![]() ![]() The user interface to the memory includes an 8-b I/O bus that handles commands, addresses, and data ( Figure 1). These restrictions mean that NAND flash devices generally are not used by themselves but require data buffering and an amount of memory control intelligence.įor example, typical NAND flash devices program 528 B at a time from an internal data register of the same size�512 B being the size of a hard disk sector with 16 B added for error correction. In contrast, NAND devices operate much more like hard disk drives because they read, write, and erase bits as a group: Sectors on disk drives correspond to pages for reading and programming (writing) or blocks for erasing in NAND flash memory. Direct access means that a program stored in NOR can be executed in place (XIP). They have the advantages of a short read time and true random access to each bit. Typically, NOR devices are used in smaller sizes because of their higher cost. Masuoka originally thought, less user-friendly NAND flash devices now are found in memory sticks, secure data (SD) memory cards, and CompactFlash (CF) cards�this in spite of NAND�s awkward user interface. That application still is maturing, but the explosive growth of flash memories has been due to the success of cell phones and digital cameras among other consumer electronic products. Originally, Intel began flash development as hard-disk mass memory replacement devices. So too, because a group of memory cells in a NAND flash memory occupies significantly less silicon area than the equivalent number of cells in a NOR device, the NAND structure will cost less and dominate the flash memory market. Again, although DRAMs must be refreshed and have other restrictions on how they�re used, they are inherently less expensive. Masuoka observed that hard disk drives didn�t have anything like the ease of use associated with direct-access SRAM, but hard disks were much cheaper per bit, so they, not SRAMs, dominated mass storage applications.Ī similar argument can be made for the huge volume of DRAMs consumed vs. Whether or not a memory technology is easy to use is irrelevant, according to a Toshiba flash memory application guide: �The most important item regarding memories is the bit cost.� This realization was the motivation behind initial development of flash memory by Toshiba�s Fujio Masuoka in the early 1980s and explains the popularity of NAND flash compared to NOR flash. ![]() In those markets where flash already dominates, Intel forecasts that flash will remain the technology of choice for at least another five years. But these factors aren�t serious practical barriers to using flash memories in most applications. It does suffer from known wear-out mechanisms, and memory cards come in several incompatible formats. Given its relatively low and decreasing cost, small size, ready availability through retail stores, and large data capacity, NAND flash memory is a very attractive storage medium. What influence could accessories used in mainstream consumer products have on the comparatively very small and specialized test and measurement business? Is the question easier to answer if narrowed down to the area of data storage? In many test instruments, data archiving, traditionally accomplished via magnetic media including tape cassettes, floppy disks, and hard disks, now is being handled by the same flash memory cards that store pictures from your digital camera or tunes for your MP-3 player. ![]() Hands off your kid�s digital camera! Buy your own memory card for data acquisition. ![]()
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