Chapter 3 – SD Card Interface Description
Revision 2.2 SD Card Product Manual
© 2004 SanDisk Corporation 3-15 12/08/04
The following sections describe the CSD fields and the relevant data types. If not explicitly
defined otherwise, all bit strings are interpreted as binary coded numbers starting with the
left bit first.
• CSD_STRUCTURE—describes the version of the CSD structure.
Table 3-12 CSD Register Structure
CSD Structure CSD Structure Version Valid for System Specification Version
0 CSD Version 1.0 v1.0 to v1.10
1-3 Reserved ---
• TAAC—defines the asynchronous part (relative to the SD Card clock (CLK)) of the
read access time.
Table 3-13 TAAC Access Time Definition
TAAC Bit Position Code
Time exponent 2:0
0=1 ns, 1=10 ns, 2=100 ns, 3=1 us, 4=10 us, 5=100 us, 6=1 ms, 7=10 ms
Time value 6:3
0=reserved, 1=1.0, 2=1.2, 3=1.3, 4=1.5, 5=2.0, 6=2.5, 7=3.0, 8=3.5, 9=4.0,
A=4.5, B=5.0, C=5.5, D=6.0, E=7.0, F=8.0
7 Reserved
• NSAC—Defines the worst case for the clock dependent factor of the data access time.
The unit for NSAC is 100 clock cycles. Therefore, the maximal value for the clock
dependent part of the read access time is 25.5k clock cycles.
The total read access time N
AC
is the sum of TAAC and NSAC. It has to be computed
by the host for the actual clock rate. The read access time should be interpreted as a
typical delay for the first data bit of a data block from the end bit on the read
commands.
• TRAN_SPEED—Table 3-14 defines the maximum data transfer rate TRAN_SPEED.
Table 3-14 Max. Data Transfer Rate Definition
TRAN_SPEED Bit Code
Transfer rate exponent 2:0
0=100 kb/s, 1=1 Mb/s, 2=10 Mb/s, 3=100 Mb/s, 4…7=reserved
Time mantissa 6:3
0=reserved, 1=1.0, 2=1.2, 3=1.3, 4=1.5, 5=2.0, 6=2.5, 7=3.0, 8=3.5, 9=4.0,
A=4.5, B=5.0, C=5.5, D=6.0, E=7.0, F=8.0
7 Reserved
• CCC—The SD Card command set is divided into subsets (command classes). The
Card Command Class Register (CCC) defines which command classes are supported
by this card. A value of “1” in a CCC bit means that the corresponding command class
is supported.
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