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93-466: The PIC16x84 is a microcontroller in the PIC family of controllers produced by Microchip Technology (originally named " Arizona Microchip"). It was Microchip's first microcontroller that utilised "EEPROM" memory technology for the program memory. The use of "EEPROM" technology for program memory has now been disused in favour of "FLASH" memory that is considerably cheaper to manufacture, releases less toxins into

186-404: A power of two multiple of the unit of address resolution (byte or word). Converting the index of an item in an array into the memory address offset of the item then requires only a shift operation rather than a multiplication. In some cases this relationship can also avoid the use of division operations. As a result, most modern computer designs have word sizes (and other operand sizes) that are

279-423: A word is the natural unit of data used by a particular processor design. A word is a fixed-sized datum handled as a unit by the instruction set or the hardware of the processor. The number of bits or digits in a word (the word size , word width , or word length ) is an important characteristic of any specific processor design or computer architecture . The size of a word is reflected in many aspects of

372-640: A 1024   GB flash chip, with eight stacked 96-layer V-NAND chips and with QLC technology. Flash memory stores information in an array of memory cells made from floating-gate transistors . In single-level cell (SLC) devices, each cell stores only one bit of information. Multi-level cell (MLC) devices, including triple-level cell (TLC) devices, can store more than one bit per cell. The floating gate may be conductive (typically polysilicon in most kinds of flash memory) or non-conductive (as in SONOS flash memory). In flash memory, each memory cell resembles

465-489: A 16   GB flash memory chip that was manufactured with 24 stacked NAND flash chips using a wafer bonding process. Toshiba also used an eight-layer 3D IC for their 32   GB THGBM flash chip in 2008. In 2010, Toshiba used a 16-layer 3D IC for their 128   GB THGBM2 flash chip, which was manufactured with 16 stacked 8   GB chips. In the 2010s, 3D ICs came into widespread commercial use for NAND flash memory in mobile devices . In 2016, Micron and Intel introduced

558-433: A 64   MB NOR flash memory chip. In 2009, Toshiba and SanDisk introduced NAND flash chips with QLC technology storing 4 bits per cell and holding a capacity of 64   Gbit. Samsung Electronics introduced triple-level cell (TLC) technology storing 3-bits per cell, and began mass-producing NAND chips with TLC technology in 2010. Charge trap flash (CTF) technology replaces the polysilicon floating gate, which

651-548: A certain number of faults (NOR flash, as is used for a BIOS  ROM, is expected to be fault-free). Manufacturers try to maximize the amount of usable storage by shrinking the size of the transistors or cells, however the industry can avoid this and achieve higher storage densities per die by using 3D NAND, which stacks cells on top of each other. NAND flash cells are read by analysing their response to various voltages. NAND flash uses tunnel injection for writing and tunnel release for erasing. NAND flash memory forms

744-517: A charge-trapping mechanism for NOR flash memory cells. CTF was later commercialized by AMD and Fujitsu in 2002. 3D V-NAND (vertical NAND) technology stacks NAND flash memory cells vertically within a chip using 3D charge trap flash (CTP) technology. 3D V-NAND technology was first announced by Toshiba in 2007, and the first device, with 24 layers, was first commercialized by Samsung Electronics in 2013. 3D integrated circuit (3D IC) technology stacks integrated circuit (IC) chips vertically into

837-426: A computer architecture is designed, the choice of a word size is of substantial importance. There are design considerations which encourage particular bit-group sizes for particular uses (e.g. for addresses), and these considerations point to different sizes for different uses. However, considerations of economy in design strongly push for one size, or a very few sizes related by multiples or fractions (submultiples) to

930-417: A computer's structure and operation; the majority of the registers in a processor are usually word-sized and the largest datum that can be transferred to and from the working memory in a single operation is a word in many (not all) architectures. The largest possible address size, used to designate a location in memory, is typically a hardware word (here, "hardware word" means the full-sized natural word of

1023-486: A count field, by a delimiting character, or by an additional bit called, e.g., flag, or word mark . Such machines often use binary-coded decimal in 4-bit digits, or in 6-bit characters, for numbers. This class of machines includes the IBM 702 , IBM 705 , IBM 7080 , IBM 7010 , UNIVAC 1050 , IBM 1401 , IBM 1620 , and RCA 301. Most of these machines work on one unit of memory at a time and since each instruction or datum

