Dma Data-In Command Protocol; Figure 5.16 Dma Data-In Command Protocol - Fujitsu MHW2120BK Maintenance Manual

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.)

Figure 5.16 DMA data-in command protocol

C141-E261
RegHD
Host
DATA
RegDH
5.4 Command Protocol
Device
5-181