How does DMA work in the High-Speed Digitizer?

Updated Aug 6, 2018

Reported In

Hardware

  • PXI Oscilloscope

Issue Details

The High-Speed Digitizer has a very large onboard memory for use at very high sampling rates. Sometimes, however, the data will come in more values than onboard memory. In this case, I have to know how to use DMA to send to the host computer via the PCI bus. How does DMA work in the High-Speed Digitizer?

Solution

The High-Speed Digitizer board uses the NI-Scope driver and uses DMA transfer over the PCI bus as the default setting. When you call the fetch function, the digitizer transfers the DMA data from the onboard memory to the host computer over the PCI bus. When importing multiple recorded measurements, the DMA operation will start and stop for each record. When continuously measuring data, the DMA operation starts and stops each time the fetch function is called. Therefore, the data transfer rate will depend on the PCI bus speed, the processor speed, and the transfer rate of the board.

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