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More memory




Type: Original Spot Quantity: 58100

Packaging: BGA batch number: NEW + ROHS

Price: Inquiry Sample: Support Specification: Contact Customer Service

Description: Flash NAND FLASH

    Toshiba, the largest semiconductor manufacturer in Japan and the second largest integrated motor manufacturer, belongs to Mitsui Group. The company was founded in July 1875, formerly known as Tokyo Shippo Electric Co., Ltd. in 1939 by the combination of Tokyo Electric Co., Ltd. and Shippo Production Co., Ltd. Toshiba‘s business areas include digital products, electronic components, social infrastructure, household appliances and so on. Since the 1980s, Toshiba has changed from an enterprise with household appliances and heavy motors as its main body to a comprehensive electronic and electrical enterprise including communications and electronics. In the 1990s, Toshiba has made rapid development in the fields of digital technology, mobile communication technology and network technology. It has successfully transformed from a giant in household appliances industry to a pioneer in IT industry.

    Nand-flash memory is a kind of flash memory. It adopts nonlinear macrocell mode, which provides a cheap and effective solution for the realization of solid state large capacity memory. Nand-flash memory has many advantages, such as large capacity, fast rewriting and so on, which is suitable for storing large amounts of data. Therefore, it has been widely applied in the industry, such as digital camera, MP3 Walkman memory card, compact U disk.
    NAND feature editing
    Capacity and cost
    The size of NAND flash is almost half that of NOR device. Because the production process is more simple, NAND structure can provide higher capacity within a given mold size, and it also lowers the price accordingly.
    NOR flash has a capacity of 1 to most 16MB flash market, while the NAND flash is used in the 8 ~ 128M B products, it also shows that NOR is mainly used in the code storage medium, NAND is suitable for data storage, NAND storage card market the largest share in CompactFlash, Secure Digital, PC Cards M and MC.
    Physical composition
    The data of NAND Flash is saved in memory cell in the way of bit, and in general, only one bit can be stored in a cell. These cell to 8 or 16 units, as bit line, the formation of the so-called byte (x8) /word (x16), this is the NAND Device interface. These Line will form Page again. (NAND Flash has many structures. The NAND Flash I use is K9F1208, the following contents are for Samsung K9F1208U0M), 528Bytes per page (512byte (Main)) (32). How many Block are required on a specific piece of flash? The Samsung k9f1208U0M I used has 4096 block, so the total capacity is 4096* (32*528B) =66MB, but 2MB is used to save extra data such as ECC check code, so it can be used 64MB in practice.
    Reliable durability
    A problem that needs to be considered in the use of flash media is reliability. Flash is a very appropriate storage scheme for systems that need to extend MTBF. The reliability of NOR and NAND can be compared from three aspects of life (durability), bit exchange, and bad block processing.
    Life (durability)
    In NAND flash memory of each block erase maximum number is one million times, while the NOR is one hundred thousand times the number of erase.
    NAND memory has a block erase cycle advantage of 10 to 1. The size of the typical NAND block is 8 times smaller than that of the NOR device, and each NAND memory block has fewer deletion times in a given time.
    Bit exchange
    All flash devices are perplexed by the phenomenon of bit switching. In some cases (rarely, the number of NAND happens more than NOR), a bit will reverse or be reversed.
    Bit reverse picture
    Bit reverse picture
    One bit of change may not be obvious, but if it happens on a key file, this small failure may cause the system to stop. If only the report has problems, it may be solved by reading a few more times.
    Of course, if this bit is really changed, the error detection / error correction (EDC/ECC) algorithm must be used. The problem of bit reversal is more likely to be seen in NAND flash, and NAND vendors suggest using the EDC/ECC algorithm when NAND flash is used.
    This problem is not fatal to the storage of multimedia information with NAND. Of course, if a local storage device is used to store operating systems, configuration files, or other sensitive information, the EDC/ECC system must be used to ensure reliability.
    Bad block treatment
    The bad blocks in the NAND device are randomly distributed. There have been efforts to eliminate bad blocks in the past, but it is found that the rate of finished products is too low and the cost is too high.
    The NAND device needs to initialize the medium to scan the bad block and mark the bad block as unavailable. In the device made, the high failure rate will be caused if the processing is not carried out by a reliable method.
    Easy to use
    A flash memory based on NOR can be used very directly, it can be connected like other memory, and the code can be run directly on it.
    Because of the need for the I/O interface, NAND is much more complicated. The access methods of various NAND devices vary from manufacturer.
    When using a NAND device, you must write the driver first to continue to perform other operations. It is quite necessary to write information to NAND devices, because designers must never write to bad blocks, which means that virtual mapping is always necessary on NAND devices.
    Software support
    When discussing software support, we should distinguish the basic read / write / erase operation and the higher level software used for disk simulation and flash memory management algorithm, including performance optimization.
    Running code on NOR device does not require any software support. When performing the same operation on NAND device, it usually needs the driver, that is, the memory technology driver (MTD). NAND and NOR devices need MTD when writing and erasing.
    The need to use the NOR device MTD is relatively less, many manufacturers have to provide for more advanced software of NOR devices, including the M-System TrueFFS driver, the driver is Wind River System, Microsoft QNX, Software System, Symbian Intel and other manufacturers are using.
    The driver is also used for the simulation of DiskOnChip products and the management of NAND flash memory, including error correction, bad block processing and loss balance. (rectify one point: when NOR is erased, it is written 1, not 0, and NOR FLASH SECTOR erase time is different depending on brand and size. For example, 4M FLASH, some SECTOR erase time is 60ms, while others need maximum 6S. The main supplier of NOR FLASH is INTEL, MICRO and other manufacturers, which used to be the mainstream products of FLASH, but now it is more difficult to be squeezed by NAND FLASH. Its advantage is that the program can be run directly from the FLASH, but the process is complex and the price is more expensive.
    The main suppliers of NAND FLASH are SAMSUNG and Toshiba. They are all FLASH in U disk, all kinds of memory cards and MP3 players. Because of different technology, they have larger storage capacity and cheaper than NOR FLASH. But there are also shortcomings, that is,
    It is not addressable to run the program directly, and data can only be stored. In addition, NAND FLASH is very vulnerable to bad zones, so there is a need to have a checkout algorithm.
    In the palmtop computer, NAND FLASH is used to store data and programs, but there must be a NOR FLASH to start. except
    SAMSUNG processors, other mainstream processors used on palmtop are not supported directly by the NAND FLASH startup program. Therefore,
    You have to start the machine with a small NOR FLASH, and it‘s very troublesome to run OS and other software from NAND FLASH into SDRAM.
    The NAND flash memory is erased in blocks. The write operation of flash memory must be carried out in the blank area. If the target area has data, it must be erased and written first, so erase operation is the basic operation of flash memory.
    And SRAM (Static RAM, static random memory) - this kind of static RAM runs very fast, is also very expensive, and its volume is relatively large. The one - level, two - level cache that we often say in CPU today is the use of this SRAM. Intel‘s Pentium III Coppermine CPU combines 256KB full speed two caching, which is actually a SRAM. Unfortunately, such SRAM is very expensive compared with its partner DRAM. Therefore, only a small number of SRAM can be used in CPU to reduce the production cost of the processor. However, because of the characteristics of SRAM -- high speed, it is very helpful for improving the system performance. The first level cache in the processor is synchronized with the CPU clock, while the two level cache can be integrated in CPU or on the edge of some Slot-1 CPU.

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