Flash card is a memory that uses flash technology to store electronic information. Generally, it is used as a storage medium in digital cameras, palmtop computers, MP3 and other small digital products, so it looks like a card, so it is called a flash card. According to different manufacturers and different applications, flash cards probably include Compact Flash(CF card), MultiMediaCard(MMC card), Secure Digital(SD card), Memory Stick (XD-Picture Card) and MICRODRIVE. Although the appearance and specifications are different, the technology is the same. MMC Card MMC (Multimedia Card) was introduced by Siemens and Sandisk in 1997, which was the first cf 1998 65438+ 10. Fourteen companies jointly established MMC Association (MMCA) in October, and now it has more than 84 members. 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-pin, 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 of CF card 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. ) the capacity is limited. Although the capacity has increased exponentially, see the original >>
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