SPRUJ55D September 2023 – July 2025 AM263P2 , AM263P2-Q1 , AM263P4 , AM263P4-Q1
In a DMA block read operation (single or multiple), the request signal SDMARREQN is asserted to its active level when a complete block is written in the buffer. The block size transfer is specified in the MMC_BLK[10:0] BLEN field.
The SDMARREQN signal is deasserted to its inactive level when the sDMA has read one single word from the buffer. Only one request is sent per block; the DMA controller can make a 1-shot read access or several DMA bursts, in which case the DMA controller must manage the number of burst accesses, according to block size BLEN field.
New DMA requests are internally masked if the sDMA has not read exactly BLEN bytes and a new complete block is not ready. As DMA accesses are in 32-bit, then the number of sDMA read is Integer(BLEN/4)+1.
The receive buffer never overflows. In multiple block transfers for block size above 512 bytes, when the buffer gets full, the MMC_CLK clock signal (provided to the card) is momentarily stopped until the sDMA or the MPU performs a read access, which reads a complete block in the buffer.
Figure 13-131 provides a summary:
Figure 13-131 DMA
Receive Mode