SDHC is the abbreviation of "Secure Digital High Capacity", which means "high-capacity SD memory card." In May 2006 SD Association released the latest version of the SD 2.0 system specification, which stipulates that SDHC is in line with the new specification and has a capacity greater than 2GB is less than or equal to 32GB SD card.
SDHC's biggest feature is the high capacity (2GB-32GB). In addition, the SD Association stipulates that SDHC must use the FAT32 file system. This is because the FAT16 file system previously used in the SD card supports a maximum capacity of 2GB and does not satisfy SDHC. The request. As the successor of the SD card, SDHC is mainly characterized in that the file format is upgraded from the previous FAT12, FAT16 to FAT32, and supports up to 32GB. Simultaneous transmission speed is redefined as Class2 (2MB/sec), Class4 (4MB/sec), Class6 (6MB / sec) and other levels, high-speed SD card can support real-time storage of high-resolution video recording. The external dimensions of the SDHC card are 32×24×2.1mm (Length×Width×Height). Like the current SD card, the copyright protection function is the same as before, but only the FAT12/16 format has been supported since the file system was changed. There is an incompatibility in the SD device, but now also supports FAT32 (SDHC) machines, which can read existing FAT12/16 format SD cards. All SD cards larger than 2G must comply with the SDHC specification. The specification states that SDHC must meet at least Class 2 speed grades and must have SDHC flags and speed grade flags on the cards. There are some brands that offer 4GB or higher capacity SD cards that do not meet the above conditions. For example, they lack the SDHC logo or speed grade logo. These memory cards cannot be called SDHC cards. Strictly speaking, they are not used by the SD Association. Approved, this kind of card is likely to appear in the use of compatibility issues with the device.
Since SDHC uses a different addressing method than the SD1.1 specification, it is not compatible with SD 2.0 specification to establish certain older SD devices produced before. Only new SD devices conforming to the SD 2.0 specification can use SDHC. If SDHC is inserted in Some older versions of SD devices will not be recognized by such devices for the purpose of protecting the data in the card. How can we confirm that the device is compatible with SDHC? There will be more obvious SDHC logo on the device, or SDHC will be indicated in the product specification. The Speed ​​Class specified by the SD Association mentioned above is quite different from the ordinary performance test in the test method. The test read rate curve and write rate curve are tested according to the degree of fragmentation in the card. Instead of testing the transmission speed of a single large file, the SD Association defines the performance curve that meets the minimum requirements of each grade, and compares the data obtained from the testing with the performance standards specified by the SD Association to determine the performance level of the card. SD2.0 specifications are divided into the following four levels for the performance of SD cards, different levels can meet different application requirements: Class 0: Including lower than Class 2 and unlabeled Speed ​​Class; Class 2: Can meet ordinary MPEG4 MPEG2 movies, SDTV, digital camera shooting; Class 4: Smooth playback of high-definition television (HDTV), digital camera continuous shooting and other needs; Class 6: Meet the requirements of SLR camera continuous shooting and professional equipment; A few days ago, SD Association showed a 2TB SDXC memory card (SD eXtended Capacity) at CES 2009.
SDXC not only has a large capacity, and its data transmission speed is also not bad. According to reports, its maximum transmission speed is expected to reach 300MB/s. With a large-capacity memory card, then use NDS to burn the card or use a memory stick The vest or any other friend can throw anything into it, but the data security performance is not clear. The SDXC memory card uses a NAND flash memory chip and uses Microsoft's exFAT file system (vista's new file system). It is said that the SDXC 1.0 specification will be officially released later this quarter.
SDHC's biggest feature is the high capacity (2GB-32GB). In addition, the SD Association stipulates that SDHC must use the FAT32 file system. This is because the FAT16 file system previously used in the SD card supports a maximum capacity of 2GB and does not satisfy SDHC. The request. As the successor of the SD card, SDHC is mainly characterized in that the file format is upgraded from the previous FAT12, FAT16 to FAT32, and supports up to 32GB. Simultaneous transmission speed is redefined as Class2 (2MB/sec), Class4 (4MB/sec), Class6 (6MB / sec) and other levels, high-speed SD card can support real-time storage of high-resolution video recording. The external dimensions of the SDHC card are 32×24×2.1mm (Length×Width×Height). Like the current SD card, the copyright protection function is the same as before, but only the FAT12/16 format has been supported since the file system was changed. There is an incompatibility in the SD device, but now also supports FAT32 (SDHC) machines, which can read existing FAT12/16 format SD cards. All SD cards larger than 2G must comply with the SDHC specification. The specification states that SDHC must meet at least Class 2 speed grades and must have SDHC flags and speed grade flags on the cards. There are some brands that offer 4GB or higher capacity SD cards that do not meet the above conditions. For example, they lack the SDHC logo or speed grade logo. These memory cards cannot be called SDHC cards. Strictly speaking, they are not used by the SD Association. Approved, this kind of card is likely to appear in the use of compatibility issues with the device.
Since SDHC uses a different addressing method than the SD1.1 specification, it is not compatible with SD 2.0 specification to establish certain older SD devices produced before. Only new SD devices conforming to the SD 2.0 specification can use SDHC. If SDHC is inserted in Some older versions of SD devices will not be recognized by such devices for the purpose of protecting the data in the card. How can we confirm that the device is compatible with SDHC? There will be more obvious SDHC logo on the device, or SDHC will be indicated in the product specification. The Speed ​​Class specified by the SD Association mentioned above is quite different from the ordinary performance test in the test method. The test read rate curve and write rate curve are tested according to the degree of fragmentation in the card. Instead of testing the transmission speed of a single large file, the SD Association defines the performance curve that meets the minimum requirements of each grade, and compares the data obtained from the testing with the performance standards specified by the SD Association to determine the performance level of the card. SD2.0 specifications are divided into the following four levels for the performance of SD cards, different levels can meet different application requirements: Class 0: Including lower than Class 2 and unlabeled Speed ​​Class; Class 2: Can meet ordinary MPEG4 MPEG2 movies, SDTV, digital camera shooting; Class 4: Smooth playback of high-definition television (HDTV), digital camera continuous shooting and other needs; Class 6: Meet the requirements of SLR camera continuous shooting and professional equipment; A few days ago, SD Association showed a 2TB SDXC memory card (SD eXtended Capacity) at CES 2009.
SDXC not only has a large capacity, and its data transmission speed is also not bad. According to reports, its maximum transmission speed is expected to reach 300MB/s. With a large-capacity memory card, then use NDS to burn the card or use a memory stick The vest or any other friend can throw anything into it, but the data security performance is not clear. The SDXC memory card uses a NAND flash memory chip and uses Microsoft's exFAT file system (vista's new file system). It is said that the SDXC 1.0 specification will be officially released later this quarter.