SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
SATA controller AHCI mode defines two types of transfers between the host system memory and a SATA peripheral device: DMA and PIO data transfers. Whether the transaction is of a DMA type or PIO type, the HBA fetches and stores data to memory, offloading the CPU. No register is implemented for direct user access to the data port.
PIO transfers specified by PIO Setup FISs are strongly discouraged because of their limited support of error indication. PIO commands use is limited to only few cases in which commands support only PIO mechanism, such as execution of the IDENTIFY DEVICE command and ATAPI command transfers in which the PACKET command is invoked. The SATA controller AHCI mechanism allows multiple DRQ blocks of data per PIO command.