Read-Only Memory (ROM)

 

read only memory applications

In information technology, a write-only memory (WOM) is a memory location or register that can be written to but not ayungs.tk addition to its literal meaning, the term may be applied to a situation when the data written by one circuit can be read only by other circuitry. Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic ayungs.tk stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing software that is rarely changed during the life of the system, sometimes known as ayungs.tkre applications for programmable devices can be . ROM Definition: It is an example of nonvolatile ayungs.tk full form is Read Only ayungs.tk is a class of storage medium used in computers and other electronic devices. Read Only Memory (ROM), also known as firmware, is an integrated circuit programmed with specific data when it is ayungs.tk instructions for starting the computer are housed on Read only memory chip.


Read-only memory - Wikipedia


Read-only memory ROM is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing software that is rarely changed during the life of the system, sometimes known as firmware.

Software applications for programmable devices can be distributed as plug-in cartridges containing read-only memory. Strictly, read-only memory refers to memory that is hard-wired, such as diode matrix or read only memory applications mask ROM integrated circuit, which cannot be changed after manufacture. Although discrete circuits can be altered in principle, integrated circuits ICs cannot, read only memory applications.

Correction of errors, or updates to read only memory applications software, require new devices to be manufactured and to replace the installed device. Erasable programmable read-only memory EPROM and electrically erasable programmable read-only memory EEPROM can be erased and re-programmed, but usually this can only be done at relatively slow speeds, may require special equipment to achieve, and is typically only possible a certain number of times.

For example, read only memory applications, users modifying the Android operating system describe files containing a modified operating system as " custom ROMs " after the type of storage the file is to be written to. The simplest type of solid-state ROM is as old as the semiconductor technology itself. Combinational logic gates can be joined manually to map n -bit address input onto arbitrary values of m -bit data output a look-up table. With the invention of the integrated circuit came mask ROM.

Mask ROM consists of a grid of word lines the address input and bit lines the data outputselectively joined together with transistor switches, and can represent an arbitrary look-up table with a regular physical layout and predictable propagation delay. In mask ROM, the data is physically encoded in the circuit, so it can only be programmed during fabrication.

This leads to a number of serious disadvantages:. Subsequent developments have addressed read only memory applications shortcomings. PROMread only memory applications, invented by Wen Tsing Chow in[2] [3] allowed users to program its contents exactly once by physically altering its structure with the application of high-voltage pulses. This addressed problems 1 and 2 above, since a company can simply order a large batch of fresh PROM chips and program them read only memory applications the desired contents at its designers' convenience.

EEPROMdeveloped by Yasuo Tarui, Yutaka Hayashi and Kiyoko Naga at the Electrotechnical Laboratory in[4] went a long way to solving problem 4, since an EEPROM can be programmed in-place if the containing device provides a means to receive the program contents from an external source for example, read only memory applications, a personal computer via a serial cable.

Flash memoryinvented by Fujio Masuoka at Toshiba in the early s and commercialized in the late s, is a form of EEPROM that makes very efficient use of chip area and can be erased and reprogrammed thousands of times without damage. All of these technologies improved the flexibility of ROM, read only memory applications, but at a significant cost-per-chip, so that in large quantities mask ROM would remain an economical choice for many years. Decreasing cost of reprogrammable devices had almost eliminated the market for mask ROM by the year Rewriteable technologies were envisioned as replacements for mask ROM.

Its designers explicitly broke from past practice, stating plainly that "the aim of Read only memory applications Flash is to replace hard disks ," [5] rather than the traditional use of ROM as a form of non-volatile primary storage.

As of [update]NAND has partially achieved this goal by offering throughput comparable to hard disks, higher tolerance of physical shock, extreme miniaturization in the form of USB flash drives and tiny microSD memory cardsfor exampleand much lower power consumption. Every stored-program computer may use a form of non-volatile storage that is, storage that retains its data when power is removed to store the initial program that runs when the computer is powered on or otherwise begins execution a process known as bootstrappingoften abbreviated to " booting " or "booting up".

Likewise, every non-trivial computer needs some form of mutable memory to record changes in its state as it executes. Forms of read-only memory were employed as non-volatile storage for programs read only memory applications most early stored-program computers, such as ENIAC after Until then it was not a stored-program computer as every program had to be manually wired into the machine, which could take days to weeks. Read-only memory was simpler to implement since it needed only a mechanism to read stored values, and not to change them in-place, and thus could be implemented with very crude electromechanical devices see historical examples below.

With the advent of integrated circuits in the s, both ROM and its mutable counterpart static RAM were implemented as arrays of transistors in silicon chips; however, a ROM memory cell could be implemented using fewer transistors than an SRAM memory cell, since the latter needs a latch comprising transistors to retain its contents, while a ROM cell might consist of the absence logical 0 or presence logical 1 of one transistor connecting a bit line to a word line.

Most home computers of the s stored a BASIC interpreter or operating system in ROM as other forms of non-volatile storage such as magnetic disk drives were too costly. This arrangement allowed for a more complex and easily upgradeable operating system. In modern PCs, "ROM" or flash is used to store the basic bootstrapping firmware for the main processor, read only memory applications, as well as the various firmware needed to internally control self-contained devices such as graphic cardshard disksDVD drivesread only memory applications, TFT screensetc.

