DMA:Data Memory Access,直接存储器访问
Ⅰ、DMA请求

Ⅱ、DMA通道

(通道1-7)

3.仲裁

软件阶段:DMA_CCRx:PL[1:0]
硬件阶段:通道编号小的优先级大,DMA1的优先级高于DMA2的优先级

DMA_InitTypeDef初始化结构体
typedef struct
{
//外设地址 DMA_CPAR寄存器
  uint32_t DMA_PeripheralBaseAddr; /*!< Specifies the peripheral base address for DMAy Channelx. */
//存储器地址 DMA_CMAR
  uint32_t DMA_MemoryBaseAddr;     /*!< Specifies the memory base address for DMAy Channelx. */
//传输方向 DMA_CCR:DIR:4
  uint32_t DMA_DIR;                /*!< Specifies if the peripheral is the source or destination.
                                        This parameter can be a value of @ref DMA_data_transfer_direction */
//传输大小
  uint32_t DMA_BufferSize;         /*!< Specifies the buffer size, in data unit, of the specified Channel. 
                                        The data unit is equal to the configuration set in DMA_PeripheralDataSize
                                        or DMA_MemoryDataSize members depending in the transfer direction. */
//存储器地址增量模式
  uint32_t DMA_PeripheralInc;      /*!< Specifies whether the Peripheral address register is incremented or not.
                                        This parameter can be a value of @ref DMA_peripheral_incremented_mode */
//存储器地址增量模式
  uint32_t DMA_MemoryInc;          /*!< Specifies whether the memory address register is incremented or not.
                                        This parameter can be a value of @ref DMA_memory_incremented_mode */
//外设数据宽度
  uint32_t DMA_PeripheralDataSize; /*!< Specifies the Peripheral data width.
                                        This parameter can be a value of @ref DMA_peripheral_data_size */
//存储器数据宽带
  uint32_t DMA_MemoryDataSize;     /*!< Specifies the Memory data width.
                                        This parameter can be a value of @ref DMA_memory_data_size */
//DMA模式0:不执行循环操作,1执行循环操作.
  uint32_t DMA_Mode;               /*!< Specifies the operation mode of the DMAy Channelx.
                                        This parameter can be a value of @ref DMA_circular_normal_mode.
                                        @note: The circular buffer mode cannot be used if the memory-to-memory
                                              data transfer is configured on the selected Channel */
//通道优先级
  uint32_t DMA_Priority;           /*!< Specifies the software priority for the DMAy Channelx.
                                        This parameter can be a value of @ref DMA_priority_level */
//存储器到存储器模式
  uint32_t DMA_M2M;                /*!< Specifies if the DMAy Channelx will be used in memory-to-memory transfer.
                                        This parameter can be a value of @ref DMA_memory_to_memory */
}DMA_InitTypeDef;