Direct memory access controller (DMA) RM0444
284/1390 RM0444 Rev 5
Peripheral-to-peripheral mode
Any DMA channel can operate in peripheral-to-peripheral mode:
• when the hardware request from a peripheral is selected to trigger the DMA channel
This peripheral is the DMA initiator and paces the data transfer from/to this peripheral
to/from a register belonging to another memory-mapped peripheral (this one being not
configured in DMA mode).
• when no peripheral request is selected and connected to the DMA channel
The software configures a register-to-register transfer by setting the MEM2MEM bit of
the DMA_CCRx register.
Programming transfer direction, assigning source/destination
The value of the DIR bit of the DMA_CCRx register sets the direction of the transfer, and
consequently, it identifies the source and the destination, regardless the source/destination
type (peripheral or memory):
• DIR = 1 defines typically a memory-to-peripheral transfer. More generally, if DIR = 1:
–The source attributes are defined by the DMA_MARx register, the MSIZE[1:0]
field and MINC bit of the DMA_CCRx register.
Regardless of their usual naming, these ‘memory’ register, field and bit are used to
define the source peripheral in peripheral-to-peripheral mode.
–The destination attributes are defined by the DMA_PARx register, the PSIZE[1:0]
field and PINC bit of the DMA_CCRx register.
Regardless of their usual naming, these ‘peripheral’ register, field and bit are used
to define the destination memory in memory-to-memory mode.
• DIR = 0 defines typically a peripheral-to-memory transfer. More generally, if DIR = 0:
–The source attributes are defined by the DMA_PARx register, the PSIZE[1:0] field
and PINC bit of the DMA_CCRx register.
Regardless of their usual naming, these ‘peripheral’ register, field and bit are used
to define the source memory in memory-to-memory mode
–The destination attributes are defined by the DMA_MARx register, the
MSIZE[1:0] field and MINC bit of the DMA_CCRx register.
Regardless of their usual naming, these ‘memory’ register, field and bit are used to
define the destination peripheral in peripheral-to-peripheral mode.
10.4.6 DMA data width, alignment and endianness
When PSIZE[1:0] and MSIZE[1:0] are not equal, the DMA controller performs some data
alignments as described in the table below.
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