ARM Technical Support Knowledge Articles

Can DMA-330 perform Scatter-gather to unaligned addresses?

Applies to: PL330 AXI DMA Controller

Answer

Yes. Scatter-gather transfers are like any other transfer in DMA-330 - they are controlled by software where you can change the source and destination addresses as well as the size and length of the transfer.

Consequently, you can set up the DMA-330 channel to read from any address, and write to any address, providing you are not reading or writing unaligned data to a FIXED address.

Since all the parameters are configurable, it is also acceptable to transfer non-word quantities to/from unaligned addresses.

In accordance with the AXI Specification, the unaligned transfer is restricted to the first transfer in a burst - all subsequent transfers will be aligned.

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