Digital Input Triggering - National Instruments DAQ X Series User Manual

Chapter 6 Digital I/O
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Note (NI USB-634x/635x/636x Devices)
hardware-timed single point (HWTSP) operations.

Digital Input Triggering

Digital input supports three different triggering actions:
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•
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Refer to the
DI Pause Trigger Signal
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 triggering options, refer to the specifications document for
your device.
X Series User Manual
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an error in this case. With continuous operations, if the user
program does not read data out of the PC buffer fast enough to
keep up with the data transfer, the buffer could reach an overflow
condition, causing an error to be generated.
Hardware-timed single point (HWTSP)—Typically, HWTSP
operations are used to read single samples at known time intervals.
While buffered operations are optimized for high throughput, HWTSP
operations are optimized for low latency and low jitter. In addition,
HWTSP can notify software if it falls behind hardware. These features
make HWTSP ideal for real time control applications. HWTSP
operations, in conjunction with the wait for next sample clock
function, provide tight synchronization between the software layer and
the hardware layer. Refer to the NI Developer Zone document,
NI-DAQmx Hardware-Timed Single Point Lateness Checking, for
more information. To access this document, go to
enter the Info Code
daqhwtsp
X Series USB devices do not support
Start trigger
Reference trigger
Pause trigger
DI Start Trigger Signal,
sections for information about these triggers.
6-4
ni.com/info
.
DI Reference Trigger Signal, and
and
ni.com