DMA 0 transfer is working

[ComAp R&D]

Posted on June 20, 2018 at 14:12

Hello,

because of my mistake I call function:

HAL_StatusTypeDef HAL_DMA_Start_IT(DMA_HandleTypeDef *hdma, uint32_t SrcAddress, uint32_t DstAddress, uint32_t DataLength)

with params:

HAL_DMA_Start_IT(hmmc_xy, from_addr, to_addr, 65536);

The function write 0 to SxNDTR, because the register is 16bit wide. In spite of that transfer of 65536 is always performed.

How it is possible?

Setting on MCU STM32F777II,

{

.Instance = DMA2_Stream3, .Init.Channel = DMA_CHANNEL_4, .Init.Direction = DMA_PERIPH_TO_MEMORY, .Init.PeriphInc = DMA_PINC_DISABLE, .Init.MemInc = DMA_MINC_ENABLE, .Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD, .Init.MemDataAlignment = DMA_MDATAALIGN_BYTE, .Init.Mode = DMA_PFCTRL, .Init.Priority = DMA_PRIORITY_VERY_HIGH, .Init.FIFOMode = DMA_FIFOMODE_ENABLE, .Init.FIFOThreshold = DMA_FIFO_THRESHOLD_1QUARTERFULL, .Init.MemBurst = DMA_MBURST_INC4, .Init.PeriphBurst = DMA_PBURST_INC4, }#ndtr #dma #0-len