MMC card
MMC (Multimedia Card) card was introduced by Siemens and SanDisk, who started CF, in 1997. 1998 65438+ 10 Fourteen companies jointly established the MMC Association (MMCA), with more than 84 members at present. The development goal of MMC is mainly aimed at digital images, music, mobile phones, PDA, e-books, toys and other products. It is claimed to be the smallest flash memory card in the world at present, with a size of only 32.32 mm x 24 mm x1.4 mm. It is very light, only 1.5 g.. MMC also puts the storage unit on the card and the controller together, so that MMC can ensure compatibility and flexibility.
MMC memory cards can be divided into two working modes: MMC and SPI. MMC mode is the standard default mode and has all the characteristics of MMC. SPI mode is the second mode of MMC memory card and a subset of MMC protocol, which is mainly used in systems that only need a few cards (usually 1) and have low data transmission rate (compared with MMC protocol). This mode can minimize the design cost, but the performance is not as good as MMC.
MMC is designed as a low-cost data platform and communication medium, and the interface design is very simple: only 7 pins! The interface cost is less than $0.50, in contrast, the interface cost of SmartMedia and memory stick is higher than $65,438 +0. On the interface, the power supply is 3 pins, and data operation only needs 3-pin serial bus (SPI mode plus 1 pin chip selection).
The working voltage of MMC is 2.7 volts to 3.6 volts, and the write/read current is only 27mA and 23mA, so the power consumption is very low. Its reading and writing methods include streaming, multi-block and single block. The minimum data transmission is in blocks, and the default block size is 5 12 bytes.
Compact flash lamp
Compact flash memory was first introduced by SanDisk in 1994. CF card has PCMCIA-ATA function and is compatible with it; The weight of CF card is only 14g, which is only the size of a cardboard match (43mm x 36m x m3.3mm). It is a solid product, that is, it works without moving parts. CF card adopts flash technology, which is a stable storage solution and does not need batteries to maintain the data stored in it. For the stored data, CF card is safer and more protective than the traditional disk drive. The reliability is 5 to 10 times higher than that of traditional disk drives and type III PC cards, and the power consumption of CF cards is only 5% of that of small disk drives. These excellent conditions make most digital cameras choose CF card as the preferred storage medium.
CF card supports 3.3 volts and 5 volts at the same time, and any CF card can work under these two voltages, which makes it widely used. The compatibility of CF memory card also lies in that it combines the flash memory module with the controller, which can make the external devices using CF cards simpler, and can read and write different CF cards through a single mechanism without worrying about compatibility problems, especially when upgrading CF cards, which can ensure the compatibility of old devices.
CF card has quite a lot of platform support, including DOS, Windows 3.x, Windows 95, Windows 98, Windows CE, OS/2, Apple System 7, Linux and many UNIX.
As a worldwide storage industry standard, CF card ensures the compatibility of CF products and the backward compatibility of CF cards. With the more and more extensive application of CF card, manufacturers actively improve the technology of CF card and promote the launch of a new generation of advanced mobile devices with small size, light weight and low energy consumption, thus improving work efficiency. CFA is headquartered in Palo Alto, Canada, and members have the right to obtain CF cards, CF trademarks and CF technical details free of charge. CFA has more than 65,438+020 members, including 3COM, Canon, Kodak, Hewlett-Packard, Hitachi, IBM, Panasonic, Motorola, NEC, SanDisk, Seiko (Epson) and Socket Communications. Moreover, major digital camera manufacturers have set up special institutions to develop CF products.
CF card has the following disadvantages:
1.) has limited capacity. Although the capacity has increased exponentially, it still can't keep up with the pixel development of digital cameras. Under the common JPEG compression format, the capacity is acceptable, but the professional TIFF(RAW) format file still can't hold several image data.
2.) Large volume. Compared with other kinds of memory cards, the size of CF card is slightly larger, which also limits the size of digital cameras using CF card, so most of the popular ultra-thin digital cameras now give up CF card and switch to smaller SD card.
3.) Performance limitations. The working temperature of CF card is generally 0-40 degrees Celsius. Therefore, in the environment below 0 degrees, digital cameras have basically become "waste". Although the cold resistance of the current military CF card has reached -40 degrees Celsius, it is still unknown when the price can be reduced to the level that ordinary people can bear.
At present, the capacity of the world's largest CF card has reached 640M. Generally, there are 8MB, 16MB, 32MB, 64MB, 128MB, 256MB, etc. (1more than 28mb is type Ⅱ).
Sd card
SD card (Secure Digital Memory Card) is a new generation storage device based on semiconductor flash memory. The SD card was jointly developed by Panasonic, Toshiba and SanDisk Company of the United States in August 1999. The stamp-sized SD memory card weighs only 2 grams, but it has high storage capacity, fast data transmission speed, great mobility and good security.
In the volume of 24mm×32mm×2. 1mm, the SD card combines SanDisk flash memory card control with MLC (multi-level unit) technology and Toshiba's NAND technologies 0. 16u and 0. 13u, and is connected with a special driver through a 9-pin interface, so there is no need for additional power supply to keep the information stored on it. Moreover, it is an integrated solid medium without any moving parts, so there is no need to worry about the damage of mechanical movement.
