5.4 Command Protocol
5.4.4 DMA data-in command protocol
DMA
•READ DMA (EXT)
•IDENTFY DEVICE
•IDENTFY DEVICE DMA
The DMA mechanism transfers data of more than one block from the device to the host. The completion of a command is reported by an interruption.
An outline of this protocol is as follows:
1)The device receives a DMA
2)If an error remaining in the device prevents command execution, the device sends the RegDH FIS with 1 set in the I bit.
3)When the device is ready to send data, it sends the Data FIS to the host.
4)When all data has been transferred, the device sends the RegDH FIS (with 1 set in the I bit) to complete execution of the command. If any data remains to be sent by the device, this protocol is repeated starting from step 3). (The maximum data size is 8 KB.)
Host
RegHD
DATA
Device
RegDH