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6.4 Read-ahead Cache
6.4 Read-ahead Cache
Read-ahead Cache is the function for automatically reading data blocks upon
completion of the read command in order to read data from disk media and save
data block on a data buffer.
If a subsequent command requests reading of the read-ahead data, data on the data
buffer can be transferred without accessing the disk media. As the result, faster
data access becomes possible for the host.
6.4.1 Data buffer structure
This device contains a data buffer. This buffer is divided into two areas: one area
is used for MPU work, and the other is used as a read cache for another command.
(See Figure 6.5)
Example of 16 MB buffer
For MPU work
For R/W command
16,384 KB (16,777,216 bytes)
Figure 6.5 Data buffer structure
The read-ahead operation is done by the following commands.
• READ SECTOR (S) (EXT)
• READ MULTIPLE (EXT)
• READ DMA (EXT)
• READ FP DMA QUEUED
C141-E280 6-13