MultiMediaCard
TM
88
Sep.22.2005
Revision 0.3
7.14 Read ahead in Multiple Block read operation
In Multiple Block read operations, in order to improve read performance, the card may fetch data from the memory array,
ahead of the host. In this case, when the host is reading the last addresses of the memory, the card attempts to fetch data
beyond the last physical memory address and generates an ADDRESS_OUT_OF_RANGE error.
Therefore, even if the host times the stop transmission command to stop the card immediately after the last byte of data
was read, the card may already have generated the error, and it will show in the response to the stop transmission com-
mand. The host should ignore this error.
7.15 Memory Array Partitioning
Same as for MultiMediaCard mode.
7.16 Card Lock/unlock Operation
Usage of card lock and unlock commands in SPI mode is identical to MultiMediaCard mode. In both cases, the command
response is of type R1b. After the busy signal clears, the host should obtain the result of the operation by issuing a
GET_STATUS command. Please refer to Chapter 6.2.10 for details.
7.17 SPI Command Set
7.17.1
Command Format
All the MultiMediaCard commands are 6 bytes long. The command transmission always starts with the left bit of the bit-
string corresponding to the command codeword. All commands are protected by a CRC. The commands and arguments
are listed in Table 7-5.
7.17.2
Command Classes
As in MultiMediaCard mode, the SPI commands are divided into several classes (See Table 7-4). Each class supports a
set of card functions. A MultiMediaCard will support the same set of optional command classes in both communication
modes (there is only one command class table in the CSD register). The available comand classes, and the supported
command for a specific class, however, are different in the MultiMediaCard and the SPI communication mode.
Bit position
Width (bits)
Value
Description
47
1
‘0’
46
1
‘1’
[45:40]
6
x
[39:8]
32
x
argument
[7:1]
7
x
CRC7
0
1
‘1’
start bit
transmission bit
Table 7-3 : Command format in SPI Mode
command index
end bit