Fujitsu MHN2100AT - Mobile 10 GB Hard Drive, Product Manual

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Operations
6-14 C141-E120-02EN
6) The device enters the sleep mode.
7) Under the state that the write data is kept in the data buffer for write
command as a caching data, new write command is issued. (write data kept
until now are invalidated)
6.4.3 Usage of read segment
This subsection explains the usage of the read segment buffer at following cases.
6.4.3.1 Mis-hit (no hit)
A lead block of the read-requested data is not stored in the data buffer. The
requested data is read from the disk media.
The read-ahead operation is performed only when the last sector address of the
previous read command and the lead sector address of this read command is
sequential (see item (2)).
1) Sets the host address pointer (HAP) and the disk address pointer (DAP) to the
lead of segment.
Segment only for read
DAP
HAP
2) Transfers the requested data that already read to the host system with reading
the requested data from the disk media.
Read-requested data
Stores the read-requested
data upto this point
Empty area
DAP
HAP