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# Topic: Combinatorial logic

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 Combinatory logic - Wikipedia, the free encyclopedia Combinatory logic was intended as a simple 'pre-logic' which would clarify the meaning of variables in logical notation, and indeed eliminate the need for them. In computer science, combinatory logic is used as a simplified model of computation, used in computability theory (the study of what can be computed) and proof theory (the study of what can be mathematically proven.) The theory, despite its simplicity, captures many essential features of the nature of computation. Combinatory logic can be looked at as a variation of the lambda calculus, in which lambda expressions (used to allow for functional abstraction) are replaced by a limited set of combinators, primitive functions which contain no free variables. en.wikipedia.org /wiki/Combinatory_logic   (2648 words)

 Encyclopedia: Combinatorial logic Combinatory logic is a simplified model of computation, used in computability theory (the study of what can be computed) and proof theory (the study of what can be mathematically proven.) The theory, despite its simplicity, captures many essential features of the nature of computation. Combinatory logic is a variation of the lambda calculus, in which lambda expressions (used to allow for functional abstraction) are replaced by a limited set of primitive functions. Combinatory logic is a model of computation equivalent to the lambda calculus, but without abstraction. www.nationmaster.com /encyclopedia/Combinatorial-logic   (353 words)

 Electronic device selectably operable as a sequential logic circuit or a combinatorial logic circuit and circuit ... An electronic device, with a plurality of logic stages for functional collaboration, is provided with selection means for selectively operating the plurality of stages to form either a sequential logic circuit or a combinatorial logic circuit. That is, the logic state and the output signals of a combinatorial logic circuit are solely determined by the instant logic input signals to the circuit. The succession of logic states adopted by a sequential logic circuit is such that a next logic state is determined under combined control of input signals and the circuit's previous logic state. www.freepatentsonline.com /6134688.html   (4649 words)

 [No title]   (Site not responding. Last check: 2007-10-21) It should be noted that the claimed combinatorial logic circuit is not a conventional encoder for an error correcting code, in that the claims concern a combinatorial logic circuit whose input/output relation is not invertible. Outputs of a subset of the sections of the combinatorial logic circuit 10 are coupled to inputs of respective ones of the sections of the correction circuit 14. However, if the combinatorial logic circuit does not operate as designed, but the number of errors does not exceed the error correcting capacity of the code, the correction determination circuit 12 and the correction circuit 14 ensure that the signal at the output 18 is nevertheless as designed. www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/76075.011011&ELEMENT_SET=DECL   (6424 words)

 Combinatorial logic   (Site not responding. Last check: 2007-10-21) In digital circuit theory, combinatorial logic(also called combinational logic) is a type of logic circuit whose output is a function of, and only of, thepresent input. This is in contrast to sequential logic, in whichthe output depends not only on the present input but also on the history of the input. For example, the part of an arithmetic logic unit, or ALU, that does mathematical calculations is made from combinatorial logic, although the ALUis controlled by a sequencer that is made from sequential logic. www.therfcc.org /combinatorial-logic-47060.html   (152 words)

 Multiple-bit error correction in computer main memory - Patent 5754753 In particular, by using a combinatorial logic network that can detect multiple bit errors a fast error detection and correction technique can be provided for use with a fast memory apparatus such as main memory in a computer system. By using combinatorial logic the prior techniques of using sequential logic to decode multiple bit error codes is eliminated thereby providing a technique which has a faster response time and thus can be used with faster memory systems without significantly impairing the performance of the memory system. The error detection and correction network includes a combinatorial logic network that can detect the presence of up to N errors in said data and correct up to N-1 errors in said data where N is an integer greater an 2. www.freepatentsonline.com /5754753.html   (14158 words)

 Circuits and methods for characterizing the speed performance of multi-input combinatorial logic - US Patent 6850123   (Site not responding. Last check: 2007-10-21) One or more multi-input combinatorial logic circuits is inserted into the loop so the oscillator produces a periodic signal having a period based, in part, on the delay through the combinatorial logic components. Each flip-flop includes a data terminal D connected to a logic one (e.g., VDD), a clock terminal, a synchronous output terminal Q, and an asynchronous clear terminal C. Test circuits 210A and 210B, identical circuits in the depicted embodiment, are two-input combinatorial logic circuits. To configure the flip-flops to respond to falling edges, the D inputs are connected to a logic voltage level representative of a logic zero and the clock terminals are inverted (i.e., are negative-edge triggered). www.patentstorm.us /patents/6850123.html   (4151 words)

