 | Readers Writers
Flash memory card readers allow you to read from or write to your flash card directly via your PC. For example, instead of connecting your digital camera to your PC by a cable you can take the card out of the camera and insert into the reader and view the pictures on your computer this way.
This can be quicker, and easier as it does not require you to install any of the software that came with your digital camera onto your computer.
Some readers accept one type of card and others accept all, or mostly all of them.
Some of the larger readers have a USB connecting cable and used as a desktop item, others look like a USB pen drive that can accept one or a small number of types of memory card directly into their side.
Some are PCMCIA cards for laptops, that can stay permanently installed within the laptop. This then allows the laptop to read a selection of cars like Compact Flash or Secure Digital for example. |
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 | Compact Flash Cards.
CompactFlash (CF) was originally developed as a type of data storage device used in portable electronic devices. For storage, CompactFlash typically uses flash memory in a standardized enclosure. This form was first specified and produced by SanDisk in 1994. The physical format is now used for a variety of devices.
There are two main subdivisions of CF cards, Type I and the thicker Type II (CF2) cards. The CF Type II slot is used by Microdrives and some other devices. There are four main speeds of cards including the original CF, CF High Speed (using CF+/CF2.0), a faster CF 3.0 standard and a yet faster CF 4.0 standard that is being adopted as of 2007. |
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 | Memory Sticks
Memory Stick was launched by Sony in October 1998 and is also used in general to describe the whole family of Memory Sticks. This family includes the Memory Stick PRO, a revision that allows greater maximum storage capacity and faster file transfer speeds; In December 2006 Sony added the Memory Stick PRO-HG, a high speed variant of the PRO, to be used for high definition still and video cameras.
The original Memory Sticks were approximately the size and thickness of a stick of chewing gum, and came in sizes from 4 MB up to and including 128 MB.
The Memory Stick PRO was introduced in 2003 as a joint effort between Sony and SanDisk and would be the longer-lasting solution to the space problem. Most devices that use the original Memory Stick form factor support both the original Memory Sticks and the PRO Sticks; some readers that were not compatible could be upgraded to Memory Stick PRO support via a Flash ROM update. Memory Stick PROs have a marginally higher transfer speed and a maximum theoretical capacity of 32 GB. High Speed Memory Stick PROs are available, and newer devices support this High Speed mode, allowing for faster file transfers. All Memory Stick PROs larger than 1 GB support this High Speed mode, and High Speed Memory Stick Pros are backwards-compatible with devices that don't support the High Speed mode.
The MagicGate standard for Memory Sticks is an encryption system allowing music to be downloaded to the card and played back by an authorized device, but not shared. Certain standard Memory Stick and all PRO sticks are MagicGate compatible.
The Memory Stick Duo is slightly smaller than the competing Secure Digital format and roughly two thirds the length of the standard form factor. It was developed in response to Sony's need for a smaller flash memory card for pocket-sized digital cameras and cell phones. Memory Stick Duos are available in all the same variants as their larger cousins: normal ones limited to 128 MB, higher capacity PRO Sticks (called Memory Stick PRO Duo in the Duo form factor), with and without High Speed mode, and with and without MagicGate support. There's also a simple adapter (often sold along with the Memory Stick Duo) which allows a Duo to be used in any device that can accept its larger cousins.
The normal and PRO versions of Memory Stick Duo are also used with the PSP, which when inserted into the Memory Stick Slot show saved game data, music, pictures and videos.
In a joint venture with SanDisk, Sony released a new Memory Stick format on February 6, 2006. The Memory Stick Micro (M2) measures 15mm × 12.5mm × 1.2mm; roughly one quarter the size of the Duo, around the size of a fingernail, with 256 MB, 512 MB, 1 GB and 2 GB capacities, with a theoretical limit of 32 GB. Maximum transfer speed is 160 Mbit/s. It comes with an adapter, much like the Duo Sticks, to ensure compatibility with current PRO devices. |
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 | Multi-Media Cards (MMC)
The MultiMediaCard (MMC) is a flash memory card standard. Unveiled in 1997 by Siemens AG and SanDisk, it is based on Toshiba's NAND-based flash memory, and is therefore much smaller than earlier systems based on Intel NOR-based memory such as CompactFlash. MMC is about the size of a postage stamp: 24 mm x 32 mm x 1.4 mm. MMC originally used a 1-bit serial interface, but newer versions of the specification allow transfers of 4 or sometimes even 8 bits at a time. They have been more or less superseded by Secure Digital cards (SD card), but still see significant use because MMCs can be used in most devices which support SD cards and they are cheaper than SD cards.
