Specifications
©Copyright 2001-2013 SD Group (Panasonic, SanDisk, Toshiba) and SD Card Association
Physical Layer Simplified Specification Version 4.10
103
4.13.2.7.2 Requirements of the Performance Parameters for Each Speed Class
Table 4-59 identifies the requirement of the parameters for each class under measurement conditions.
Pw min.
[MB/sec]
Pm min.
[MB/sec]
Pr min.
[MB/sec]
T
FW
(ave.)
[ms]
T
FW
(max.)
[ms]
T
FR
(4KB)
max. [ms]
Class 2
2
0
2
100
750
20
Class 4
4
0
4
100
750
20
Class 6
6
0
6
100
750
20
Class 10
10
0
10
100
750
20
Table 4-59 : Performance Requirements for Each Class (SDXC)
4.13.2.7.3 Requirements of SD File System
This specification can be applied only to the SD file system formatted card defined by the File System
Specification Version 3.00. This includes complying with the format parameter calculation specified in
the Appendix C of the File System Specification Version 3.00.
Furthermore, the Number of Hidden Sectors shall be adopted as minimum number that meets
Boundary Unit Recommendation for Data Area. And in case of exFAT file system, Allocation Bitmap
shall be stored in the first 4MB of Cluster Heap.
4.13.2.8 Speed Class Control Command (CMD20)
CMD20 is defined to optimize card operation to support Speed Class recording. Figure 4-54 shows the
definition of CMD20 timing and arguments. If any error occurs during the CMD20 busy period, it will be
reported in the R1 response of next command. The host may issue CMD13 to check the occurrence of
an error.
Speed Class Control (SCC) in the argument controls several functions which assist the card in
supporting and meeting Class performance.
The response type of CMD20 is R1b. The maximum busy indication period depends on the function
selected by SCC in the argument.
Figure 4-54 : Definition of CMD20
CMD
Busy
CMD20 R1b
DAT[0]
t
BUSY
(max.)
R1
Error Check
Speed Class Control t
BUSY
(max.)
0000b: Start Recording 1 second
0001b: Update DIR 10ms
0010b: Reserved for Multiple Streams Recording
0011b: Reserved for Multiple Streams Recording
0100b: Update CI 10ms
others: Reserved
Speed Class Control Command (CMD20)
S T Index SCC Reserved CRC7 E
0 1 010100 xxxx all 0 xx 1
CMD13
if CMD20 does not indicate busy, following
CMD13 is not required.
Figure 4-53 : Definition of CMD20