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Chapter 2 Function Reference — WFM_DB_Config
NI-DAQ FRM for PC Compatibles 2-412
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National Instruments Corporation
oldDataStop is a flag whose value enables or disables the mechanism whereby NI-DAQ stops
the waveform generation when NI-DAQ it is about to generate old data (data that has already
been generated) a second time. Setting oldDataStop to 1 ensures seamless double-buffered
waveform generation.
0: Allow regeneration of data.
1: Disallow regeneration of data.
partialTransferStop is a flag indicating whether to stop waveform generation when NI-DAQ
transfers a partial half buffer to the analog output buffer using a
WFM_DB_Transfer call.
NI-DAQ stops the waveform when NI-DAQ has output the partial half buffer.
0: Allow partial half buffer transfers.
1: Stop waveform generation after partial half buffer transfers.
Using This Function
Use WFM_DB_Config to turn double-buffered waveform generation on and off. With the
double-buffered mode enabled, you can use
WFM_DB_Transfer to transfer new data into the
waveform buffer (selected by
WFM_Load) as NI-DAQ generates the waveform. Because of the
extra bookkeeping involved, unless you are going to use
WFM_DB_Transfer, you should
leave double buffering disabled. Refer to Chapter 5, NI-DAQ Double Buffering, of the
NI-DAQ User Manual for PC Compatibles for a detailed discussion of double buffering.
If you are using DMA, enabling partialTransferStop (or oldDataStop) causes an artificial
split in the waveform buffer, which requires DMA reprogramming at the end of each half
buffer. Therefore, you should only enable these options if necessary.
(AT-AO-6/10 only) For double-buffered waveform generation with group 1 channels using
DMA: If oldDataStop is enabled, partial half buffer transfers (using
WFM_DB_Transfer
calls) are only allowed if partialTransferStop is enabled.
For double-buffered waveform generation with group 1: The total number of points for all the
group 1 channels (specified in
WFM_Load) should be at least twice the size of the FIFO. Refer
to the AT-AO-6/10 User Manual for information on the AT-AO-6/10 FIFO size.
(AT-MIO-16F-5 only) When using the double-buffered waveform generation and
oldDataStop mode is enabled, the driver can alter bit 15 of the data points in the
waveform buffer.