FLASH小結
1.Flash概念敘述
- Flash是一種非易失性存儲器(Non-volatile),也叫Flash EEPROM
- Nor FLASH
NOR FLASH芯片,不僅具有很強的可擦寫次數,還具有完備的地址和數據總線,支持隨機尋址,非常適合代替早期的ROM芯片(ROM、PROM、EEPROM),比如BIOS和機頂盒固件等,早期的可移動存儲也使用NOR FLASH芯片,只是後來轉向性價比更高的NAND FLASH。
- NAND FLASH
具有更強的可擦寫次數,相比NOR FLASH具有更高的集成度和更低的製造成本,可惜NAND FLASH不支持隨機尋址,只支持BLOCK塊尋址
- Nor Flash和Nand Flash的區別
|
NOR FLASH |
NAND FLASH |
擦寫時間 |
40ms-6s |
4ms |
擦除塊 |
64-128KB |
8-32KB |
接口 |
帶SRAM接口 |
普通I/O |
擦寫次數 |
10W- |
100W- |
用途 |
多用在程序存儲 |
多用在數據塊存儲 |
其它 |
支持片內執行 |
- |
此外,NOR FLASH的寫入速度要比NAND FLASH稍低,但其讀取速度要比NAND FLASH略快。NAND FLASH還分SLC(Single Level Cell)、MCL(Multi-Level Cell)、MirrorBit等技術類型,SLC顧名思義是單比特單元,MLC是雙比特單元,而MirrorBit則是四比特單元,NOR FLASH也有這種MirrorBit技術架構。大容量存儲產品現在主要都是使用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