NI PXI/PCI-5401
Generating Waveforms

The NI 5401 generates waveforms using Function Generation mode, which is implemented with direct digital synthesis technology. Direct digital synthesis generates standard waveforms that are repetitive in nature, such as sine, TTL, square, and triangular waveforms. Function Generation mode using direct digital synthesis limits you to one waveform, and the waveform size must be exactly equal to 16,384 samples.

The following figure is a block diagram of the Data path for waveform generation.

The data for waveform generation comes from DDS lookup memory. This data is interpolated by a half-band digital filter then fed to a high-speed DAC. The data has a pipeline delay of 26 Sample clocks through this digital filter. Although the digital filter can be disabled through software, there is still a 26 Sample clock delay.

On the NI 5401, the high-speed DAC is always updated at 80 MHz, but the Sample clock for memory is 40 MHz.