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1116-466: A different architecture, relying on a serial access approach. This makes NAND suitable for high-density data storage but less efficient for random access tasks. NAND flash is often employed in scenarios where cost-effective, high-capacity storage is crucial, such as in USB drives, memory cards, and solid-state drives ( SSDs ). The primary differentiator lies in their use cases and internal structures. NOR flash

1209-501: A fast read access time but it is not as fast as static RAM or ROM. In portable devices, it is preferred to use flash memory because of its mechanical shock resistance since mechanical drives are more prone to mechanical damage. Because erase cycles are slow, the large block sizes used in flash memory erasing give it a significant speed advantage over non-flash EEPROM when writing large amounts of data. As of 2019, flash memory costs greatly less than byte-programmable EEPROM and had become

1302-463: A floating point instruction can only address words while an integer arithmetic instruction can specify a field length of 1-64 bits, a byte size of 1-8 bits and an accumulator offset of 0-127 bits. In a byte-addressable machine with storage-to-storage (SS) instructions, there are typically move instructions to copy one or multiple bytes from one arbitrary location to another. In a byte-oriented ( byte-addressable ) machine without SS instructions, moving

1395-454: A fresh design has to coexist as an alternative size to the original word size in a backward compatible design. The original word size remains available in future designs, forming the basis of a size family. In the mid-1970s, DEC designed the VAX to be a 32-bit successor of the 16-bit PDP-11 . They used word for a 16-bit quantity, while longword referred to a 32-bit quantity; this terminology

1488-425: A more typical 10,000 or 100,000 erase cycles, up to 1,000,000 erase cycles. NOR-based flash was the basis of early flash-based removable media; CompactFlash was originally based on it, though later cards moved to less expensive NAND flash. NAND flash has reduced erase and write times, and requires less chip area per cell, thus allowing greater storage density and lower cost per bit than NOR flash. However,

1581-518: A planar charge trap cell into a cylindrical form. As of 2020, 3D NAND flash memories by Micron and Intel instead use floating gates, however, Micron 128 layer and above 3D NAND memories use a conventional charge trap structure, due to the dissolution of the partnership between Micron and Intel. Charge trap 3D NAND flash is thinner than floating gate 3D NAND. In floating gate 3D NAND, the memory cells are completely separated from one another, whereas in charge trap 3D NAND, vertical groups of memory cells share

1674-404: A power of two times the size of a byte. As computer designs have grown more complex, the central importance of a single word size to an architecture has decreased. Although more capable hardware can use a wider variety of sizes of data, market forces exert pressure to maintain backward compatibility while extending processor capability. As a result, what might have been the central word size in

1767-401: A primary size. That preferred size becomes the word size of the architecture. Character size was in the past (pre-variable-sized character encoding ) one of the influences on unit of address resolution and the choice of word size. Before the mid-1960s, characters were most often stored in six bits; this allowed no more than 64 characters, so the alphabet was limited to upper case. Since it

1860-421: A separate die inside the package. The origins of flash memory can be traced back to the development of the floating-gate MOSFET (FGMOS) , also known as the floating-gate transistor. The original MOSFET was invented at Bell Labs between 1955 and 1960, after Frosch and Derick discovered surface passivation and used their discovery to create the first planar transistors. Dawon Kahng went on to develop

1953-692: A shorter word (16 or 32 bits) may be used in contexts where the range of a wider word is not needed (especially where this can save considerable stack space or cache memory space). For example, Microsoft's Windows API maintains the programming language definition of WORD as 16 bits, despite the fact that the API may be used on a 32- or 64-bit x86 processor, where the standard word size would be 32 or 64 bits, respectively. Data structures containing such different sized words refer to them as: A similar phenomenon has developed in Intel's x86 assembly language – because of

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2046-489: A single 3D IC chip package. Toshiba introduced 3D IC technology to NAND flash memory in April 2007, when they debuted a 16   GB eMMC compliant (product number THGAM0G7D8DBAI6, often abbreviated THGAM on consumer websites) embedded NAND flash memory chip, which was manufactured with eight stacked 2   GB NAND flash chips. In September 2007, Hynix Semiconductor (now SK Hynix ) introduced 24-layer 3D IC technology, with

2139-495: A single byte from one arbitrary location to another is typically: Individual bytes can be accessed on a word-oriented machine in one of two ways. Bytes can be manipulated by a combination of shift and mask operations in registers. Moving a single byte from one arbitrary location to another may require the equivalent of the following: Alternatively many word-oriented machines implement byte operations with instructions using special byte pointers in registers or memory. For example,

