Fujitsu MPB3052AT User Manual download pdf (Page 170)

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)).

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Fujitsu MPB3052AT User Manual Page 170