SD Card Interface Description
3-18
SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION
ERASE_BLK_EN
—defines whether erase of one write block (see WRITE_BL_LEN) is allowed (other than
SECTOR_SIZE given below). If ERASE_BLK_EN is 0, the host can erase a unit of SECTOR_SIZE. If
ERASE_BLK_EN is 1, the host can erase either a unit of SECTOR_SIZE or a unit of WRITE_BLK_LEN.
SECTOR_SIZE
—The size of an erasable sector. The contents of this register is a 7-bit binary coded value,
defining the number of write blocks (see WRITE_BL_LEN). The actual size is computed by increasing this number
by one. A value of zero means 1 write block, 127 means 128 blocks.
WP_GRP_SIZE
—The size of a write protected group. The contents of this register is a 7-bit binary coded value,
defining the number of Erase Groups (see SECTOR_SIZE). The actual size is computed by increasing this number
by one. A value of zero means 1 erase group, 127 means 128 erase groups.
WP_GRP_ENABLE
—A value of ‘0’ means no group write protection possible.
R2W_FACTOR
—Defines the typical block program time as a multiple of the read access time. Table 3-20 defines
the field format.
Table 3-20. R2W_FACTOR
R2W_FACTOR
Multiples of Read Access Time
0 1
1
2 (write half as fast as read)
2 4
3 8
4 16
5 32
6, 7
Reserved
WRITE_BL_LEN
—The maximum write data block length is computed as 2
WRITE_BL_LEN
. The maximum block
length might therefore be in the range from 512 up to 2048 bytes. A Write Block Length of 512 bytes is always
supported. Note that in the SD Card, the WRITE_BL_LEN is always equal to READ_BL_LEN.
Table 3-21. Data Block Length
WRITE_BL_LEN Block
Length
0-8 Reserved
9
29 = 512 Bytes
….
11
211 = 2048 Bytes
12-15 Reserved
WRITE_BL_PARTIAL
—Defines whether partial block sizes can be used in block write commands.
WRITE_BL_PARTIAL=‘0’ means that only the WRITE_BL_LEN block size, and its partial derivatives in
resolution of units of 512 blocks, can be used for block oriented data write.
WRITE_BL_PARTIAL=‘1’ means that smaller blocks can be used as well. The minimum block size is one byte.
FILE_FORMAT_GROUP—
Indicates the selected group of file formats. This field is read-only for ROM. The
usage of this field is shown in Table 3-22.
