s3c2440 nandflash initialization-EEWORLD

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1. What is nand flash?

FLASH Flash Memory The English name of Flash Memory is "Flash Memory", generally referred to as "Flash". It is a type of memory device and a non-volatile memory.

NOR and NAND are the two main non-volatile flash memory technologies on the market today. Intel first developed NOR flash technology in 1988, which completely changed the situation that was previously dominated by EPROM and EEPROM. Then, in 1989, Toshiba released the NAND flash structure, which emphasized lower cost per bit, higher performance, and easy upgrade through interfaces like disks.

Flash memory is non-volatile memory that can be erased and reprogrammed in blocks of memory cells called blocks. Any write operation to any flash device can only be performed in empty or erased cells, so in most cases, an erase operation must be performed before a write operation. NAND devices are very simple to perform erase operations, while NOR requires that all bits in the target block be written to 0 before an erase operation can be performed.

Since NOR devices are erased in blocks of 64 to 128KB, it takes 5 seconds to perform a write/erase operation. In contrast, NAND devices are erased in blocks of 8 to 32KB, and the same operation takes only 4ms at most. The difference in block size when performing erase further widens the performance gap between NOR and NAND.

2. What is the difference between NAND and NOR flash?

● The read speed of NOR is slightly faster than that of NAND.

● The write speed of NAND is much faster than that of NOR.

● The erase speed of NAND is much faster than that of NOR.

● NAND's erase unit is smaller and the corresponding erase circuit is simpler.

● The actual application of NAND is much more complicated than that of NOR.

● NOR can be used directly and the code can be run directly on it, while NAND requires an I/O interface and therefore requires a driver when used.

The above picture is the pin diagram of nandflash (K9F2G08U0C).

The I/O bit data input and output pins also serve as address pins and command pins.

CLE: Command latch pin, high level is valid.

ALE: Address latch pin, high level is valid.

Note: When CLE and ALE are both low, data is transmitted through I/OC

nWE: Write signal, low level is valid.

nRE: Read signal, high level is valid.

nCE: Chip select signal, low level is valid.

Keywords：s3c2440 nandflash Reference address：s3c2440 nandflash initialization

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