All You Ever Needed to Know About SD Cards
The Secure Digital Storage device (SD Card) started life in 1999 when three major corporations Matsushita, Toshiba and Sandisk begun to develop the secure digital storage device. The devices are used in many products such as mobile phones,cameras,hand held computers notebooks and media players.The look is an non volatile memory card its size 32mm,24mm by 2.1mm which gave DRM approximately SDMI and for that time a more substantial memory. - sdhc card reader
The Sony Memory Stick was developed the year before therefore the SD card was designed to take on the stick. The style was based on the Multi Media Card format however with differences.
In order to insert the way in which the card has asymmetrically shape. SD cards at 2.1mm are thicker compared to MMC at 1.4mm. Recessed beneath the surface are the electrical contacts put that way as not to touch the operators fingers.
Transfer rates are in the 10-20 mbs range though development that would change.
Devices that used MMC will not take SD cards but in reverse MMC will go into devices using SD.
The file system in the SD card is formatted with either FAT16 for cards with 4 GB or less and for cards 4 GB and above they could be only be used by data system that props up grater storage size like FAT32 which is positioned on top of the MBR partition scheme.By using this system will allow access from the card to any host with a SD card reader.
SD cards use a write protection tab about the left side when the tab is present then your card cannot be written to when the tab is closed the credit card can be written to. Some of the other SD family such as the micro or mini SD cards would not have write protect tabs. Devices by using this format request a 128-bit identification string,12 bits are utilized in the memory clusters which can be in the range of 1 to 4096, 3 bits are employed to identify the block cluster which when decoded could read 4,8,16,32,64,128,256,512.blocks.
Speed ratings with the SD cards are:
class 2 16 MBit-s (2 mbyte-s)
class 4 32 MBit-s (4 mbyte-s)
class 6 48 MBit-s (6 mbyte-s)
Fragmentation of a Secure Digital card isn't ideal because it will degrade the card limited to the amount of writes before the card may fail is 100,000 times.
In 2000 the SD Association was formed from the three corporations Matsushita, SanDisk and Toshiba and the SD is now under the control of the association. They now define 1 GB cards and two GB cards specifications there design.The SD specification can also be covered by patents like US patent 5602987. - sdhc card reader