Flash Memory Cards – CF, SM, MMC, SD, MemoryStick and xD
The use of mobile devices grows every day and this is making the memory cards are increasingly used. These devices have a certain storage capacity of data and are used for storing and transporting files from cameras digital, audio players, smartphones, etc. This article will quickly the types of card more known and the technology used in them, the Flash memory. With this, you will learn about the main characteristics of each pattern and will know how to recognize what is the best option for your needs.
The memory cards are, essentially, based on Flash technology, a type of memory EPROM (Electrically-Erasable Programmable Read Only Memory) developed by Toshiba in the 1980s. The Flash chips are slightly similar to the memory RAM (Random Access Memory) used in computers, but its properties make data will not be lost when there is no supply of energy (for example, when the battery is finished, or the device is off). Making a comparison in gross, the concept of recording data in a Flash chip is similar the process of data recording media CD-RW: according to the intensity of energy applied (in the case of CD-RW, laser), there is a recording or erasing information.
The Flash memory consumes little power, occupies very little physical space (so it is ideal for portable devices) and is known to be resistant, or durable enough. The big problem Flash memory is its high price. Fortunately, the popularization of this technology is making that their costs decrease with the passage of time.
The Flash technology makes use of chips of the solid state (solid state) and that does not have moving parts, which avoids the problems of mechanical cause. By joining this factor the protection features, such as ECC (Error Correction Code), the Flash memory shows to be quite reliable.
Flash NOR and Flash NAND
There are basically two types of Flash memory: NOR and NAND. Let’s look at each category the following:
NOR: the Flash memory is the NOR (Not OR) allows access to the memory cells in a random fashion,but with high speed. In other words, the NOR enables the access of data in different positions of the memory in a way that quick, without the need of this operation to be sequential. The NOR is generally applied in the BIOS chip, mobile phones and under network adapters special, for example;
NAND: for its time, the Flash memory is NAND (Not AND) also works in high speed, but makes sequential access to the memory cells and treats them in conjunction, this it is, in blocks of cells, instead of accessing them an individual way.
The various types of memory cards
Although they are based on the same technology, we have currently around a dozen types of memory cards. What is the reason for such a quantity? Unlike what happened with other technologies, as the USB and the CD, the manufacturers of memory does not entered into an agreement to work on a single standard card. As a consequence, the market today a variety of types this device. The most common are discussed below.
The memory card CompactFlash (CF) was developed by the company SanDisk in mid-1994, and it ended up being the first type to popularize. This is a card with the following dimensions: 43 mm x 3 mm x 5 mm in type I and 43 mm x 3 mm x 3.3 mm in the type II.
This type of card makes use of Flash memory type NAND, however, was initially developed to work with Flash technology NOR. Despite being the type with the larger cards CompactFlash are used until today, mainly in professional digital cameras and digital camcorders. Although rare, it is possible to find cards with up to 128 GB capacity.
The CompactFlash is maintained by the CompactFlash Association and its construction also it is applied on cards for Wi-Fi (wireless networks), modems, etc.
The memory card SmartMedia (whose original name is Solid State Floppy Disk Card – SSFDC) calls attention soon from the start to be similar with the already retarded floppy disks 3.5-inch. Released by Toshiba in mid-1995, this type card has size of 45 mm x 37 mm x 0.76 mm and its manufacture it is more simple when compared with competing technologies.
This characteristic is due to the fact this type of card does not have circuit-controllers, reducing cost of production. Because of this, the functions of control had to be inserted in the equipment that work with SmartMedia. This represents a disadvantage in the question of the capacity increase,because these devices “know” to work with cards that store more data than programmed into their circuits.
As a result, the SmartMedia card the most common have size up to 128 MB, very little for the current needs. For this reason, are almost in disuse.
Fujifilm, Olympus and Toshiba have been companies that have made use of of this technology. This use occurred almost exclusively on digital cameras.
MultiMedia Card (MMC)
Launched in 1997 through a partnership between SanDisk and Siemens, memory card, MultiMedia Card (MMC) has smaller dimensions in comparison to the standards previously shown: 24 mm x 32 mm x 1.4 mm. The type of Flash used in the MMC is the NAND.
This type of card was initially developed for cell phones and pagers, but it only became significantly well-known after the Palm inserted it in their handhelds (handheld computers). The standard, however, lost space for the cards of type SD. In spite of this, the specifications for the MMC are still being used by the the industry, though on a smaller scale. The default account even with variations, such as the cards MMCmicro, SecureMMC and MMCmobile.
Secure Digital (SD)
Cards Secure Digital (SD) were announced in 1999 and are the result of a partnership between SanDisk, Panasonic and Toshiba. This is a variation of MMC, having including almost the same dimensions: 24 mm x 32 mm x 2.1 mm. Among its differentials in relation to this are: compatibility with security regulations of the Secure Digital Music Initiative (SDMI), which aims to prevent illegal distribution of music; a small catch security that prevents the deletion of data device; and a better performance in data transfer.
SD cards are currently the most popular type of Flash memory, being widely used in mobile phones,digital cameras, game consoles, and other devices portable. Size success is due, in part, to their variations: the cards, miniSD and microSD, that have reduced dimensions, as indicated by their names (20 mm x 21.5 mm x 1.4 mm and 11 mm x 15 mm x 1 mm, respectively). Regardless of the category, the cards SD can be found currently with capabilities quite high, such as 32 or 64 GB.
The card MemoryStick was developed by Sony and is used mainly in cameras and digital camcorders of the company. Although it is smaller than the CompactFlash and the SmartMedia, its size does not it is one of the lowest in: 50 mm x 21.5 mm x 2.8 mm.
The first cards MemoryStick could store only some megabytes. A version known for MemoryStick PROwas released later with capacities ranging from 256 MB to 16 GB and higher speed read and write: 160 Mb/s against To 14.4 Mb/s (write) and 19.6 Mb/s (read) from the first version.
Were released also versions known as MemoryStick Duo and MemoryStick PRO Duo. Because of their smaller size the cards, MemoryStick standard (31 mm x 20 mm x 1.6 mm), the formats Duo are not compatible with older appliances, not to be by the use of adapters.
As if that weren’t enough, there is also a version more recent call MemoryStick Micro (M2), which was launched by the Sony in partnership with SanDisk in 2006. As well as the MiniSD and theMicroSD, MemoryStick Micro is directed to the market of portable devices, such as smartphones, given their dimensions: 15 mm x 12.5 mm x 1.2 mm.
eXtreme Digital (xD-Picture)
The memory card xD-Picture was released in 2002 by Fujifilm in conjunction with Olympus, being almost exclusively applied only in digital cameras of these. Theoretically, the ability stored with this standard, can reach 8 GB. Its dimensions are the following: 20 mm x 25 mm x 1,78 mm.
Seen as a replacement for SmartMedia, xD-Picture also does not has circuits internal drivers, which means that devices more the former are not able to read cards of that type with new storage capabilities. Not to be very popular, the companies involved with this type of card had to develop adapters for the xD-Picture is read in interfaces such as PC-Card (former PCMCIA) and CompactFlash.
Because of the popularization of SD cards, this is a standard practically in disuse.
In addition to digital cameras, mobile phones, players audio and other mobile devices, of course, isnecessary for the computers to be able to read cards memory. For this, conventionally, the use of readers cards compatible with the various formats. These devices are usually connected to the computer via the USB port, but can also be offered built-in desktops.