Fujitsu MJA2500BH Maintenance Manual - Page 256
DMA data-in command protocol,
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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.) Host RegHD DATA RegDH Device Figure 5.16 DMA data-in command protocol 5-182 C141-E293