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Fetch (Fetch Waveform (Direct DMA)) (G Dataflow)

Version:
Last Modified: September 27, 2017

Transfers acquired waveform data from device memory directly to PC memory allocated by a Direct DMA-compatible device.

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session in

Instrument session obtained from the Initialize Acquisition Session node, the Initialize Generation Session node, or the Initialize External Calibration node.

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error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

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samples to read

The specified number of samples to fetch.

If you specify a value for samples to read that is greater than the number of samples in the device memory, NI-HSDIO returns the samples that are acquired after max time milliseconds. Setting this parameter to -1 acquires the samples per record specified in the niHSDIO Configure Acquisition Size node.

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maximum time (ms)

The time, in milliseconds, allotted for the node to complete before NI-HSDIO returns a timeout error.

If you set the value to -1, the node never times out. If you set this parameter to 0, the node returns immediately with up to the number of samples specified in samples to read.

If samples to read is greater than the number of samples in the device memory and all the available samples are acquired before a timeout, NI-HSDIO returns the available samples.

Default: 10000

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record to fetch

Parameter that specifies which record you want to fetch from onboard memory.

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buffer address

The location for the buffer in memory at which to transfer acquired data.

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buffer size

The size (in bytes) of the buffer in memory at which to transfer acquired data.

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session out

Handle that identifies the session in all subsequent node calls.

The session out parameter is obtained from the Initialize Acquisition Session node or the Initialize Generation Session node.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.
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offset to first sample

The offset of the first sample acquired within the specified buffer. Data transferred from device memory in 128 byte increments, so the first sample of the acquired data typically occurs at some offset from the start of the buffer when using a Reference trigger.

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waveform info

The absolute and relative timestamp for the operation, the dt, and the actual number of samples read.

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absolute timestamp

absolute timestamp returns the absolute timestamp for the operation.

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relative timestamp

relative timestamp returns the relative timestamp for the operation.

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dt

dt returns the time between values in the waveform.

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actual samples read

The returned number of samples read.

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reserved 1

reserved 1 is reserved for future use.

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reserved 2

reserved 2 is reserved for future use.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application


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