Today, many of these "read-only" memories — especially the BIOS — are often replaced with Flash memory see belowread only memory applications, to permit in-place reprogramming should the need for a firmware upgrade arise.

However, simple and mature sub-systems such as the keyboard or some communication controllers in the integrated circuits on the main board, for example may employ mask ROM or OTP one-time programmable. ROM and successor technologies such as flash are prevalent in embedded systems. These are in everything from industrial robots to home appliances and consumer electronics MP3 playersset-top boxesread only memory applications, etc. With software usually tightly coupled to hardware, program changes are rarely needed in such devices which typically lack hard disks for reasons of cost, size, or power consumption, read only memory applications.

As ofread only memory applications, most products use Flash rather than mask ROM, and many provide some means for connecting to a PC for firmware updates; for example, a digital audio player might be updated to support a new file format.

Some hobbyists have taken read only memory applications of this flexibility to reprogram consumer products for new purposes; for example, the iPodLinux and OpenWrt projects have enabled users to run full-featured Linux distributions on their MP3 players and wireless routers, respectively.

ROM is also useful for binary storage of cryptographic data, as it makes them difficult to replace, which may be desirable in order to enhance information security. Since ROM at least in hard-wired mask form cannot be modified, read only memory applications, it is only suitable for storing data which is not expected to need modification for the life of the device.

To that end, ROM has been used in many computers to store look-up tables for the evaluation of mathematical and logical functions for example, a floating-point unit might tabulate the sine function in order to facilitate faster computation. Notably, the display adapters of early personal computers stored tables of bitmapped font characters in ROM. This usually meant that the text display font could not be changed interactively. The use of ROM to store such small amounts of data has disappeared almost completely in modern general-purpose computers.

However, Flash ROM has taken over a new role as a medium for mass storage or secondary storage of files. Classic mask-programmed ROM chips are integrated circuits that physically encode the data to be stored, and thus it is impossible to change their contents after fabrication.

Other types of non-volatile solid-state memory permit some degree of modification:, read only memory applications. By applying write protectionread only memory applications, some types of reprogrammable ROMs may temporarily become read-only memory. There are other types of non-volatile memory which are not based on solid-state IC technology, including:. Although the relative speed of RAM vs. Because they are written by forcing electrons through a layer of electrical insulation onto a read only memory applications transistor gate, rewriteable ROMs can withstand only a limited number of write read only memory applications erase cycles before the insulation is permanently damaged.

The limited endurance, read only memory applications, as well as the higher cost per bit, means that Flash-based storage is unlikely to completely supplant magnetic disk drives in the near future. The timespan over which a ROM remains accurately readable is not limited by write cycling. Leakage is accelerated by high temperatures or radiation. The contents of ROM chips can be extracted with special hardware devices and relevant controlling software.

This practice is common for, as a main example, reading the contents of older video game console cartridges. The resultant memory dump files are known as ROM images or abbreviated ROMsand can be used to produce duplicate ROMs - for example to produce new cartridges or as digital files for playing in console emulators.

The term ROM image originated when most console games were distributed on cartridges containing ROM chips, but achieved such widespread usage that it is still applied to images of newer games distributed on CD-ROMs or other optical media. ROM images of commercial games, firmware, read only memory applications, etc. The unauthorized copying and distribution of copyrighted software is a violation of copyright laws in many jurisdictions, although duplication for backup purposes may be considered fair use depending on location.

From Wikipedia, the free encyclopedia. The concept of read-only data can also refer to file system permissions. For the British book publisher, see Read-Only Memory publisher. For other uses, see ROM disambiguation. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.

Main article: ROM image. This audio file was created from a revision of the article " Read-only memory " datedand does not reflect subsequent edits to the article. Audio help. More spoken articles. Embedded System Design with C Cengage Learning. Archived from the original on 27 April Archived from the original on 12 Read only memory applications Retrieved 22 July Computer History Museum.

Retrieved 20 June Retrieved 19 June Retrieved 6 July The products are sorted by date" PDF. Intel museum. Intel Corporation.

July Archived from the original PDF on August 9, Retrieved July 31, Bibcode : ITED NEC Microcomputers. January Retrieved 27 June Retrieved 26 June NEC Electronics. Retrieved 25 June Retrieved 2 July Retrieved 21 June SK Hynix.

 

RAM vs ROM - Difference and Comparison | Diffen

 

read only memory applications

 

In information technology, a write-only memory (WOM) is a memory location or register that can be written to but not ayungs.tk addition to its literal meaning, the term may be applied to a situation when the data written by one circuit can be read only by other circuitry. Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic ayungs.tk stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing software that is rarely changed during the life of the system, sometimes known as ayungs.tkre applications for programmable devices can be . Read-only memory (ROM) is a type of storage medium that permanently stores data on personal computers (PCs) and other electronic devices. It contains the programming needed to start a PC, which is essential for boot-up; it performs major input/output tasks and holds programs or software instructions.