Exclusive Test and its Application to Fault Diagnosis

1
Exclusive Test and its Application to Fault
Diagnosis

• Vishwani D. Agrawal
• Dong Hyun Baik
• Yong C. Kim
• Kewal K. Saluja

2
Overview

• Problem Statement
• Introduction
• Background on Diagnosis
• Definitions for Diagnosis
• Main Idea
• Exclusive Test
• Example of Exclusive Test
• Exclusive Test Generation
• Properties of Exclusive Test
• Diagnosis Method
• Results
• Conclusion

3
Problem Statement

• Obtain high resolution diagnostic test using a
  single-fault ATPG.

4
Introduction Background on Diagnosis

• Single-fault dictionary approaches
• Simulation based Chang et al.
• Fault Diagnosis of Digital Systems, NY,
  Wiley-Interscience, 1970
• Most common method for diagnosis
• Diagnostic test pattern generation Specialized
  ATPGs
• Implication based Gruning et al.
• DIATEST A Fast Diagnostic Test Pattern
  Generator for Combinational circuits - ICCAD,
  1991
• Multiple-pass strategy Savir et al. -
• Testing for, and Distinguishing between Failures
  - FTCS, 1982

5
Introduction Definitions for Diagnosis

• Consider CUT on the right
• All 10 faults are detected by 5 test vectors T1
  001, T2 010, T3 011, T4 101, T5 111

• Diagnostic dictionary

T1T2T3T4T5
a1 1 0 1 0 0
b1 0 0 0 1 0
c0 0 0 1 0 1
c1 0 1 0 1 0
d1 0 0 0 1 0
f1 0 0 1 0 0
g0 0 0 0 0 1
h0 0 1 0 0 0
i0 0 1 0 0 1
i1 1 0 1 1 0
T6
0
1
0
0
0
0
0
0
0
1
Add T6 000

• DR 10/91.11
• 10 Faults, but only 9 syndromes
• b1 and d1 cannot be distingushied

• DR 10/101.00
• 10 syndromes
• b1 and d1 are now distinguished

6
Main Idea

• Exclusive test
• An Input vector that detects only one fault from
  a pair of targeted faults at a primary output

• C0 A fault free circuit
• C1 CUT with fault f1
• C2 CUT with fault f2

7
Example of Exclusive Test

• Application
• Generate an additional vector to improve
  diagnostic resolution
• distinguish a pair of faults, b1 and d1.
• Example

• Diagnostic dictionary

T1T2T3T4T5
a1 1 0 1 0 0
b1 0 0 0 1 0
c0 0 0 1 0 1
c1 0 1 0 1 0
d1 0 0 0 1 0
f1 0 0 1 0 0
g0 0 0 0 0 1
h0 0 1 0 0 0
i0 0 1 0 0 1
i1 1 0 1 1 0
T6
0
1
0
0
0
0
0
0
0
1
T6 000
8
Exclusive Test GenerationKim, Agrawal and Saluja
- Multiple Faults Modeling, Simulation and
test VLD 2002
Exclusive test for (b1,d1), T6 000
b1
d1
9
Properties of Exclusive Test

• If there exists an exclusive test two faults then
  they can be distinguished from each other by
  using that test.
• If no exclusive test exists then the faults
  cannot be distinguished two faults form an
  equivalent fault set.

10
Diagnosis Method
Make dictionary and isolate undiagnosed fault sets
Yes
No
Yes
No
Test exists?
Append the test
ATPG aborted
11
Results Model

• For illustration, an XOR-tree is added to the
  output of the circuit under test to make it a
  single output circuit.
• We use to denote a modified circuit with a
  single output XOR-tree at its outputs.
• General multiple-PO case is discussed later.

