Tuesday, 18 June 2013

Flash Memory

It is a type of EEPROM that is much faster than traditional EEPROM. It reads or writes data in form of blocks. Block size is usually 512 bytes.

Sometimes flash memory is termed as flash RAM. But there is a much difference between flash RAM and flash memory. Flash RAM requires constant power to maintain its contents whereas flash ROM can store its contents even without any power.

Inside Flash Chips

Boot Block Section: - This area is used for booting and may consist of one or more blocks that is kept secure from erasing blocks. This block is generally used to store firmware of for memory management.

Block Erase Section: -It is the user working area and is divided into blocks. This area can be accessed randomly for read/write operations. Memory Erased blocks contain no data.

Types of Flash Memories

1) Simultaneous Read/Write
2) Burst Mode
3) Ultra NAND
4) Page Mode

Simultaneous Read/Write:- These types of flash can be erased or accessed simultaneously AM29DL; AM29DS are Simultaneous read/write Flash.

Burst Mode Flash: - These types of flash are used in microcomputers and embedded systems. These chips work at 2.7v-3.6v operating voltage. In these chips 32- word sequential burst mode access are achieved with 65ns access time followed by 17ns burst mode. Example AM29BL

Page Mode Flash Memory:- This type of flash is used in printers and network cards. This type of flash consists of multiple word pages. AM29PL consist of 8 pages. These types of memory usually available in 44 pin SSOP and operates at 2.7-3.6V supply.

Ultra NAND Flash:- It is very similar to sequential access, page mode devices. Each page contains 512 bytes storage data. Each page also contains 16 Byte that is uses to store spare data. Data is transferred in or out by using 528 bytes data transfer register at 50ns per byte. Example Am30LV0064D

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