Di Sample Clock Signal; Using An Internal Source; Using An External Source - National Instruments NI 6221 User Manual

Chapter 6 Digital I/O

DI Sample Clock Signal

M Series User Manual
You can configure each DIO line to be an output, a static input, or a digital
waveform acquisition input.
Use the DI Sample Clock (di/SampleClock) signal to sample the
P0.<0..31> terminals and store the result in the DI waveform acquisition
FIFO. M Series devices do not have the ability to divide down a timebase
to produce an internal DI Sample Clock for digital waveform acquisition.
Therefore, you must route an external signal or one of many internal signals
from another subsystem to be the DI Sample Clock. For example, you can
correlate digital and analog samples in time by sharing your AI Sample
Clock or AO Sample Clock as the source of your DI Sample Clock. To
sample a digital signal independent of an AI, AO, or DO operation, you can
configure a counter to generate the desired DI Sample Clock or use an
external signal as the source of the clock.
If the DAQ device receives a di/SampleClock when the FIFO is full,
it reports an overflow error to the host software.

Using an Internal Source

To use di/SampleClock with an internal source, specify the signal source
and the polarity of the signal. The source can be any of the following
signals:
• AI Sample Clock
• AI Convert Clock
• AO Sample Clock
• Counter n Internal Output
• Frequency Output
• DI Change Detection Output
Several other internal signals can be routed to di/SampleClock through
RTSI. Refer to Device Routing in MAX in the NI-DAQmx Help or the
LabVIEW Help in version 8.0 or later for more information.

Using an External Source

You can route any of the following signals as di/SampleClock:
• PFI <0..15>
• RTSI <0..7>
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