RATS Reliability and Testability Seminar Transition Fault Collapsing

RATS (Reliability and Testability Seminar) Transition Fault Collapsing by Dominance By Intaik Park, RATS, Spring 2005

Outline • • Introduction Transition fault collapsing Experimental Results Conclusion Intaik Park, RATS, Spring 2005 2

Introduction • Transition test – Thorough test quality – Long test generation time – Large pattern size • Generation time, pattern size ∝ fault list size – Reduce fault list size faster test generation! smaller test pattern! Intaik Park, RATS, Spring 2005 3

Definitions • Equivalent faults : faults that are indistinguishable from each other • Dominance : fault f 1 dominates fault f 2 if all tests for f 2 detects f 1 Intaik Park, RATS, Spring 2005 4

Stuck-at fault collapsing Fault Test (A, B) A/0 (1, 1) A/1 (0, 1) B/0 (1, 1) B/1 (1, 0) • A/0, B/0, Z/0 equivalent Z/0 (1, 1) • Z/1 dominates A/1, B/1 Z/1 (0, 1) (1, 0), (0, 0) A B Z Intaik Park, RATS, Spring 2005 5

Stuck-at fault collapsing (cont. ) • Fanout Free network – Test for faults on all the inputs all the faults on inner nodes and output • Stuck-at fault collapsing – Limit faults to all the inputs of the fanout free network Intaik Park, RATS, Spring 2005 6

Outline • • Introduction Transition fault collapsing Experimental Results Conclusion Intaik Park, RATS, Spring 2005 7

Transition fault collapsing A B Z Fault Test (AB AB) A stf (11 01) (10 01) A str (01 11) (00 11) B stf (11 10) (01 10) B str (10 11) (00 11) Z stf • Z str dominates A str, B str Z str Intaik Park, RATS, Spring 2005 (11 01) (11 10) (11 00) (01 11) (10 11) (00 11) 8

Transition fault collapsing A B Z Fault Test (AB AB) A stf (11 01) (10 01) A str (01 11) (00 11) B stf (11 10) (01 10) B str (10 11) (00 11) Z stf • Z str dominates A str, B str • Z stf dominates A stf, B stf Z str Intaik Park, RATS, Spring 2005 (11 01) (11 10) (11 00) (01 11) (10 11) (00 11) 9

Definition • One-way robust transition test : Transition delay test in which all sensitizing inputs do not change in one of the transitions A B Z • A stf, B stf : Robust transition • A str, B str : non-robust transition Intaik Park, RATS, Spring 2005 10

One way robust transition test • One way robust transition test for all inputs of fanout free network test for all inner nodes and output A B C D Z • A stf, B stf, C stf, D stf: Robust transition • A str, B str, C str, D str: non-robust transition Intaik Park, RATS, Spring 2005 11

Methodology • Extract inputs of fanout free network • One way robust transition test for all inputs • Transition test for all uncovered faults Intaik Park, RATS, Spring 2005 12

Outline • • Introduction Transition fault collapsing Experimental Results Conclusion Intaik Park, RATS, Spring 2005 13

Experiment 1 setup • Transition test generation Test 1: all faults Test 2: faults on inputs of fanout free regions (additional top-off patterns) Intaik Park, RATS, Spring 2005 14

Experiment 1 results test set # pat # faults test 1 6, 137 278, 750 97. 75 83. 08 5, 566 114, 450 96. 97 71. 05 437 8, 307 97. 74 45. 37 6, 003 278, 750 97. 74 116. 42 initial test 2 top-off total Intaik Park, RATS, Spring 2005 cov (%) cpu (s) 15

Experiment 2 setup Test 1: Test 2: Test 3: Transition test One way robust transition test (all inputs of gates) One way robust transition test (all inputs gates of fanout free network) * No random fill Intaik Park, RATS, Spring 2005 16

Experiment 2 results Test # pat # fault cov (%) cpu Test 1 17, 038 261, 690 90. 46 6 h 49 m Test 2 22, 785 295, 588 90. 53 8 h 38 m Test 3 18, 829 168, 366 89. 93 6 h 25 m Intaik Park, RATS, Spring 2005 17

Outline • • Introduction Transition fault collapsing Experimental Results Conclusion Intaik Park, RATS, Spring 2005 18

Conclusion • Experiment 1: reduced pattern size • Experiment 2: reduced generation time • Future work: – Combine both benefits? – Robust test for entire fanout free region? (using path delay fault ATPG) Intaik Park, RATS, Spring 2005 19