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Browsing by Author "Lee, Hyung Ki"

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    Fault simulation and test pattern generation for synchronous and asynchronous sequential circuits
    Lee, Hyung Ki (Virginia Tech, 1993-12-05)
    In this dissertation, we propose two fault simulators, called HOPE and HOPE2, and an autolllatic test pattern generator (ATPG), called ATHENA, for synchronous and asynchronous sequential circuits. HOPE is a parallel fault simulator for synchronous sequential circuits. In HOPE, a packet of 32 faults is simulated in parallel. Several new heuristics are employed in HOPE to accelerate the parallel fault simulation. The heuristics are 1) a reduction of faults to be simulated in parallel, 2) a new fault injection method called functional fault injection, and J) a combination of static and dynamic fault ordering methods. According to our experiments, HOPE is about 2.2 times, on the average, faster than a competing fault simulator, called PROOFS (1]--[2]. for 16 ISCAS89 benchmark circuits [3]. HOPE2 and ATHENA are a fault simulator and an A TPG for asynchronous sequential circuits, respectively. The key idea employed in HOPE2 and ATHENA is 10 transform an asynchronous sequential circuit into a synchronous sequential circuit through remodeling memory elements. We proposed various modeling techniques which transform any asynchronous sequential circuit into a synChronous sequential circuit. Once an asyncllfonous circuit is transformed into a synchronous circuit, various techniques developed for synchronous sequential circuits are employed in HOPE2 and ATHENA. HOPE2 employs the parallel simulation techniques of HOPE. ATHENA employs the back algorithm [4] for test generation, and the parallel fault simulation teChnique for fault simulation. HOPE2 and ATHENA can manage industrial circuits consisting of latches, flip-flops with set/reset, tristate gates, BUS elements, bi-directional I/O pins, mutiplexers, ROMs and RAMs. OUf experimental results on various industrial circuits show that HOPE2 is about two times faster than a commercial fault simulator, the Verifault fault simulator of Cadence, while requiring much smaller memory size. ATHENA also shows high performance for various industrial circuits.
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    On detection of stuck-open faults using stuck-at test sets in CMOS combinational circuits
    Lee, Hyung Ki (Virginia Tech, 1989-03-15)
    The traditional line stuck-at fault model does not properly represent transistor stuck-open (SOP) faults in complementary metal oxide semiconductor (CMOS) circuits. In general, test generation methods for detecting CMOS SOP faults are complex and time consuming due to the sequential behavior of faulty circuits. The majority of integrated circuit manufacturers still rely on stuck-at test sets to test CMOS combinational circuits at the risk of some SOP faults not being detected. In this thesis we investigate two aspects regarding the detection of SOP faults using stuck-at test sets. First, we measure the SOP fault coverage of stuck-at test sets for various CMOS combinational circuits. The SOP fault coverage is compared with that of random pattern test sets. Second, we propose a method to improve the SOP fault coverage of stuck-at test sets by organizing the test sequences of stuck-at test sets. The performance of the proposed method is compared with those of competing methods. Experimental results show that the proposed method leads to smaller test sets and shorter processing time while achieving high SOP fault coverage.