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Chapter 2 Function Reference — DIG_DB_Transfer
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National Instruments Corporation 2-163 NI-DAQ FRM for PC Compatibles
size. NI-DAQ ignores this field for all other cases (input or output without partial transfers
enabled) and the transfer count is equal to half the buffer size.
Range: 0 to half the size of the digital block buffer.
Using This Function
If you have set the partial transfer flag for an output group, the ptsTfr field allows NI-DAQ
to make transfers of less than half the buffer size to an output buffer. This is useful when
NI-DAQ must output a long stream of data but the amount of data is not evenly divisible by
half the buffer size. If ptsTfr is equal to half the buffer size, the transfer is identical to a
transfer without the partial transfer flag set. If ptsTfr is less than half the buffer size, however,
NI-DAQ makes the transfer to the circular output buffer and alters the DMA reprogramming
information so that the digital output operation will halt after the new data is output.
Refer to Chapter 5, NI-DAQ Double Buffering, of the NI-DAQ User Manual for PC
Compatibles for an explanation of double buffering and possible error and warning
conditions.