2232-424: A single memory product. A single-level NOR flash cell in its default state is logically equivalent to a binary "1" value, because current will flow through the channel under application of an appropriate voltage to the control gate, so that the bitline voltage is pulled down. A NOR flash cell can be programmed, or set to a binary "0" value, by the following procedure: To erase a NOR flash cell (resetting it to

2325-409: A single supply voltage and produce the high voltages that are required using on-chip charge pumps . Over half the energy used by a 1.8 V-NAND flash chip is lost in the charge pump itself. Since boost converters are inherently more efficient than charge pumps, researchers developing low-power SSDs have proposed returning to the dual Vcc/Vpp supply voltages used on all early flash chips, driving

2418-488: A standard metal–oxide–semiconductor field-effect transistor (MOSFET) except that the transistor has two gates instead of one. The cells can be seen as an electrical switch in which current flows between two terminals (source and drain) and is controlled by a floating gate (FG) and a control gate (CG). The CG is similar to the gate in other MOS transistors, but below this, there is the FG insulated all around by an oxide layer. The FG

2511-482: A technology known as CMOS Under the Array/CMOS Under Array (CUA), Core over Periphery (COP), Periphery Under Cell (PUA), or Xtacking, in which the control circuitry for the flash memory is placed under or above the flash memory cell array. This has allowed for an increase in the number of planes or sections a flash memory chip has, increasing from 2 planes to 4, without increasing the area dedicated to

2604-843: A time. NAND flash also uses floating-gate transistors , but they are connected in a way that resembles a NAND gate : several transistors are connected in series, and the bit line is pulled low only if all the word lines are pulled high (above the transistors' V T ). These groups are then connected via some additional transistors to a NOR-style bit line array in the same way that single transistors are linked in NOR ;flash. Compared to NOR flash, replacing single transistors with serial-linked groups adds an extra level of addressing. Whereas NOR flash might address memory by page then word, NAND flash might address it by page, word and bit. Bit-level addressing suits bit-serial applications (such as hard disk emulation), which access only one bit at

2697-453: A time. Execute-in-place applications, on the other hand, require every bit in a word to be accessed simultaneously. This requires word-level addressing. In any case, both bit and word addressing modes are possible with either NOR or NAND flash. To read data, first the desired group is selected (in the same way that a single transistor is selected from a NOR array). Next, most of the word lines are pulled up above V T2 , while one of them

2790-506: A type of flash memory with a charge trap method. In 1998, Boaz Eitan of Saifun Semiconductors (later acquired by Spansion ) patented a flash memory technology named NROM that took advantage of a charge trapping layer to replace the conventional floating gate used in conventional flash memory designs. In 2000, an Advanced Micro Devices (AMD) research team led by Richard M. Fastow, Egyptian engineer Khaled Z. Ahmed and Jordanian engineer Sameer Haddad (who later joined Spansion) demonstrated

2883-435: A variable number of cycles, depending on the size of the operands. The memory model of an architecture is strongly influenced by the word size. In particular, the resolution of a memory address, that is, the smallest unit that can be designated by an address, has often been chosen to be the word. In this approach, the word-addressable machine approach, address values which differ by one designate adjacent memory words. This

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2976-450: A variation, the floating-gate MOSFET, with Taiwanese-American engineer Simon Min Sze at Bell Labs in 1967. They proposed that it could be used as floating-gate memory cells for storing a form of programmable read-only memory ( PROM ) that is both non-volatile and re-programmable. Early types of floating-gate memory included EPROM (erasable PROM) and EEPROM (electrically erasable PROM) in

3069-515: Is also often used to store configuration data in digital products, a task previously made possible by EEPROM or battery-powered static RAM . A key disadvantage of flash memory is that it can endure only a relatively small number of write cycles in a specific block. NOR flash is known for its direct random access capabilities, making it apt for executing code directly. Its architecture allows for individual byte access, facilitating faster read speeds compared to NAND flash. NAND flash memory operates with

3162-444: Is an electrically insulating tunnel oxide layer between the floating gate and the silicon, so the gate "floats" above the silicon. The oxide keeps the electrons confined to the floating gate. Degradation or wear (and the limited endurance of floating gate Flash memory) occurs due to the extremely high electric field (10 million volts per centimeter) experienced by the oxide. Such high voltage densities can break atomic bonds over time in

