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Encyclopedia > Digital electronics
A digital circuit that acts as a binary clock, hand-wired on a series of breadboards
A digital circuit that acts as a binary clock, hand-wired on a series of breadboards

Digital electronics are electronics systems that use digital signals. Digital electronics are representations of Boolean algebra and are used in computers, mobile phones, and other consumer products. Image File history File linksMetadata Download high-resolution version (2560x1920, 2297 KB) author: Diogo Sousa aka orium description: A binary watch made by me File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Digital electronics Binary clock Metadata This... Image File history File linksMetadata Download high-resolution version (2560x1920, 2297 KB) author: Diogo Sousa aka orium description: A binary watch made by me File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Digital electronics Binary clock Metadata This... A binary clock is a clock which displays traditional sexagesimal time in a binary format. ... A breadboard with a completed circuit A breadboard is a reusable solderless device used to build a (generally temporary) prototype of an electronic circuit and for experimenting with circuit designs. ... This article is about the engineering discipline. ... The term digital signal is used to refer to more than one concept. ... Boolean algebra is the finitary algebra of two values. ... This article is about the machine. ... A consumer product is generally any tangible personal property for sale and that is used for personal, family, or household purposes. ...


Digital electronics or any digital circuit are usually made from large assemblys of logic gates, simple electronic representations of Boolean logic functions. A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. ...


To most electronic engineers, the terms "digital circuit", "digital system" and "logic" are interchangeable in the context of digital circuits. Logic (from Classical Greek λόγος logos; meaning word, thought, idea, argument, account, reason, or principle) is the study of the principles and criteria of valid inference and demonstration. ...

Contents

Advantages

The usual advantages of digital circuits when compared to analog circuits are:

  • Digital systems interface well with computers and are easy to control with software. New features can often be added to a digital system without changing hardware. Often this can be done outsided a factory by replacing the product's software. So, the product's design errors can be corrected after the product is in a customer's hands.
  • Information storage can be easier in digital systems than in analog ones. The noise-immunity of digital systems permit data to be stored ans retrieved without degradation. In an analog system, noise from aging and wear degrade the information stored. In a digital system, as long as the total noise is below a certain level, the information can be recovered perfectly.

This article is about the machine. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ...

Robustness

One of the primary advantages of digital electronics is its robustness. Digital electronics is robust because if the noise is less than the noise margin then the system performs as if there were no noise at all. Therefore, digital signals can be regenerated to achieve lossless data transmission, within certain limits. In electrical engineering, noise margin is the amount by which a signal exceeds the minimum amount for proper operation. ...


Analog signal transmission and processing, by contrast, always introduces noise.


Disadvantages

Digital circuits use more energy than analog circuits to accomplish the same tasks, thus producing more heat as well. In portable or battery-powered systems this can limit use of digital ssytems.


When power is plentiful, a digital system is often preferred because of all the advantages listed above.


For example battery-powered cellular telephones often use a low-power analog front-end to amplify and tune in the radio signals from the base station. However, a base station has grid power and can use power-hungry, but very flexible software radios. Such base stations can be easily reprogrammed to process the signals used in new cellular standards. For the British rock band of the same name, see Amplifier (band). ... A tuner is a circuit module or free-standing equipment which detects radio-frequency (RF) signals usually of low amplitude and amplifies them and converts them to a form suitable for further processing. ... A software-defined radio (SDR) system is a radio communication system which uses software for the modulation and demodulation of radio signals. ...


Digital circuits are sometimes more expensive, especially in small quantities.


The sensed world is analog, and signals from this world are analog quantities. For example, light, temperature, sound, electrical conductivity, electric and magnetic fields are analog. Most useful digital systems must translate from continuous analog signals to discrete digital signals. This causes quantization errors. Look up quantization in Wiktionary, the free dictionary. ...


Quantization error can be reduced if the system to stores enough digital data to represent the signal to the desired degree of fidelity. The Nyquist-Shannon sampling theorem provides an important guideline as to how much digital data is needed to accurately portray a given analog signal. For the financial services company, see Fidelity Investments. ... The Nyquist-Shannon sampling theorem is the fundamental theorem in the field of information theory, in particular telecommunications. ...


