5.4 Command Protocol
C141-E224 5-151
5.4.4 DMA data-in command protocol
DMA data-in commands include the following commands:
• 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 data-in command with the RegHD FIS.
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.)
Device
Host
RegHD
DATA
RegDH
Figure 5.14 DMA data-in command protocol
