International journal of computer trends and technology. It is notable that the logic diagnosis of combinational circuits is an inherently. This thesis is concerned with the detection of non transient faults in linear sequential circuits lsc over gf2 8. Both algorithms can be used to identify difficulttotest faults and to quickly construct test sets for specific. Consist of a combinational circuit to which storage elements are connected to form a feedback path. A fault analysis in reversible sequential circuits b. On application of output masking to undetectable faults in. Keywords combinational circuits, fault detection, genetic algorithm, ilp, stuckatfaults, test minimization. The behavior of a clocked sequential circuit is determined from its inputs, outputs. Consequently the output is solely a function of the current inputs.
Their usage in digital circuits provides temporary storage of the. Different types of sequential circuits basics and truth. Fault detection requires at least one redundant measurement, and can be done with a parity space algorithm. Fault diagnosis in sequential circuits sciencedirect. Digital electronics part i combinational and sequential logic. The detection approach is the major part in the design of an afci. Fault detection and classification with optimization. Difference between combinational circuit and sequential. Asynchronous sequential circuits do not use a clock signal as synchronous circuits do. You can see some basic concept of fault detection and location in sequential circuits notes edurev sample questions with examples at the bottom of this page. Initialization fault fault prevents initialization of the faulty circuit. So sequential circuits are sometimes called finitestate machines. The values stored in memory elements define the state of a sequential component.
It is assumed that all testing must be performed on the external terminals of the circuits. Build combinational circuit memoryless devices using gates. Several other approaches to the test generation for sequential machines have appeared. Hughes, virgil willis, fault diagnosis of sequential circuits 1969. The best way around the fault isolation problem is not. Both algorithms can be used to identify difficulttotest faults and to quickly construct test sets for specific faults. On one hand the reversible community has been applying methods used in classical circuits to test. Hyperactive fault fault induces much internal signal activity without reaching po. Here is a sequential circuit with two jk flipflops.
Since memory is finite, therefore, the sequence size must always be finite, which means that the sequential logic can contain only a finite number of states. Fault detecting experiments for sequential circuits. Galey, norby and roth derived tests by logically cutting all the feedback loops. Flip flop is a sequential circuit which generally samples its inputs and changes its outputs only at particular instants of time and not continuously. Agrawal the objective of the research reported in this thesis is to develop new test generation algorithms using mathematical optimization techniques. We show by a simple example that this result does not hold for multioutput circuits even when each output function is prime and irredundant. Different types of sequential circuits basics and truth table. But sequential circuit has memory so output can vary based on input. A fault detection method for combinational circuits. Memory cells are very important in digital systems.
The task of determining whether the fault is present in the system or circuits or not is called fault detection, and identification where it actually occurred is called fault location, and the combined task of detection and location is called as fault diagnosis. The arc fault circuit interrupter afci is a device which can detect the occurring of electric arc in the low voltage circuits, and then it can switch off the power source before the occurring of fire caused by series or parallel electric arc faults. For the development of safety, and efficient advanced systems of supervision, faultdetection and fault diagnosis become increasingly important for many technical processes. Fault detection and diagnostic test set minimization. This type of circuits uses previous input, output, clock and a memory element. Fault detection in combinational circuits using boolean. Yet virtually all useful systems require storage of. Binary counters simple design b bits can count from 0 to 2b. Basic concept of fault detection and location in sequential circuits notes edurev summary and exercise are very important for perfect preparation.
Digital electronics part i combinational and sequential. A sequential circuit is a combination of combinational circuit and a storage element. That is, a detection test in this case must consist of applying certain signals at the circuit s external input terminals and ob. Methods of fault detection in this chapter most of the major techniques of fault detection are described. Instead the circuit is driven by the pulses of the inputs. Combinational logic a combinational system device is a digital system in which the value of the output at any instant depends only on the value of the input at that same instant and not on previous values. Block diagram flip flop flip flop is a sequential circuit which generally samples its. A fault is defined to have occurred when any circuit variable assumes a value 1, 0, or x which differs from that expected, that. Printed in great britain fault detection in combinational circuits using boolean matrices suresh rm and k. Later, we will study circuits having a stored internal state, i. Autumn 2003 cse370 vi sequentai llogci 1 sequential logic sequential circuits simple circuits with feedback latches edgetriggered flipflops timing methodologies cascading flipflops for proper operation clock skew asynchronous inputs metastability and synchronization basic registers shift registers simple counters hardware description languages and sequential logic. These procedures are particularly easy to apply when the given state table is reduced, stronglyconnected, and has a distinguishing sequence, and when the actual circuit has no more states than the given table. Since all the circuit action will take place under the control of a clock, so these circuits are known as.
