Figure 4-13: scatter/gather dma for data transfer – ADLINK PXI-2208 User Manual
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Operation Theory
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Figure 4-13 shows a linked list that is constructed by three DMA
descriptors. Each descriptor contains a PCI address, a local
address, a transfer size, and the pointer to the next descriptor.
You can allocate many small size memory blocks and chain their
associative DMA descriptors altogether by their application pro-
grams. The DAQ-/DAQe-/PXI-2204/2205/2206/2208 card soft-
ware driver provides simple settings for the scatter/gather
function, including some sample programs in the ADLINK All-in-
One CD.
Figure 4-13: Scatter/gather DMA for Data Transfer
In non-chaining mode, the maximum DMA data transfer size is 2
M double words (8M bytes). However, there is no limitation on the
DMA data transfer size when using scatter/gather chaining mode.
You can also link the descriptor nodes circularly to achieve a multi-
buffered mode DMA.