© National Instruments
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Bus Interface
The bus interface circuitry of X Series devices efficiently moves data between host memory and
the measurement and acquisition circuits. X Series devices are available for the following
platforms:
•
PCI Express
•
PXI Express
•
USB
Data Transfer Methods
Refer to the following sections for information about bus interface data transfer methods for
X Series devices.
PCI Express/PXI Express Device Data Transfer
Methods
The primary ways to transfer data across the PCI Express bus are as follows:
•
Direct Memory Access (DMA)
—DMA is a method to transfer data between the device
and computer memory without the involvement of the CPU. This method makes DMA the
fastest available data transfer method. NI uses DMA hardware and software technology to
achieve high throughput rates and increase system utilization. DMA is the default method
of data transfer for PCI Express and PXI Express devices.
NI PCI Express and PXI Express X Series devices have eight fully-independent DMA
controllers for high-performance transfers of data blocks. One DMA controller is available
for each measurement and acquisition block:
–
Analog input
–
Analog output
–
Counter 0
–
Counter 1
–
Counter 2
–
Counter 3
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