NI 9775 Acquisition Modes (FPGA Interface)

NI CompactRIO Device Drivers Help

Edition Date: December 2017

Part Number: 373197L-01

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The NI 9775 has three different acquisition modes: continuous mode, record mode, and advanced mode.

Continuous Mode

In continuous mode, the NI 9775 transfers real-time data to the chassis at an aggregate rate of 4MS/s across all channels. The NI 9775 will default to continuous mode after executing the Start I/O Node. You can configure the data rate through the Module Property Continuous Data Rate. The maximum value of the data rate varies based on the configuration, and can be found in the device datasheet at ni.com/manuals.

Implementing Continuous Mode

1. Configure the Timing Mode, Continuous Data Rate and Analog Filter Configuration.
2. Run the Start I/O Node.
3. Run the AIx I/O Node as many times as needed.
4. Run the Stop I/O Node.

Record Mode

In record mode, the NI 9775 stores samples into onboard memory at up to 20 MS/s then transfers the data to the chassis at a slower rate. The start of the data collection is based on a trigger signal sent to the device. This signal can be digital or analog. The collected data is stored in the buffer until the entire acquisition is restarted.

Implementing Record Mode

1. Configure the Timing Mode, Record Data Rate, Record Samples, Record Pre-Trigger Samples, and Analog Configuration.
2. Run the Start I/O Node.
3. Trigger a record using any of the following nodes: Trigger Record, Trigger Record on HW Event, or Trigger Record on HW Event (Multiple Sources).
4. Run the Fetch Record Data Method Node until there are no more samples available to fetch.
5. Run the Stop I/O Node.

Advanced Mode

In advanced mode, the NI 9775 combines the functionality of continuous mode and record mode to enable more complex triggering. Advanced mode can use live data from continuous mode to trigger a faster collection rate using record mode. This can be used for applications such as pattern detection or frequency triggering, and gives you more advanced triggering options.

Implementing Advanced Mode

1. Configure Timing Mode, Record Data Rate, Record Samples, Record Pre-Trigger Samples, Analog Filter Configuration, and Continuous Data Rate.
2. Run the Start I/O Node.
3. Use the AIx I/O Node to build a custom trigger condition.
4. Trigger on the custom trigger condition using any Trigger Record Method Node for as many times as needed, up to the number of available records.
5. Run the Fetch Record Data Method Node until there are no more samples available to fetch.
6. Run the Stop I/O Node.