Fragility

Digital systems can be fragile, in that if a single piece of digital data is lost or misinterpreted, the meaning of large blocks of related data can completely change.


Digital fragility can be reduced by designing a digital system for robustness. For example, a parity bit or other error management method can be inserted into the signal path. These schemes help the system measure and correct errors, or at least ask for a new copy of the data. In a state-machine, the state transition logic can be designed to catch unused states and trigger a reset sequence or other error recovery routine. For example, it is standard practice in embedded software design to fill unused program memory with interrupt instructions that point to an error recovery routine, to help guard against a failure that corrupts the microcontroller's instruction pointer which could otherwise cause random code to be executed. A parity bit is a binary digit that indicates whether the number of bits with value of one in a given set of bits is even or odd. ... It has been suggested that this article or section be merged with Forward error correction. ... A router, an example of an embedded system. ...


Analog issues in digital circuits

Digital circuits are made from analog components. The design must assure that the analog nature of the components doesn't dominate the desired digital behavior. Digital systems must manage noise and timing margins, parasitic inductances and capacitances, and filter power connections. Television signal splitter consisting of a hi-pass filter (left) and a low-pass filter (right). ...


Bad designs have intermittent problems such as "glitches", vanishingly-fast pulses that may trigger some logic but not others, "runt pulses" that do not reach valid "threshold" voltages, or unexpected ("undecoded") combinations of logic states.


Since digital circuits are made from analog components, digital circuits calculate mor eslowly than analog circuits that use a similar amount of space and power. However, the digital circuit will calculate more repeatably, because of its high noise immunity.


Construction

A digital circuit is often constructed from small electronic circuits called logic gates. Each logic gate represents a function of boolean logic. A logic gate is an arrangement of electrically controlled switches. A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. ... Boolean logic is a complete system for logical operations. ...


The output of a logic gate is an electrical flow or voltage, that can, in turn, control more logic gates. In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... Electrical potential is the potential energy per unit charge associated with a static (time-invariant) electric field, also called the electrostatic potential or the electric potential, typically measured in volts. ...


Logic gates often use the fewest number of transistors in order to reduce their size, power consumption and cost, and increase their reliability.


Integrated circuitss, are the least expensive way to make logic gates in large volumes. Integrated circuits are usually designed by engineers using electronic design automation software (See below for more information). Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ... PCB Layout Program Electronic design automation (EDA) is the category of tools for designing and producing electronic systems ranging from printed circuit boards (PCBs) to integrated circuits. ...


Another form of digital circuit is constructed from lookup tables, (many sold as "programmable logic devices", though other kinds of PLDs exist). Lookup tables can perform the same functions as machines based on logic gates, but can be easily reprogrammed without changing the wiring. This means that a designer can often repair design errors without changing the arrangement of wires. Therefore, in small volume products, programmable logic devices are often the preferred solution. They are usually designed by engineers using electronic design automation software (See below for more information). A programmable logic device or PLD is an electronic component used to build digital circuits. ... PCB Layout Program Electronic design automation (EDA) is the category of tools for designing and producing electronic systems ranging from printed circuit boards (PCBs) to integrated circuits. ...


When the volumes are medium to large, and the logic can be slow, or involves complex algorithms or sequences, often a small microcontroller is programmed to make an embedded system. These are usually programmed by software engineers. It has been suggested that this article or section be merged with embedded microprocessor. ... A computer program is a collection of instructions that describe a task, or set of tasks, to be carried out by a computer. ... A router, an example of an embedded system. ... Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software. ...


When only one digital circuit is needed, and its design is totally customized, as for a factory production line controller, the conventional solution is a programmable logic controller, or PLC. These are usually programmed by electricians, using ladder logic. PLC & input/output arrangements A Programmable Logic Controller, PLC, or Programmable Controller is a digital computer used for automation of industrial processes, such as control of machinery on factory assembly lines. ... Ladder logic is a method of drawing electrical logic schematics. ...


Structure of digital systems

Engineers use many methods to minimize logic functions, in order to reduce the circuit's complexity. When the complexity is less, the circuit also has fewer errors and less electronics, and is therefore less expensive.


