Chapter 10
Bus Interface
©
National Instruments Corporation
10-5
operations. Refer to the
section of
, for more information.
Changing Data Transfer Methods
(NI PCI/PCIe/PXI/PXIe Devices)
On PCI, PCI Express, PXI, and PXI Express
M Series devices, each measurement and acquisition circuit (that is, AI,
AO, and so on) has a dedicated DMA channel. So in most applications, all
data transfers use DMA.
However, NI-DAQmx allows you to disable DMA and use interrupts. To
change your data transfer mechanism between DMA and interrupts in
NI-DAQmx, use the
Data Transfer Mechanism
property node.
(USB Devices)
USB M Series devices have four dedicated USB Signal
Stream channels. These channels are assigned to the first four
measurement/acquisition circuits that request one. If a USB Signal Stream
is not available, you must set the data transfer mechanism to programmed
I/O; otherwise the driver returns an error. To change your data transfer
mechanism between USB Signal Stream and programmed I/O, use the
Data Transfer Mechanism
property node function in NI-DAQmx.