Direct memory access controller (DMA) RM0444
282/1390 RM0444 Rev 5
Channel configuration procedure
The following sequence is needed to configure a DMA channel x:
1. Set the peripheral register address in the DMA_CPARx register.
The data is moved from/to this address to/from the memory after the peripheral event,
or after the channel is enabled in memory-to-memory mode.
2. Set the memory address in the DMA_CMARx register.
The data is written to/read from the memory after the peripheral event or after the
channel is enabled in memory-to-memory mode.
3. Configure the total number of data to transfer in the DMA_CNDTRx register.
After each data transfer, this value is decremented.
4. Configure the parameters listed below in the DMA_CCRx register:
– the channel priority
– the data transfer direction
– the circular mode
– the peripheral and memory incremented mode
– the peripheral and memory data size
– the interrupt enable at half and/or full transfer and/or transfer error
5. Activate the channel by setting the EN bit in the DMA_CCRx register.
A channel, as soon as enabled, may serve any DMA request from the peripheral connected
to this channel, or may start a memory-to-memory block transfer.
Note: The two last steps of the channel configuration procedure may be merged into a single
access to the DMA_CCRx register, to configure and enable the channel.
Channel state and disabling a channel
A channel x in active state is an enabled channel (read DMA_CCRx.EN = 1). An active
channel x is a channel that must have been enabled by the software (DMA_CCRx.EN set
to 1) and afterwards with no occurred transfer error (DMA_ISR.TEIFx = 0). In case there is a
transfer error, the channel is automatically disabled by hardware (DMA_CCRx.EN = 0).
The three following use cases may happen:
• Suspend and resume a channel
This corresponds to the two following actions:
– An active channel is disabled by software (writing DMA_CCRx.EN = 0 whereas
DMA_CCRx.EN = 1).
– The software enables the channel again (DMA_CCRx.EN set to 1) without
reconfiguring the other channel registers (such as DMA_CNDTRx, DMA_CPARx
and DMA_CMARx).
This case is not supported by the DMA hardware, that does not guarantee that the
remaining data transfers are performed correctly.
• Stop and abort a channel
If the application does not need any more the channel, this active channel can be
disabled by software. The channel is stopped and aborted but the DMA_CNDTRx
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