25.5.2.8 Internal FIFO

To improve the bandwidth, the DMAC can support FIFO operation. When single-beat burst configuration is selected (CHCTRALx.BURSTLEN = SINGLE), the channel waits until the FIFO can transmit or accept a single beat transfer before it requests a bus access to write to the destination address. In all other cases, the channel waits until the FIFO threshold is reached before it requests a bus access to write to the destination address. The threshold is configurable and can be set by writing the THRESHOLD bits in the Channel x Control A register.

If the DMAC completes the read operations before the threshold is reached, the write to the destination is automatically enabled. If the FIFO is empty and the read from source is ongoing, the DMA will wait again until the FIFO threshold is reached before it requests a bus access to write the destination.