How Does The Advanced Acquisition Mode Work In The NI-9775 Module?

Updated Sep 7, 2023

Reported In

Hardware

  • NI-9775

Software

  • LabVIEW FPGA Module
  • LabVIEW

Issue Details

According to the NI-9775 datasheet , this module has three acquisition modes: continuous mode, record mode, and advanced mode. There is a little more information for the continuous and record modes but I would like to know more details regarding the advanced mode. I have found that this mode is only available for cRIO, but how does it work? What is the maximum sampling rate that can be achieved? How can it be set up?

Solution

Advanced mode is accomplished by implementing a custom FPGA implementation allowing application specific triggering conditions and mixing of the lower rate and higher rate data. There is a shipping example showing custom 9775 FPGA implementations:
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The main point of the 9775 is that it allows acquiring data at faster rates than the cRIO backplane can normally handle, albeit for shorter durations of time. The 9775 internally buffers data at a high rate into records and then transfers those records to the RT host at a rate that the cRIO backplane can handle.

Triggering can be implemented against the continuous mode readings to trigger record recording that can then be transferred to the host. If desired, the continuous mode data read by the FPGA can also be streamed to the RT host to have constant values until a record is triggered so even the host can have access to both speeds of data, albeit with some gaps between using the different modes.

The above example shows using a regular I/O node for the continuous rate data reads and other invoke nodes to control the record collection of the module:
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