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Flash memory
Flash memory is a form of EEPROM
that allows multiple memory
locations to be erased or written in one programming operation.
Normal EEPROM only allows one location at a time to be erased or
written. All types of flash memory and EEPROM wear out after a
certain number of erase operations.
Flash memory is made in two forms: NOR
flash and NAND
flash. The names refer to the type of logic
gate used in each storage cell. NOR flash was the first type
to be developed, and was invented by Intel
in 1988.
It has long erase and write times, but has a full address/data
(memory) interface that allows random access to any
location.
This makes it suitable for storage of program code that needs to
be infrequently updated, as in digital
cameras and PDAs.
Its endurance is 10,000 to 100,000 erase cycles. NAND flash from
Toshiba
followed in 1989.
It has shorter erase and write times, higher density and lower
cost per bit than NOR flash, and ten times the endurance, but
its I/O interface allows only sequential access to data. This
makes it suitable for mass-storage devices such as PC
cards and various memory
cards like Compact
Flash and Secure
Digital media.
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content from Wikipedia
is licensed under the GNU
Free Documentation License.
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