Chapter 4 – SD Card Protocol Description
Revision 2.2
SanDisk SD Card Product Manual
© 2004 SanDisk Corporation
4-31
12/08/04
4.8.2 Command
Format
The command length shown in Figure 4-15 is 48 bits.
Figure 4-15
Format (1.92 µs @ 25 MHz)
0
1
bit 5….bit 0
bit 31….bit 0
bit 6….bit 0
1
start bit
host
command
argument
CRC7
end bit
Commands and arguments are listed in Table 4-13.
7-bit CRC Calculation: G(x) = x
7+
x
3+
1
M(x) = (start bit)*x
39
+ (host bit)*x
38
+…+ (last bit before CRC)*x
0
CRC[6…0] = Remainder[(M(x)*x
7
)/G(x)]
4.8.3 Command
Classes
The command set of the SD Card is divided into several classes (refer to Table 4-15). Each
class supports a set of card functions.
The supported Card Command Classes (CCC) is coded as a parameter in the CSD Register
data of each card, providing the host with information on how to access the card.
Table 4-15
Card Command Classes
Class 0
1
2
3
4 5 6 7 8 9 10
11
CMD
Basic R Block
Read
R
Block
Write
Erase
Write
Protec
tion
Lock
Card
App-
Specific
I/O
Mode
Switch R
CMD0
+
CMD2
+
CMD3
+
CMD4
+
CMD5
+
CMD6
20
+
CMD7
+
CMD9
+
CMD10
+
CMD12
+
CMD13
+
CMD15
+
CMD16 + +
+
CMD17
+
CMD18
+
CMD24
+
CMD25
+
CMD27
+
20
This command is newly defined in SD Card Physical Description Spec. v1.10