The most widely used simplification is a minimization algorithm like the Espresso heuristic logic minimizer within a CAD system, although historically, binary decision diagrams, an automated Quine–McCluskey algorithm, truth tables, Karnaugh Maps, and Boolean algebra have been used. The Espresso heuristic logic minimizer is a widely used computer program for efficiently reducing the complexity of digital electronic gate circuits. ... “CAD” redirects here. ... A binary decision diagram (BDD), like a negation normal form (NNF) or a propositional directed acyclic graph (PDAG), is a data structure that is used to represent a Boolean function. ... The Quine–McCluskey algorithm is a method used for minimization of boolean functions. ... Truth tables are a type of mathematical table used in logic to determine whether an expression is true or whether an argument is valid. ... An example Karnaugh map The Karnaugh map, also known as a Veitch diagram (K-map or KV-map for short), is a tool to facilitate management of Boolean algebraic expressions. ... Boolean algebra is the finitary algebra of two values. ...


Representations are crucial to an engineer's design of digital circuits. Some analysis methods only work with particular representations.


The classical way to represent a digital circuit is with an equivalent set of logic gates. Another way, often with the least electronics, is to construct an equivalent system of electronic switches (usually transistors). One of the easiest ways is to simply have a memory containing a truth table. The inputs are fed into the address of the memory, and the data outputs of the memory become the outputs. A logic gate is an arrangement of electronically-controlled switches used to calculate operations in Boolean algebra. ... For other uses, see Transistor (disambiguation). ... Truth tables are a type of mathematical table used in logic to determine whether an expression is true or whether an argument is valid. ...


For automated analysis, these representations have digital file formats that can be processed by computer programs. Most digital engineers are very careful to select computer programs ("tools") with compatible file formats.


To choose representations, engineers consider types of digital systems. Most digital systems divide into "combinatorial systems" and "sequential systems." A combinatorial system always presents the same output when given the same inputs. It is basically a representation of a set of logic functions, as already discussed.


A sequential system is a combinatorial system with some of the outputs fed back as inputs. This makes the digital machine perform a "sequence" of operations. The simplest sequential system is probably a flip flop, a mechanism that represents a binary digit or "bit". In digital circuits, the flip-flop, latch, or bistable multivibrator is an electronic circuit which has two stable states and thereby is capable of serving as one bit of memory. ... The binary or base-two numeral system is a system for representing numbers in which a radix of two is used; that is, each digit in a binary numeral may have either of two different values. ... A numeral is a symbol or group of symbols that represents a number. ... This article is about the unit of information. ...


Sequential systems are often designed as state machines. In this way, engineers can design a system's gross behavior, and even test it in a simulation, without considering all the details of the logic functions. In the theory of computation, a finite state machine (FSM) or finite state automaton (FSA) is an abstract machine that has only a finite, constant amount of memory. ...


Sequential systems divide into two further subcategories. "Synchronous" sequential systems change state all at once, when a "clock" signal changes state. "Asynchronous" sequential systems propagate changes whenever inputs change. Synchronous sequential systems are made of well-characterized asynchronous circuits such as flip-flops, that change only when the clock changes, and which have carefully designed timing margins. A synchronous circuit is a digital circuit in which the parts are synchronized by a clock signal. ... In a synchronous system, operations are coordinated under the centralized control of a fixed-rate clock signal or several clocks. ...


The usual way to implement a synchronous sequential state machine is divide it into a piece of combinatorial logic and a set of flip flops called a "state register." Each time a clock signal ticks, the state register captures the feedback generated from the previous state of the combinatorial logic, and feeds it back as an unchanging input to the combinatorial part of the state machine. The fastest rate of the clock is set by the most time-consuming logic calculation in the combinatorial logic.


The state register is just a representation of a binary number. If the states in the state machine are numbered (easy to arrange), the logic function is some combinatorial logic that produces the number of the next state.


In comparison, asynchronous systems are very hard to design because all possible states, in all possible timings must be considered. The usual method is to construct a table of the minimum and maximum time that each such state can exist, and then adjust the circuit to minimize the number of such states, and force the circuit to periodically wait for all of its parts to enter a compatible state. (This is called "self-resynchronization.") Without such careful design, it is easy to accidentally produce asynchronous logic that is "unstable", that is, real electronics will have unpredictable results because of the cumulative delays caused by small variations in the values of the electronic components. Certain circuits (such as the synchronizer flip-flops, switch debouncers, and the like which allow external unsynchronized signals to enter synchronous logic circuits) are inherently asynchronous in their design and must be analyzed as such.


