Chapter 3 – SD Card Interface Description
Revision 2.2 SD Card Product Manual
© 2004 SanDisk Corporation 3-16 12/08/04
Table 3-15 Supported Card Command Classes
CCC Bit Supported Card Command Class
0 Class 0
1 Class 1
----
11 Class 11
• READ_BL_LEN—The maximum read data block length is computed as 2
READ_BL_LEN
.
The maximum block length might therefore be in the range 512…2048 bytes. In the
SD Memory Card, the WRITE_BL_LEN is always equal to READ_BL_LEN.
Table 3-16 Data Block Length
READ_BL_LEN Block Length
0 to 8 Reserved
9 2 * 512 bytes
……
11 2
11
= 2048 b
tes
12-15 Reserved
• READ_BL_PARTIAL—defines whether partial block sizes can be used in block read
commands.
Table 3-17 Bit Definition
READ_BL_PARTIAL Definition
0 Only the READ_BL_LEN block size can be used for block-oriented data
transfers.
1 Smaller blocks can be used. The minimum block size will be equal to
minimum addressable unit (one byte).
• WRITE_BLK_MISALIGN—Defines if the data block to be written by one
command can be spread over more than one physical block of the memory device. The
size of the memory block is defined in WRITE_BL_LEN.
Table 3-18 Bit Definition
WRITE_BLK_MISALIGN Definition
0 Crossing physical block boundaries is invalid.
1 Crossing physical block boundaries is allowed.
• READ_BLK_MISALIGN—defines if the data block read by one command can be
spread over more than one physical block of the memory device. The size of the
memory block is defined in READ_BL_LEN.
Table 3-19 Bit Definition
READ_BLK_MISALIGN Definition
0 Crossing physical block boundaries is invalid.
1 Crossing physical block boundaries is allowed.
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