ARM Technical Support Knowledge Articles

When will PL080 use the TransferSize value

Applies to: PL08x DMAC (DM & SM)

Scenario

When DMA is used to transfer data from memory to peripheral, and the peripheral is the flow controller, the TRM says "If you program this TransferSize to non-zero, DMAC might attempt to use this value".  When will DMA use TransferSize and when will it not?

Answer

When the peripheral is the flow controller and TransferSize contains a non-zero value, the behaviour of the controller is UNDEFINED and cannot be relied upon to provide a meaningful indication of end-of-transfer. TransferSize is only used when the PL080 itself is the flow controller.


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