Interface

5.4.4 DMA data-in command protocol

DMA data-in commands include the following commands:

•READ DMA (EXT)

•IDENTFY DEVICE DMA

•READ LOG DMA EXT

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.)

RegHD

Host

Device

DATA

RegDH

Figure 5.16 DMA data-in command protocol

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