Flash memory is secondary memory and so it is not volatile which means it persists the data even if there is not an electrical supply provided. This flash memory works on the principle of EEPROM. EEPROM stands for Electrical Erasable Programmable Read-Only Memory. ROM operation can only one time write and many times read and we can’t erase it. But Flash Memory can be erased multiple times and update the data or program integrated into it. So it gives flexibility to the updation of the program but ROM has no such type of feature.
History of Flash Memory
Flash memory is developed by Dr. Masuoka Fujio and his team at Toshiba Corporation in the mid-1980. He was a Japanese engineer. When they discovered the flash memory semiconductor technology get the boom in that time frame. Many devices such as digital cameras, camcorders, MP3 players, and audio/video are developed using flash memory.
Features of Flash Memory
- Non-volatile: There is no loss of date when there is no electricity supply.
- Solid-state: It is SS technology so it is faster than HDD type storage.
- Fast access times: It supports solid-state technology so it has faster access time.
- Large storage capacity: Flash memory devices can store large amounts of data, from a few GB (Gigabytes) to several TB(Terabytes).
- Low power consumption: It is not based on header like HDD so no mechanical components in flash memory so it uses less amount of electricity from read the data.
- Flexibility towards Erase and write operations: Flash memory can be erased electrically multiple times and read multiple times so flexibility towards read/write operation is more in flash memory.
How Does Flash Memory Work?
These two are the main steps.
- Writing the data into flash memory: Flash memory is made up of small-small memory cells which are made up of floating-gate transistors. All memory cells are organized in the sequential order called an array of memory cells. Data can be stored to the hardware in the form of 0 and 1 only. So to store the data into the flash memory we should give the electric supply to add the pattern of 0 and 1 into the flash memory and once this pattern is embedded on to the chip then corresponding data is also stored in the flash memory. If we want to erase the data from flash memory then we have to do it by supplying electrical impulse to make all bits of memory cell to 0.
- Reading the data into flash memory: By reading the stored 0 and 1 into the cell we can get our data stored in the flash memory. So to read the bit which can contain 0 or 1 we have to apply voltage to the gate of transistor, and whatever the current flow in the circuit is measured and by using that measurement we are good to go to identify the bit present in the cell.
Types of Flash Memory
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NAND flash memory: NAND flash memory has high memory cell density so it has high capacity to store the data. Memory cards, USB drives, and SSD (Solid State Drive) use this type of flash memory which uses low power to store data, it has low power consumption. NAND flash memory cell is made up of two gates.
- Control gate
- Floating gate
- NOR flash memory: NOR Flash Memory is made up of FGMOS or FGMOSFETs (Floating Gate Metal Oxide Field Effect Transistors). FGMOS is an electronic component in NOR flash memory that can contain 0 or 1. So we can say that the memory cell in the NOR flash memory is FGMOS. Cells of NOR flash memory are attached in a parallel manner so reading speed of this type of flash memory is faster compared to other.
- 3D flash memory: It is a newer type of flash memory. It has a memory cell density greater than NAND flash memory also. It is used in high capacity SSDs.
Difference between NAND and NOR Flash Memory
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NAND Flash |
NOR Flash |
|---|---|
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NAND flash memory is organized in a series of memory cells |
NOR flash memory is organized in a parallel of memory cells |
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NAND flash memory has a higher density(store more data in a smaller space) |
NOR flash memory has a lower density than NAND Flash |
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NAND flash memory has a faster read speed. |
NOR flash memory has faster random access times than NAND flash memory, |
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NAND flash memory can survive less erase/write cycles before starting to degrade than NOR |
NOR flash memory can survive more erase/write cycles before starting to degrade than NAND |
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It is commonly used in high-density storage applications. |
NOR flash memory is used in applications that require frequent read and write operations. |
Limitations of Flash Memory
- Limited lifespan: Writing onto the flash memory by electrical supply may damage the hardware so it has some limitations to the lifespan of flash memory.
- Slower write speeds: Frequency of writing speed so less than RAM and to write the data by using an electrical pulse every time may take more time than RAM.
- Limited storage capacity: Flash memory has a high storage density, but lesser than some other memory devices such as HDDs or tape drives.
- Data corruption: When we are writing to the flash memory by using electrical pulse and when power supply is cut off accidentally then loss of data will be there.
Benefits of Flash Memory
- Large storage capacity: Flash memory has high memory density so it is able to store a high volume of data.
- High speed: Some flash memory has parallel architecture of memory cells so it has faster speed to read and write operation.
- Persistent Data: Without supply of electricity it persist the data like HDDs.
- Low power consumption: Flash memory don’t have mechanical components like HDD’s so it consume less amount of power than HDDs.
Applications of Flash Memory
- Used in SSDs: Flash memory is used in SSDs to increase the speed of read/write of operations.
- Embedded systems: Flash memory is used in embedded systems. Examples: digital cameras, camcorders, MP3 players etc.
- Smartphones and tablets: Flash memory is used in smartphones and tablets.
- USB drives: Flash memory is commonly used in USB drives.