Typically, an MMC is used as storage media for a portable device, in a form that can easily be removed for access by a PC. For example, a digital camera would use an MMC for storing image files. With an MMC reader (typically a small box that connects via USB or some other serial connection, although some can be found integrated into the computer itself), a user could copy the pictures taken with the digital camera off to his or her computer. Modern computers, both laptops and desktops, often have SD slots, which can additionally read MMCs if the operating system drivers support them.
MMCs are currently available in sizes up to and including 4 GB with 8 GB models announced but not yet available. They are used in almost every context in which memory cards are used, like cellular phones, digital audio players, digital cameras and PDAs. Since the introduction of Secure Digital card and SDIO (Secure Digital Input/Output) slot few companies build MMC slots into their devices (an exception is some mobile devices like the Nokia 9300 communicator, where the smaller size of the MMC is a benefit), but the slightly thinner, pin-compatible MMCs can be used in almost any device that supports SD cards if the software/firmware on the devices support them. |
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 | RS and Mobile MMC
MMCs also come in a smaller form factor, of about half the size: 24 mm × 18 mm × 1.5 mm. This alternate form factor is known as Reduced-Size MultiMediaCard, or RS-MMC, and was introduced in 2004. RS-MMCs are simply smaller MMCs; by using a simple mechanical adapter to elongate the card, an RS-MMC can be used in any MMC (or SD) slot. RS-MMCs are currently available in sizes up to and including 2 GB with 4 GB models announced but unavailable.
The only significant hardware licensors of RS-MMCs were Nokia and Siemens, who used to use RS-MMC in their Series 60 Symbian smartphones, the Nokia 770 Internet Tablet (Nokia), and generations 65 and 75 (Siemens).
One of the first substantial changes in MMC was the introduction of dual-voltage cards that support operations at 1.8 V in addition to 3.3 V. Running at lower voltages reduces the card's power consumption, which is important in mobile devices.
The version 4.x of the MMC standard, introduced in 2005, brought in two very significant changes to compete against SD cards. These were support for running at higher speeds (26MHz, 52MHz) than the original MMC (20MHz) or SD (25MHz, 50MHz) and 4 or 8 bit wide data buses.
Version 4.x full-size cards and reduced-size cards can be marketed as MMCplus and MMCmobile respectively.
Version 4.x cards are fully backward compatible with existing readers but require updated hardware/software to use their new capabilities; even though the 4 bit wide bus and high-speed modes of operation are deliberately electrically compatible with SD, the initialization protocol is different, so firmware/software updates are required to allow these features to be enabled when the card is used in an SD reader. |
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 | Micro MMC
MMCmicro is a micro-size version of MMC with dimensions of 14 mm × 12 mm × 1.1 mm, it is even smaller and thinner than RS-MMC. Like MMCmobile, MMCmicro supports dual voltage, is backward compatible with MMC, and can be used in full-size MMC and SD slots with a mechanical adapter. MMCmicro cards support the high-speed and 4 bit bus features of the 4.x spec, but not the 8 bit bus, due to the absence of the extra pins.
MMCmicro cards appears very similar to microSD but the two formats are not physically compatible and have irreconcilable pinouts. |
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 | Secure Digital Cards
Secure Digital (SD) is a flash (non-volatile) memory card format developed by Matsushita, SanDisk and Toshiba for use in portable devices, including digital cameras, handheld computers, PDAs and GPS units. The format has proven to be very popular. However, users should be careful of compatibility issues between older devices and the newer 2GB and larger cards and the SDHC format. It has a physical profile of 24 mm × 32 mm × 2.1 mm.
The "Secure" in Secure Digital comes from the card's origin. To create the SD card, Toshiba added encryption hardware to the already-existent MMC, to calm music industry concerns that MMCs would allow for easy piracy of music. (A similar scheme is the MagicGate standard used in Memory Sticks.)
SD cards are based on the older MultiMediaCard (MMC) format, but have a number of differences:
The SD card is asymmetrically shaped so that it cannot be inserted upside down, whereas an MMC will go in most of the way but not make contact if inverted.
Most SD cards are physically thicker than MMCs. SD cards generally measure 32 mm × 24 mm × 2.1 mm, but can be as thin as 1.4 mm, just like MMCs.
The contacts are recessed beneath the surface of the card (like Memory Stick cards), protecting the contacts from contact with the fingers.
SD cards typically have higher data transfer rates, but this is always changing, particularly in light of recent improvements to the MMC standard.
Digital rights management features are available but are seldom used.
