Nfault detection in sequential circuits pdf

In contrast to a combinational logic, which is fully specified by a truth table, a sequential circuit requires a state. 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. Here is a sequential circuit with two jk flipflops. The stable output of a combinational circuit does not depend on the order in which its.

Give a precise definition of synchronous sequential circuits. Apr 15, 2020 basic concept of fault detection and location in sequential circuits notes edurev is made by best teachers of. Delay testing that requires the application of consecutive twopattern tests is not an easy task in a scanbased environment. This type of circuits uses previous input, output, clock and a memory element. The flipflop outputs also go back into the primitive gates on the left. A fault detection method for combinational circuits aliabbasszoraghchian1, moslem didehban2, mohammadreza mehrabian3 1. Pdf a dynamic diagnosis scheme for synchronous sequential circuits is proposed. Fault modeling of combinational and sequential circuits at. Sequential circuits use current input variables and previous input variables by storeing the information and putting back into the circuit on the next clock activation cycle. In case of sequential circuits a part of the generated vectors has to be applied to the ppis. Leakage current reduction in sequential circuits by.

We now consider the analysis and design of sequential circuits. We will now study the behavior of sequential circuits where their output values are computed. Issues controlling and observing internal states of a sequential circuit scan design solves this problem establishing a known initial state need for backtrace through multiple time. This document is highly rated by students and has been viewed 3462 times. Read, highlight, and take notes, across web, tablet, and phone. The basic circuits from which all flipflops are constructed. For partial scan circuits, we first describe a test application scheme for detect ing transition faults. The initial state however has to be set by a sequence of initialisation vectors, generated by a test pattern generator for sequential circuits, as. This paper proposes a novel approach to the delay fault testing problem in scanbased sequential circuits. On potential fault detection in sequential circuits.

All sequential circuits contain combinational logic in addition to the memory elements. Fault detection in logical circuits by samprakash majumdar, b. Fault diagnosis in sequential circuits sciencedirect. It is assumed that all testing must be performed on the external terminals of the circuits. The values of the flipflops q 1q 0 form the state, or the memory, of the circuit. Introduce several structural and behavioral models for synchronous sequential circuits. Testing digital systems i lecture 11 14 copyright 2010, m. Transition fault testing for sequential circuits ieee xplore. Fault diagnosis in sequential circuits 19 which distinguishes the most faults which. Fault detecting experiments for sequential circuits. Testing 2 fault model stuckat model assume selected wires gate input or output are stuck at logic value 0 or 1 models curtain kinds of fabrication flaws that short circuit. As the asynchronous sequential circuit has become more and more important to digital systems in recent years high reliability and simple maintenance of the circuit is stressed. The figure above shows a theoretical view of how sequential circuits are made up from combinational logic and some storage elements. A thesis in electrical engineering submitted to the graduate faculty of texas tech university in partial fulfillment of the requirements for the degree of master of science in electrical engineering approved c accepted may, 1975.

In contrast with schemes like fault dictionaries no prior. Later, we will study circuits having a stored internal state, i. The design of a synchronous sequential circuit starts from a set of specifications and culminates in a logic diagram or a list of boolean functions from which a logic diagram can be obtained. We suggest a method of finding a set of sequential circuit nodes in. In this type of logic circuits outputs depend only on the current inputs. For combinational circuits, the limit of this research, the results in all cases were favorable to the test sequence.

Fault detection and isolation techniques for quasi delayinsensitive circuits christopher lafrieda and rajit manohar computer systems laboratory cornell university ithaca ny 14853, u. Useful for storing binary information and for the design of asynchronous sequential circuits. Sr or jk flipflops are used zsince truth tables with dont care entries frequently result in circuit simplifications, this favors jk flipflops. For fault detection, the test which detects the most faults which have not yet been detected, is the best choice. Hughes, virgil willis, fault diagnosis of sequential circuits 1969. Since all the circuit action will take place under the control of. A scanbist structure to test delay faults in sequential. For the final vector this part is the next state as produced by the initial vector. Combinational logic circuits circuits without a memory. A fault tolerance technique for combinational circuits based on selectivetransistor redundancy article pdf available in ieee transactions on very large scale integration vlsi systems may.

