Memory Array Partitioning - SanDisk SDSDB-32-201-80 - Industrial Grade Flash Memory Card Product Manual

1.5.9.5. Memory Array Partitioning

The basic unit of data transfer to/from the SD Card is one byte. All data transfer operations which require a block
size always define block lengths as integer multiples of bytes. Some special functions need other partition
granularity. Figure 1-2 shows the Memory Array Partitioning.
For block-oriented commands, the following definition is used:
Block—The unit that is related to the block-oriented read and write commands. Its size is the number
of bytes that are transferred when one block command is sent by the host. The size of a block is either
programmable or fixed. The information about allowed block sizes and the programmability is stored
in the CSD.
The granularity of the erasable units is in general not the same as for the block-oriented commands:
Sector—The unit that is related to the erase commands. Its size is the number of blocks that are erased
in one portion. The size of a sector is fixed for each device. The information about the sector size (in
blocks) is stored in the CSD.
For devices that include write protection, the following definition is used:
WP Group—The minimal unit that may which may have individual write protection. Its size is the
number of groups which will be write protected by one bit. The size of a WP-group is fixed for each
device. The information about the size is stored in the CSD.
SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION
Introduction to the SD Card
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