 [No title]   (Site not responding. Last check: 2007-10-21) Outputs of combinatorial logic circuits 14a-b are coupled to registers 16a-b, which in turn have outputs coupled to the logic circuit 17. This data is then processed in the combinatorial circuits 14a-b and a result of processing is latched in the registers 16a-b at the end of this next clock cycle, that is, at the end of the clock cycle in which the multiport memory comes up with the data. By way of example, combinatorial logic circuit 14a is shown to perform an addition 15, but other logic and/or arithmetic operations may be used, either combining data from different ports or using data from one port only. www.wipo.int /cgi-pct/guest/getbykey5?KEY=00/19438.000406&ELEMENT_SET=DECL   (2840 words)

 combinatorial logic - a Whatis.com definition Combinatorial logic is a concept in which two or more input states define one or more output states, where the resulting state or states are related by defined rules that are independent of previous states. In combinatorial logic, the output is a function of the input at a specific time. This contrasts combinatorial logic with sequential logic, in which the current state of the device is affected by previous states. whatis.techtarget.com /definition/0,,sid9_gci826118,00.html   (261 words)

 System for detecting and correcting errors in a CMOS computer system - Patent 4553236 A computer system, in which the scannable latch circuit is used, in conjunction with combinatorial logic and error detection circuitry, may thus monitor the latch output, which is not loaded down by the shift register output, for error detection and other purposes without having to slow down the system operating speed. This logic circuitry performs the designed logic function on the data and at the end of the clock cycle, the output of the combinatorial logic is stored in the next set of latches. Further, error detecting logic may be designed into the combinatorial logic circuits, e.g., parity bits may be added to the word, parity generating and checking circuitry may be added to the combinatorial logic, and the outputs from redundant circuits may be added and their outputs checked to see if they are identical. www.freepatentsonline.com /4553236.html   (4825 words)

 Combinatorial Logic (Using Simulink) The Combinatorial Logic block implements a standard truth table for modeling programmable logic arrays (PLAs), logic circuits, decision tables, and other Boolean expressions. To implement this adder with the Combinatorial Logic block, you enter the 8-by-2 matrix formed by columns c' and s as the Truth table parameter. Sequential circuits (that is, circuits with states) can also be implemented with the Combinatorial Logic block by including an additional input for the state of the block and feeding the output of the block back into this state input. www.tau.ac.il /cc/pages/docs/matlab/help/toolbox/simulink/combinatoriallogic.html   (492 words)

 Combinatorial logic In digital circuit theory, combinatorial logic is a type of logic circuit whose output is a function of, and only of, the present input. Combinatorial logic should not be confused with combinatory logic, a mathematical theory useful in the theory of computation. The text of this article is licensed under the GFDL. www.ebroadcast.com.au /lookup/encyclopedia/co/Combinatorial_logic_(electronics).html   (164 words)

 Digital Logic Logically, we can use these symbols or we can equate them with others according to the needs of the moment. One essential reason for basing logical operations on the binary number system is that it is easy to design simple, stable electronic circuits that can switch back and forth between two clearly-defined states, with no ambiguity attached. Digital logic may be divided into two classes: combinational logic, in which the logical outputs are determined by the logical function being performed and the logical input states at that particular moment; and sequential logic, in which the outputs also depend on the prior states of those outputs. www.play-hookey.com /digital   (645 words)

 CHAPTER TWO: BOOLEAN ALGEBRA (Part 3) This is a combinatorial circuit that accepts four inputs and determines which of the seven segments on a seven-segment LED display should be on (logic one) or off (logic zero). Each logic function should produce a one (segment on) for a given input if that particular segment should be illuminated. Combinatorial circuits are the basis for many components of a basic computer system. www.arl.wustl.edu /~lockwood/class/cs306/books/artofasm/Chapter_2/CH02-3.html   (3515 words)

 EDN Access — 05.12.94 Transition maps guide successful asynchronous state-machine design Combinatorial circuits are those with output values that depend exclusively on the input signal levels. Assume the primitive gates to have zero delay and that the output of the combinatorial circuit (Z*) is the next-state variable. Case 3: The logic diagram in Fig 6a and transition map (Fig 6b) correspond to an unstable circuit. www.edn.com /archives/1994/051294/10df2.htm   (3302 words)

 Circuit and method for implementing combinatorial logic functions - Patent 6208166 A Transfer Logic Cell (TLC) circuit performing non-boolean logic elementary operations between a dual-rail input and a dual-rail output upon assertion of signals on at least one control terminal to operate said circuit into one of four logic modes of operation i.e. It is a further objective of the invention to permit a straightforward cascading of said transfer logic cells to form simply wide logic operators and complex functions without triggering a corresponding dramatic increase of wiring complexity. Obviously, logical functions can be combined into mixed functions such as AND/OR functions and partial results are usable as shown in [640] which is the OR function of bits 0-2 while the bottom result is the OR function on all bits of the A bus. www.freepatentsonline.com /6208166.html   (3194 words)

 System for aiding in the design of combinatorial logic and sequential state machines - Patent 6898563 A computer software tool for aiding in the design of combinatorial logic and sequential state machines comprising, according to the preferred embodiment, an apparatus and methods for representing and displaying a mathematical transform between a binary output variable and a set of binary input variables. The present invention relates, generally, to the field of tools for aiding in the design of combinatorial logic and sequential state machines and, in its preferred embodiments, to the field of computer software and methods for representing and displaying a transform between a binary variable and a set of binary input variables. Implementations of logic, such as code or schematic logic diagrams, may be automatically analyzed and displayed by the method of the present invention through the use of a transform defining the relationship(s) between inputs and outputs. www.freepatentsonline.com /6898563.html   (10223 words)

