SanDisk SDMB-16, Руководство по эксплуатации продукта

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MultiMediaCard Product Manual
12 SanDisk MultiMediaCard Product Manual Rev. 2 © 2000 SANDISK CORPORATION
1.5.8.5 Memory Array Partitioning
Although the MultiMediaCard memory space is
byte addressable with addresses ranging from 0 to
the last byte, it is not a simple byte array but
divided into several structures.
Memory bytes are grouped into 512 byte blocks
called sectors. Every block can be read, written
and erased individually.
Sectors are grouped into erase groups of 16 or 32
sectors depending on card size. Any combination of
sectors within one group or, any combination of
erase groups can be erased in a single erase
command. A write command implicitly erases the
memory before writing new data into it. Explicit
erase command can be used for pre-erasing of
memory which will speed up the next write
operation.
Erase groups are grouped into Write Protect Groups
(WPG) of 32 erase groups. The write/erase access
to each WPG can be limited individually. A
diagram of the memory structure hierarchy is
shown in Figure 1-2.
The number of various memory structures, for the
different MultiMediaCards are summarized in
Table 1-3. The last (highest in address) WPG will
be smaller and contain less than 32 erase groups.
WP Group 2
WP Group 1
Erase Group
Erase Group
Sector
Sector
Write Protect Group 0
Sector 1: Bytes 512 - 1,023
Erase Group 0
Sector 0: Bytes 0 - 511
Figure 1-3 Memory Array Partitioning