The data transmission and physical specifications of SD card are developed from MMC, and the size is similar to MMC, with the size of 32 mm x 24 mm x 2. 1 mm ... The length and width are the same as MMC, but the thickness is increased by 0.7 mm to adapt to larger storage units. The SD card and MMC card remain upward compatible, that is, new SD devices can access MMC, and the compatibility depends on the application software, but the SD card cannot be accessed by MMC devices. (The shape of SD card adopts the track design with the same thickness as MMC, so that SD equipment can be applied to MMC. )
SD interface not only keeps 7 pins of MMC, but also adds 2 pins on both sides as data lines. NAND flash memory is adopted, which is basically the same as that of SmartMedia, and the average data transmission rate can reach 2MB/s. ..
The structure of SD card can ensure the security of digital file transmission, and it is also easy to reformat, so it has a wide range of applications, and multimedia files such as music, movies and news can be conveniently stored in SD card. So many digital cameras have started to support SD cards.
Many memory card companies have developed SD cards. Panasonic is the main manufacturer of SD cards at present. In 2000, the capacity of SD card was divided into four different grades from 8MB to 64MB to meet the needs of different occasions. The data transmission rate was 2 MB/s. By the end of 5438+0 in 2006, the capacity of a single card had reached 5 12MB, and the data transmission rate was also increased to10 MB/s. Panasonic plans to launch the capacity of/kloc.
memory stick
Memory stick, developed by Sony, has a size of 50mm x 2 1.5mm x 2.8mm and weighs 4 grams. It uses a delicate and striking blue case (the new MG is white) and has a write protection switch.
Unlike many flash memory cards, the specifications of memory sticks are not open and there is no standardization organization. Adopt Sony's own appearance, protocol, physical format and copyright protection technology. To use its specifications, it is necessary to negotiate and sign a license with Sony. The memory stick also includes a controller, a 10 pin interface and a serial data bus. The maximum frequency is 20MHz, the voltage is 2.7V to 3.6V, and the average current is 45mA. It can be seen that this specification is quite similar to MMC that appeared at about the same time.
After the introduction of memory stick, a series of companies such as Samsung, Aihua, Sanyo, Casio, Fujitsu, Olympus and Sharp all expressed their support for this format. Sony is still seeking the recognition of memory chip format in the home appliance industry and IT industry. Sony will introduce more products representing the latest development of memory sticks to the domestic market in the future.
The disadvantage of memory stick is that it can only be used on Sony digital camera, and its capacity is not large enough.
Xd picture card
XD card, called XD-PICTURE CARD, is a small memory card specially designed for digital cameras jointly launched by Fuji and Olympus. With single-sided 18 pin interface, it is the smallest memory card at present. . XD is taken from "limit number", which means "limit number". XD card is a relatively new flash memory card. Compared with other flash cards, it has many advantages. The size of the pocket is 20mm×25mm× 1.7mm, and the total volume is only 0.85cm, about 2g. It is the lightest and smallest digital flash memory card in the world. Excellent compatibility, equipped with various card readers, easy to connect personal computers. The storage capacity is huge, and the theoretical maximum capacity of XD card can reach 8GB, which has a lot of room for expansion. At present, XD cards seen in the market have different capacity specifications such as 16MB, 32MB, 64MB, 128MB, 256MB, etc.
md/microdrive
Microdrive was originally a super mini hard disk drive developed by IBM. Its initial capacity was 340MB and 5 12MB, and now the product capacity is 1GB, 2GB and 4GB. Compared with the past, the current micro hard disk reduces the rotational speed (from 4,200 rpm to 3,600 rpm), thus reducing the power consumption, but enhancing the stability.
Most devices that can use CF cards can directly use Microdrive, such as digital cameras, palmtop computers, MP3 players and so on. Laptop computer is transmitted through PCMCIA adapter. Because Microdrive is slightly thicker than CF card, the device needs to meet CFII standard. Large-capacity Microdrive(4GB) requires devices to support FAT32 file system. Compared with CF, Microdrive's biggest advantage is its lower price per storage capacity. Microdrive adopts hard disk technology, which has the characteristics of low cost and high capacity and can replace solid-state storage technology.
At present, Kodak, Sanyo, Fujitsu, Epson and other companies have begun to design digital camera products that support Microdrive. It is foreseeable in the future that products including digital cameras or other computer peripherals will gradually join the ranks of supporting Microdrive.
Matters needing attention when using:
First of all, be careful not to get close to magnetic substances or strong magnetic fields; Storage and use in the environment above -40℃ or below 65℃; Beware of being soaked in water or other liquids (if you accidentally get water stains, dry them as soon as possible); Prevent the surface from being squeezed by heavy objects or external forces; Be careful not to fall to the ground from a height; When not used for a long time, it should be put back in the plastic packaging box.
When dealing with micro hard disks, you should also pay attention. The correct way is to hold both sides of the micro-hard disk, not forcibly hold both sides of the hard disk, and pay attention to handling it gently; Before holding the micro hard disk with your hands, you should pay attention to discharging the static electricity on other metal objects to avoid its influence, especially in dry autumn and winter.
In addition, with the increasing capacity of micro hard disk, we must pay attention to whether the product (digital camera) provides FAT32 file system support when purchasing 4GB micro hard disk. Most existing digital cameras use FAT 16 on the memory card file system, which can only recognize the maximum capacity of 2GB. In order to use a 4GB micro hard disk, the product must support FAT32.