It is on this technology that the keys or memory cards are based, for example, and it can even replace computer hard disks. Here’s everything you need to know about flash memory.
Flash memory: what is it?
Flash memory is a form of non-volatile memory, born from the combination of EPROM and E2PROM. This technology uses the same programming method as the standard EPROM, and the erase method of the E2PROM.
Compared to the EPROM, one of the main advantages of flash memory is that it can be electrically erased. However, it is not possible to delete each cell of a flash memory individually unless a large amount of additional circuitry is added to the chip.
This approach dramatically increases the cost, which is why most manufacturers have abandoned it. Thus, the whole chip or a large part is crushed in block or a flash. That’s where the name of this technology comes from.
Flash memory: how does it work?
The technology used to manufacture flash memory chips is based on that of EEPROM chips (electrically erasable programmable read-only memory). It is a memory bank formed of storage cells arranged in a grid of columns and rows.
Flash memory: how long does this storage technology last?
When it first appeared, the flash memory had a relatively short life. Repeated use of cells caused memory degradation. That’s why this technology was only used for a limited number of reading and write cycles.
Subsequently, however, this technology has undergone many improvements. To reduce the impact of use on storage cells, the wear-leaning technique is used. Thus, the life of the flash memory is greatly extended.
Flash memory: advantages and disadvantages
Flash memory has many strengths, but also disadvantages. Depending on the use case, it is not always the most appropriate storage technology.
Among its main benefits, the fact that it is a form of nonvolatile memory. This makes it ideal for short- and medium-term storage. Moreover, it is a “portable” technology since it can take the form of keys, cards and other lightweight media. Finally, it is mechanically robust.
On the other hand, its cost per bit is higher than for hard disks. It is also slower than other forms of memory, and its number of writing and erase cycles is limited. Another flaw: it is necessary to delete the data before new data can be written. Finally, as mentioned above, the data is usually erased and written in blocks.
Flash memory NAND and NOR: what is the difference?
There are mainly two types of flash memory. Both types use the same basic technology, but the way they write and read the data is different.
In the case of NAND flash memory, the memory is accessed in a manner similar to the hard disks. When the flash memory is to be read, the contents must first be paginated in the RAM memory-mapped. This is the reason why the memory management unit is essential here.
On the contrary, the NOR flash memory is able to read individual flash memory cells, as in the case of a traditional ROM. For erase and write functions, commands are written to the first page of the mapped memory. Note that some systems use a combination of these two types of flash memory.