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Chapter 2

Function Reference — Lab_ISCAN_Check

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 National Instruments Corporation

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NI-DAQ FRM for PC Compatibles

sample from channel 1, the oldest data point belongs to channel 0. So finalScanOrder 
returns:

finalScanOrder[0] = 0.
finalScanOrder[1] = 2.
finalScanOrder[2] = 1.

So the first sample in the buffer belongs to channel 0, the second sample belongs to channel 
2, the third sample belongs to channel 1, the fourth sample belongs to channel 0, and so on.

Lab_ISCAN_Check

 checks the current background data acquisition operation to determine 

whether it has completed and returns the number of samples acquired at the time that you 
called 

Lab_ISCAN_Check

. If the operation is complete, 

Lab_ISCAN_Check

 sets 

daqStopped = 1. Otherwise, daqStopped is set to 0. Before 

Lab_ISCAN_Check

 returns 

daqStopped = 1, it calls 

DAQ_Clear

, allowing another Start call to execute immediately.

If 

Lab_ISCAN_Check

 returns an overFlowError or an overRunError, NI-DAQ has 

terminated the data acquisition operation because of lost A/D conversions due to a sample rate 
that is too high (sample interval was too small). An overFlowError indicates that the A/D 
FIFO memory overflowed because the data acquisition servicing operation was not able to 
keep up with sample rate. An overRunError indicates that the data acquisition circuitry 
was not able to keep up with the sample rate. Before returning either of these error codes, 

Lab_ISCAN_Check

 calls 

DAQ_Clear

 to terminate the operation and reinitialize the data 

acquisition circuitry.