As of 2005, almost all digital machines are synchronous designs because it is much easier to create and verify a synchronous design -- the software currently used to simulate digital machines does not yet handle asynchronous designs. However, asynchronous logic is thought to be superior, if it can be made to work, because its speed is not constrained by an arbitrary clock; instead, it simply runs at the maximum speed permitted by the propagation rates of the logic gates from which it is constructed. Building an asynchronous circuit using faster parts implicitly makes the circuit "go" faster.


More generally, many digital systems are data flow machines. These are usually designed using synchronous register transfer logic, using hardware description languages such as VHDL or Verilog. In integrated circuit design, Register Transfer Level (RTL) description is a way of describing the operation of a synchronous digital circuit. ... VHDL, or VHSIC Hardware Description Language, is commonly used as a design-entry language for field-programmable gate arrays and application-specific integrated circuits in electronic design automation of digital circuits. ... Verilog is a hardware description language (HDL) used to model electronic systems. ...


In register transfer logic, binary numbers are stored in groups of flip flops called registers. The outputs of each register are a bundle of wires called a "bus" that carries that number to other calculations. A calculation is simply a piece of combinatorial logic. Each calculation also has an output bus, and these may be connected to the inputs of several registers. Sometimes a register will have a multiplexer on its input, so that it can store a number from any one of several buses. Alternatively, the outputs of several items may be connected to a bus through buffers that can turn off the output of all of the devices except one. A sequential state machine controls when each register accepts new data from its input. The binary or base-two numeral system is a system for representing numbers in which a radix of two is used; that is, each digit in a binary numeral may have either of two different values. ... For other uses, see Number (disambiguation). ... In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to frequently used values—typically, these values are involved in multiple expression evaluations occurring within a small region on the program. ... In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers and typically is controlled by device driver software. ... Schematic of a 2-to-1 Multiplexer. ... In electronics a 3-state digital logic gate is one in which the output circuit can be completely switched off, putting the output in a high-impedance state. ...


In the 1980s, some researchers discovered that almost all synchronous register-transfer machines could be converted to asynchronous designs by using first-in-first-out synchronization logic. In this scheme, the digital machine is characterized as a set of data flows. In each step of the flow, an asynchronous "synchronization circuit" determines when the outputs of that step are valid, and presents a signal that says, "grab the data" to the stages that use that stage's inputs. It turns out that just a few relatively simple synchronization circuits are needed.


The most general-purpose register-transfer logic machine is a computer. This is basically an automatic binary abacus. The control unit of a computer is usually designed as a microprogram run by a microsequencer. A microprogram is much like a player-piano roll. Each table entry or "word" of the microprogram commands the state of every bit that controls the computer. The sequencer then counts, and the count addresses the memory or combinatorial logic machine that contains the microprogram. The bits from the microprogram control the arithmetic logic unit, memory and other parts of the computer, including the microsequencer itself. This article is about the machine. ... The Canard Digérateur of Jacques de Vaucanson, hailed in 1739 as the first automaton capable of digestion. ... The binary or base-two numeral system is a system for representing numbers in which a radix of two is used; that is, each digit in a binary numeral may have either of two different values. ... It has been suggested that Abax be merged into this article or section. ... A control unit is the part of a CPU or other device that directs its operation. ... A microprogram implements a CPU instruction set. ... In the field of computer architecture and engineering, a sequencer or microsequencer, is a part of a control unit of a CPU. It generates the addresses used to step through the microprogram of a control store. ... The arithmetic logic unit/arithmetic-logic unit (ALU) of a computers CPU is a part of the execution unit, a core component of all CPUs. ... For other uses, see Memory (disambiguation). ... In the field of computer architecture and engineering, a sequencer or microsequencer, is a part of a control unit of a CPU. It generates the addresses used to step through the microprogram of a control store. ...


In this way, the complex task of designing the controls of a computer is reduced to a simpler task of programming a relatively independent collection of much simpler logic machines.


