples. X Series devices
have a DMA controller dedicated to moving data from the system memory
to the DO waveform generation FIFO. The DAQ device moves samples
from the FIFO to the DIO terminals on each rising or falling edge of a clock
signal, DO Sample Clock. You can configure each DIO signal to be an
input, a static output, or a digital waveform generation output.
The FIFO supports a retransmit mode. In the retransmit mode, after all the
samples in the FIFO have been clocked out, the FIFO begins outputting all
of the samples again in the same order. For example, if the FIFO contains
five samples, the pattern generated consists of sample #1, #2, #3, #4, #5,
#1, #2, #3, #4, #5, #1, and so on.
X Series devices feature the following DO (waveform generation) timing
signals:
• DO Sample Clock Signal
*
• DO Sample Clock Timebase Signal
• DO Start Trigger Signal
*
• DO Pause Trigger Signal
*
Signals with an
*
support digital filtering. Refer to the PFI Filters section
of Chapter 8, PFI, for more information.
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