July 14, 2003 sequential circuit analysis 11 what do sequential circuits look like. Detection of arc fault on low voltage power circuits in. Basic concept of fault detection and location in sequential. Next states and outputs are functions of inputs and present states of storage elements 54 two types of sequential circuits. Elec 326 19 sequential circuit analysis derive the state table from the transition table. Sequential logic sequential circuits simple circuits with feedback latches edgetriggered flipflops timing methodologies cascading flipflops for proper operation clock skew basic registers shift registers simple counters hardware description languages and sequential logic. This process is called fault detection and isolation fdi. The arcfault circuit interrupter afci is a device which can detect the occurring of electric arc in the low voltage circuits, and then it can switch off the power source before the occurring of fire caused by series or parallel electric arc faults. A study is made of singlefault fault collapsing in sequential logic circuits. A pulsed output as used in the block diagrams above is an output that lasts for the duration of a particular input. Flip flop is a sequential circuit which generally samples its inputs and changes its outputs only. This paper presents an integrated technique for fault diagnosis and classification.
Fault diagnosis in sequential circuits 19 which distinguishes the most faults which have not yet been distinguished, should be selected first. This paper focuses on the problem of bounding fault detection probabilities in combinational circuits. This document is highly rated by students and has been viewed 3464 times. For such circuits with many input and output terminals, the suggested algorithm simultaneously gives the boolean differences with respect to all the. In sequential fault diagnosis the process of fault location is carried out step by step, where each step depends on the result of the diagnostic experiment at the previous step. You will not need to know anymore about asynchronous circuits for this course. Bounding fault detection probabilities in combinational. Using a result from the programmable logic array technology, we give an output ordering constraint that.
International journal of computer trends and technology volume2issue2 2011. Multiple transient faults in combinational and sequential circuits. The values of the flipflops q 1q 0 form the state, or the memory, of the circuit. International journal of computer trends and technology volume2issue2 2011 issn. The intersection of faults detected by all failing test sets is used as the reduced fault list. A sequential circuit is a logical circuit, where the output depends on the present value of the input signal as well as the sequence of past inputs. In this paper,the researchers propose the design of reversible circuits using reversible.
It is convenient to group sequential circuits as to whether the generate sequences, detect sequences, or. Easy to build using jk flipflops use the jk 11 to toggle. It is often stated that in irredundant twolevel logic circuits, a test set for all single stuck faults will also detect all multiple stuck faults. Scan 1, 2 is the most popular dft technique for synchronous sequential circuits.
For fault detection, the test which detects the most faults which have not yet been detected, is the best choice. Fault detection techniques 3 12 fault detection techniques 12. The flipflop outputs also go back into the primitive gates on the left. Q x0 x1 aa b0 bb d0 cc a1 dd c1 q z elec 326 20 sequential circuit analysis 4. Fault detection and diagnostic test set minimization mohammed ashfaq shukoor master of science, may 9, 2009 b. Bounding fault detection probabilities in combinational circuits. Multiple transient faults in combinational and sequential. Pdf singlefault faultcollapsing analysis in sequential logic. These circuits do not have memory cells and their output depends only upon the current value of the input.
Synchronous sequential circuits a synchronous sequential circuits is one in which the contents of the memory can change only at discrete instants time or on the of transitions of a clock. Fault detection in combinational circuits using boolean matrices. Diagnostic fault simulation of sequential circuits citeseerx. Sequential logic sequential circuits simple circuits with feedback latches edgetriggered flipflops timing methodologies cascading flipflops for proper operation clock skew asynchronous inputs metastability and synchronization basic registers shift registers simple counters hardware description languages and sequential logic. Jul 19, 2015 may 04, 2020 basic concept of fault detection and location in sequential circuits notes edurev is made by best teachers of. Pdf online multiple fault detection in reversible circuits. To retain the diagnostic capability of the original tests, we combine the. Block diagram flip flop flip flop is a sequential circuit which generally samples its inputs and changes its outputs only at. The concept of augmented boolean matrices is introduced and the same is used to derive an algorithm to find the boolean differences, and hence fault detection tests for combinational circuits. The global test generation algorithm for sequential circuits is tested using the is. It requires a sequence of vectors to detect a single stuckat fault in a. Currently there have been two distinct approaches to testing of reversible and quantum circuits. While a combinational circuit is a function of present input only.
Gatelevel test generation for sequential circuits people. Detection of arc fault on low voltage power circuits in time. Where 00 a, 01 b, 10 c, 11 d derive the state diagram from the state table. The difference between combinational logic circuits and sequential logic circuits. Instead, we provide a few examples to illustrate the technique. Sivakumar2 1department of ece, karpagam university, coimbatore, tamilnadu, india. Turn the circuit into a sequential one need a sequence of at least 2 tests to detect a single fault unique to cmos circuits stuckon a single transistor is permanently shorted irrespective of its gate voltage detection of a stuckopen fault requires two vectors detection of a stuckon fault requires the. It has been noted repeatedly that redundant faults in the original circuit before dft insertion become detectable after dft insertion. Path sensitization for combinational logic circuits one powerful approach to test generation relies on path sensitizing, the applica tion of input such that the output depends directly on the condition of the lead being tested. A systematic approach november 2010 ieee transactions on computeraided design of integrated circuits and systems 2910. Kennings page 1 analysis of clocked synchronous sequential circuits now that we have flipflops and the concept of memory in our circuit, we might want to determine what a circuit is doing. In this method fault detection test may be found by examining the paths of transmission from the location of an assumed fault to one of its primary outputs.
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