National Instruments 321645c-01 用户手册
Chapter 2
Function Reference — AO_Change_Parameter
NI-DAQ FRM for PC Compatibles
2-36
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National Instruments Corporation
paramValue to 0 or 100. By setting it to 0, the SYNC output goes to 0 V. If you set it to 100,
it goes to +5 V.
it goes to +5 V.
Using This Function
Use this function to customize the behavior of the analog output section of your device. Call
this function before calling NI-DAQ functions that cause output on the analog output
channels. You can call this function as often as needed.
this function before calling NI-DAQ functions that cause output on the analog output
channels. You can call this function as often as needed.
End of Buffer Interrupts
On PCI E Series boards that use the PCI-MITE for DMA transfers, NI-DAQ causes the
PCI-MITE to generate an interrupt after a full buffer has been transferred from host memory
to the DAQ device. With one-shot operations, where the buffer is only output once, or even
during continuous operations where the buffer is very large, these interrupts place very little
burden on the system. However, when outputting a large number of iterations with small
buffers or at high speeds, these interrupts can affect overall system performance.
PCI-MITE to generate an interrupt after a full buffer has been transferred from host memory
to the DAQ device. With one-shot operations, where the buffer is only output once, or even
during continuous operations where the buffer is very large, these interrupts place very little
burden on the system. However, when outputting a large number of iterations with small
buffers or at high speeds, these interrupts can affect overall system performance.
These interrupts are generated so that NI-DAQ will read the state of the DMA controller and
track the number of iterations and the number of points transferred since the beginning of the
operation. The PCI-MITE has a 32-bit counter that counts bytes transferred. The only
drawback in turning off these interrupts is that NI-DAQ might not have a chance to detect an
overflow of the counter. For example, when generating a waveform on one channel at 1 M
samples/s, the counter will overflow in 36 minutes. If you disable end-of-buffer interrupts and
do not query NI-DAQ for status information before the counter overflows, NI-DAQ will not
be able to take the overflow into account, and the status information returned could be
incorrect.
track the number of iterations and the number of points transferred since the beginning of the
operation. The PCI-MITE has a 32-bit counter that counts bytes transferred. The only
drawback in turning off these interrupts is that NI-DAQ might not have a chance to detect an
overflow of the counter. For example, when generating a waveform on one channel at 1 M
samples/s, the counter will overflow in 36 minutes. If you disable end-of-buffer interrupts and
do not query NI-DAQ for status information before the counter overflows, NI-DAQ will not
be able to take the overflow into account, and the status information returned could be
incorrect.
To enable/disable end of buffer interrupts, set paramID to
ND_LINK_COMPLETE_INTERRUPTS
and set paramValue to either
ND_ON
or
ND_OFF
. You
may specify any channel in the waveform group, and the setting will apply to all channels in
the group.
the group.
Note
This option is valid only for PCI/CPCI/PXI E Series devices.
Table 2-15. Parameter Setting Information for the SYNC Duty Cycle
Device Type
Per Channel
Selection Possible
Legal Range
for
paramValue
Default Setting
for paramValue
DAQArb AT-5411
DAQArb PCI-5411
DAQArb PCI-5411
Yes
20 to 80
50