Memory that "forgets" when the power goes off is called Random Access Memory (RAM). There is another kind of memory called Read-Only Memory (ROM) that doesn't suffer from this problem.
ROM chips are pre-stored with information when they are manufactured, so they don't "forget" what they know when the power is switched on and off.
Flash Memory has certain things in common with both RAM and ROM.
Like ROM, it remembers information when the power is off;
Like RAM, it can be erased and rewritten over and over again.
Flash memory, also known as flash storage, is a type of nonvolatile memory that erases data in units called blocks and rewrites data at the byte level.
Flash memory is widely used for storage and data transfer in consumer devices, enterprise systems and industrial applications.
Flash memory retains data for an extended period of time, regardless of whether a flash-equipped device is powered on or off.
There are 2 main types of flash memory used within devices, being NAND and NOR. The type of memory within a device is depending upon the type of data that is required to be stored as well as the use of that data.
Samsung Flagships use UFS and some others series use eMMC(usually NAND).
[Universal Flash Storage or UFS is a common flash storage specification for digital cameras, mobile phones, and other consumer electronic devices. The main idea behind UFS is to bring higher data transfer speed and increased reliability to flash memory storage.
eMMC is short for "embedded Multi-Media Controller" and refers to a package consisting of both flash memory and a flash memory controller integrated on the same silicon die.Today's embedded applications such as digital cameras, smart phones, and tablets almost always store their content on flash memory]
1. How is flash memory on a phone so compact?
Due to Transistors which are smaller in size.
Flash memory is a type of EEPROM chip, which stands for Electronically Erasable Programmable Read Only Memory. It has a grid of columns and rows with a cell that has two transistors at each intersection
(I answered this question once in google Q&A)
2. Why it is called Flash?
Shoji Ariizumi, reportedly coined the term "flash" because the process of erasing all the data from a semiconductor chip reminded him of the flash of a camera.
Flash memory is also used for in-memory computing to help speed performance and scalability of systems that manage and analyse large sets of data.
How it Works:
The two transistors are separated from each other by a thin oxide layer. One of the transistors is known as a floating gate, and the other one is the control gate. The floating gate's only link to the row, or wordline, is through the control gate. As long as this link is in place, the cell has a value of 1. To change the value to a 0 requires a curious process called Fowler-Nordheim tunneling.
Fowler-Nordheim tunneling removes electrons from the floating gate. Either Fowler-Nordheim tunneling or a phenomenon known as channel hot-electron injection traps the electrons in the floating gate.
Data is erased via a strong negative charge on the control gate. This forces electrons into the channel, where a strong positive charge exists.
The reverse happens when using Fowler-Nordheim tunneling to trap electrons in the floating gate. Electrons manage to forge through the thin oxide layer to the floating gate in the presence of a high electric field, with a strong negative charge on the cell's source and the drain and a strong positive charge on the control gate.
A Simple Explanation:
Flash works using an entirely different kind of transistor that stays switched on (or switched off) even when the power is turned off. A normal transistor has three connections (wires that control it) called the source, drain, and gate. Think of a transistor as a pipe through which electricity can flow as though it's water.
One end of the pipe (where the water flows in) is called the source—think of that as a tap or faucet.
The other end of the pipe is called the drain—where the water drains out and flows away.
In between the source and drain, blocking the pipe, there's a gate. When the gate is closed, the pipe is shut off, no electricity can flow and the transistor is off. In this state, the transistor stores a zero. When the gate is opened, electricity flows, the transistor is on, and it stores a one. But when the power is turned off, the transistor switches off too.
When you switch the power back on, the transistor is still off, and since you can't know whether it was on or off before the power was removed, you can see why we say it "forgets" any information it stores.
A flash transistor is different because it has a second gate above the first one. When the gate opens, some electricity leaks up the first gate and stays there, in between the first gate and the second one, recording a number one.
Even if the power is turned off, the electricity is still there between the two gates. That's how the transistor stores its information whether the power is on or off. The information can be erased by making the "trapped electricity" drain back down again.
Few examples of flash memory:
Challenges with flash memory technology
1. Flash memory wears out over time. Inside the memory chip, bits of data are stored on cells. Each time data is erased from or written to a cell, it causes wear. Over time and repeated cycles of writing and erasing, the cells degrade and eventually become unusable.
2. Typical file system software can cause data fragmentation. While built-in features reduce fragmentation, this phenomenon still causes a decrease in performance over time. That’s because the system has to jump around the memory layout to read or write all the bits of data that form a file.
Possible solution :Strong involvement in the ecosystem.
Samsung's Contribution and innovation in this Technolgy:
-September 2006, Samsung announced the development of PRAM -- Phase-change Random Access Memory. This new type of memory combines the fast processing speed of RAM with the non-volatile features of flash memory, leading some to nickname it "Perfect RAM." PRAM is supposed to be 30 times faster than conventional flash memory and have 10 times the lifespan
-In 2013, Samsung formally launched 3D flash ("stacked") technology in which dozens of different layers of memory cells can be grown on the same silicon wafer to increase storage capacity (just like the multiple floors of a high-rise office block let us pack more offices into the same area of land). Instead of using floating gates (as described above), 3D flash uses an alternative (though sometimes less reliable) technique called charge-trap, which allows us to engineer much higher capacity memories in the same amount of space, well into the terabit (Tbit) scale (1 trillion bits = 1,000,000,000,000 bits).
-In Jan 2019, Samsung has announced that it’ll start offering the world’s first 1TB eUFS (embedded Universal Flash Storage) solution for phone manufacturers
For Comparison : Samsung’s previous 512GB unit and has read speeds of up to 1,000 megabytes a second; that’s 10 times the speed of a typical microSD card.
1. Flash Memory in Phone:
2. Flash Memory in USB:
-Thank You For Your Support.
-Referenced from my Old books about Microchips and website SearchStorage
-To know more about Flash Memory [non-volatile memory (nvm)] developments, forecasts and information: flash memory summit's are held every year and you can follow them. Next Summit might be scheduled in August,2020.