 INI Programme LAA - Theoretical Computer Science is broadly divided into disciplines dealing with logic, semantics and formal methods on the one hand, and algorithmics and computational complexity on the other. Finite Model Theory: This draws on logic and combinatorial methods to study the expressive power of logical languages in the finite. Constraint Satisfaction: This describes a class of combinatorial search problems that arise in a wide variety of areas of computer science and which have been the focus of sustained research drawing on a rich variety of techniques from algebra, logic and graph theory. www.newton.cam.ac.uk /programmes/LAA   (263 words)

 Introduction to Programmable Logic Programmable logic refers to a general class of devices which can be configured to perform a variety of logic functions. Remember from our discussion of combinatorial logic that any logic function can be implemented as a sum-of-products expression. It is not unusual for a logic design to contain a mix of the two major methods. www.uwm.edu /Course/318-457/proglogic/intro_pld.htm   (1929 words)

 Intelligent Logic For example if you had a combinatorial circuit consisting of mechanical switches you would need to connect each output to be fed back to a relay device and use a contact on the relay for the feedback signal. The convention is that contacts shown as open represent logic true variables and contacts shown as closed represent logic false variables, indicated by a prime after the variable. Perhaps a more significant point is the demonstration that memory appears naturally when there is feedback in a combinatorial logic system and the combination of the logic and the memory in the system leads to the beginnings of intelligence in a system. users.senet.com.au /~dwsmith/async.htm   (4698 words)

 Combinatorial logic - Wikipedia, the free encyclopedia In other words, sequential logic has memory while combinatorial logic does not. Practical computer circuits normally contain a mixture of combinatorial and sequential logic. This page was last modified 19:47, 9 October 2005. en.wikipedia.org /wiki/Combinatorial_logic   (174 words)

 How Do I Generate the ACTgen Reports?   (Site not responding. Last check: 2007-10-21) Logic levels in the "INPUT PORT" section defines the number of combinatorial modules between the input port signal and the sequential macro. The CLK-Q delay is considered the first delay level, and then all combinatorial modules between the flip-flop output and the same or other flip-flop inputs are added to arrive at the total number of logic levels on the internal path. Interpreting Logic Level Data for Combinatorial Macros: For combinatorial macros, the "INPUT PORT" section defines the maximum number of combinatorial modules between the defined input and any output which that input affects. www.actel.com /apps/guru/sep97/mk506.htm   (368 words)

 3 Inferring the sensitivity list for combinatorial logic In MyHDL, combinatorial logic is described by a generator function with a sensitivity list that contains all inputs signals (the signals that are read inside the function). It may be easy to forget some input signals, especially it there are a lot of them or if the code is being modified. However, the semantics of this style are not entirely correct: at the start of the simulation, the combinatorial output will not reflect the initial state of the inputs. jandecaluwe.com /Tools/MyHDL/whatsnew03/section-combinatorial.html   (295 words)

 Asynchronous Logic: Background   (Site not responding. Last check: 2007-10-21) The state is held in a set of flip-flops (registers), and combinatorial logic is used to derive the new state and outputs from the old state and inputs. Level sensitive circuits typically represent a logic one by a high voltage and a logic zero by a low voltage. The advantage of this approach over transition signalling is that the logic processing elements can be much simpler; familiar logic gates process levels whereas the circuits required to process transitions require state and are generally more complex. www.cs.man.ac.uk /async/background/return_async.html   (2612 words)

 PHY107 Combinatorial Logic Circuits   (Site not responding. Last check: 2007-10-21) Choose the representation of the binary data states 0 (False) and 1 (True) for the electronic ciruit. Note that combinatorial logic circuits consist of an output that is independent of the input conditions as a function of time. It is also important to note that in switching from positive coding to negative coding the circuit functionality has gone from AND to OR and not, as might be expected, from AND to NAND. www.shef.ac.uk /physics/teaching/phy107/logic.html   (209 words)

 ipedia.com: Combinatory logic Article   (Site not responding. Last check: 2007-10-21) Combinatory logic is a simplified model of computation, used... Combinatory logic is a variation of the lambda calculus, in which lambda expressions (used to allow for functional abstraction) are replaced by a limited set of combinators, primitive functions which contain no free variables. where V is a variable, P is one of the primitive functions, or E1 and E2 are combinatorial terms. www.ipedia.com /combinatory_logic.html   (2466 words)

 Combinatorial logic : Combinatorial logic (electronics)   (Site not responding. Last check: 2007-10-21) terms defined : Combinatorial logic : Combinatorial logic (electronics) In other words, sequential logic has memory while combinatorial logic doesn't. All is still licensed under the GNU FDL. www.termsdefined.net /co/combinatorial-logic-(electronics).html   (251 words)

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