NI PXI-5411/5431
External and High-Resolution Clocking

You can connect an external clock to the PLL Ref input connector of the NI PXI-5411/5431. To do this, you must set up the clock source in the software. Refer to the Configure Reference Clock and Configure Clock Mode VIs or the niFgen_ConfigureRefClockSource and niFgen_ConfigureClockMode functions for more information about setting up the clock. You can use an external clock as the Sample clock. The maximum frequency of the external clock is 40 MHz.

Caution  You must not change the frequency of this clock during waveform generation (sweeping of external clock is not available). Changing the frequency of the clock during waveform generation can result in malfunctioning of the device. Change the clock frequency only before initiating the waveform generation. If any malfunction occurs, stop the waveform generation and reset the device to a known state before restarting.

NI PXI-5411/5431 signal generators also support an internal high-resolution clocking mode. When you use this type of clock, you can set the Sample clock frequency to any value from 0–40 MHz with a resolution of approximately 40 MHz. This mode is useful for applications that require a precise clock source, which is not possible using the default counter-based clocking scheme. Use this clocking mode for applications such as CDMA, GSM, and ADSL waveform generation.