Sourcing and Capturing Waveforms

Source and capture functionality allows data to be inserted into or extracted from a pattern burst. Use source or capture functionality when the data you need to use is site-specific or only determined at run time. For example, if there is a digital protocol associated with passing data to or from the DUT, the pattern defines the protocol, such as clocking or chip selects, but you can source the data from source memory or capture the data into capture memory.

The source and capture functionality is useful in the following cases:

  • When the data you need to use can be separate from the pattern, such as tests that require site-specific data, data stimulus to a DAC, or data response from an ADC.
  • If the data that needs to be written is only determined at run time, such as register reads or writes.

The functionality prevents the need to compile new patterns in the middle of a test execution or to have all possible response patterns pre-loaded. Each digital pattern instrument includes source and capture functionality for up to eight sites. You can send source waveforms and receive capture waveforms through any of the pins on the digital pattern instrument. Refer to the PXIe-6571 Specifications for more information about the number of channels you can connect for each digital pattern instrument.

Note Ensure that the total average data rate for the source or capture data falls within the maximum source or capture rate for the digital pattern instrument. Visit ni.com/info and enter the Info Code DigitalSourceCapture to access Calculating Source and Capture Bandwidth for Digital Pattern Instruments for more information.
Note To use source and capture functionality that spans multiple digital pattern instruments synchronized with NI-TClk, you must configure the functionality on each synchronized digital pattern instrument.

Refer to the Digital Pattern User Manual for more information about NI-Digital Pattern Driver source and capture API, source and capture configuration in Digital Pattern Editor, and source and capture opcodes.

Sourcing Waveforms

Configuring Source Waveforms

Use the source waveform configuration document in the Digital Pattern Editor or the NI-Digital Pattern Driver source API to configure source waveforms.

You can configure source waveforms for serial or parallel use:

  • In serial waveform type, each vector that contains a source opcode serially shifts 1 bit on the pin using the drive from source pin state (D) to indicate what value to drive. The data width of the serial source sample is set up at configuration, and after an appropriate number of bits have been shifted, the source engine moves on to the next sample.
  • In parallel waveform type, the entire waveform sample is sourced on all specified pins in parallel for each vector that contains a source opcode. Use the drive from source pin state (D) for each pin on each such vector that corresponds to the pins to source.
Note Ensure that the total average data rate for the source or capture data falls within the maximum source or capture rate for the digital pattern instrument. Visit ni.com/info and enter the Info Code DigitalSourceCapture to access Calculating Source and Capture Bandwidth for Digital Pattern Instruments for more information.

When configuring serial and parallel source waveforms, you can specify one of the following data mapping options:

  • Site Unique—Sources unique waveform data to each site.
  • Broadcast—Writes the same waveform data to all sites if multiple sites are configured in the pin map.

    • Sending Source Waveforms

    You can send source waveforms at run time using opcodes in the pattern file. Use the source_start and source opcodes to send waveform data when you burst the pattern. Use the source_d_replace opcode to change the behavior of the source data.

    Source Considerations

    • You can send multiple source waveforms with the same configuration in a single pattern burst.
    • You can load up to 512 source waveforms on the instrument at a time.
    • The total number of pins supported by source functionality is 32.

    Refer to the PXIe-6571 Specifications for more information about source capacity.

    Capturing Waveforms

    Configuring Waveforms

    You can configure capture functionality for serial or parallel use.

    Use the capture waveform configuration document in the Digital Pattern Editor or the NI-Digital Pattern Driver capture API to configure capture waveforms.

    You can configure capture waveforms for serial or parallel use:

    • In serial waveform type, each vector that contains a capture opcode serially shifts 1 bit on pins using the pin state V. The data width of the serial capture sample is set up at configuration, and after an appropriate number of bits have been shifted, the capture engine moves on to the next sample.
    • In parallel waveform type, the entire waveform sample is captured on all specified pins in parallel for each vector that contains a capture opcode. Use the pin state V for each pin on each such vector that corresponds to the pins for which you want to capture waveform samples.
    Note Capture memory stores a single bit per channel per capture cycle. A 1 is stored for any line where Vout > Voh and Vout > Vol. Otherwise, a 0 is stored. M pin states are seen as 0 in capture memory.
    Note Ensure that the total average data rate for the source or capture data falls within the maximum source or capture rate for the digital pattern instrument. Visit ni.com/info and enter the Info Code DigitalSourceCapture to access Calculating Source and Capture Bandwidth for Digital Pattern Instruments for more information.

    Receiving Capture Waveforms

    You can receive capture waveform data at run time using opcodes in the pattern file. Use the capture_start, capture, and capture_stop opcodes to store values when you burst a pattern.

    Capture Considerations

    • You can receive multiple capture waveforms with the same configuration in a single pattern burst.
    • You can use up to 512 capture waveforms on the digital pattern instrument at a time.
    • The total number of pins supported by capture functionality is 32.

    Refer to PXIe-6571 Specifications for more information about the number of samples you can capture for all patterns in a burst operation.