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3-3
Data Transfer Methods
The primary ways to transfer data across the PXI Express bus are as follows:
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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.
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Programmed I/O—Programmed I/O is a data transfer mechanism where the user’s program
is responsible for transferring data. Each read or write call in the program initiates the
transfer of data. Programmed I/O is typically used in software-timed (on-demand)
operations.
