FLASH小结
1.Flash概念叙述
- Flash是一种非易失性存储器(Non-volatile),也叫Flash EEPROM
- Nor FLASH
NOR FLASH芯片,不仅具有很强的可擦写次数,还具有完备的地址和数据总线,支持随机寻址,非常适合代替早期的ROM芯片(ROM、PROM、EEPROM),比如BIOS和机顶盒固件等,早期的可移动存储也使用NOR FLASH芯片,只是后来转向性价比更高的NAND FLASH。
- NAND FLASH
具有更强的可擦写次数,相比NOR FLASH具有更高的集成度和更低的制造成本,可惜NAND FLASH不支持随机寻址,只支持BLOCK块寻址
- Nor Flash和Nand Flash的区别
|
NOR FLASH |
NAND FLASH |
擦写时间 |
40ms-6s |
4ms |
擦除块 |
64-128KB |
8-32KB |
接口 |
带SRAM接口 |
普通I/O |
擦写次数 |
10W- |
100W- |
用途 |
多用在程序存储 |
多用在数据块存储 |
其它 |
支持片内执行 |
- |
此外,NOR FLASH的写入速度要比NAND FLASH稍低,但其读取速度要比NAND FLASH略快。NAND FLASH还分SLC(Single Level Cell)、MCL(Multi-Level Cell)、MirrorBit等技术类型,SLC顾名思义是单比特单元,MLC是双比特单元,而MirrorBit则是四比特单元,NOR FLASH也有这种MirrorBit技术架构。大容量存储产品现在主要都是使用NAND FLASH。
- Application
- serial flash
Serial flash is a small, low-power flash memory that provides only serial access to the data - rather than addressing individual bytes, the user reads or writes large contiguous groups of bytes in the address space serially. Serial Peripheral Interface Bus (SPI) is a typical protocol for accessing the device.
- Flash memory as a replacement for hard drives
- Archival or long-term storage
- FLash Interface
- Common Flash Interface (CFI)
- Spi for serial flash
- Wishbone for parallel flash