AO Sample Clock Signal

You can use the AO Sample Clock (ao/SampleClock) signal to initiate AO samples. Each sample updates the outputs of all of the DACs.

The source of the ao/SampleClock signal can be internal or external. You can specify whether the DAC update begins on the rising edge or falling edge of the ao/SampleClock signal.

Using an Internal Source

By default, ao/SampleClock is created internally by dividing down the ao/SampleClockTimebase.

Several other internal signals can be routed to the sample clock. Refer to Device Routing in MAX in the NI-DAQmx Help for more information.

Using an External Source

You can use a signal connected to any PFI or RTSI <0..6> pin as the source of ao/SampleClock. The following figure shows the timing requirements of the ao/SampleClock source.

Outputting the AO Sample Clock Signal

You can configure the PFI 5/AO SAMP CLK pin to output the ao/SampleClock signal. The output pin reflects the ao/SampleClock signal regardless of what signal you specify as its source.

The output is an active high pulse. The following figure shows the timing behavior of the PFI 5/AO SAMP CLK pin when the pin is an output.

The PFI 5/AO SAMP CLK is configured as an input by default.

Other Timing Requirements

A counter on your device internally generates ao/SampleClock unless you select some external source. The ao/StartTrigger signal starts this counter. It is stopped automatically by hardware after a finite acquisition completes or manually through software. When using an internally generated ao/SampleClock in NI-DAQmx, you can also specify a configurable delay from the ao/StartTrigger to the first ao/SampleClock pulse. By default, this delay is two ticks of the ao/SampleClockTimebase signal.

The following figure shows the relationship of the ao/SampleClock signal to the ao/StartTrigger signal.