Fujitsu MPB3021AT, Руководство по эксплуатации продукта

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C141-E045-02EN 6 - 15
(3) Invalidating caching data
Caching data in the data buffer is invalidated in the following case.
1) Following command is issued to the same data block as caching data.
•
WRITE SECTOR(S)
•
WRITE DMA
•
WRITE MULTIPLE
2) Command other than following commands is issued (all caching data are invalidated)
•
READ SECTOR (S)
•
READ DMA
•
READ MULTIPLE
•
WRITE SECTOR(S)
•
WRITE MULTIPLE
•
WRITE DMA
3) Caching operation is inhibited by the SET FEATURES command.
4) Issued command is terminated with an error.
5) Soft reset or hard reset occurs, or power is turned off.
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)
6.5.3 Usage of read segment
This subsection explains the usage of the read segment buffer at following cases.
(1) Miss-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 till the buffer becomes full when the received lead
sector address is sequential to the last sector address of previous read command. When it is
not sequential, the drive checks that the sequential read command is executed for last received
ten read commands. When no sequential read command is issued, the read-ahead operation is
stopped (refer to item (2)).