The memory cell is the fundamental building block of computer memory. The memory cell is an electronic circuit that stores one bit of binary information and it must be set to store a logic 1 (high voltage level) and reset to store a logic 0 (low voltage level). Its value is maintained/stored until it is changed by the set/reset process. The value in the memory cell can be accessed by reading it.
The SRAM (static RAM) memory cell is a type of flip-flop circuit, typically implemented using MOSFETs. These require very low power to maintain the stored value when not being accessed. A second type, DRAM (dynamic RAM), is based on MOS capacitors. Charging and discharging a capacitor can store either a '1' or a '0' in the cell. However, since the charge in the capacitor slowly dissipates, it must be refreshed periodically. Due to this refresh process, DRAM consumes more power, but it can achieve higher storage densities.
The memory cell is the fundamental building block of memory. It can be implemented using different technologies, such as bipolar, MOS, and other semiconductor devices. It can also be built from magnetic material such as ferrite cores or magnetic bubbles.[1] Regardless of the implementation technology used, the purpose of the binary memory cell is always the same. It stores one bit of binary information that can be accessed by reading the cell and it must be set to store a 1 and reset to store a 0.[2]
Significance
Logic circuits without memory cells are called combinational, meaning the output depends only on the present input.
But memory is a key element of digital systems. In computers, it allows to store both programs and data and memory cells are also used for temporary storage of the output of combinational circuits to be used later by digital systems.
Logic circuits that use memory cells are called sequential circuits, meaning the output depends not only on the present input, but also on the history of past inputs.
This dependence on the history of past inputs makes these circuits stateful and it is the memory cells that store this state.
These circuits require a timing generator or clock for their operation.[3]
Computer memory used in most contemporary computer systems is built mainly out of DRAM cells; since the layout is much smaller than SRAM, it can be more densely packed yielding cheaper memory with greater capacity. Since the DRAM memory cell stores its value as the charge of a capacitor, and there are current leakage issues, its value must be constantly rewritten. This is one of the reasons that make DRAM cells slower than the larger SRAM (static RAM) cells, which has its value always available. That is the reason why SRAM memory is used for on-chipcache included in modern microprocessor chips.[4]
On December 11, 1946 Freddie Williams applied for a patent on his cathode-ray tube (CRT) storing device (Williams tube) with 128 40-bit words. It was operational in 1947 and is considered the first practical implementation of random-access memory (RAM).[5] In that year, the first patent applications for magnetic-core memory were filed by Frederick Viehe.[6][7] Practical magnetic-core memory was developed by An Wang in 1948, and improved by Jay Forrester and Jan A. Rajchman in the early 1950s, before being commercialised with the Whirlwind computer in 1953.[8]Ken Olsen also contributed to its development.[9]
Semiconductor memory began in the early 1960s with bipolar memory cells, made of bipolar transistors. While it improved performance, it could not compete with the lower price of magnetic-core memory.[10]
In 1957, Frosch and Derick were able to manufacture the first silicon dioxide field effect transistors at Bell Labs, the first transistors in which drain and source were adjacent at the surface.[11] Subsequently, a team demonstrated a working MOSFET at Bell Labs 1960.[12][13] The invention of the MOSFET enabled the practical use of metal–oxide–semiconductor (MOS) transistors as memory cell storage elements, a function previously served by magnetic cores.[14]
The first modern memory cells were introduced in 1964, when John Schmidt designed the first 64-bit p-channel MOS (PMOS) static random-access memory (SRAM).[15][16]
SRAM typically has six-transistor cells, whereas DRAM (dynamic random-access memory) typically has single-transistor cells.[17][15] In 1965, Toshiba's Toscal BC-1411 electronic calculator used a form of capacitive bipolar DRAM, storing 180-bit data on discrete memory cells, consisting of germanium bipolar transistors and capacitors.[18][19] MOS technology is the basis for modern DRAM. In 1966, Robert H. Dennard at the IBM Thomas J. Watson Research Center was working on MOS memory. While examining the characteristics of MOS technology, he found it was capable of building capacitors, and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while the MOS transistor could control writing the charge to the capacitor. This led to his development of a single-transistor DRAM memory cell.[20] In 1967, Dennard filed a patent for a single-transistor DRAM memory cell, based on MOS technology.[21]
The first commercial bipolar 64-bit SRAM was released by Intel in 1969 with the 3101 SchottkyTTL. One year later, it released the first DRAM integrated circuit chip, the Intel 1103, based on MOS technology. By 1972, it beat previous records in semiconductor memory sales.[22] DRAM chips during the early 1970s had three-transistor cells, before single-transistor cells became standard since the mid-1970s.[17][15]
