Flash
memory was first thoroughly explored by Dr. Fugio Masuoka who was an employee
of the tech empire Toshiba. The name ‘Flash’ memory was given because of the
erasure process that the memory consisted of (The flash of the Camera). Seeing
the immense potential that the Flash memory had, Intel took over the idea and
launched the first commercial flash chip called NOR in 1988.This chip was able
to erase and store data multiple times as well as provide data buses and full
addresses. This allowed access to any part of the chip and any given time.
These memory chips replaced the old ROM chips, which were used to store
programs that required little to no updates such as a BIOS. A better and more
improved NAND chip was developed which required less chip area per cell and had
a better endurance then the NOR chip. The data on this chip has to be read on a
block-wise basis, this was its disadvantage.
Overview
Used in embedded system applications, Flash memory is a non-volatile memory meaning it can retain data even if the power source is cut-off. It is a type of electrically erasable programmable read-only memory (EEPROM). It is often used to control code such as the BIOS on a computer. Flash memory is used for program code as well as data storage. In order to access flash memory there must an application present that executes the memory. Flash memory is read in the same way other memories are read but the only difference is that the flash memory has special format for its data storage. The execution for flash memory is the same as other memories. Some advantages of this memory includes that it transfers data fast, it is completely electronic, it can be erased and reprogrammed, it is very durable and it can contain a total memory of 16 GBs.
System Description
All memories in a computer system or any system for a matter of fact work in similar ways. Basically, a memory chip consists of many transistors, electronic switches that turn on and off when they are being interacted with electricity. The strength of this method is that a device can easily store data using electricity. The weakness occurs when there is a power shortage and the chip loses all its data. This type of memory chip is called the RAM (Random Access Memory). The chip that can store its data permanently is known as ROM (Read Only Memory). Flash
memory stands in the middle as it can be erased and reprogrammed over and over
again. What allows the flash memory to do this is its design. The transistors
in a flash chip consist of two gates on top. It is an n-p-n sandwich with two
gates located above called the control gate and the floating gate. Oxide layers
allow electric current to pass. When there is no flow of electricity which is
stored a zero. The
source and drain contain many electrons, but the current is resisted due to the
p material. However to overcome this, a positive voltage can be applied to the
system using the word line and the bit line. This cause a rush and the
electrons flow from the source to drain. In the process some electrons, get
through the oxide layer and into the floating gate through a tunneling
process. The presence of electron in the floating gate is what the flash memory
uses to store a one. These electron will stay there even if the power turns
off. By putting a negative charge through the word line, the electrons can be
repelled to their original locations. This clears the floating gate and a zero
is recorded once again.
Component Description
This is just one cell out of many others and each cell can hold one bit of information either a zero or a one. These cells can be arranged in rows or columns. The important thing is to have that n-p-n sandwich formation. This is very important as it allows for the current flow. It is also important to have a ground pin which can be used to discharge the chip causing the data to be erased and making space to program.