
NI cDAQ-9178/9174 User Guide and Specifications 12 ni.com
USB-STC3
The USB-STC3 features independent high-speed data streams; flexible AI, AO, and DIO sample timing;
triggering; PFI signals for multi-device synchronization; flexible counter/timers with hardware gating;
digital waveform acquisition and generation; and static DIO.
AI, AO, and DIO Sample Timing
The USB-STC3 contains advanced AI, AO, and DIO timing engines. A wide range of timing and
synchronization signals are available through the PFI lines. Refer to the Analog Input Timing Signals,
Analog Output Timing Signals, Digital Input Timing Signals, and Digital Output Timing Signals
sections for more information about the configuration of these signals.
Triggering Modes
The NI cDAQ-9178/9174 supports different trigger modes, such as start trigger, reference trigger, and
pause trigger with analog, digital, or software sources. Refer to the Analog Input Triggering, Analog
Output Triggering, and Digital Output Triggering sections for more information.
Independent Data Streams
The NI cDAQ-9178/9174 supports seven independent high-speed data streams, allowing for up to
seven simultaneous hardware timed tasks, such as analog input, analog output, buffered counter/timers,
and hardware-timed digital input/output.
PFI Signals
The PFI signals provide access to advanced features such as triggering, synchronization, and
counter/timers. PFI signals are available through hardware-timed digital input and output modules
installed in up to two chassis slots and through the two PFI terminals provided on the NI cDAQ-9178
chassis. Refer to the PFI section for more information.
Flexible Counter/Timers
The NI cDAQ-9178/9174 includes four general-purpose 32-bit counter/timers that can be used to count
edges, measure pulse-widths, measure periods and frequencies, and perform position measurements
(encoding). In addition, the counter/timers can generate pulses, pulse trains, and square waves with
adjustable frequencies. You can access the counter inputs and outputs using hardware-timed digital I/O
modules installed in up to two slots, or by using the two chassis PFI terminals (NI cDAQ-9178 only).
Refer to the Counters section for more information.
Analog Input
To perform analog input measurements, insert a supported analog input C Series I/O module into any
slot on the cDAQ chassis. The measurement specifications, such as number of channels, channel
configuration, sample rate, and gain, are determined by the type of C Series I/O module used. For more
information and wiring diagrams, refer to the documentation included with your C Series I/O modules.
The NI cDAQ-9178/9174 has three AI timing engines, which means that three analog input tasks can be
running at a time on a chassis. An analog input task can include channels from multiple analog input
modules. However, channels from a single module cannot be used in multiple tasks.
Multiple timing engines allow the NI cDAQ-9178/9174 to run up to three analog input tasks
simultaneously, each using independent timing and triggering configurations. The three AI timing
engines are ai, te0, and te1.
Analog Input Triggering
A trigger is a signal that causes an action, such as starting or stopping the acquisition of data. When you
configure a trigger, you must decide how you want to produce the trigger and the action you want the