CMOS memory was commercialized by RCA, which launched a 288-bit CMOS SRAM memory chip in 1968.[23] CMOS memory was initially slower than NMOS memory, which was more widely used by computers in the 1970s.[24] In 1978, Hitachi introduced the twin-well CMOS process, with its HM6147 (4kb SRAM) memory chip, manufactured with a 3 μm process. The HM6147 chip was able to match the performance of the fastest NMOS memory chip at the time, while the HM6147 also consumed significantly less power. With comparable performance and much less power consumption, the twin-well CMOS process eventually overtook NMOS as the most common semiconductor manufacturing process for computer memory in the 1980s.[24]
The two most common types of DRAM memory cells since the 1980s have been trench-capacitor cells and stacked-capacitor cells.[25] Trench-capacitor cells are where holes (trenches) are made in a silicon substrate, whose side walls are used as a memory cell, whereas
stacked-capacitor cells are the earliest form of three-dimensional memory (3D memory), where memory cells are stacked vertically in a three-dimensional cell structure.[26] Both debuted in 1984, when Hitachi introduced trench-capacitor memory and Fujitsu introduced stacked-capacitor memory.[25]
The following schematics detail the three most used implementations for memory cells:
The dynamic random access memory cell (DRAM);
The static random access memory cell (SRAM);
Flip-flops like the J/K shown below, using only logic gates.
Operation
DRAM memory cell
Storage
The storage element of the DRAM memory cell is the capacitor labeled (4) in the diagram above. The charge stored in the capacitor degrades over time, so its value must be refreshed (read and rewritten) periodically. The nMOS transistor (3) acts as a gate to allow reading or writing when open or storing when closed.[37]
Reading
For reading the Word line (2) drives a logic 1 (voltage high) into the gate of the nMOS transistor (3) which makes it conductive and the charge stored at the capacitor (4) is then transferred to the bit line (1). The bit line will have a parasitic capacitance (5) that will drain part of the charge and slow the reading process. The capacitance of the bit line will determine the needed size of the storage capacitor (4). It is a trade-off. If the storage capacitor is too small, the voltage of the bit line would take too much time to raise or not even rise above the threshold needed by the amplifiers at the end of the bit line. Since the reading process degrades the charge in the storage capacitor (4) its value is rewritten after each read.[38]
Writing
The writing process is the easiest, the desired value logic 1 (high voltage) or logic 0 (low voltage) is driven into the bit line. The word line activates the nMOS transistor (3) connecting it to the storage capacitor (4). The only issue is to keep it open enough time to ensure that the capacitor is fully charged or discharged before turning off the nMOS transistor (3).[38]
SRAM memory cell
Storage
The working principle of SRAM memory cell can be easier to understand if the transistors M1 through M4 are drawn as logic gates. That way it is clear that at its heart, the cell storage is built by using two cross-coupled inverters. This simple loop creates a bi-stable circuit. A logic 1 at the input of the first inverter turns into a 0 at its output, and it is fed into the second inverter which transforms that logic 0 back to a logic 1 feeding back the same value to the input of the first inverter. That creates a stable state that does not change over time. Similarly the other stable state of the circuit is to have a logic 0 at the input of the first inverter. After being inverted twice it will also feedback the same value.[39]
Therefore there are only two stable states that the circuit can be in:
= 0 and = 1
= 1 and = 0
Reading
To read the contents of the memory cell stored in the loop, the transistors M5 and M6 must be turned on. when they receive voltage to their gates from the word line (), they become conductive and so the and values get transmitted to the bit line () and to its complement ().[39] Finally this values get amplified at the end of the bit lines.[39]
Writing
The writing process is similar, the difference is that now the new value that will be stored in the memory cell is driven into the bit line () and the inverted one into its complement (). Next transistors M5 and M6 are open by driving a logic 1 (voltage high) into the word line (). This effectively connects the bit lines to the by-stable inverter loop. There are two possible cases:
If the value of the loop is the same as the new value driven, there is no change;
if the value of the loop is different from the new value driven there are two conflicting values, in order for the voltage in the bit lines to overwrite the output of the inverters, the size of the M5 and M6 transistors must be larger than that of the M1-M4 transistors. This allows more current to flow through first ones and therefore tips the voltage in the direction of the new value, at some point the loop will then amplify this intermediate value to full rail.[39]
The flip-flop has many different implementations, its storage element is usually a latch consisting of a NAND gate loop or a NOR gate loop with additional gates used to implement clocking. Its value is always available for reading as an output. The value remains stored until it is changed through the set or reset process. Flip-flops are typically implemented using MOSFETs.
