SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
In a DMA block write operation (single or multiple), the request signal MMCi_DMA_TX is asserted to its active level when a complete block is to be written to the buffer. The block size transfer is specified in the MMCi.MMCHS_BLK[10:0] BLEN bit field.
MMCi_DMA_TX is deasserted to its inactive level when a certain device DMA writes one word to the buffer.
Only one request is sent per block; the DMA controller can make a 1-shot write access or multiple write DMA bursts, in which case the DMA controller must manage the number of burst accesses, according to the BLEN bit field block size.
New DMA requests are internally masked if the DMA has not written exactly BLEN bytes (because DMA accesses are 32-bit accesses, the number of DMA reads is Integer(BLEN / 4) + 1) and if there is not enough memory space to write a complete block in the buffer.
To summarize:
Figure 27-19 shows DMA transmit mode.