Specifications

©Copyright 2001-2013 SD Group (Panasonic, SanDisk, Toshiba) and SD Card Association
Physical Layer Simplified Specification Version 4.10
102
If a host tries to protect recorded data from any error including power failure, it may update CI
frequently.
• A cluster is allocated to store CI and when it is filled, a new cluster is allocated. The first update
of CI in a stream recording may be written from any point in an existing cluster. After the existing
cluster is filled, a new cluster is allocated and all subsequent updates are written from the
beginning to the end before a new cluster is allocated.
• The address to which CI is written may change during a stream recording. The same address
may be overwritten several times. When the address is changed, it is always increased
sequentially within the cluster. When a CI cluster is filled and a new one is allocated, the CI
cluster address is changed randomly. (Any free cluster can be allocated).
The Speed Class specification for SDXC defines the CI Update sequence and operation time. The
sequence is similar to the directory entry update. CI is always written by a 512-byte single block write
(either CMD24 or CMD25) and preceded by CMD20 Update CI command. The CI update operation
time is maximum 250ms.
Note that Insertion of CI update never affects Pw.
Application Note:
It is recommended that CI be updated after Speed Class recording is finished. In this case, the CI
update is performed outside of Speed Class recording and the
host does not need to consider it as
overhead.
4.13.2.6 Distinction of Data Type
During Speed Class recording, several types of data (Stream data, FAT, Bitmap, directory entry and CI)
are written by the host.
To satisfy Class performance, an SDXC card needs to distinguish between each type of data in order to
treat them properly.
For example, directory entry and CI can be distinguished by their data size (always written by 512B), so
the card can store them in separate areas from the stream data.
Locations of the FAT and bitmap are described in Section 4.13.2.7.3.
Since directory entry and CI are written by 512-byte single block write (either CMD24 or CMD25), in
user area, they should be distinguished by CMD20.
4.13.2.7 Measurement Conditions and Requirements of the Speed Class for SDXC
4.13.2.7.1 Measurement Conditions
The measurement conditions of Speed Class for SDXC are defined in Table 4-58. Class 10 card shall
meet Class 6 performance under Class 6 condition.
Card Capacity
SDXC
Over 32GB ~ 2TB
AU Size (max.)
64MB
Unit of Performance Measurement
4MB
RU Size
Class2, 4, 6
256KB
Class 10
512KB
Notes: Class 2 to 6 are measured at 20MHz in Default Speed Mode
Class 10 is measured at 40MHz in High Speed Mode
Table 4-58 : Measurement Conditions of Speed Class (SDXC)
Host needs to use higher frequency clock than that of measurement condition.