Measurement Computing UL for NI LabVIEW - Manual (Page 30)

Universal Library Virtual Instruments (VIs) Analog Input VIs
ExtMemory Data is returned to a data buffer (array). EXTMEMORY causes the command to
send the data to a connected memory board via the DT-Connect interface rather
than returning the data to data buffer (array). Every time this option is used it
overwrites any data already stored in the memory board. The data should be
unloaded with the MemRead.VI before collecting new data.
Do not use EXTMEMORY and DTCONNECT together.
Mode Trigger and transfer method options
Mode Setting Explanation
DEFAULTIO 0 Default and recommended sampling mode. The optimum
sampling mode is chosen based on board type and sampling
speed.
SINGLEIO 1 A/D conversions and transfers to memory are initiated by an
interrupt. One interrupt per conversion.
DMAIO 2 A/D conversions are initiated by a trigger. Transfers are
initiated by a DMA request.
BLOCKIO 3 A/D conversions are initiated by a trigger. Transfers are
handled by REP-INSW.
BURSTIO 4 Allows higher sampling rates for sample counts up to full
FIFO. Data is collected into the local FIFO. Data transfers to
the PC are held off until after the scan is complete.
BURSTIO is the default mode for non-Continuous fast scans
(aggregate sample rates above 1000 Hz) with sample counts up
to full-FIFO. To avoid the BURSTIO default, specify
BLOCKIO.
BURSTIO is not a valid option for most boards. It is used
mainly for USB products.
BurstMode Enables burst mode sampling. Scans from LowChan to HighChan are clocked at the
maximum A/D rate between samples to minimize channel-to-channel skew. Scans
are initiated at the rate specified by
Rate .
ExtTrigger If this option is specified, the sampling will not begin until the trigger condition is
met. On many boards, this trigger condition is programmable (see SetTrig.VI on
page 33 and board-specific information for details). On other boards, only 'polled
gate' triggering is supported. In this case, assuming active high operation, data
acquisition will commence immediately if the trigger input is high. If the trigger
input is low, acquisition will be held off until it goes high. If only 'polled gate'
triggering is supported, this option is most useful if the signal is a pulse with a very
low duty cycle (trigger signal in TTL low state most of the time) so that triggering
will be held off until the occurrence of the pulse.
NoToDints If this option is specified, the system's time-of-day interrupts are disabled for the
duration of the scan. These interrupts are used to update the system’s real time
clock and are also used by various other programs. These interrupts can limit the
maximum sampling speed of some boards - particularly the PCM-DAS08. If the
interrupts are turned off using this option, the real-time clock will fall behind by
the length of time that the scan takes.
NoCalData Turns off real-time software calibration for boards which are software-calibrated
by applying calibration factors to the data on a sample by sample basis as it is
acquired. Examples are the PC-CARD-DAS16/330 and PC-CARD-DAS16x/12.
Turning off software calibration saves CPU time during a high speed acquisition
run. This may be required if your processor is less than a 150 MHz Pentium and
you desire an acquisition speed in excess of 200 kHz. These numbers may not
apply to your system. Only trial and error testing will tell for sure.
DO NOT use this option if it is not necessary. If this option is used, the data must
be calibrated after the data acquisition with the ACalData.VI.
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