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, game consoles, cell phones, and 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.
Data table of selected memory card formats
NameAcronymForm factorDRM PC Card PCMCIA 85.6 × 54 × 3.3 mm None CompactFlash I CF-I 43 × 36 × 3.3 mm None CompactFlash II CF-II 43 × 36 × 5.5 mm None SmartMedia SM / SMC 45 × 37 × 0.76 mm None Memory Stick MS 50.0 × 21.5 × 2.8 mm MagicGate Memory Stick Duo MSD 31.0 × 20.0 × 1.6 mm MagicGate Memory Stick PRO Duo MSPD 31.0 × 20.0 × 1.6 mm MagicGate Memory Stick PRO-HG Duo MSPDX 31.0 × 20.0 × 1.6 mm MagicGate Memory Stick Micro M2 M2 15.0 × 12.5 × 1.2 mm MagicGate Multimedia Card MMC 32 × 24 × 1.5 mm None Reduced Size Multimedia Card RS-MMC 16 × 24 × 1.5 mm None MMCmicro Card MMCmicro 12 × 14 × 1.1 mm None Secure Digital card SD 32 × 24 × 2.1 mm CPRM SxS SxS Universal Flash Storage UFS miniSD card miniSD 21.5 × 20 × 1.4 mm CPRM microSD card microSD 11 × 15 × 0.7 mm CPRM xD-Picture Card xD 20 × 25 × 1.7 mm None Intelligent Stick iStick 24 x 18 x 2.8 mm None Serial Flash Module SFM 45 x 15 mm None µ card µcard 32 x 24 x 1 mm Unknown NT Card NT NT+ 44 x 24 x 2.5 mm None Since many EEPROM devices only allow a limited number of write cycles, some of these cards incorporate wear levelling algorithms to spread the wear and to avoid wearing out specific places which are often written to.
[size=67%][edit]Overview of all memory card types
Main article: Comparison of memory cards
[size=94%]  [size=94%] 
Miniaturization is evident in memory card creation; over time, the physical sizes of the memory cards grow smaller while their respective logical sizes grow larger. The memory cards listed from left to right are: Compact flash (32 MB), SD (128 MB), miniSD (1.0 GB), and microSD (2.0 GB).
- PCMCIA ATA Type I Flash Memory Card (PC Card ATA Type I) (max 8 GB (8 GiB) flash as of 2005)
- PCMCIA Linear Flash Cards, SRAM cards, etc.
- PCMCIA Type II, Type III cards
- CompactFlash Card (Type I), CompactFlash High-Speed (max 32 GB as of 2008)
- CompactFlash Type II, CF+(CF2.0), CF3.0
- Microdrive (max 6 GB as of 2005)
- MiniCard (Miniature Card) (max 64 MB (64 MiB))
- SmartMedia Card (SSFDC) (max 128 MB) (3.3 V,5 V)
- xD-Picture Card, xD-Picture Card Type M
- Memory Stick, MagicGate Memory Stick (max 128 MB); Memory Stick Select, MagicGate Memory Stick Select ("Select" means: 2x128 MB with A/B switch)
- SecureMMC
- Secure Digital (SD Card), Secure Digital High-Speed, Secure Digital Plus/Xtra/etc (SD with USB connector)
- miniSD Card
- microSD Card (aka Transflash, T-Flash)
- SDHC
- MU-Flash (Mu-Card) (Mu-Card Alliance of OMIA)
- C-Flash
- SIM card (Subscriber Identity Module)
- Smart card (ISO 7810 Card Standard , ISO 7816 Card Standard, etc.)
- UFC (USB FlashCard) [1] (uses USB)
- FISH Universal Transportable Memory Card Standard (uses USB)
- Disk memory cards:
- Intelligent Stick (iStick, a USB-based flash memory card with MMS)
- SxS (S-by-S) memory card, a new memory card specification developed by Sandisk and Sony. SxS complies to the ExpressCard industry standard. [2]
- Nexflash Winbond Serial Flash Moduel (SFM) cards, size range 1 mb, 2 mb and 4 mb.
[size=67%][edit]Memory cards in video game consoles
Many video game consoles have used proprietary solid-state memory cards to store data. In recent years read-only optical discs have replaced these memory cards in most current home console systems. However most portable gaming systems still rely on custom memory cartridges, due to their low power consumption, smaller physical size and reduced mechanical complexity.
The sizes in parenthesis are those of the official, first-party memory cards.
[size=67%][edit]See also
[size=67%][edit]External links
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发表于 2009-1-14 05:02:31
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