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Memory Organisation
Published in Pranabananda Chakraborty, Computer Organisation and Architecture, 2020
Working with ROMs and PROMs can be a wasteful business. Even though they are inexpensive per chip, the cost can add up overtime. To address this issue, a compromise between the performance of ROM and the erasability of RAM system is made, and that is by the use of erasable and programmable ROM or EPROM. The EPROM chip is optically erasable, and can be rewritten many times. The EPROM is erased off-line and it requires a special tool that emits a certain frequency of ultraviolet (UV) light. EPROM is read and written electrically like PROM, but it is more expensive. To program (write into) an EPROM, it is configured using a particular type of tool that provides voltage at specified levels depending on the type of EPROM used. Multiple update capability is its distinct advantage.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
Like RAM chips, the family of ROM devices also consists of an orthogonal grid of wires, with a bit stored at each grid point. Members of the family differ according to the type of circuit element at each grid point. In a ROM, the presence or absence of a diode between the row and column wires fixes the bit value stored at a grid point. A diode permits current flow between the column and row when energized, while the two wires are isolated if there is no diode at the grid point. A PROM allows the user to program the pattern of 0 ’s and l’s at the grid points, rather than building it in at the time of manufacture. Equipment known as a PROM programmer is used to selectively blow out fuses between the column and rows at each grid point. Once programmed, the PROM cannot be altered. An EPROM permits the stored information to be altered, by first erasing the information using ultraviolet light, and then reprogramming the grid. Each grid point contains a two-transistor device that exploits quantum tunneling to coerce electrons to cross an insulating barrier in the presence of an applied voltage. When the voltage is removed, the electrons are trapped. Erasure using ultraviolet light causes the entire memory to be reset. An EEPROM permits selective erasure of the device by the application of a suitable electrical voltage. This allows the EEPROM to be altered in place without removing the chip, and without the need for specialized equipment. However, EEPROMs are too slow for applications that must make rapid changes to the stored data.
Programmable Logic Control Systems
Published in L. Ashok Kumar, M. Senthilkumar, Automation in Textile Machinery, 2018
L. Ashok Kumar, M. Senthilkumar
There are a few basic types of computer memory that are in use today. RAM (Random Access Memory): This memory is fast, but it will lose its contents when power is lost; this is known as volatile memory. Every PLC uses this memory for the central CPU when running the PLC.ROM (Read Only Memory): This memory is permanent and cannot be erased. It is often used for storing the operating system for the PLC.EPROM (Erasable Programmable Read Only Memory): This is memory that can be programmed to behave like ROM, but it can be erased with ultraviolet light and reprogrammed.EEPROM (Electronically Erasable Programmable Read Only Memory): This memory can store programs like ROM. It can be programmed and erased using a voltage, so it is becoming more popular than EPROMs.
Effect of gamma and beta radiation on I–V characterization of the solar cell panel
Published in Radiation Effects and Defects in Solids, 2018
Ban Mazin Al-Shabander, Nesreen B. Naji, Iftikhar M. Ali
Vujisi et al. (8) compared the radiation hardness of Eras able Programmable Read Only Memory (EPROM) and Electrically Erasable Programmable Read Only Memory (E2PROM) components exposed to 60Co.gamma radiation. EPROM components exhibited higher radiation reliability than E2PROMs. The influence of gamma radiation is basically manifested through the change of the net floating gate surface charge density, and consequently of transistor threshold voltage, Zdravković et al. (9) showed that the higher neutron irradiation doses decreased series resistance. Through the fabrication process of any semiconducting device, structural defects and impurities that were unavoidably made produce tension in the crystal lattice. Some irradiation doses could lead to the relaxation of the crystal structure and the decease of series resistance. Pejović et al. (10) investigated the response of pMOS dosimeters during two sequential gamma irradiations to 35 Gy and further annealing at room and elevated temperature. The results show that pMOS dosimeters can be re-used for the measurement of radiation dose if they are annealed after the first irradiation at room and elevated temperature.
Radiation-Induced Damage–Based System and Method for Indirectly Monitoring High-Dose Ionizing Radiation
Published in Nuclear Technology, 2018
Karen Colins, Yu Liu, Liqian Li, Kiranpreet Birdee
Read-only memory (ROM) plays an important role in modern computing systems to store lookup tables for the evaluation of mathematical and logical functions, etc. Also, a typical IC is sensitive to radiation damage. In past decades, several types of nonvolatile ROM were invented and then widely used in different fields. Among them, ultraviolet-erasable programmable ROM (EPROM) needs only one transistor for one cell, but it requires high voltage for programming. In contrast, an EEPROM cell consists of two transistors, and the high voltage for program/erase is internally generated. An EEPROM is programmed by forcing an electrical charge (a range of 105 to 106 electrons) onto a polysilicon floating gate. When the charge is present, it represents a logical value of false, or 0, and when this charge is not present, it represents a logical value of true, or 1.