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Each DMA data transfer consists of three operations:
Data access: determine the source address (DMA_PADDRx or DMA_MADDRx) according to the transfer
direction and read data from the source address.
Data storage: determine the destination address (DMA_PADDRx or DMA_MADDRx) according to the transfer
direction and store the read data into the destination address space.
Calculate the number of outstanding operations, perform a decrement operation of the DMA_TXNUMx register,
and update the source and destination addresses of the next operation.
8.4.2
Channel priority and arbitration
The DMA uses an arbitration strategy to handle multiple requests from different channels. The priority of each
channel is programmable in the channel control register (DMA_CHCFGx).
4 levels of priority:
Very high priority
High priority
Medium priority
Low priority
By default, channel with lower index has higher priority if the programmed priority is the same.
8.4.3
DMA channels and number of transfers
Each channel can perform DMA transfer between the peripheral register at the specified address and the memory
address. The number of data transferred by DMA is programmable, and the maximum supported value is 65535. The
DMA_TXNUM register is decremented after each transfer.
8.4.4
Programmable data bit width
Peripheral and memory transfer data bit width supports byte, half-word and word, which can be programmed through
DMA_CHCFGx.PSIZE and DMA_CHCFGx.MSIZE.
When DMA_CHCFGx.PSIZE and DMA_CHCFGx.MSIZE are different, the DMA module aligns the data according
to the Table 8-1 below.