A floating-gate memory cell is basically an MOS transistor with a gate completely surrounded by dielectrics (Fig. 1.2), the floating-gate (FG), and electrically governed by a capacitive-coupled control-gate (CG). Being electrically isolated, the FG acts as the storing electrode for the cell device. Charge injected into the FG is maintained there, allowing modulation of the ‘apparent’ threshold voltage (i.e. VT seen from the CG) of the cell transistor.[29]
^Kahng, D.; Sze, S.M. (1967). "A floating-gate and its application to memory devices". The Bell System Technical Journal. 46 (6): 1288–95. doi:10.1002/j.1538-7305.1967.tb01738.x.
^Masuoka, F.; Momodomi, M.; Iwata, Y.; Shirota, R. (1987). "New ultra high density EPROM and flash EEPROM with NAND structure cell". Electron Devices Meeting, 1987 International. IEDM 1987. IEEE. doi:10.1109/IEDM.1987.191485.
Artikel ini sebatang kara, artinya tidak ada artikel lain yang memiliki pranala balik ke halaman ini.Bantulah menambah pranala ke artikel ini dari artikel yang berhubungan atau coba peralatan pencari pranala.Tag ini diberikan pada November 2022. NongkrongSutradara Ismail Bob Hashim Produser David Teo Ditulis olehPemeranShaheizy Sam Angah Raja Lawak Epy Raja Lawak NurLiana RafiaiTanggal rilis10 Mei 2012Durasi89 menitNegara MalaysiaBahasa Melayu Nongkrong adalah film tahun 2012 yang bergen...
2003/04 was het 106de seizoen in de Engelse voetbalcompetitie. Arsenal werd landskampioen zonder één wedstrijd te verliezen. Prijzen Competitie Winnaar FA Premier League Arsenal FA Cup Manchester United Carling Cup Middlesbrough Football League Trophy Blackpool Football League First Division Norwich City Football League Second Division Plymouth Argyle Football League Third Division Doncaster Rovers FA Community Shield Manchester United Premier League Eindstand alle wedstrijden Rang Team We ...
Amsal 11Kitab Amsal lengkap pada Kodeks Leningrad, dibuat tahun 1008.KitabKitab AmsalKategoriKetuvimBagian Alkitab KristenPerjanjian LamaUrutan dalamKitab Kristen20← pasal 10 pasal 12 → Amsal 11 (disingkat Ams 11) adalah bagian dari Kitab Amsal dalam Alkitab Ibrani dan Perjanjian Lama di Alkitab Kristen.[1][2] Teks Naskah sumber utama: Masoretik, Septuaginta dan Naskah Laut Mati. Pasal ini terdiri dari 31 ayat. Berisi amsal-amsal raja Salomo bin Daud.[3] St...
