Tuesday, April 15, 2008

Flash Memory

Flash Memory

Flash memory is a type of EEPROM chip. It has a grid of columns and rows with a cell that has two transistors at each intersection. This card is media of data depositor which is very small1. John (Chip Magazine 11-20 May 2004):
Flash memory is using for Digital Camera, PDA, MP3, player, hand phone, etc. With using flash memory in your electronic stuff, you can increase the capacity of memory. It mean’s you can save more picture in your Digital Camera, and also your song collection in your MP3 player. Flash memory capacity has many variance, such as 16 MB, 64 MB, 128 MB or 4 GB. Size of this cards are smaller than match box. There’re portable, furthermore there’re easy lost. But because of these simple size, you can put these flash memory card in your wallet. If one card is already full with your pictures, you can remove it from Digital Camera, then change it with an empty new card from your others pictures. And, the card which is full of your pictures must be save in PC2.
There are many kind of flash memory card, such as Compact Flash, Smart Media, xD, Memory Stick, and others. Compact Flash technology was developed by SanDisk in 1994, making it one of the oldest flash memory formats currently in use. According to the Compact Flash Association, Compact Flash cards have the potential for capacities up to 137 GB and data transfer rates of up to 66 MB/s. But, current devices can realistically be expected to have capacities of up to 12 GB and data transfer rates of up to 16 MB/s. Both of which are still very impressive (and currently very expensive for the large capacity cards). Every Compact Flash card is 43mm wide

and 36mm long, but depending on the type of card, they can have two different thicknesses. Type 1 Compact Flash cards are 3.3mm thick, Type 2 Compact Flash cards are 5.5mm thick, and these dimensions make the cards fairly large as compared to other flash memory. The connections for these cards are found at one end and feature two rows of 25 sockets that supply either 3.3V or 5V to the card (they can operate on either). This 1 GB San Disk model is an example of a typical Type II Compact Flash card. The larger size of the Compact Flash cards may seem like a disadvantage, but it is necessary for one of the main advantages. It is the only format of flash memory where the controller is actually onboard, making it more universally compatible and capable of increased performance by unloading the processing burden from slower devices that it may interface with. The thickness of the cards can also be considered a bonus for two other reasons. There is plenty of space inside for large capacity high density memory modules, and the longevity of the device may be increased since they are more rugged than many other form factors. Microdrives are a separate type of compact storage device first developed by IBM, but they share the same interface and general dimensions as a Type 2 Compact Flash card (Microdrives actually have tiny spinning discs in them – they are not solid state flash memory like Compact Flash). Computer Geeks sells a 2.2 GB Microdrive by MagicStor.
Smart Media was first developed by Toshiba, and the technical name for it is actually Solid-State Floppy-Disk Card (or SSFDC for short). Just as Compact Flash has a group backing it, Smart Media is promoted by the SSFDC Forum. All Smart Media is 37 mm wide by 45 mm long by about 0.75 mm thick, with a notch found in one corner, and exposed “golden” contacts on the back side. At less than 1mm thick, Smart Media is easily the thinnest of the flash memory formats. The maximum capacity one can expect to find for Smart Media is a mere 128 MB, making it a less than appealing solution for modern mass storage. Smart Media’s popularity has been on the decline for years as more powerful technologies have emerged to replace it. Computer Geeks stocks 128 MB and 64MB Smart Media cards as well as a couple of adapters that let you use a Smart Media card in a Compact Flash or PCMCIA (notebook) slot. The extremely low profile is in part achieved by the lack of an onboard controller, and by the fact that Smart Media is basically just memory

modules embedded in a plastic card. The controlling is conducted by the device using the memory, which is how all flash memory but Compact Flash operate anyway. Early Smart Media cards operated on 5V, but the current standard uses 3.3V. Older 5V cards can not be used in 3.3V Smart Media devices, so it is important to know the difference between them. Holding a Smart Media card so the exposed electrical contacts are facing you and positioned at the top of the card, if the notch is on the left it operates on 5V, if the notch is on the right it operates on 3.3V. This notch also prevents one type of card from being fully inserted into a device that is not designed to accept it.
The xD (eXtreme Digital) format was launched by Fujifilm and Olympus in 2002, and is promoted by the group at the official xD-Picture Card website. With a complete name of xD-Picture Card, this format was intended solely for use with digital cameras, although it did find applications elsewhere. Fujifilm and Olympus were two of the biggest supporters of Smart Media, and the launch of xD was a pretty good sign that the future of Smart Media was limited. Each xD card measures a mere 20mm by 25mm by 1.7mm, making them smaller in overall size than even SD and MMC cards. The maximum capacity of xD cards is expected to be 8 GB, but typical cards can be expected up to 1 GB in size. The read speeds of xD cards is up to 5 MB/s, while write speeds can be up to 3 MB/s, making them fast, but not the fastest. xD cards also operate on 3.3V, and are promoted not only for their minimal size, but for their low power consumption. This 128MB Olympus model is an example of a typical xD card.
Memory Stick flash memory was first launched back in 1998, and although it has the support of many manufacturers, it seems to be most prominently used in Sony brand devices, including digital audio devices, cameras and even televisions. Memory Stick is promoted by the group at the official Memory Stick website, which has a good deal of information about the media and applications for it. Memory Stick flash memory looks a bit like a stick of gum, but slightly smaller, measuring about 50 mm by 21.5 mm by 2.8 mm. Current models can be expected with capacities of up to 2 GB, and Memory Sticks with capacities of 4 GB to 8 GB may be available soon. According to the Memory Stick website, maximum (theoretical) data transfer rates of

up to 160 Mbps can be expected, although real world results will most definitely be lower. Expect a memory Stick to actually provide read speeds of up to 2.45 MB/s, and write speeds of up to 1.5 MB/s. Memory Sticks come in four flavors (so to speak) the original Memory Stick, Memory Stick PRO and Duo versions of each. Memory Stick PRO offers faster speeds and larger capacities over the original Memory Stick. The Duo modules are smaller and actually use an adapter to fit into Memory Stick slots. Note that not all devices that take Memory Sticks can use Memory Stick PRO modules – be sure to check your manual. This 128MB Lexar model is an example of a typical Memory Stick card3.

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