SD Memory
Secure Digital cards are today's hottest memory
Secure Digital or SD is a format of flash memory card used in mobile devices. Like all typical flash memory cards, it's used in most mobile electronic devices that have a need for portable mass storage. The available capacity of an SD card isn't static, they can be found in 128, 256, 512 MB, and up to 1, 2 and even 4 Gig. The upper limit to the format is far beyond 4 Gig, it's quite likely SD memory cards will surpass that size soon. The word Secure in the name of the SD format refers to its built in DRM. The digital rights management feature was embedded into the SD card called Content Protection for Recordable Media.
It was added when the format was being developed and it was feared that removable storage would run into trouble if it didn't come with a ready-made system of content protection. It's been under utilized, but it was a safe thing to add as memory cards used for media players are constantly going to be used to transfer sensitive property. Media players aren't the only place you'll find an SD slot.
- Cell Phones
- PDA Devices
- Pocket PCs
- Digital Cameras
- TV
- Camcorders
Secure Digital represents several breakthroughs in flash memory technology. Like all technology, flash memory storage is advancing into new formats every few years. But it's not just the capacity that is pushing the current of change in the flash memory industry. Other innovations have been brought about by a moderate openness of the standards of the Secure Digital Card Association (SDCA). The SDCA is the governing body of the format and holds the patents for SD memory. One of the key mandates of the SDCA has been the fusion of the SD and MultiMedia Card standard. An SD slot is to be backward compatible to an MMC card. Often you'll see that the memory slot on a portable device or handheld supports the SD/MMC standard or both. Basically, that means it's an SD slot, which is always backward compatible to an MMC card.
Need for Speed
One of the key advances found in SD is the speed. Several speeds of SD cards are available. The cards can range in transfer rates from lower speeds of up to 400 kilobit per second to faster varieties that can race up to 100 Megabits per second. The speed depends on the mode in which they run. These modes are being developed within the guidelines of the SD/SDIO's governing body, the SDCA.
SDIO
One of the most innovative developments of the SD format is SDIO. If a device supports SDIO, it means the SD slot becomes a multipurpose input/output resource for peripheral devices, like a USB port on a PC. Complex devices such as a pocket PC can use what's called SD form factor with an SDIO interface. This can be in the form of a GPS receiver, wi-fi or Bluetooth adaptor. Just about anything that you can think of with data exchange requirements with a computer could be built for an SDIO slot.
One other interesting bit of trivia relates to the format's logo. Originally, Toshiba developed the SD logo to be used with the Super-Density Optical Disk. It was a false start for the next generation optical storage format war. The SDOD project was scrapped, but the logo lived on. This is why the D in the SD logo looks like a broken line, it's supposed to be a shiny disc.