Di Sample Clock Signal (Ni 6731/6733 Only); Using An Internal Source; Using An External Source; I/O Protection - National Instruments 6711 User Manual

Chapter 4 Digital I/O

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 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.

I/O Protection

To minimize the risk of damaging the DIO and PFI terminals of your device, follow these
guidelines.
• If you configure a PFI or DIO line as an output, do not connect it to any external signal
source, ground signal, or power supply.
• If you configure a PFI or DIO line as an output, understand the current requirements of the
load connected to these signals. Do not exceed the specified current output limits of the
DAQ device. NI has several signal conditioning solutions for digital applications requiring
high current drive.
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