What is flash

Flash is a type of memory chip, also known as flash memory. The data inside can be modified through a specific program; FLASH often means Flash Memory in the field of electronics and semiconductors, which is what is usually called "flash memory" , the full name is Flash EEPROM Memory.

The operating environment of this article: Windows7 system, DELL G3 computer

What is flash?

Flash (one of the memory chips)

Flash is a type of memory chip, and the data inside can be modified through a specific program. FLASH often means Flash Memory in the field of electronics and semiconductors, which is what is usually called "flash memory". Its full name is Flash EEPROM Memory.

Flash memory is also called flash memory. It combines the advantages of ROM and RAM. It not only has the performance of electronically erasable programmable (EEPROM), but also can quickly read data (the advantage of NVRAM), so that the data cannot be Will be lost due to power outage.

Basic introduction

This kind of memory is used in U disks and MP3s. In the past 20 years, embedded systems have been using ROM (EPROM) as their storage device. However, in recent years, Flash has completely replaced the position of ROM (EPROM) in embedded systems and is used to store bootloaders and operating systems or programs. code, or use it directly as a hard disk (U disk).

At present, there are two main types of Flash: NORFlash and NAND Flash. Reading NORFlash is the same as reading our common SDRAM. Users can directly run the code loaded in NORFLASH, which can reduce the capacity of SRAM and save costs. NAND Flash does not use random reading technology of memory. Its reading is carried out in the form of reading one block at a time, usually 512 bytes at a time. Flash using this technology is relatively cheap. Users cannot directly run the code on NAND Flash, so many development boards using NAND Flash not only use NAND Flash, but also add a small NORFlash to run the startup code.

Generally, NORFlash is used for small capacity because it has fast reading speed and is mostly used to store important information such as the operating system. NANDFLASH is used for large capacity. The most common NANDFLASH application is DOC (Disk) used in embedded systems. On Chip) and the "flash drive" we usually use, can be erased online. Currently, FLASH on the market mainly comes from Intel, AMD, Fujitsu and Mxic, while the main manufacturers of NAND Flash include Samsung, Toshiba, Micron and Hynix.

CISCO

That is, electrically erasable programmable read-only memory, used to save CISCO's IOS (Cisco system). But generally speaking, the size of flash is related to the hardware and CF card. Of course, some people will also transfer some of their configuration information to FLASH. It should be noted here that when you want to delete files in flash, you must bring the file name, such as eraseflash: Once this command is executed, the IOS and files in flash will be deleted. The router will not be able to load IOS the next time it is started. Causes the startup to fail. The correct method is: delelteflash:xxxxx.xx (ios file name).

Switch

Provides permanent storage function, mainly saving configuration files and system files: Flash can quickly restore services and effectively ensure the normal operation of the switch. At the same time, it also provides a convenient and fast way to upgrade and maintain equipment, such as using FTP, TFTP to upgrade or configure, etc.

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