[Repost] An article to understand non-volatile memory and volatile memory
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Non-volatile memory Non-volatile memory technology is a technology that prevents data from being lost when the computer is turned off or suddenly or accidentally turned off. Non-volatile memory technology has developed rapidly. Non-volatile memory is mainly divided into two categories: block addressing and byte addressing. In many storage system write operation procedures, memory is an important bridge between the controller and the hard disk, providing faster performance. However, if a sudden power outage occurs, how to protect the data in the memory from being lost is a common topic in storage systems. Volatile memory means that when the computer is turned off or suddenly or accidentally turned off, the data in it will be lost, just like memory. In the above cases, data will not be lost in non-volatile memory, like hard disks and other external storage. RRAM is a non-volatile memory, also known as a memristor, which paves the way for the manufacture of non-volatile storage devices that simulate the way the human brain processes information. RRAM consists of two metal electrodes sandwiched by a thin dielectric layer. In normal conditions, it is an insulator. It is a nonlinear resistor with memory function based on nano-device processing technology. Each memristor has a bottom wire that contacts one side of the device and a top wire that contacts the other side. Memristor is a semiconductor with a two-terminal, double-layer cross-switch structure consisting of a tin oxide layer sandwiched by two metal electrodes. One layer of tin oxide is doped with oxygen vacancies to become a semiconductor; the adjacent layer is not doped with anything to keep its natural properties as an insulator. By detecting the resistance of the electrodes at both ends of the cross-switch, the "on" or "off" state of RRAM can be determined. In addition to its unique "memory" function, memristor has two major characteristics that make it widely favored by the industry. First, it has a shorter storage access time and faster read and write speed. It integrates some characteristics of flash memory and DRAM. Second, its storage unit is small and the manufacturing industry can be upgraded. The size of the memristor can be several nanometers, which is likely to bring the development of microelectronics technology to the next decade. Moreover, it is compatible with CMOS technology and is the development trend of the next generation of non-volatile storage technology. Volatile memory It can be read and written at any time. RAM is usually used as a temporary storage medium for operating systems or other running programs (can be called system memory). However, RAM cannot retain data when the power is turned off. If data needs to be saved, they must be written to a long-term storage (such as a hard disk). Because of this, RAM is sometimes called "variable memory". RAM memory can be further divided into two categories: static RAM (SRAM) and dynamic memory (DRAM). DRAM is widely used as the main memory of the system due to its low unit capacity price. Different applications require different operating frequencies under different capacitive loads. This requirement is closely related to the performance of the chipset and the layout and complexity of the circuit board. For example, high-frequency operating environments usually require strict optimization of electrical performance. Design engineers need to consider the electrical noise on the entire circuit board to reduce the parasitic capacitance of the line. In this case, reducing the strength of the memory output driver is more popular. In addition, the instruction execution speed must be optimized according to the operating frequency. Sometimes, in order to achieve a suitable and efficient throughput after sending a command, the number of empty clock cycles must be reduced. In the application board test stage, in order to properly stimulate the memory and view the memory's response, the microcontroller requires a full set of commands and functions. This operational flexibility test is often used to test all system components to ensure the functionality of the product during the life cycle. In contrast, standard customer end applications use only a reduced instruction set. For example, when using SPI Flash, the end application typically uses read instructions (normal, fast, and/or 4-bit I/O input and output) to download boot code to RAM memory. Designers should optimize non-volatile memory to reduce code read and download time during system power-up. On new advanced platforms, such as automotive electronics, computer optical drives, or Bluetooth modules, SPI Flash may be used to read parts of the system firmware directly from non-volatile memory to shorten the process of downloading the system firmware to high-speed volatile memory. Of course, the latest applications currently emerging have more stringent requirements for memory flexibility. Source: Internet, if infringed, please delete.
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