Flash Memory

Flash with is a kind of long life as nonvolatile (when power can still maintain the data stored information) Memory, not in a single data deletion of bytes for unit but with a fixed block for the unit (note: the TTL Flash in bytes storage). , the block size is commonly 256KB to 20 MB. The flash is electronic can erase read-only memory (EEPROM) variations of the block, EEPROM and flash different is, it can in byte level to delete and rewrite rather than the whole chip, such CaXie EEPROM memory than the updated speed. Due to its power cuts can still preserving data, flash are often used to save Settings information, such as in computer BIOS (basic input/output program), personal digital assistant (PDA), digital camera kept in material, etc.

The concept of flash

The flash is a kind of the beltpassword nonvolatile storage, namely blackouts data also not lost. Because flash unlike RAM (random access memory) as in bytes for unit rewrite the data, so cannot replace RAM.

Flash hello is to use Flash with technology to achieve storage of the electronic information storage, normally used in digital cameras, PDA, MP3 digital products such as small as a storage medium, so look small, like a piece of Card, so called Flash Card. According to different manufacturer and different applications, Flash Card about SmartMedia (SM) Card, Compact Flash (CF Card), MultiMediaCard (skillfully Card), Secure Digital (SD Card), with what (Memory Stick), XD - they hello (XD) Card and little hard disk (MICRODRIVE) these Flash Card although appearance, different specifications, but technical principles are the same.

Methods and features

The TTL NAND flash memory of type and type a big difference, for example, said the TTL type flash more like memory, have independent address lines and data lines, but the price is more expensive, capacity is relatively small, But more like hard disk, NAND type address lines and Shared data is the I/O lines, similar to the hard disk all of the information is transmitted through a hard line to general, and with the TTL NAND flash memory type type, compared to lower costs, while large capacity. Therefore, the TTL type flash is suitable for frequent random reading and writing occasions, is often used to store program code and directly in flash run inside, cell phone is to use the large TTL type flash, so mobile phone "memory" capacity is generally not, NAND flash memory mainly used to store data type, we often use flash memory products, such as flash disk, digital memory are used in NAND type flash memory.

Here we need to correct a concept that flash speed actually very limited, itself operation speed, frequency, much lower than the memory, and NAND flash memory similar hard disk type of operating mode efficiency than the direct memory access method much slower. So don't assume flash disk performance bottlenecks in interface, and even take it for granted that flash USB2.0 interface disc is after'll be a great performance improvements.

Mentioned NAND type flash mode of operation, low efficiency, this and its architecture design and interface design relevant, it operate up indeed very like hard disk (actually NAND flash memory at the beginning of design type really considered and hard disk compatibility), its performance characteristics are like hard disk: small block operating speed slowly and large data block speed quickly, this difference than other storage medium. This performance characteristics very worthy of our attention. Flash memory access more quickly, without noise, heat is small. You buy it actually can not consider so much, same storage space buy flash memory. If hard disk space big buy hard disk, also can satisfy your application requirements.

The classification of flash

By type can

U dish

CF card

SM card

SD/skillfully card

The memory stick

XD card

MS card

TF card