Chapter 4
Digital I/O
Analog Output Series User Manual
4-4
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DI Sample Clock Signal (NI 6731/6733 Only)
Use the DI Sample Clock (di/SampleClock) signal to sample the P0.<0..7>
terminals and store the result in the DI waveform acquisition FIFO.
Because there is no dedicated internal clock for timed digital operations,
you can use an external signal or one of several internal signals as the
DI Sample Clock. You can correlate digital and analog samples in time by
choosing the same signal as the source of the DI Sample Clock, AI Sample
Clock, or DO Sample Clock.
If the DAQ device receives a di/SampleClock when the FIFO is full, the
DAQ device 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:
•
AO Sample Clock
•
Counter 0 Out
Program the DAQ device to sample the DIO terminals on the rising edge or
falling edge of di/SampleClock.
Using an External Source
You can use a signal connected to any RTSI <0..6> pin as the source of
di/SampleClock. You can sample data on the rising or falling edge of
di/SampleClock.
Any PFI line that can be routed to RTSI can also be used as the clock
source. Refer to
Device Routing in MAX
in the
NI-DAQmx Help
or the
LabVIEW Help
in version 8.0 for more information.
You must ensure that the time between two active edges of the
di/SampleClock is not too short. If the time is too short, the DI waveform
generation FIFO is not able to store the sample fast enough.
