Chapter 1 – Introduction
Revision 2.2
SanDisk SD Card Product Manual
© 2004 SanDisk Corporation
1-8
12/08/04
Part No.
Block
Size
(Bytes)
Data Area +
Protected size
(Blocks)
Protected Area
2
size
(Blocks)
User Area
(Blocks0
SDSDJ-32 512
60,512
736
59,776
SDSDB-16 512
29,152
352
28,800
1.12.6 Read/Write
Operations
The SD Card supports two read/write modes as shown in Figure 1-3 and defined in Table
1-2.
Figure 1-3
Data Transfer Formats
Table 1-2
Mode Definitions
Mode Description
Single Block
In this mode the host reads or writes one data block in a pre-specified length. The
data block transmission is protected with 16-bit CRC that is generated by the
sending unit and checked by the receiving unit.
The block length for read operations is limited by the device sector size (512 bytes)
but can be as small as a single byte. Misalignment is not allowed. Every data block
must be contained in a single physical sector.
The block length for write operations must be identical to the sector size and the
start address aligned to a sector boundary.
Multiple Block
This mode is similar to the single block mode, except for the host can read/write
multiple data blocks (all have the same length) that are stored or retrieved from
contiguous memory addresses starting at the address specified in the command.
The operation is terminated with a stop transmission command.
Misalignment and block length restrictions apply to multiple blocks and are identical
to the single block read/write operations.
1.12.7
Data Transfer Rate
The SD Card can be operated using either a single data line (DAT0) or four data lines
(DAT0-DAT3) for data transfer. The maximum data transfer rate for a single data line is 50-
Mb per second, and 200-Mb (25 MB) per second using four data lines.
Multiple Block Mode
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Memory
Sectors
Start Address
(Write)
Start Address
(Read/Write)
Start Address
(Read)
Write
Start Address
Stop
Start
Read
Stop
Single Block Mode
Misalignment Error