Gate delay fault test generation for nonscan circuits. Easy to build using jk flipflops use the jk 11 to toggle. Pdf on redundancy and fault detection in sequential. Faults are defined and classified, the problems of detection and. Fault modeling electrical engineering and computer science. These circuits employ storage elements and logic gates. Not practical for use in synchronous sequential circuits. Sequential circuit testing 3 electrical engineering and. We propose an alternative measure of fault detection for potentially detected faults, that is easy to. Fault detection and test minimization methods for combinational circuits a survey.

Insertion of malicious subcircuits that can destroy logical circuit or cause leakage of confidential information from a system necessitates the detection of such subcircuits followed by their masking if possible. Detection equivalence two faults are called detection equivalent if and only if all the tests that detect one fault also detect the other fault, not necessarily at the same output. A sequential circuit may pass through several incorrect states due to a fault, while maintaining correct outputs before the error is detected. Binary counters simple design b bits can count from 0 to 2b. This section discusses three typical highside current sensing implementations, with their advantages and disadvantages. Fault detection in asynchronous sequential circuits. Basically, sequential circuits have memory and combinational circuits do not. Index termscombinational and sequential circuits, fault detec since the union of the two sets in the previous sentence is all of pi, tion, redundancy, testing. Consequently the output is solely a function of the current inputs. Digital electronics part i combinational and sequential. On redundancy and fault detection in sequential circuits. Lecture 11 27 modulo3 counter cyclic structure sequential depth is undefined.

Pdf on potential fault detection in sequential circuits. Diagnostic equivalence implies detection equivalence. Block diagram flip flop flip flop is a sequential circuit which generally samples its inputs and changes its outputs only at. Fault detection in linear sequential cirucits by aleksa petrovic this thesis is concerned with the detection of non transient faults in digital networks. Flip flop is a sequential circuit which generally samples its inputs and changes its outputs only at particular instants of time and not continuously. This solution is based on the combination of a bist structure with a scanbased design to apply delay test pairs to the circuit under test. Pdf fault detection and test minimization methods for. We should know the importance of employing combinational circuits in applicable chips processing is rising, as they are simpler, operate faster, and consume less power than sequential ones. Modifications to test generation and fault simulation algorithms. Note that there are dont care entries whenever there are fewer states than possible state vectors.

Pdf dynamic diagnosis of sequential circuits based on stuckat. This paper describes the design of experimental procedures for determining whether or not a sequential switching circuit is operating in accordance with a given statetable description. Sequential circuits sequential circuits are those with memory, also called feedback. Sequential detection of discretetime signals introduction all of the detection problems we have considered in this class have involved a.

In this, they differ from combinational circuits, which have no memory. This paper is concerned with the diagnosis of faults in synchronous sequential machines. A fault detection method for combinational circuits. July 14, 2003 sequential circuit analysis 11 what do sequential circuits look like. Ripple counter increased delay as in ripplecarry adders delay proportional to the number of bits. Sequential circuits applicable for detecting different types of faults1. Testing of logic circuits fault models test generation and coverage fault detection design for test cs 150 fall 2005 lec. Under the condition that the gain of the inverter in the transient region is larger than 1, onlya. A fault tolerance technique for combinational circuits. Abstract this paper presents a novel circuit fault detection and isolation technique for quasi delayinsensitive asynchronous circuits.

Pdf on redundancy and fault detection in sequential circuits. Department of computer engineering and information technology amirkabir university. 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. In this chapter, we will first consider the simplest form of sequential circuit. But sequential circuit has memory so output can vary based on input.

Also used for cycleaccurate synchronous sequential circuits for logic verification efficient for highly active circuits, but inefficient for lowactivity circuits highlevel e. In this type of logic circuits outputs depend on the current inputs and previous inputs. Fault modeling of combinational and sequential circuits at register transfer level article pdf available in international journal of vlsi design and communication systems 24. Fault detection and isolation techniques for quasi delay. The following important conjecture is easily proven to be valid. Fault detection methods in sequential systems sciencedirect. In comparison, any fault in a combinational circuit can be detected by a single vector. Diagnostic and detection fault collapsing for multiple. Reliability of physical systems is provided by reliability of their parts including logical ones.