Computer architecture is a specialized engineering activity that tries to arrange the registers, calculation logic, buses and other parts of the computer in the best way for some purpose. Computer architects have applied large amounts of ingenuity to computer design to reduce the cost and increase the speed and immunity to programming errors of computers. An increasingly common goal is to reduce the power used in a battery-powered computer system, such as a cell-phone. Many computer architects serve an extended apprenticeship as microprogrammers. A typical vision of a computer architecture as a series of abstraction layers: hardware, firmware, assembler, kernel, operating system and applications (see also Tanenbaum 79). ...


"Specialized computers" are usually a conventional computer with a special-purpose microprogram.


Automated design tools

To save costly engineering effort, much of the effort of designing large logic machines has been automated. The computer programs are called "electronic design automation tools" or just "EDA." PCB Layout Program Electronic design automation (EDA) is the category of tools for designing and producing electronic systems ranging from printed circuit boards (PCBs) to integrated circuits. ...


Simple truth table-style descriptions of logic are often optimized with EDA that automatically produces reduced systems of logic gates or smaller lookup tables that still produce the desired outputs. The most common example of this kind of software is the Espresso heuristic logic minimizer. The Espresso heuristic logic minimizer is a widely used computer program for efficiently reducing the complexity of digital electronic gate circuits. ...


Most practical algorithms for optimizing large logic systems use algebraic manipulations or binary decision diagrams, and there are promising experiments with genetic algorithms and annealing optimizations. Quine-McCluskey algorithm is a method used for minimization of Boolean functions. ... A binary decision diagram (BDD), like a negation normal form (NNF) or a propositional directed acyclic graph (PDAG), is a data structure that is used to represent a Boolean function. ... A genetic algorithm (or GA) is a search technique used in computing to find true or approximate solutions to optimization and search problems. ... For other uses, see Annealing. ...


To automate costly engineering effort, some EDA can take state tables that describe state machines and automatically produce a truth table or a function table for the combinatorial part of a state machine. The state table is a piece of text that lists each state, together with the conditions controlling the transitions between them and the belonging output signals. This page meets Wikipedias criteria for speedy deletion. ... In the theory of computation, a finite state machine (FSM) or finite state automaton (FSA) is an abstract machine that has only a finite, constant amount of memory. ... Truth tables are a type of mathematical table used in logic to determine whether an expression is true or whether an argument is valid. ...


It is common for the function tables of such computer-generated state-machines to be optimized with logic-minimization software such as Minilog. The Espresso heuristic logic minimizer is a widely used computer program for efficiently reducing the complexity of digital electronic gate circuits. ...


Often, real logic systems are designed as a series of sub-projects, which are combined using a "tool flow." The tool flow is usually a "script," a simplified computer language that can invoke the software design tools in the right order.


Tool flows for large logic systems such as microprocessors can be thousands of commands long, and combine the work of hundreds of engineers.


Writing and debugging tool flows is an established engineering specialty in companies that produce digital designs. The tool flow usually terminates in a detailed computer file or set of files that describe how to physically construct the logic. Often it consists of instructions to draw the transistors and wires on an integrated circuit or a printed circuit board. Photo of transistor types (tape measure marked in centimeters) Transistor in the SMD form factor The transistor is a solid state semiconductor device used for amplification and switching. ... Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ... Part of a 1983 Sinclair ZX Spectrum computer board. ...


Parts of tool flows are "debugged" by verifying the outputs of simulated logic against expected inputs. The test tools take computer files with sets of inputs and outputs, and highlight discrepancies between the simulated behavior and the expected behavior.


Once the input data is believed correct, the design itself must still be verified for correctness. Some tool flows verify designs by first producing a design, and then scanning the design to produce compatible input data for the tool flow. If the scanned data matches the input data, then the tool flow has probably not introduced errors.


The functional verification data are usually called "test vectors." The functional test vectors may be preserved and used in the factory to test that newly constructed logic works correctly. However, functional test patterns don't discover common fabrication faults. Production tests are often designed by software tools called "test pattern generators." These generate test vectors by examining the structure of the logic and systematically generating tests for particular faults.