3255-463: Is an improved version of the PIC16C84, and almost completely compatible, with better program security and using flash memory instead of EEPROM memory for program memory. The PIC16F84/PIC16F84A has 68 bytes of RAM whilst the PIC16C84 has 36 bytes. Since the two chips are so similar they are often referred to by the term PIC16x84 (x is used as a wildcard when referring to chips). The PIC16C84

3348-496: Is easy to erase and requires no special tools to do so. The PIC16F84 and its updated version, the PIC16F84A both utilised FLASH program memory. The PIC16C84, PIC16C84A, PIC16F84 and the PIC16F84A all contain an additional 64 Bytes of EEPROM addressed from the "DATA" memory map. This additional memory is intended for use as "user data", hence the reason it can only be addressed from the "DATA" memory mapping. The PIC16F84/PIC16F84A

3441-483: Is efficient in time and space to have the word size be a multiple of the character size, word sizes in this period were usually multiples of 6 bits (in binary machines). A common choice then was the 36-bit word , which is also a good size for the numeric properties of a floating point format. After the introduction of the IBM System/360 design, which uses eight-bit characters and supports lower-case letters,

3534-525: Is interposed between the CG and the MOSFET channel. Because the FG is electrically isolated by its insulating layer, electrons placed on it are trapped. When the FG is charged with electrons, this charge screens the electric field from the CG, thus, increasing the threshold voltage (V T ) of the cell. This means that the V T of the cell can be changed between the uncharged FG threshold voltage (V T1 ) and

3627-405: Is natural in machines which deal almost always in word (or multiple-word) units, and has the advantage of allowing instructions to use minimally sized fields to contain addresses, which can permit a smaller instruction size or a larger variety of instructions. When byte processing is to be a significant part of the workload, it is usually more advantageous to use the byte , rather than the word, as

3720-484: Is optimal for applications requiring quick access to individual bytes, like in embedded systems for program execution. NAND flash, on the other hand, shines in scenarios demanding cost-effective, high-capacity storage with sequential data access. Flash memory is used in computers , PDAs , digital audio players , digital cameras , mobile phones , synthesizers , video games , scientific instrumentation , industrial robotics , and medical electronics . Flash memory has

3813-636: Is programmed in blocks while EEPROM is programmed in bytes. According to Toshiba, the name "flash" was suggested by Masuoka's colleague, Shōji Ariizumi, because the erasure process of the memory contents reminded him of the flash of a camera . Masuoka and colleagues presented the invention of NOR flash in 1984, and then NAND flash at the IEEE 1987 International Electron Devices Meeting (IEDM) held in San Francisco. Toshiba commercially launched NAND flash memory in 1987. Intel Corporation introduced

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3906-422: Is pulled up to V I . The series group will conduct (and pull the bit line low) if the selected bit has not been programmed. Despite the additional transistors, the reduction in ground wires and bit lines allows a denser layout and greater storage capacity per chip. (The ground wires and bit lines are actually much wider than the lines in the diagrams.) In addition, NAND flash is typically permitted to contain

3999-484: Is sandwiched between a blocking gate oxide above and a tunneling oxide below it, with an electrically insulating silicon nitride layer; the silicon nitride layer traps electrons. In theory, CTF is less prone to electron leakage, providing improved data retention. Because CTF replaces the polysilicon with an electrically insulating nitride, it allows for smaller cells and higher endurance (lower degradation or wear). However, electrons can become trapped and accumulate in

4092-461: Is several units long, each instruction takes several cycles just to access memory. These machines are often quite slow because of this. For example, instruction fetches on an IBM 1620 Model I take 8 cycles (160 μs) just to read the 12 digits of the instruction (the Model II reduced this to 6 cycles, or 4 cycles if the instruction did not need both address fields). Instruction execution takes

4185-528: Is the x86 family, of which processors of three different word lengths (16-bit, later 32- and 64-bit) have been released, while word continues to designate a 16-bit quantity. As software is routinely ported from one word-length to the next, some APIs and documentation define or refer to an older (and thus shorter) word-length than the full word length on the CPU that software may be compiled for. Also, similar to how bytes are used for small numbers in many programs,

4278-510: Is the 64-bit member of that architecture family, continues to refer to 16-bit halfword s, 32-bit word s, and 64-bit doubleword s, and additionally features 128-bit quadword s. In general, new processors must use the same data word lengths and virtual address widths as an older processor to have binary compatibility with that older processor. Often carefully written source code – written with source-code compatibility and software portability in mind – can be recompiled to run on