В Википедии есть статьи о других людях с такой фамилией, см. Гамильтон; Гамильтон, Ричард. Ричард Гамильтонангл. Richard Streit Hamilton Имя при рождении англ. Richard Streit Hamilton Дата рождения 10 января 1943(1943-01-10) (80 лет) Место рождения Цинциннати, Огайо, США Страна США Научная сфера ма
Season of television series Survivor 43Region 1 DVD coverPresented byJeff ProbstNo. of days26No. of castaways18WinnerMike GablerRunner-upCassidy ClarkLocationMamanuca Islands, Fiji Country of originUnited StatesNo. of episodes13ReleaseOriginal networkCBSOriginal releaseSeptember 21 (2022-09-21) –December 14, 2022 (2022-12-14)Additional informationFilming datesMay 2 (2022-05-02) –May 27, 2022 (2022-05-27)Season chronology← PreviousSeason 42 Next ...
La Caleta De arriba abajo y de izquierda a derecha; el palacio de la tinta, vista de la bahía de Málaga desde el barrio, playa de La Caleta, Hotel Miramar y palmeras en el paseo marítimo. País España España• Com. autónoma Andalucía Andalucía• Ciudad Málaga• Distrito CentroUbicación 36°43′15″N 4°24′09″O / 36.7209, -4.40257[editar datos en Wikidata] La Caleta es uno de los barrios en los que se divide...
هذه المقالة يتيمة إذ تصل إليها مقالات أخرى قليلة جدًا. فضلًا، ساعد بإضافة وصلة إليها في مقالات متعلقة بها. (أبريل 2016) حمام المسخوطين أو حمام دباغ حمام معدني على مسافة 25 كلم غرب عاصمة ولاية قالمة، الجزائر ويعتبر الحمام جوهرة سياحية. يقصد للتداوي من عدة أمراض، منها الروماتيزم و
Historian Nicholas AdontzBorn(1871-01-10)January 10, 1871Brnakot, Sisian, Russian EmpireDiedJanuary 27, 1942(1942-01-27) (aged 71)Brussels, BelgiumAlma materSaint Petersburg State UniversityKnown for-Histoire d'Arménie (1946) -Armenia in the Period of Justinian: the Political Conditions based on the Naxarar System (1908)Scientific careerFieldsByzantine studies, Armenian studiesInstitutionsRussian Academy of Sciences Nicholas Adontz (Armenian: Նիկողայոս Ադոնց, rom...
1967 studio album by Wanda Jackson and the Party TimersYou'll Always Have My LoveStudio album by Wanda Jackson and the Party TimersReleasedSeptember 1967 (1967-09)Recorded1966 – 1967StudioColumbia StudioGenreCountry[1]LabelCapitolProducerKen NelsonWanda Jackson chronology Reckless Love Affair(1967) You'll Always Have My Love(1967) Made in Germany(1967) Singles from You'll Always Have My Love Both Sides of the LineReleased: March 1967 You'll Always Have My LoveRelea...
Private liberal arts college in Hanover, Indiana, US Hanover CollegeSeal: Philosophia pietati ancillans (Latin) Knowledge in service of pietyFormer nameHanover Academy (1827–1833)TypePrivate collegeEstablishedJanuary 1, 1827; 196 years ago (1827-01-01)Religious affiliationPresbyterian Church (USA)Endowment$142.8 million (2020)[1]PresidentLake Lambert IIIAcademic staff89 Full-time & 7 Part-time[2]Undergraduates1,070[3]LocationHanover, Indiana, U....
Psychological construct A parenting style is a pattern of behaviors, attitudes, and approaches that a parent uses when interacting with and raising their child. The study of parenting styles is based on the idea that parents differ in their patterns of parenting and that these patterns can have a significant impact on their children's development and well-being. Parenting styles are distinct from specific parenting practices, since they represent broader patterns of practices and attitudes th...
2017 film by Dean Israelite This article is about the 2017 film. For the 1995 film, see Mighty Morphin Power Rangers: The Movie. For the 1997 film, see Turbo: A Power Rangers Movie. For the fan film, see Power/Rangers. Power RangersTheatrical release posterDirected byDean IsraeliteScreenplay byJohn GatinsStory byMatt SazamaBurk SharplessMichele MulroneyKieran MulroneyBased onPower Rangersby Haim SabanSuper Sentaiby Toei Company Ltd.Produced by Haim Saban Brian Casentini Marty Bowen Wyck Godfr...