Once a design exists, and is verified and testable, it often needs to be processed to be manufacturable as well. Modern integrated circuits have features smaller than the wavelength of the light used to expose the photoresist. Manufacturability software adds interference patterns to the exposure masks to eliminate open-circuits, and enhace the masks' resolution and contrast.


Design for testability

A large logic machine (say, with more than a hundred logical variables) can have an astronomical number of possible states. Obviously, in the factory, testing every state is impractical if testing each state takes a microsecond, and there are more states than the number of microseconds since the universe began. Unfortunately, this ridiculous-sounding case is typical.


Fortunately, large logic machines are almost always designed as assemblies of smaller logic machines. To save time, the smaller sub-machines are isolated by permanently-installed "design for test" circuitry, and are tested independently.


One common test scheme known as "scan design" moves test bits serially (one after another) from external test equipment through one or more serial shift registers known as "scan chains". Serial scans have only one or two wires to carry the data, and minimize the physical size and expense of the infrequently-used test logic. In digital circuits a shift register is a group of flip flops set up in a linear fashion which have their inputs and outputs connected together in such a way that the data are shifted down the line when the circuit is activated. ...


After all the test data bits are in place, the design is reconfigured to be in "normal mode" and one or more clock pulses are applied, to test for faults (e.g. stuck-at low or stuck-at high) and capture the test result into flip-flops and/or latches in the scan shift register(s). Finally, the result of the test is shifted out to the block boundary and compared against the predicted "good machine" result. In digital circuits, the flip-flop, latch, or bistable multivibrator is an electronic circuit which has two stable states and thereby is capable of serving as one bit of memory. ...


In a board-test environment, serial to parallel testing has been formalized with a standard called "JTAG" (named after the "Joint Testing Acting Group" that proposed it). JTAG, an acronym for Joint Test Action Group, is the usual name used for the IEEE 1149. ...


Another common testing scheme provides a test mode that forces some part of the logic machine to enter a "test cycle." The test cycle usually exercises large independent parts of the machine.


Trade-offs

Several numbers determine the practicality of a system of digital logic. Engineers explored numerous electronic devices to get an ideal combination of speed, low cost and reliability.


The cost of a logic gate is crucial. In the 1930s, the earliest digital logic systems were constructed from telephone relays because these were inexpensive and relatively reliable. After that, engineers always used the cheapest available electronic switches that could still fulfill the requirements. Face The 1930s (years from 1930–1939) were described as an abrupt shift to more radical and conservative lifestyles, as countries were struggling to find a solution to the Great Depression, also known in Europe as the World Depression. ...


The earliest integrated circuits were a happy accident. They were constructed not to save money, but to save weight, and permit the Apollo Guidance Computer to control an inertial guidance system for a spacecraft. The first integrated circuit logic gates cost nearly $50 (in 1960 dollars, when an engineer earned $10,000/year). To everyone's surprise, by the time the circuits were mass-produced, they had become the least-expensive method of constructing digital logic. Improvements in this technology have driven all subsequent improvements in cost. Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ... An inertial guidance system consists of an Inertial Measurement Unit (IMU) combined with a set of guidance algorithms and control mechanisms, allowing the path of a vehicle to be controlled according to the position determined by the inertial navigation system. ...


With the rise of integrated circuits, reducing the absolute number of chips used represented another way to save costs. The goal of a designer is not just to make the simplest circuit, but to keep the component count down. Sometimes this results in slightly more complicated designs with respect to the underlying digital logic but nevertheless reduces the number of components, board size, and even power consumption. An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ...


For example, in some logic families, NAND gates are the simplest digital gate to build. All other logical operations can be implemented by NAND gates. If a circuit already required a single NAND gate, and a single chip normally carried four NAND gates, then the remaining gates could be used to implement other logical operations like logical and. This could eliminate the need for a separate chip containing those different types of gates. ... ... ... ... Logical conjunction (usual symbol and) is a logical operator that results in true if both of the operands are true. ...


The "reliability" of a logic gate describes its mean time between failure (MTBF). Digital machines often have millions of logic gates. Also, most digital machines are "optimized" to reduce their cost. The result is that often, the failure of a single logic gate will cause a digital machine to stop working.


