lec7 - Lecture 7 Fault Simulation s s s s Problem and...

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Copyright 2001, Agrawa VLSI Test: Lecture 7 1 Lecture 7 Fault Simulation Problem and motivation Fault simulation algorithms Serial Parallel Deductive Concurrent Random Fault Sampling Summary
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Copyright 2001, Agrawa VLSI Test: Lecture 7 2 Problem and Motivation Fault simulation Problem: Given A circuit A sequence of test vectors A fault model Determine Fault coverage - fraction (or percentage) of modeled faults detected by test vectors Set of undetected faults Motivation Determine test quality and in turn product quality Find undetected fault targets to improve tests
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Copyright 2001, Agrawa VLSI Test: Lecture 7 3 Fault simulator in a VLSI Design Process Verified design netlist Verification input stimuli Fault simulator Test vectors Modeled fault list Test generator Test compactor Fault coverage ? Remove tested faults Delete vectors Add vectors Low Adequate Stop
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Copyright 2001, Agrawa VLSI Test: Lecture 7 4 Fault Simulation Scenario Circuit model: mixed-level Mostly logic with some switch-level for high-impedance (Z) and bidirectional signals High-level models (memory, etc.) with pin faults Signal states: logic Two (0, 1) or three (0, 1, X) states for purely Boolean logic circuits Four states (0, 1, X, Z) for sequential MOS circuits Timing: Zero-delay for combinational and synchronous circuits Mostly unit-delay for circuits with feedback
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Copyright 2001, Agrawa VLSI Test: Lecture 7 5 Fault Simulation Scenario (Continued) Faults: Mostly single stuck-at faults Sometimes stuck-open, transition, and path-delay faults; analog circuit fault simulators are not yet in common use Equivalence fault collapsing of single stuck-at faults Fault-dropping -- a fault once detected is dropped from consideration as more vectors are simulated; fault- dropping may be suppressed for diagnosis Fault sampling -- a random sample of faults is simulated when the circuit is large
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This note was uploaded on 01/26/2010 for the course ECE 682 taught by Professor Tom during the Spring '10 term at University of South Dakota.

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lec7 - Lecture 7 Fault Simulation s s s s Problem and...

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