Chapter 4
Digital I/O
©
National Instruments Corporation
4-3
Analog Output Series User Manual
Using an Internal Source
To use do/SampleClock with an internal source without making any
external connections, specify the signal source and the polarity of the
signal. The source can be one of the following signals:
•
AO Sample Clock
•
Counter 0 Out
Program the DAQ device to update the DIO pins on the rising edge or
falling edge of do/SampleClock.
Using an External Source
You can use a signal connected to any RTSI <0..6> pin as the source of
do/SampleClock. You can generate samples on the rising or falling edge of
do/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
do/SampleClock is not too short. If the time is too short, the DO waveform
generation FIFO is not able to read the next sample fast enough.
Digital Waveform Acquisition (NI 6731/6733 Only)
The NI 6731/6733 can acquire digital waveforms. This behavior is also
referred to as correlated digital I/O because there is no dedicated clock
source for the digital operation. Refer to the
section for a list of possible sources.
The DI waveform acquisition FIFO stores the digital samples. The
NI 6731/6733 can use DMA transfers to move data from the DI waveform
acquisition FIFO to system memory. The DAQ device samples the DIO
lines on each rising or falling edge of a clock signal, di/SampleClock. For
more information on DMA transfers, refer to the
section of Chapter 9,
.
You can configure each DIO line to be an output, a static input, or a digital
waveform acquisition input.