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Chapter 7 Analog Output

The source also can be one of several other internal signals on your DAQ

device. Refer to Device Routing in MAX in the NI-DAQmx Help or the

LabVIEW 8.x Help for more information.

You also can specify whether the samples are paused when ao/PauseTrigger

is at a logic high or low level.

AO Sample Clock Signal

Use the AO Sample Clock (ao/SampleClock) signal to initiate AO samples.

Each sample updates the outputs of all of the DACs. You can specify an

internal or external source for ao/SampleClock. You also can specify

whether the DAC update begins on the rising edge or falling edge of

ao/SampleClock.

Using an Internal Source

One of the following internal signals can drive ao/SampleClock.

• AO Sample Clock Timebase (divided down)

• Counter n Internal Output

A programmable internal counter divides down the AO Sample Clock

Timebase signal.

Using an External Source

Use the external signals PFI <0..3> or PFI <8..11> as the source of

ao/SampleClock.

Routing AO Sample Clock Signal to an Output

Terminal

You can route ao/SampleClock (as an active low signal) out to any

PFI <4..7> or PFI <12..15> terminal.

Other Timing Requirements

A counter on your device internally generates ao/SampleClock unless you

select some external source. ao/StartTrigger starts the counter and either the

software or hardware can stop it once a finite generation completes. When

using an internally generated ao/SampleClock, you also can specify a

configurable delay from ao/StartTrigger to the first ao/SampleClock pulse.

By default, this delay is two ticks of ao/SampleClockTimebase.

National Instruments NI USB-621x User Manual

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