Digital machines first became useful when the MTBF for a switch got above a few hundred hours. Even so, many of these machines had complex, well-rehearsed repair procedures, and would be nonfunctional for hours because a tube burned-out, or a moth got stuck in a relay. Modern transistorized integrated circuit logic gates have MTBFs of nearly a trillion (1x10^12) hours, and need them because they have so many logic gates.


The "fan out" describes how many logic inputs can be controlled by a single logic output. The minimum practical fan out is about five. Modern electronic logic using CMOS transistors for switches have fanouts near fifty, and can sometimes go much higher. For other uses, see CMOS (disambiguation). ... For other uses, see Transistor (disambiguation). ...


The "switching speed" describes how many times per second an inverter (an electronic representation of a "logical not" function) can change from true to false and back. Faster logic can accomplish more operations in less time. Digital logic first became useful when switching speeds got above fifty hertz, because that was faster than a team of humans operating mechanical calculators. Modern electronic digital logic routinely switches at five gigahertz (5x109 hertz), and some laboratory systems switch at more than a terahertz (1x1012 hertz). This article is about the SI unit of frequency. ... A gigahertz is a billion hertz or a thousand megahertz, a measure of frequency. ... The hertz (symbol: Hz) is the SI unit of frequency. ...


Non-electronic logic

It is possible to construct non-electronic digital mechanisms. In principle, any technology capable of representing discrete states and representing logic operations could be used to build mechanical logic. Danny Hillis, co-author of The Connection Machine, once built a working computer from Tinker Toys, string, a brick, and a sharpened pencil, which is supposed to be in the Houston Museum of Science. This article needs to be cleaned up to conform to a higher standard of quality. ... Thinking Machines CM-2 at the Computing Museum in San Jose. ...


Hydraulic, pneumatic and mechanical versions of logic gates exist and are used in situations where electricity cannot be used. The first two types are considered under the heading of fluidics. One application of fluidic logic is in military hardware that is likely to be exposed to a nuclear electromagnetic pulse (nuclear EMP, or NEMP) that would destroy electrical circuits. Fluidic logic , also known as fluidics , is the implementation of Boolean algebra functions using streams of fluid (such as water or air). ... The term electromagnetic pulse (EMP) has the following meanings: electromagnetic radiation from an explosion (especially a nuclear explosion) or an intensely fluctuating magnetic field caused by Compton-recoil electrons and photoelectrons from photons scattered in the materials of the electronic or explosive device or in a surrounding medium. ...


Mechanical logic is frequently used in inexpensive controllers, such as those in washing machines. Famously, the first computer design, by Charles Babbage, was designed to use mechanical logic. Mechanical logic might also be used in very small computers that could be built by nanotechnology. Babbage redirects here. ... Buckminsterfullerene C60, also known as the buckyball, is the simplest of the carbon structures known as fullerenes. ...


Another example is that if two particular enzymes are required to prevent the construction of a particular protein, this is the equivalent of a biological "NAND" gate.


Recent developments

The discovery of superconductivity has enabled the development of Rapid Single Flux Quantum (RSFQ) circuit technology, which uses Josephson junctions instead of transistors. Most recently, attempts are being made to construct purely optical computing systems capable of processing digital information using nonlinear optical elements. A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. ... In electronics, rapid single flux quantum (RSFQ) is a digital electronics technology that relies on quantum effects in superconducting materials to switch signals, instead of transistors. ... Josephson junctions, first postulated by B. D. Josephson and first made by John Rowell and Philip Anderson, are quantum-mechanical circuit elements of superconducting devices. ... An Optical Computer is a computer that performs its computation with photons as opposed to the more traditional electron-based computation. ... To do: 20th century mathematics chaos theory, fractals Lyapunov stability and non-linear control systems non-linear video editing See also: Aleksandr Mikhailovich Lyapunov Dynamical system External links http://www. ...