4371-465: Is the same as the terminology used for the PDP-11. This was in contrast to earlier machines, where the natural unit of addressing memory would be called a word , while a quantity that is one half a word would be called a halfword . In fitting with this scheme, a VAX quadword is 64 bits. They continued this 16-bit word/32-bit longword/64-bit quadword terminology with the 64-bit Alpha . Another example

4464-513: Is thus highly suitable for use in mass-storage devices, such as memory cards and solid-state drives (SSD). For example, SSDs store data using multiple NAND flash memory chips. The first NAND-based removable memory card format was SmartMedia , released in 1995. Many others followed, including MultiMediaCard , Secure Digital , Memory Stick , and xD-Picture Card . A new generation of memory card formats, including RS-MMC , miniSD and microSD , feature extremely small form factors. For example,

4557-479: The C Programming Language . Flash memory Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash , are named for the NOR and NAND logic gates . Both use the same cell design, consisting of floating-gate MOSFETs . They differ at the circuit level depending on whether

4650-502: The PDP-10 byte pointer contained the size of the byte in bits (allowing different-sized bytes to be accessed), the bit position of the byte within the word, and the word address of the data. Instructions could automatically adjust the pointer to the next byte on, for example, load and deposit (store) operations. Different amounts of memory are used to store data values with different degrees of precision. The commonly used sizes are usually

4743-502: The "1" state), a large voltage of the opposite polarity is applied between the CG and source terminal, pulling the electrons off the FG through Fowler–Nordheim tunneling (FN tunneling). This is known as Negative gate source source erase. Newer NOR memories can erase using negative gate channel erase, which biases the wordline on a NOR memory cell block and the P-well of the memory cell block to allow FN tunneling to be carried out, erasing

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4836-712: The 1970s. However, early floating-gate memory required engineers to build a memory cell for each bit of data, which proved to be cumbersome, slow, and expensive, restricting floating-gate memory to niche applications in the 1970s, such as military equipment and the earliest experimental mobile phones . Modern EEPROM based on Fowler-Nordheim tunnelling to erase data was invented by Bernward and patented by Siemens in 1974. And further developed between 1976 and 1978 by Eliyahou Harari at Hughes Aircraft Company and George Perlegos and others at Intel. This led to Masuoka's invention of flash memory at Toshiba in 1980. The improvement between EEPROM and flash being that flash

4929-426: The 36-bit word being especially common on mainframe computers . The introduction of ASCII led to the move to systems with word lengths that were a multiple of 8-bits, with 16-bit machines being popular in the 1970s before the move to modern processors with 32 or 64 bits. Special-purpose designs like digital signal processors , may have any word length from 4 to 80 bits. The size of a word can sometimes differ from

5022-438: The FG is charged. The binary value of the cell is sensed by determining whether there is current flowing through the transistor when V I is asserted on the CG. In a multi-level cell device, which stores more than one bit per cell, the amount of current flow is sensed (rather than simply its presence or absence), in order to determine more precisely the level of charge on the FG. Floating gate MOSFETs are so named because there

5115-540: The I/O interface of NAND flash does not provide a random-access external address bus. Rather, data must be read on a block-wise basis, with typical block sizes of hundreds to thousands of bits. This makes NAND flash unsuitable as a drop-in replacement for program ROM, since most microprocessors and microcontrollers require byte-level random access. In this regard, NAND flash is similar to other secondary data storage devices , such as hard disks and optical media , and

5208-408: The atmosphere and is much more reliable than "EEPROM". Both "EEPROM" and "FLASH" utilise similar forms of "floating gate" technologies to operate. The device features one 8-bit timer, and 13 I/O pins. The PIC16x84 became popular in many hobbyist applications because it uses a serial programming algorithm that lends itself to very simple programmers. Additionally, the PIC16C84 uses EEPROM memory, so it

5301-466: The cell block. Older memories used source erase, in which a high voltage was applied to the source and then electrons from the FG were moved to the source. Modern NOR flash memory chips are divided into erase segments (often called blocks or sectors). The erase operation can be performed only on a block-wise basis; all the cells in an erase segment must be erased together. Programming of NOR cells, however, generally can be performed one byte or word at

5394-502: The cell by increasing the MOSFET's threshold voltage. This, in turn, changes the drain-source current that flows through the transistor for a given gate voltage, which is ultimately used to encode a binary value. The Fowler-Nordheim tunneling effect is reversible, so electrons can be added to or removed from the floating gate, processes traditionally known as writing and erasing. Despite the need for relatively high programming and erasing voltages, virtually all flash chips today require only

