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Designing the Switch/Router
Published in James Aweya, Designing Switch/Routers, 2023
Flash memory retains its contents when the system is powered down or restarted, and provides storage for system software images and microcode. A system restart on a router is also often referred to as a reload. In most designs, the OS image is typically stored in a Flash memory. The Flash memory is used as the primary storage of software images, configuration files, and microcode. Multiple router OS software and microcode images can be remotely loaded and stored in Flash memory. For example, a new image can be downloaded from a remote or local server over the network, and added to Flash memory or the new image can replace existing images. The router can then boot either manually or configured to boot automatically from any of the multiple stored images.
Memory-Related Macros
Published in Murat Uzam, PIC16F1847 Microcontroller-Based Programmable Logic Controller, 2020
There are three basic memory types used in computers, PLCs, microcontrollers, etc., namely flash memory, SRAM, and EEPROM. Flash memory is an electronic (solid-state) non-volatile storage medium that can be electrically erased and reprogrammed. In PLCs, flash memory is mainly used to store programs. They can also be used to store constants. SRAM (Static Random Access Memory) uses flip-flop circuitry to store each bit, but it is still volatile memory as it will lose its contents when power is lost. PLCs use this memory for running the central CPU. SRAM is used to store variables. EEPROM (Electronically Erasable Programmable Read Only Memory) is a type of non-volatile memory used to store relatively small amounts of data but allowing individual bytes to be erased and reprogrammed.
Memory Organisation
Published in Pranabananda Chakraborty, Computer Organisation and Architecture, 2020
Computers of today access modern flash memory systems very much like hard disk drives, where the controller system has full control over where information is actually stored. The low power consumption of flash memory makes it attractive for use, especially, in portable equipment implemented mostly by embedded systems that are driven by battery. Typical potential applications include cell phones, digital cameras, MP3 music players, hand-held computers, and many more, in which flash memory holds the essential software and needed data, thereby alleviating the need of a disk drive to be used. To meet the actual requirement, larger memory modules consisting of a number of such chips are thus often needed. Two commonly used implementation of such modules are of primary interest: flash cards and flash drives.
Resistive Random Access Memory: A Review of Device Challenges
Published in IETE Technical Review, 2020
Varshita Gupta, Shagun Kapur, Sneh Saurabh, Anuj Grover
An SRAM cell stores information on the two nodes of a cross-coupled inverter pair. A DRAM cell uses a capacitor to store charge and distinguish between the “0” state and the “1” state. A Flash memory cell stores charge in the floating gate of a transistor and can store different amounts of charge to effectively store more than 1 bit of information per transistor [2]. This charge dependence of the storage mechanisms limit the scaling possibilities of present memory technologies. For example, the SRAM cell scaling is limited by the variability and the consequent impact on the functionality (read/write margins). The DRAM cell scaling is limited by the amount of charge that is stored on the scaled capacitor. The Flash memory scaling is limited due to the requirement of a high electric field in the program and the erase operations. Therefore, researchers are actively exploring non-charge-based memories that can be scaled to a greater extent [1,2].
Building memory devices from biocomposite electronic materials
Published in Science and Technology of Advanced Materials, 2020
Xuechao Xing, Meng Chen, Yue Gong, Ziyu Lv, Su-Ting Han, Ye Zhou
Since the birth of the first computer, the structure of the modern computer system is still based on the von Neumann principle, which is mainly composed of five parts: memory, arithmetic, controller, input equipment and output equipment. Among them, memory is used to store all kinds of data, which is an indispensable part of the computer. In addition, memory can be divided into volatile memory and non-volatile memory according to the data storing time in the memory. Volatile memory, where information is lost after a power outage, is mainly used to store programs that are used for a short period of time, such as dynamic random access memory (DRAM) [22–24]. The non-volatile memory can retain stored information after switching off the power, such as flash memory. With the popularization of mobile phones, digital cameras and other portable electronic devices, non-volatile memory is playing an increasingly important role in modern human’s daily life. With progresses of science and technology, the application of new non-volatile memory will bring a qualitative change to the performance of computers and people’s operating habits. The International Technology Roadmap for Semiconductor (ITRS), released in 2013, recommends RRAM after classifying and evaluating new types of memory currently being studied, and recommends acceleration of the commercialization.
Bipolar resistive switching characteristics of amorphous SrTiO3 thin films prepared by the sol-gel process
Published in Journal of Asian Ceramic Societies, 2019
Hui Tang, Xin-Gui Tang, Yan-Ping Jiang, Qiu-Xiang Liu, Wen-Hua Li, Li Luo
In recent decades, continuous optimization of computer technologies marking the rapid development of modern information technology has progressively changed people’s lifestyles. Memory is an indispensable carrier of information technology and is regarded as one of the most important technologies in the field of integrated circuits [1]. Semiconductor memory has been widely applied in various fields, such as information technology, social security, aerospace, defense and military [2]. Compared with volatile memory, however, non-volatile memory has great superiority in the field of mobile storage media owing to its ability, to maintain its internal storage properties even after a power failure. With the burgeoning of technologies, various types of new electronic products have emerged in an endless stream. These electronic products also have more stringent requirements for memory performance, such as high reading and writing speeds, high storage density, low power consumption, long life, greater thinness and smaller size [3,4]. The flash memory devices that play significant roles in the current electronic market still suffer from many disadvantages, such as the low operation speed, poor endurance and high write voltage problems. Eventually, miniaturization limits will be a critical issue for flash memory in future application [5]. As a result, most of today’s electronic technology research is focussing on new types of memory devices nowadays. There are many kinds of memory devices based on different mechanisms and materials that are highly likely to replace non-volatile memory, such as resistive random access memory (ReRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), and phase change memory (PCM) [1–6]. Among these new types of memory, resistive switching (RS) memory has been widely studied due to such advantages as its simple preparation process, low energy consumption, predominant memory density, small size, and good compatibility with the conventional CMOS process [7,8]. The ReRAM memory device is a novel non-volatile memory based on the principle of resistance change of thin film materials [9,10]. The ReRAM’s metal/insulator/metal (MIM) structure is composed of a thin film functioning as an insulating layer, with conductive materials as bottom and top electrodes [11,12]. This development has attracted widespread attention in the industry and academia, and many new investigations of resistive memory have been initiated by researchers [13,14]. The RS effect of the insulator layer has been discovered in various kinds of amorphous metal oxides, such as ZnO, HfO2, TiO2, MgO, Al2O3, and Y2O3 [15–19]; and in amorphous perovskite and layered perovskite oxides such as YCrO3, Pr0.67Sr0.33MnO3, Bi3.15Bd0.85Ti3O12, SrTiO3 and Nb-doped SrTiO3 [20–26], etc. Among these, the amorphous strontium titanate-based memory structure uses the following electrodes: Pt, Ti, and indium tin oxide (ITO) [23–26]. These form Pt/amorphous-SrTiO3 (a-STO)/Pt [23], Pt/Ti/a-STO/Pt [24], Pt/Ti/a-Nb:STOx/Pt [25] and ITO/Ti/Ti2O3/a-STO/ITO [26] memory cells, respectively.