2005 single by AnggunSaviourSingle by Anggunfrom the album Luminescence and Transporter 2: Original Motion Picture Soundtrack Released12 May 2005Recorded2004GenrePop rockLength[[3:40]]LabelHeben Music (Sony BMG)Songwriter(s)Anggun, Evelyne Kral, Frédéric Jaffré,Anggun singles chronology In Your Mind (2005) Saviour (2005) I'll Be Alright (2006) Saviour (English) / Cesse la pluie (French) / Mantra (Indonesian) is a song recorded by Indonesian singer Anggun. Written originally in French by Ev...
Range of poverty indicators Multidimensional Poverty Indices use a range of indicators to calculate a summary poverty figure for a given population, in which a larger figure indicates a higher level of poverty. This figure considers both the proportion of the population that is deemed poor, and the 'breadth' of poverty experienced by these 'poor' households, following the Alkire & Foster 'counting method'.[1] The method was developed following increased criticism of monetary and c...
2013–14 concert tour by John Mayer Born and Raised World TourTour by John MayerPromotional poster for the tourLocationNorth AmericaAssociated albumBorn and RaisedParadise ValleyStart dateJuly 6, 2013End dateSeptember 20, 2014Legs9No. of shows96John Mayer concert chronology Battle Studies World Tour(2009–10) Born and Raised World Tour(2013–14) The Search for Everything World Tour(2017) The Born and Raised World Tour was the sixth headlining concert tour by American singer John Mayer in s...
For the women's competition, see Malaysia Premier Futsal League (Women). Football leagueMalaysia Premier Futsal LeagueFounded2004; 19 years ago (2004)(rebranded in 2019)CountryMalaysiaConfederationAFCNumber of teams14Level on pyramid1Domestic cup(s)Malaysia Futsal CupInternational cup(s)AFC Futsal Club Championship AFF Futsal Club ChampionshipCurrent championsPahang Rangers (1st title)Most championshipsSelangor MAC (3 titles)TV partnersAstro ArenaWebsitewww.fam.org.my/mpfl-2...
Fariz RM & Dian PP in Collaboration withAlbum kompilasiDirilis14 Oktober 2014GenrePop, jazz, R&BDurasi52:52LabelTarget PopSwara Sangkar EmasProduserSeno M. Hardjo Fariz RM & Dian PP in Collaboration with adalah album kompilasi dari penyanyi Fariz R.M. dan Dian Pramana Poetra yang dirilis pada tahun 2014 di bawah label Target Pop. Album ini berisi tiga belas lagu dari kedua musisi yang didaur ulang oleh berbagai penyanyi. Daftar lagu No.JudulLirikPenampilDurasi1.Kau Seputih Melati ...
LuxembourgBiệt danhD'Roud Léiwen Les Lions Rouges Die Roten Löwen (Những chú sư tử đỏ)Hiệp hộiLiên đoàn bóng đá LuxembourgLiên đoàn châu lụcUEFA (châu Âu)Huấn luyện viên trưởngLuc HoltzĐội trưởngLaurent JansThi đấu nhiều nhấtMario Mutsch (102)Ghi bàn nhiều nhấtLéon Mart (16)Sân nhàSân vận động LuxembourgMã FIFALUX Áo màu chính Áo màu phụ Áo màu khác Hạng FIFAHiện tại 89 (20 tháng 7 năm 2023) ...
Former ice hockey arena in South Ayrshire, Scotland, UK Centrum ArenaComputer generated image of the ArenaLocation125 Ayr Road, Prestwick, ScotlandCoordinates55°29′14″N 4°36′59″W / 55.48722°N 4.61639°W / 55.48722; -4.61639OwnerBarr Holdings LimitedOperatorBarr Leisure LimitedCapacity2733 (all seated)Field size200 ft × 103 ft (61 m × 31 m)SurfaceIIHF SpecificationConstructionBroke ground1986Built1996Opened25 August 1996Closed2...
⟨⟨⟩⟩Hill fort in Maharashtra, India For the town in Chhattisgarh, see Raigarh. Not to be confused with Rajgad Fort. 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.Find sources: Raigad Fort – news · newspapers · books · scholar · JSTOR (June 2022) (Learn how and when to remove this template mes...