5487-402: The cells are logically set to 1. Data can only be programmed in one pass to a page in a block that was erased. The programming process is set one or more cells from 1 to 0. Any cells that have been set to 0 by programming can only be reset to 1 by erasing the entire block. This means that before new data can be programmed into a page that already contains data, the current contents of the page plus

5580-498: The chip. As PIC16C84 supplies became limited due to it being discontinued, the PIC16F84 became popular as it is an almost drop-in replacement. New programming software was needed as the programming algorithm is different but the programming hardware required was the same. Even later (1998) Microchip Technology introduced the improved PIC16F84A which allowed for faster clock speeds (up to 20 MHz), faster programming, and decreased

5673-584: The control or periphery circuitry. This increases the number of IO operations per flash chip or die, but it also introduces challenges when building capacitors for charge pumps used to write to the flash memory. Some flash dies have as many as 6 planes. As of August 2017, microSD cards with a capacity up to 400 GB (400 billion bytes) are available. The same year, Samsung combined 3D IC chip stacking with its 3D V-NAND and TLC technologies to manufacture its 512   GB KLUFG8R1EM flash memory chip with eight stacked 64-layer V-NAND chips. In 2019, Samsung produced

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5766-404: The core of the removable USB storage devices known as USB flash drives , as well as most memory card formats and solid-state drives available today. The hierarchical structure of NAND flash starts at a cell level which establishes strings, then pages, blocks, planes and ultimately a die. A string is a series of connected NAND cells in which the source of one cell is connected to the drain of

5859-686: The current draw of the chip. The PIC16x84 microcontroller is a member of Microchip's 14-bit series (the instruction word size is 14 bits for all instructions), making the '84 a good development prototype for other similar but cheaper one-time-programmable 14-bit devices. Microchip's product line has gone through many revisions since the 16x84 and more powerful, flexible, cheaper pin-compatible PICs have been developed. Existing PIC 16x84 code may require some modifications for these variants, namely making sure pins with multiple functions have been set up properly. The latter two are 8-bit enhanced mid-range core with 14 additional instructions and optimizations for

5952-576: The dominant memory type wherever a system required a significant amount of non-volatile solid-state storage . EEPROMs, however, are still used in applications that require only small amounts of storage, e.g. in SPD implementations on computer memory modules. Flash memory packages can use die stacking with through-silicon vias and several dozen layers of 3D TLC NAND cells (per die) simultaneously to achieve capacities of up to 1 tebibyte per package using 16 stacked dies and an integrated flash controller as

6045-575: The entire device. NOR flash memory allows a single machine word to be written – to an erased location – or read independently. A flash memory device typically consists of one or more flash memory chips (each holding many flash memory cells), along with a separate flash memory controller chip. The NAND type is found mainly in memory cards , USB flash drives , solid-state drives (those produced since 2009), feature phones , smartphones , and similar products, for general storage and transfer of data. NAND or NOR flash memory

6138-416: The expected due to backward compatibility with earlier computers. If multiple compatible variations or a family of processors share a common architecture and instruction set but differ in their word sizes, their documentation and software may become notationally complex to accommodate the difference (see Size families below). Depending on how a computer is organized, word-size units may be used for: When

6231-497: The first commercial NOR type flash chip in 1988. NOR-based flash has long erase and write times, but provides full address and data buses , allowing random access to any memory location . This makes it a suitable replacement for older read-only memory (ROM) chips, which are used to store program code that rarely needs to be updated, such as a computer's BIOS or the firmware of set-top boxes . Its endurance may be from as little as 100 erase cycles for an on-chip flash memory, to

6324-462: The flash storage device (such as SSD ), the data actually written to the flash memory may be 0011 1100. Vertical NAND (V-NAND) or 3D NAND memory stacks memory cells vertically and uses a charge trap flash architecture. The vertical layers allow larger areal bit densities without requiring smaller individual cells. It is also sold under the trademark BiCS Flash , which is a trademark of Kioxia Corporation (formerly Toshiba Memory Corporation). 3D NAND

6417-418: The floating gate. This is why data retention goes down and the risk of data loss increases with increasing degradation. The silicon oxide in a cell degrades with every erase operation. The degradation increases the amount of negative charge in the cell over time due to trapped electrons in the oxide and negates some of the control gate voltage, this over time also makes erasing the cell slower, so to maintain

