EEPROM Memories (Electrically eraseable programmable read only memory, or electrically erasable read-only programmable memory) are also erasable PROM memories, but unlike these, they can be erased by a simple electric current, it is Say, even if they are in position on the computer.
There is a variant of these memories, known as flash memory (TambiénFlash ROM or Flash EPROM). Unlike the classic EEPROM memories, which use 2 or 3 transistors for each bit to memorize, the EPROM Flash memory uses a single transistor. In addition, the EEPROM memory can be written and read Word by word, while the Flash can only be erased by pages (page size is constantly declining).
Finally, Flash memory is denser, implying that chips can be produced that contain hundreds of megabytes. Thus, EEPROM memories are preferable when you have to memorize configuration information, while Flash memory is used for programmable code (IT programs).
The action of reprogramming a EEPROM memory is called update.
It is a type of ROM memory that can be programmed, erased and reprogrammed electrically, unlike the EPROM to be erased by a device that emits ultraviolet rays. These are non-volatile memories.
The memory cells of a EEPROM consist of a MOS transistor, which has a floating gate (SAMOS structure), its normal state is cut and the output provides a logical 1.
Although a EEPROM can be read an unlimited number of times, it can only be deleted and reprogrammed between 100,000 and a million times.
These devices are often communicated through protocols such as I ² C, SPI and Microwire. At other times, it integrates into chips as micro-controllers and DSPs to achieve faster.
Flash memory is an advanced form of EEPROM created by Dr. Fujio Masuoka while working for Toshibaen 1984 and was presented at the IEEE 1984 electronic gadgets meeting. Intel saw the potential of the invention and in 1988 launched the first commercial chip of type NOR.
The flash memory derived from EEPROM memory allows the reading and writing of multiple memory positions in the same operation. Thanks to this, the flash technology, always by means of electrical impulses, allows much higher operating speeds compared to the original EEPROM technology, that only allowed to act on a single memory cell in each programming operation. It is about the technology used in devices called USB memory.
An USB Memory. The chip on the left is the flash memory. The controller is on the right.
The history of flash memory has always been closely linked to the advancement of the rest of the technologies to which it provides its services such as routers, modems, PC BIOS, wireless, etc. It was Fujio Masuoka in 1984, who invented this type of memory as an evolution of the existing EEPROM at the time. Intel tried to attribute the creation of this without success, although if it commercialized the first flash memory of common use.
Between the years 1994 and 1998, the main types of memory that we know today, such as the SmartMedia or the CompactFlash, were developed. Technology soon posed applications in other fields. In 1998, the Rio company commercialized the first digital audio player without mobile parts taking advantage of the mode of operation of the flash memory. This product would inaugurate a new class of players that would cause a revolution in the music industry leading to the Napster scandal, the launch of the IPod and the eventual replacement of tape and CD players.
In 1994 SanDisk began marketing memory cards (CompactFlash) based on these circuits, and since then evolution has reached small handheld devices of consumer electronics like portable MP3 players, memory cards for Video consoles and mobile phones, storage capacity for PC cards that allow to connect to wireless networks and a long etcetera, even arriving in space aeronautics.
Economically speaking, the price on the market meets Moore’s law by increasing its capacity and lowering the price.
Some of its advantages are great resistance to blows, high speed, low energy consumption and quiet operation, as it does not contain mechanical actuators or moving parts. Its small size is also a determining factor when choosing for a portable device, as well as its lightness and versatility for all the uses towards which it is oriented. In view of this, SSD discs that use flash memory instead of dishes begin to become popular.
However, all types of flash memory only allow a limited number of writes and deletions, usually between 10,000 and one million, depending on the cell, the precision of the manufacturing process and the voltage needed for deletion. In addition, its cost-capacity ratio is less favorable compared to other media such as optical disks and hard losdiscos.
Another feature has been the thermal resistance of some encapsulated memory cards oriented to high-end digital cameras. This allows operation in extreme temperature conditions such as deserts or glaciers as the temperature range supported ranges from-25 °c to 85 ° C.
The most common applications are:
· The USB keychain that, in addition to storage, can include other services like, fingerprint reader, FM Radio, voice recording and, especially as portable MP3 players and other audio formats.
· The PC Card (discontinued.)
· Flash memory cards that are used to store photos and videos on digital cameras. They are also common in mobile phones and tablets to expand storage capacity.
There are several standards of encapsulations promoted and manufactured by most of the multinationals dedicated to the production of hardware. The most common these days are Secure Digital, Compact Flash, and Memory Stick.