I have never understood the difference between nor flash, nand flash and emmc before.
nor: NOR Flash takes a long time to erase, but it provides a complete addressing and data bus, and allows random access to any area on the memory , which makes it ideal for replacing older ROM chips . At that time, ROM chips were mainly used to store code that hardly needed to be updated, such as the BIOS of a computer or the firmware of a set-top box. NOR Flash can endure 10,000 to 1 million erase cycles, and it was also the basis for early removable flash storage media. CompactFlash was originally based on NOR Flash, although it later switched to lower-cost NAND Flash.
nand: NAND Flash type Toshiba published at the International Solid State Circuit Symposium (ISSCC) in 1989, to read and write data on NandFlash, external master control and circuit design are required . . NAND Flash has faster erasing time and smaller area of each memory cell, which makes NAND Flash have higher storage density and lower cost per bit than NOR Flash . At the same time, its erasable times are ten times higher than NOR Flash . However, the I/O interface of NAND Flash does not have random access to the external address bus, it must be read in blocks, and the typical block size of NAND Flash is hundreds to thousands of bits.
Because most microprocessors and microcontrollers require byte-level random access, NAND Flash is not suitable to replace those ROMs used to load programs. From this point of view, NAND Flash is more like secondary storage devices such as optical discs and hard disks . NAND Flash is ideal for mass storage devices such as memory cards . The first removable storage media created on the basis of NAND Flash was SmartMedia, and since then many storage media have also adopted NAND Flash, including MultiMediaCard, Secure Digital, Memory Stick and xD card.
emmc: eMMC (Embedded Multi Media Card) is established by the MMC Association. eMMC is equivalent to NandFlash+ main control IC . The external interface protocol is the same as SD and TF card. It is mainly aimed at the embedded memory standard of products such as mobile phones or tablet computers. Specification. A clear advantage of eMMC is the integration of a controller in the package , which provides a standard interface and manages the flash memory , allowing handset makers to focus on other parts of product development and reducing time-to-market. These features are equally important to NAND suppliers looking to shrink lithography and reduce costs.
eMMC consists of an embedded storage solution with MMC (Multimedia Card) interface, flash memory device (Nand Flash) and host controller , all in a small BGA package. With interface speeds up to 52MBytes per second, eMMC has fast, scalable performance. At the same time, its interface voltage can be 1.8v or 3.3v.
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