lec31 - Lecture 31 System Test (Lecture 22alt in the...

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Copyright 2001, Agrawa VLSI Test: Lecture 31/22alt 1 Lecture 31 System Test (Lecture 22alt in the Alternative Sequence) Definition Functional test Diagnostic test Fault dictionary Diagnostic tree System design-for-testability (DFT) architecture System partitioning Core test-wrapper DFT overhead Summary
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Copyright 2001, Agrawa VLSI Test: Lecture 31/22alt 2 A System and Its Testing A system is an organization of components (hardware/software parts and subsystems) with capability to perform useful functions. Functional test verifies integrity of system: Checks for presence and sanity of subsystems Checks for system specifications Executes selected (critical) functions Diagnostic test isolates faulty part: For field maintenance isolates lowest replaceable unit (LRU), e.g., a board, disc drive, or I/O subsystem For shop repair isolates shop replaceable unit (SRU), e.g., a faulty chip on a board Diagnostic resolution is the number of suspected faulty units identified by test; fewer suspects mean higher resolution
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Copyright 2001, Agrawa VLSI Test: Lecture 31/22alt 3 System Test Applications Application Functional test Diagnostic test Resolution Manufacturing Yes LRU, SRU Maintenance Yes Field repair LRU Shop repair SRU LRU: Lowest replaceable unit SRU: Shop replaceable unit
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Copyright 2001, Agrawa VLSI Test: Lecture 31/22alt 4 Functional Test All or selected (critical) operations executed with non-exhaustive data. Tests are a subset of design verification tests (test- benches). Software test metrics used: statement, branch and path coverages; provide low (~70%) structural hardware fault coverage. Examples: Microprocessor test – all instructions with random data (David, 1998). Instruction-set fault model – wrong instruction is executed (Thatte and Abraham, IEEETC -1980).
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Copyright 2001, Agrawa VLSI Test: Lecture 31/22alt 5 Gate-Level Diagnosis e d a b c T3 T1 T2 T4 a b c Stuck-at fault tests: T1 = 010 T2 = 011 T3 = 100 T4 = 110 Logic circuit Karnaugh map (shaded squares are true outputs)
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Copyright 2001, Agrawa VLSI Test: Lecture 31/22alt
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lec31 - Lecture 31 System Test (Lecture 22alt in the...

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