Devices with SD slots can use the thinner MMCs, but the standard SD cards will not fit into the thinner MMC slots. SD cards can be used in CompactFlash or PC card slots with an adapter. miniSD and microSD cards can be used directly in SD slots with a physical interface adapter. There are some SD cards with a USB connector for dual-purpose use, and there are card readers which allow SD cards to be accessed via many connectivity ports such as USB, FireWire, and the common parallel port. SD cards can also be accessed via a floppy disk drive with a FlashPath adapter.
When looking at the card from the top there is one required notch on the right side (the side with the diagonal notched corner). On the left side there is usually a tab. This is the write-protect tab. The MMC has neither notch. The tab / notch works the same way as the notches on compact audio cassettes and videotape cassette tapes or floppy disks.
When this write-protect tab is in the down position (away from the end that is inserted) then it is write protected and read-only. When the tab is in the up position it is write enabled. |
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 | Mini SD Cards
The mini SD Card is a removable and portable memory device intended for use in cell phones, digital cameras, MP3 players and many other gadgets.
Announced for the first time by SanDisk Corporation at CeBIT 2003, the miniSD joined the Memory Stick Duo and xD-Picture Card at this small form factor.
The miniSD card was adopted in 2003 by the SD Association as an ultra-small form factor extension to the SD card standard. While the new cards were designed especially for use in mobile phones, they are usually packaged with a miniSD adapter which enables compatibility with all devices equipped with a standard SD Memory Card slot.
MiniSD cards are made by several different manufacturers and come in different brand names. Their compatibility is universal.
MiniSD cards are often confused with MicroSD cards which are a different specification and are not compatible. |
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 | Micro SD (Transflash)
microSD is a small, removable flash memory card format originally based on the SanDisk TransFlash card format. It is primarily used in mobile phones, but because of its size and increasing capacity it is also being used in handheld GPS devices, portable audio players, flashcards for Nintendo DS, and expandable USB flash memory drives.
At 15 mm × 11 mm × 0.7 mm-about the size of a fingernail-it is currently the smallest memory card format commercially available. It is about one quarter of the size of a standard SD card but can be inserted into an adapter which allows the card to be used in devices with an SD card slot.
TransFlash and microSD cards are essentially the same, and each can be used in devices made for the other type. There is one exception, which is that unlike TransFlash, microSD devices have the capability to support NFC (Near Field Communication). |
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 | USB Memory (Pen Drives)
USB flash drives are NAND-type flash memory data storage devices integrated with a USB (universal serial bus) interface. They are typically small, lightweight, removable and rewritable.
USB flash drives offer potential advantages over other portable storage devices, particularly the floppy disk. They are more compact, generally faster, hold more data, and are more reliable (due to both their lack of moving parts, and their more durable design) than floppy disks. These types of drives use the USB mass storage standard, supported natively by modern operating systems such as Linux, Mac OS X, Unix, and Windows.
To access the data stored in a flash drive, the drive must be connected to a computer, either by plugging it into a USB host controller built into the computer, or into a USB hub. Flash drives are active only when plugged into a USB connection and draw all necessary power from the supply provided by that connection. However, some flash drives, especially high-speed drives utilizing the USB 2.0 standard, may require more power than the limited amount provided by a bus-powered USB hub, such as those built into some computer keyboards or monitors. These drives will not work unless plugged directly into a host controller (i.e., the ports found on the computer itself) or a self-powered hub. |
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 | XD Memory Cards
The xD-Picture Card is a type of flash memory card, used mainly in digital cameras. xD originally stood for extreme Digital. The cards were developed by Olympus and Fujifilm and introduced into the market in July 2002. Toshiba Corporation and Samsung Electronics manufacture the cards for Olympus and Fujifilm. xD cards are now sold under other brands, including Kodak, SanDisk, and Lexar.
xD cards are used in Olympus and Fujifilm digital cameras and Olympus digital voice recorders; Fujifilm also made an MP3 player that used the cards. xD cards have dimensions of 20 mm × 25 mm × 1.78 mm, and each weighs 2.8 grams.
The original xD cards were available in 16 MB to 512 MB capacities. The Type M card, released in February 2005 uses Multi Level Cell (MLC) architecture to achieve a theoretical storage capacity of up to 8 GB. As of August 2006, Type M cards are available in sizes from 256 MB to 2 GB. However, the Type M suffers slower read-write speeds than the original cards.
The Type H card, first released in November 2005 offers higher data rates than Type M cards (theoretically as much as 3 times faster) and are required in newer models to capture video at high rate (640x480x30).
Due to changes in the cards' storage architecture, newer Type M and H cards may suffer compatibility issues with some older cameras (especially video recording). Compatibility lists are available for Olympus and Fujifilm at http://www.olympusamerica.com/cpg_section/cpg_xdcompatibility.asp.
The newer cards are also incompatible with some card readers. |
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