SD card classification(2)

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SD card classification(2)

SDHC

SDHC is the abbreviation of "secure digital high capacity", namely "High Capacity SD memory card". In May 2006, SD Association issued the latest version of SD 2.0 system specification, which stipulates that SDHC is an SD card with a capacity of more than 2GB but less than or equal to 32GB, which complies with the new specification

The biggest feature of SDHC is its high capacity (2gb-32gb). In addition, the SD Association stipulates that SDHC must adopt FAT32 file system, because the FAT16 file system previously used in SD card supports a maximum capacity of 2GB, which does not meet the requirements of SDHC.

As the successor of SD card, the main feature of SDHC is that the file format has been upgraded from FAT12 and FAT16 to FAT32, and the maximum support is 32GB. At the same time, the transmission speed is redefined as class2 (2Mb / sec), class4 (4MB / sec), Class6 (6MB / sec), etc. the high-speed SD card can support the real-time storage of high-resolution video recording.

The overall dimension of the SDHC card is 32 × 24 × 2.1mm (length × width × height). Like the SD card, the copyright protection function is the same as before. However, due to the change of the file system, the former SD device only supports FAT12 / 16 format is not compatible, and the FAT32 (SDHC) machine is also supported, which can read the existing FAT12 / 16 format SD card.

All SD cards with capacity greater than 2G must conform to the SDHC specification, which indicates that SDHC must conform to the speed level of class 2 at least, and there must be SDHC mark and speed level mark on the card.

In the market, there are some brands that provide 4GB or higher capacity SD cards that do not meet the above conditions, such as the lack of SDHC logo or speed level logo. These memory cards cannot be called SDHC cards. Strictly speaking, they are not recognized by SD Association. Such cards are likely to have compatibility problems with equipment in use.

SDXC

SD Association presented a 2TB [3] SDXC memory card (SD extended capacity) at CES 2009.

SDXC not only has a large capacity, but also has a good data transmission speed. According to the introduction, its maximum transmission speed is expected to reach 300MB / s. If you have a large capacity memory card, you can burn it with NDS or use a memory stick vest or other friends to throw anything into it. However, the data security performance is not clear for the time being This SDXC memory card uses NAND flash memory chip and Microsoft's [4] exFAT file system (Vista's new file system).

(1) the current maximum capacity of SDXC memory card can reach 64GB. Theoretical capacity is 2TB

(2) support UHS 104, a new super high speed SD interface specification, the highest standard of the new SD memory card standard ver.3.00, which realizes the bus transmission speed of 104mb / s on the SD interface, thus realizing the maximum write speed of 35MB / s and the maximum read speed of 60MB / s.

(3) the uhs104 provides the traditional SD interface -- 3.3V DS (25MHz) / HS (50MHz). The new SDHC memory card supporting the uhs104 is compatible with the existing SDHC corresponding equipment.

(4) the SDXC memory card is only compatible with the corresponding SDXC device with the exFAT file system. It cannot be used for SD or SDHC corresponding devices.

(5) adopt the most reliable CPRM copyright protection technology.

(6) uhs104 is a new ultra-high speed interface specification with data bus transmission rate of 104mb / s. This is the highest standard in the new SD memory card standard ver.3.00.

(7) SDXC memory card is the next generation SD memory card standard defined by SD Association in April 2009. In order to meet the growing demand of mass storage media and provide faster data transmission rate for rich storage applications. Compared with the SDHC memory card standard, which provides 4GB to 32GB capacity, the new SDXC memory card standard can achieve a capacity of more than 32GB and a maximum of 2TB (TB: terabyte, trillion bytes, 1TB = 1024gb).