User manual

Chapter 3 Software Overview
NI-DAQ User Manual for PC Compatibles 3-24 ni.com
DAQ_DB_HalfReady
Checks if the next half buffer of data is
available during a double-buffered data
acquisition.
DAQ_DB_Transfer
Transfers half of the data from the buffer
being used for double-buffered data
acquisition to another buffer, which is
passed to the function. This function waits
until the data to be transferred is available
before returning. You can execute
DAQ_DB_Transfer
repeatedly to return
sequential half buffers of the data.
Data Acquisition Application Tips
Lab and 1200 Device Counter/Timer Signals
For the Lab and 1200 devices, counter A2 produces the total sample
interval for data acquisition timing. However, if the total sample interval
is greater than 65,535 µs, counter B0 generates the clock for a slower
timebase, which counter A2 uses for the total sample interval. Thus, the
ICTR_Setup
and
ICTR_Reset
functions cannot use counter B0 for the
duration of the data acquisition operation.
In addition, the Waveform Generation functions cannot use counter B0
if the total update interval for waveform generation is also greater
than 65,535 µs and counter B0 must produce a timebase for waveform
generation different from the timebase counter B0 produced for data
acquisition. If waveform generation is not in progress, counter B0 is
available for data acquisition if you have made no
ICTR_Setup
call
on counter B0 since startup, or if you have made an
ICTR_Reset
call on
counter B0. If waveform generation is in progress and is using counter B0
to obtain the timebase required to produce the total update interval,
counter B0 is only available for data acquisition if this timebase is the
same as that required by the Data Acquisition functions to produce the total
sample interval. In this case, counter B0 provides the same timebase for
data acquisition and waveform generation.