National Instruments Eight-slot USB Chassis NI cDAQ-9172 - Manual (Page 36)

NI cDAQ-9172 User Guide and Specifications 36 ni.com
Static DIO
Each of the DIO lines can be used as a static DI or DO line. You can use
static DIO lines to monitor or control digital signals on some C Series I/O
modules. Each DIO line can be individually configured as a digital input
(DI) or digital output (DO), depending on the C Series I/O module being
used.
All samples of static DI lines and updates of static DO lines are
software-timed.
Digital Waveform Acquisition (Correlated Input)
You can acquire digital waveforms using correlated digital modules in
slots 1 through 4. The DI waveform acquisition FIFO stores the digital
samples. The NI cDAQ-9172 chassis samples the DIO lines on each rising
or falling edge of the di/SampleClock signal.
DI Sample Clock Signal
Use the DI Sample Clock (di/SampleClock) signal to sample digital I/O on
slots 1 through 4, using correlated digital modules, and store the result in
the DI waveform acquisition FIFO. The NI cDAQ-9172 chassis does not
have an independent DI Sample Clock circuit. Therefore, you must route
an external signal or one of many internal signals from another subsystem
to function as the DI Sample Clock. For example, you can correlate digital
and analog samples in time by setting the AI Sample Clock or AO Sample
Clock as the source of the 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 DI Sample Clock.
If the NI cDAQ-9172 chassis receives a di/SampleClock signal when the
FIFO is full, it reports an overflow error to the host software.
5 Yes Yes Yes —
6 Yes Yes Yes —
7 Yes — — —
8 Yes — — —
1 Requires the use of a correlated digital I/O module.
Table 4. Digital Module Slot Features (Continued)
Slots Static DIO PFI 1 Counter/Timer 1
Digital
Waveform/Change
Detection 1