© National Instruments 10-1 X Series User Manual
10
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 X Series and PXI Express 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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