6510-435: The high Vpp voltage for all flash chips in an SSD with a single shared external boost converter. In spacecraft and other high-radiation environments, the on-chip charge pump is the first part of the flash chip to fail, although flash memories will continue to work – in read-only mode – at much higher radiation levels. In NOR flash, each cell has one end connected directly to ground, and

6603-415: The higher charged FG threshold voltage (V T2 ) by changing the FG charge. In order to read a value from the cell, an intermediate voltage (V I ) between V T1 and V T2 is applied to the CG. If the channel conducts at V I , the FG must be uncharged (if it were charged, there would not be conduction because V I is less than V T2 ). If the channel does not conduct at the V I , it indicates that

6696-659: The microSD card has an area of just over 1.5 cm , with a thickness of less than 1 mm. NAND flash has achieved significant levels of memory density as a result of several major technologies that were commercialized during the late 2000s to early 2010s. NOR flash was the most common type of Flash memory sold until 2005, when NAND flash overtook NOR flash in sales. Multi-level cell (MLC) technology stores more than one bit in each memory cell . NEC demonstrated multi-level cell (MLC) technology in 1998, with an 80   Mb flash memory chip storing 2 bits per cell. STMicroelectronics also demonstrated MLC in 2000, with

6789-422: The new data must be copied to a new, erased page. If a suitable erased page is available, the data can be written to it immediately. If no erased page is available, a block must be erased before copying the data to a page in that block. The old page is then marked as invalid and is available for erasing and reuse. This is different from operating system LBA view, for example, if operating system writes 1100 0011 to

6882-465: The next one. Depending on the NAND technology, a string typically consists of 32 to 128 NAND cells. Strings are organised into pages which are then organised into blocks in which each string is connected to a separate line called a bitline. All cells with the same position in the string are connected through the control gates by a wordline. A plane contains a certain number of blocks that are connected through

6975-474: The nitride, leading to degradation. Leakage is exacerbated at high temperatures since electrons become more excited with increasing temperatures. CTF technology however still uses a tunneling oxide and blocking layer which are the weak points of the technology, since they can still be damaged in the usual ways (the tunnel oxide can be degraded due to extremely high electric fields and the blocking layer due to Anode Hot Hole Injection (AHHI). Degradation or wear of

7068-450: The norm, although there is some use of the IEC binary prefixes . Several of the earliest computers (and a few modern as well) use binary-coded decimal rather than plain binary , typically having a word size of 10 or 12 decimal digits, and some early decimal computers have no fixed word length at all. Early binary systems tended to use word lengths that were some multiple of 6-bits, with

7161-413: The number of bits increases, the number of possible states also increases and thus the cell is less tolerant of adjustments to programming voltages, because there is less space between the voltage levels that define each state in a cell. The process of moving electrons from the control gate and into the floating gate is called Fowler–Nordheim tunneling , and it fundamentally changes the characteristics of

7254-516: The other end connected directly to a bit line. This arrangement is called "NOR flash" because it acts like a NOR gate: when one of the word lines (connected to the cell's CG) is brought high, the corresponding storage transistor acts to pull the output bit line low. NOR flash continues to be the technology of choice for embedded applications requiring a discrete non-volatile memory device. The low read latencies characteristic of NOR devices allow for both direct code execution and data storage in

7347-435: The oxides is the reason why flash memory has limited endurance, and data retention goes down (the potential for data loss increases) with increasing degradation, since the oxides lose their electrically insulating characteristics as they degrade. The oxides must insulate against electrons to prevent them from leaking which would cause data loss. In 1991, NEC researchers including N. Kodama, K. Oyama and Hiroki Shirai described

7440-413: The performance and reliability of the NAND chip, the cell must be retired from use. Endurance also decreases with the number of bits in a cell. With more bits in a cell, the number of possible states (each represented by a different voltage level) in a cell increases and is more sensitive to the voltages used for programming. Voltages may be adjusted to compensate for degradation of the silicon oxide, and as

7533-620: The processor, as opposed to any other definition used). Documentation for older computers with fixed word size commonly states memory sizes in words rather than bytes or characters. The documentation sometimes uses metric prefixes correctly, sometimes with rounding, e.g., 65 kilowords (kW) meaning for 65536 words, and sometimes uses them incorrectly, with kilowords (kW) meaning 1024 words (2 ) and megawords (MW) meaning 1,048,576 words (2 ). With standardization on 8-bit bytes and byte addressability, stating memory sizes in bytes, kilobytes, and megabytes with powers of 1024 rather than 1000 has become