Branch pages

Electronics - Combinatorial logic - Boolean algebra - Fuzzy electronics - Logic analyzer - Logic gate - Glitch - Ringing - Programmable logic device - Reconfigurable system - Register This article is about the engineering discipline. ... This article is not about combinatory logic, a topic in mathematical logic. ... Boolean algebra is the finitary algebra of two values. ... Fuzzy electronics is using of fuzzy logic, instude of two value logic in Digital electronics. ... A logic analyzer displays signals in a digital circuit that are too fast to be observed by a human being and presents it to a user so that the user can more easily check correct operation of the digital system. ... A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. ... For other uses, see Glitch (disambiguation). ... In electrical circuits, ringing is an unwanted oscillation of a voltage or current. ... A programmable logic device or PLD is an electronic component used to build digital circuits. ... In electronics and computing, a reconfigurable system is a computer that can, by executing code, change the function of the digital circuits of which it is composed. ... In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to frequently used values—typically, these values are involved in multiple expression evaluations occurring within a small region on the program. ...


See also

This is a list of communications, computers, electronic circuits, fiberoptics, microelectronics, medical electronics, reliablity, and semiconductors. ... It has been suggested that this article or section be merged with Analog electronics. ... An electronic circuit is an electrical circuit that also contains active electronic devices such as transistors or vacuum tubes. ... For other uses, see CMOS (disambiguation). ... Econdin the process of the receptor able to transmit data effectively and Data strobe encoding (or D/S encoding) is an encoding scheme for transmitting data in digital circuits. ... note that demorgans laws are also a big part in circut design. ... A digital system is one that uses discrete values (often electrical voltages), especially those representable as binary numbers, or non-numeric symbols such as letters or icons, for input, processing, transmission, storage, or display, rather than a continuous spectrum of values (ie, as in an analog system). ... Digital signal processing (DSP) is the study of signals in a digital representation and the processing methods of these signals. ... This article does not cite any references or sources. ... This article is about the engineering discipline. ... Large power N-channel field effect transistor The field-effect transistor (FET) is a transistor that relies on an electric field to control the shape and hence the conductivity of a channel in a semiconductor material. ... Fig. ... In the context of hardware and software systems, formal verification is the act of proving or disproving the correctness of intended algorithms underlying a system with respect to a certain formal specification or property, using formal methods of mathematics. ... In electronics, a hardware description language or HDL is any language from a class of computer languages for formal description of electronic circuits. ... Instruction pipelining is a method for increasing the throughput of a digital circuit, particularly a CPU, and implements a form of instruction level parallelism. ... Integrated circuit of Atmel Diopsis 740 System on Chip showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window, showing the integrated circuit inside. ... The method of logical effort, a term coined by Ivan Sutherland and Robert Sproull in 1991, is a straight-forward technique used to estimate delay in a CMOS circuit. ... Boolean minimization may refer to: Karnaugh map Quine-McCluskey algorithm Espresso heuristic logic minimizer Category: ... In digital circuit theory, sequential logic is a type of logic circuit whose output depends not only on the present input but also on the history of the input. ... Microelectronics is a subfield of electronics. ... For other uses, see Glitch (disambiguation). ... In electrical circuits, ringing is an unwanted oscillation of a voltage or current. ... NMOS logic uses n-type metal-oxide-semiconductor field effect transistors (MOSFETs) to implement logic gates and other digital circuits. ... For other uses, see Transistor (disambiguation). ... A Motorola 68000-based computer with various TTL chips. ... A transparent latch is an electronic data storage device with a data input (D), an enable input (E) and a data output (Q). ... A ternary, three-valued or trivalent logic is a term to describe any of several multi-valued logic systems in which there are three truth values indicating true, false and some third value. ... In digital circuits, a runt pulse is a narrow pulse that, due to non-zero rise and fall times of the signal, does not reach a valid high or low level. ... A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electromagnetic waves or acoustic waves, as well as electric power transmission. ... A VHSIC is a Very-High-Speed Integrated Circuit, a type of digital logic circuit. ... Claude Elwood Shannon (April 30, 1916 - February 24, 2001) has been called the father of information theory, and was the founder of practical digital circuit design theory. ... Boolean algebra is the finitary algebra of two values. ... This is a list of electrical input/output standards that have more or less well-defined electrical properties like operating voltage, driving current, level switching behavior, circuit implementation etc. ...

External links

References

  • R.H. Katz, Contemporary Logic Design, The Benjamin/Cummings Publishing Company, 1994.
  • P.K. Lala, Practical Digital Logic Design and Testing, Prentice Hall, 1996.

 
 

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