AO Sample Clock Timebase Signal

You can select any PFI or RTSI pin as well as many other internal signals as the AO Sample Clock Timebase (ao/SampleClockTimebase) signal. This signal is not available as an output on the I/O connector. The ao/SampleClockTimebase is divided down to provide the Onboard Clock source for the ao/SampleClock. You specify whether the samples begin on the rising or falling edge of ao/SampleClockTimebase.

You might use the ao/SampleClockTimebase signal if you want to use an external sample clock signal, but need to divide the signal down. If you want to use an external sample clock signal, but do not need to divide the signal, then you should use the ao/SampleClock signal rather than the ao/SampleClockTimebase. If you do not specify an external sample clock timebase, NI-DAQ uses the Onboard Clock.

The following figure shows the timing requirements for the ao/SampleClockTimebase signal.

The maximum allowed frequency is 20 MHz, with a minimum pulse width of 10 ns high or low. There is no minimum frequency.

Unless you select an external source, either the 20MHzTimebase or 100kHzTimebase generates the ao/SampleClockTimebase signal.