MEMORY CARDS
A memory card or flash memory card
is a solid-state electronic flash memory data storage device used with digital cameras, handheld and Mobile computers, telephones, music players, video game consoles, and other electronics. They offer high re-record-ability, power-free storage, small form factor, and rugged environmental specifications. There are also non-solid-state memory cards that do not use flash memory, and there are different types of flash memory.There are many different types of memory cards and jobs they are used for.
Some common places include in digital cameras, in game consoles, in cell phones, and in industrial applications. PC card (PCMCIA) were among first commercial memory card formats (type I cards) to come out in the 1990s, but are now only mainly used in industrial applications and for I/O jobs (using types I/II/III), as a connection standard for devices (such as a modem). Also in 1990s, a number of memory card formats smaller than PC Card came out, including CompactFlash, SmartMedia, and Miniature Card. In other areas, tiny embedded memory cards (SID) were used in cell phones, game consoles started using proprietary memory card formats, and devices like PDAs and digital music players started using removable memory cards.
From the late 1990s into the early 2000s a host of new formats appeared, including SD/MMC, Memory Stick, xD-Picture Card, and a number of variants and smaller cards. The desire for ultra-small cards for cell-phones, PDAs, and compact digital cameras drove a trend toward smaller cards that left the previous generation of “compact” cards looking big. In digital cameras SmartMedia and CompactFlash had been very successful, in 2001 SM alone captured 50% of the digital camera market and CF had a strangle hold on professional digital cameras.
By 2005 however, SD/MMC had nearly taken over SmartMedia’s spot, though not to the same level and with stiff competition coming from Memory Stick variants, xD, as well as CompactFlash. In industrial fields, even the venerable PC card (PCMCIA) memory cards still manage to maintain a niche, while in cell-phones and PDAs, the memory card market is highly fragmented.Nowadays, most new PCs have built-in slots for a variety of memory cards; Memory Stick,
CompactFlash,
SD, etc. Some digital gadgets support more than one memory card to ensure compatibility.
1.Secure Digital (SD)
is a flash (non-volatile) memory card format developed by Matsushita, SanDisk, and Toshiba for use in portable devices. Today it is widely used in digital cameras, handheld computers, PDAs, mobile phones, GPS receivers, and video game consoles. Standard SD card capacities range from 8 MB to 4 GB and for high capacity SDHC cards 8 MB to 32 GB as of 2008.The format has proven to be very popular.
However, a change in the format, while allowing capacities greater than 4 GB (SDHC), has created compatibility issues with older devices which cannot read the new format. Since SDHC format cards have the same physical shape and form factor as the older format, this has caused considerable confusion for consumers.[1][2] SDHC cards require an SDHC capable device firmware, generally not found with older devices.
Speeds
There are different speed grades available which are measured with the same system as CD-ROMs, in multiples of 150 kB/s (1x = 150 kB/s). Basic cards transfer data up to six times (6x) the data rate of the standard CD-ROM speed (900 kB/s vs. 150 kB/s). High-speed cards are made with higher data transfer rates like 66x (10 MB/s), and high-end cards have speeds of 150x or higher. Note that maximum read speed and maximum write speed may be different, with maximum write speed typically lower than maximum read speed. Some digital cameras require high-speed cards (write speed) to record video smoothly or capture multiple still photographs in rapid succession. The SD card specification 1.01 allows for a maximum speed of 66x. Higher speeds of up to 150x are defined by specification 1.1.The following table lists some common ratings and their respective maximum transfer rates.
| Rating |
Speed (MB/s) |
| 6x |
0.9 |
| 32x |
4.8 |
| 40x |
6.0 |
| 66x |
10.0 |
| 133x |
20.0 |
| 150x |
22.5 |
2.Compact Flash (CF)
is a mass storage device format used in portable electronic devices. For storage, CompactFlash typically uses flash memory in a standardized enclosure.The format was first specified and produced by SanDisk in 1994.[1] The physical format is now used for a variety of devices.CompactFlash became a popular storage medium for digital cameras. In recent years it has been widely replaced by smaller Secure Digital cards on the consumer end, but it is still a preferred format for D-SLR cameras, for its superior capacity and reliability.
Type I and Type II
The only difference between the two types is that the Type II devices are 5 mm thick while Type I devices are 3.3 mm thick.[8] The vast majority of all Type II devices are Microdrives and other miniature hard drives. Flash based Type II devices are rare but a few examples do exist.[9][10] Even the largest capacity cards commonly available are Type I cards. Most card readers will read both formats, with the exception of some early CF based cameras or poorer quality USB card readers where the slot is too small.
3.The xD-Picture Card
is a type of flash memory card, used mainly in digital cameras. xD originally stood for extreme Digital.[1] The cards were developed by Olympus and Fujifilm, and introduced into the market in July 2002. Toshiba Corporation and Samsung Electronics manufacture the cards forOlympus and Fujifilm. xD cards are now sold under other brands, including Kodak, SanDisk, PNY, and Lexar, but are not branded with the respective companies’ logos, except for Kodak.
xD cards are used in Olympus and Fujifilm digital cameras and Olympus digital voice recorders; Fujifilm also made an MP3 player (xD-MP3) that used the cards. As of 2008, xD cards are available in capacities of 16 MB (16 MiB), 32 MB, 64 MB, 128 MB, 256 MB, 512 MB, 1 GB (1 GiB), and 2 GB.
Submitted by Vincent, II MA, July, 2008.
Share This