7626-459: The relatively thin oxide, gradually degrading its electrically insulating properties and allowing electrons to be trapped in and pass through freely (leak) from the floating gate into the oxide, increasing the likelihood of data loss since the electrons (the quantity of which is used to represent different charge levels, each assigned to a different combination of bits in MLC Flash) are normally in

7719-410: The same bitline. A flash die consists of one or more planes, and the peripheral circuitry that is needed to perform all the read, write, and erase operations. The architecture of NAND flash means that data can be read and programmed (written) in pages, typically between 4 KiB and 16 KiB in size, but can only be erased at the level of entire blocks consisting of multiple pages. When a block is erased, all

7812-407: The same silicon nitride material. An individual memory cell is made up of one planar polysilicon layer containing a hole filled by multiple concentric vertical cylinders. The hole's polysilicon surface acts as the gate electrode. The outermost silicon dioxide cylinder acts as the gate dielectric, enclosing a silicon nitride cylinder that stores charge, in turn enclosing a silicon dioxide cylinder as

7905-574: The serial-linked groups in which conventional NAND flash memory is configured. There is also string stacking, which builds several 3D NAND memory arrays or "plugs" separately, but stacked together to create a product with a higher number of 3D NAND layers on a single die. Often, two or 3 arrays are stacked. The misalignment between plugs is in the order of 30 to 10nm. Growth of a group of V-NAND cells begins with an alternating stack of conducting (doped) polysilicon layers and insulating silicon dioxide layers. Machine word In computing ,

7998-426: The standard size of a character (or more accurately, a byte ) becomes eight bits. Word sizes thereafter are naturally multiples of eight bits, with 16, 32, and 64 bits being commonly used. Early machine designs included some that used what is often termed a variable word length . In this type of organization, an operand has no fixed length. Depending on the machine and the instruction, the length might be denoted by

8091-622: The state of the bit line or word lines is pulled high or low: in NAND flash, the relationship between the bit line and the word lines resembles a NAND gate; in NOR flash, it resembles a NOR gate. Flash memory, a type of floating-gate memory, was invented by Fujio Masuoka at Toshiba in 1980 and is based on EEPROM technology. Toshiba began marketing flash memory in 1987. EPROMs had to be erased completely before they could be rewritten. NAND flash memory, however, may be erased, written, and read in blocks (or pages), which generally are much smaller than

8184-590: The support for various sizes (and backward compatibility) in the instruction set, some instruction mnemonics carry "d" or "q" identifiers denoting "double-", "quad-" or "double-quad-", which are in terms of the architecture's original 16-bit word size. An example with a different word size is the IBM System/360 family. In the System/360 architecture , System/370 architecture and System/390 architecture, there are 8-bit byte s, 16-bit halfword s, 32-bit word s and 64-bit doubleword s. The z/Architecture , which

8277-418: The tunnel dielectric that surrounds a central rod of conducting polysilicon which acts as the conducting channel. Memory cells in different vertical layers do not interfere with each other, as the charges cannot move vertically through the silicon nitride storage medium, and the electric fields associated with the gates are closely confined within each layer. The vertical collection is electrically identical to

8370-438: The unit of address resolution. Address values which differ by one designate adjacent bytes in memory. This allows an arbitrary character within a character string to be addressed straightforwardly. A word can still be addressed, but the address to be used requires a few more bits than the word-resolution alternative. The word size needs to be an integer multiple of the character size in this organization. This addressing approach

8463-417: Was first announced by Toshiba in 2007. V-NAND was first commercially manufactured by Samsung Electronics in 2013. V-NAND uses a charge trap flash geometry (which was commercially introduced in 2002 by AMD and Fujitsu ) that stores charge on an embedded silicon nitride film. Such a film is more robust against point defects and can be made thicker to hold larger numbers of electrons. V-NAND wraps

8556-555: Was introduced in 1993 and has been hailed as the first PIC microcontroller to feature a serial programming algorithm and EEPROM memory (it was preceded by the Motorola MC68HC805B6 and MC68HC805C4 along with the MC68HC11E2 with serial bootloader and EEPROM program storage released in the late 1980s). These chips lend themselves to hobby use: only a simple and cheap programmer is required to program, erase and reprogram

8649-457: Was used in the IBM 360, and has been the most common approach in machines designed since then. When the workload involves processing fields of different sizes, it can be advantageous to address to the bit. Machines with bit addressing may have some instructions that use a programmer-defined byte size and other instructions that operate on fixed data sizes. As an example, on the IBM 7030 ("Stretch"),

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