12
Test Generation-ISCAS85 Circuits
Circuit names c432 c880 c1908 c3540
of fault detection tests 82 104 176 239
of equiv. collapsed faults 524 942 1879 3428
of redundant faults 4 5 4 90
of aborted faults 0 2 27 81
of detected faults 520 935 1848 3257
Fault coverage () 99.24 99.26 98.35 95.01
Fault efficiency () 100 99.79 98.56 97.57
13
Diagnostic Results-ISCAS85 Circuits
Circuit names c432 c880 c1908 c3540
of faults 520 935 1848 3257
of syndromes 426 789 1450 2706
of diagnosed faults 354 686 1121 2351
Diagnostic resolution ( DR) 1.22 1.19 1.27 1.20
Max. faults per syndrome 5 6 8 12
of fault detection vectors 82 104 176 239
of syndromes 506 870 1579 2844
of diagnosed faults 492 808 1331 2559
Diagnostic resolution (DR) 1.03 1.07 1.17 1.14
Max. faults per syndrome 2 3 8 8
Total test vectors 126 152 262 328
of exclusive tests added 44 48 86 89
of equivalent pairs 0 0 0 1
of aborted pairs 14 79 321 662
14
Test Generation-c432
Detection tests c432 c432 c432
of fault detection tests 82 82 82
of equiv. collapsed faults 524 524 524
of redundant faults 4 4 4
of aborted faults 0 0 0
of detected faults 520 520 520
Fault coverage () 99.24 99.24 99.24
Fault efficiency () 100 100 100
15
Diagnostic Results-c432
Circuit names c432 c432 c432
of faults 520 520 520
of syndromes 428 495 500
of diagnosed faults 354 471 479
Diagnostic resolution (DR) 1.22 1.05 1.04
Max. faults per syndrome 5 5 4
of fault sets 506 507 507
of syndromes 506 507 507
of diagnosed faults 492 494 494
Diagnostic resolution (DR) 1.00 1.00 1.00
Max. faults per syndrome 1 1 1
Total test vectors 131 131 123
of exclusive tests 49 13 41
of equivalent pairs 14 13 13
of aborted pairs 0 0 0

• C432 Simulated using tests derived with c432,
  then targeted only undiagnosed faults

16
Conclusion

• Definition of an exclusive test and an ATPG
  method are introduced.
• A comprehensive exclusive test based diagnostic
  method is presented where a conventional single
  fault ATPG can be used.
• Results for ISAS85 benchmark circuits are
  presented.

17
(No Transcript)
18
Supplement 1 Multiple Fault Model

• Kim, Agrawal and Saluja -
• Multiple Faults Modeling, Simulation and test
  - VLSI Design,2002
• Convert multiple fault test generation problem
  into single fault test generation problem.

19
Supplement 2 Test Generation-ISCAS85 Circuits
Circuit names c17 c432 c499 c880 c1355 c1908 c2670 c3540
of detection tests 6 82 58 104 104 176 236 239
of equiv. faults 22 524 758 942 1574 1879 2747 3428
of redundant faults 0 4 0 5 0 4 84 90
of aborted faults 0 0 32 2 32 27 884 81
of detected faults 22 520 726 935 1542 1848 1779 3257
Fault coverage () 100 99.24 95.78 99.26 97.97 98.35 64.76 95.01
Fault efficiency () 100 100 95.78 99.79 97.97 98.56 66.8 97.57
20
Supplement 3 Diagnostic Results-ISCAS85 Circuits
Circuit names c17 c432 c499 c880 c1355 c1908 c2670 c3540
of faults 22 520 726 935 1542 1848 1779 3257
of syndromes 14 426 691 789 873 1450 1285 2706
of diagnosed faults 9 354 661 686 360 1121 972 2351
DR 1.57 1.22 1.05 1.19 1.77 1.27 1.38 1.2
Max. faults per syndrome 4 5 4 6 11 8 11 12
Diagnosis with detection and exclusive tests Diagnosis with detection and exclusive tests Diagnosis with detection and exclusive tests Diagnosis with detection and exclusive tests Diagnosis with detection and exclusive tests Diagnosis with detection and exclusive tests Diagnosis with detection and exclusive tests Diagnosis with detection and exclusive tests Diagnosis with detection and exclusive tests
of faults 22 520 726 935 1542 1848 1779 3256
of syndromes 22 506 710 870 902 1579 1385 2844
of diagnosed faults 22 492 694 808 366 1331 1097 2559
DR 1 1.03 1.02 1.07 1.71 1.17 1.28 1.14
Max. faults per syndrome 1 2 2 3 3 8 11 8
Total test vectors 11 126 72 152 129 262 293 328
of exclusive tests 5 44 14 48 25 86 57 89
of equivalent pairs 0 0 0 0 0 0 0 1
of aborted pairs 0 14 16 79 744 321 630 662