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August 29, 2003Agrawal: VDAT'031 It is Sufficient to Test 25% of Faults Vishwani D. Agrawal Rutgers University, ECE Dept., Piscataway, NJ 08854, USA

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Presentation on theme: "August 29, 2003Agrawal: VDAT'031 It is Sufficient to Test 25% of Faults Vishwani D. Agrawal Rutgers University, ECE Dept., Piscataway, NJ 08854, USA"— Presentation transcript:

1 August 29, 2003Agrawal: VDAT'031 It is Sufficient to Test 25% of Faults Vishwani D. Agrawal Rutgers University, ECE Dept., Piscataway, NJ 08854, USA vishwani02@yahoo.com http://cm.bell-labs.com/cm/cs/who/va A. V. S. S. Prasad and Madhusudan V. Atre Agere Systems, Bangalore 560066, India avssp@agere.comavssp@agere.com mvatre@agere.commvatre@agere.com 7 th International Design & Test Workshops – VDAT’03 Bangalore, August 28-30, 2003

2 August 29, 2003Agrawal: VDAT'032 Test Vector Generation DUT Generate fault list Collapse fault list Generate test vectors Fault Model Required fault coverage

3 August 29, 2003Agrawal: VDAT'033 Definitions Given –T1 is set of all tests for fault F1 –T2 is set of all tests for fault F2 F1 dominates F2 F1 and F2 are equivalent T1 T2 T1=T2

4 August 29, 2003Agrawal: VDAT'034 Structural Equ. and Dom. Structural Equivalence Structural Dominance a b c a 0 a 1 b0b1b0b1 c 0 c 1 a b c a 0 a 1 b0b1b0b1 c 0 c 1

5 August 29, 2003Agrawal: VDAT'035 ISCAS’85 Circuits Circuit name Total faults Collapsed faults (collapse ratio) Equivalence*Dominance** C173422 (0.65)16 (0.47) C432864524 (0.61)449 (0.52) C499998758 (0.76)706 (0.71) C135527101574 (0.58)1210 (0.45) C190838161879 (0.49)1566 (0.41) C267052762747 (0.52)2318 (0.44) C354070803428 (0.48)2794 (0.39) C5315106305350 (0.50)4500 (0.42) C6288125767744 (0.62)5824 (0.46) C7552150127550 (0.50)6134 (0.41) * Fastest, Gentest, Hitec, TetraMax **Fastest

6 August 29, 2003Agrawal: VDAT'036 Problem Statement Reduce the collapsed fault set below 40-60% level. Outline of method: –Use hierarchical fault collapsing (ITC’02) –Use functional dominance (ITC’03)

7 August 29, 2003Agrawal: VDAT'037 Functional Dominance f1f1 f0f0 f2f2 Always 0 f 1 f 2 f 0 + f 1 f 2 f 0 = 0 T1 T2

8 August 29, 2003Agrawal: VDAT'038 An Example a e c a 0 a 1 b0 b1b0 b1 c0 c1c0 c1 d f d 0 d 1 f0 f1f0 f1 e0e1e0e1 b Total faults = 12 Structural Equivalence collapsed faults = 8 Structural Dominance collapsed faults = 6 Three tests, {00,01,10}, cover all faults

9 August 29, 2003Agrawal: VDAT'039 AND Gate a b c a 0 a 1 b 0 b 1 c 0 c 1 a0a0 b0b0 c0c0 a1a1 b1b1 c1c1 a0a1b0b1c0c1a0a1b0b1c0c1 a0111a0111 a11a11 b0111b0111 b11b11 c0111c0111 c1111c1111 Dominance graph Dominance matrix

10 August 29, 2003Agrawal: VDAT'0310 OR Gate c0c0 d0d0 f0f0 c1c1 d1d1 f1f1 c0c1d0d1f0f1c0c1d0d1f0f1 c01c01 c1111c1111 d01d01 d1111d1111 f0111f0111 f1111f1111 Dominance graph Dominance matrix c d f c 0 c 1 d 0 d 1 f 0 f 1

11 August 29, 2003Agrawal: VDAT'0311 Fanout a e c a 0 a 1 b0 b1b0 b1 c 0 c 1 d f d0 d1d0 d1 f 0 f 1 e0e1e0e1 b b0b0 d0d0 e0e0 b1b1 d1d1 e1e1 e0e1b0b1d0d1e0e1b0b1d0d1 e01e01 e11e11 b01b01 b11b11 d01d01 d11d11 Dominance graph Dominance matrix

12 August 29, 2003Agrawal: VDAT'0312 Dominance matrix of Circuit a0a1b0b1c0c1a0a1b0b1c0c1 a0111a0111 a11a11 b0111b0111 b11b11 c0111c0111 c1111c1111 d0d1f0f1d0d1f0f1 111111 d01d01 d111111d111111 f01111f01111 f111111f111111 e0e1e0e1 e0111e0111 e111111e111111 Entries in black obtained from functional dominance expression.

13 August 29, 2003Agrawal: VDAT'0313 Transitive Closure of Dominance matrix a0a1b0b1c0c1a0a1b0b1c0c1 a0111a0111 a11a11 b0111b0111 b11b11 c0111c0111 c1111c1111 d0d1f0f1d0d1f0f1 111111 d01d01 d1111111d1111111 f0111111f0111111 f1111111f1111111 e0e1e0e1 e0111111e0111111 e1111111e1111111 Entries in orange are added in transitive closure.

14 August 29, 2003Agrawal: VDAT'0314 Dominance Fault Collapsing a0a1b0b1c0c1a0a1b0b1c0c1 a0111a0111 a11a11 b0111b0111 b11b11 c0111c0111 c1111c1111 d0d1f0f1d0d1f0f1 111111 d01d01 d1111111d1111111 f0111111f0111111 f1111111f1111111 e0e1e0e1 e0111111e0111111 e1111111e1111111

15 August 29, 2003Agrawal: VDAT'0315 Dominance Collapsed Set a e c a 0 a 1 b0 b1b0 b1 c0 c1c0 c1 d f d0 d1d0 d1 f0 f1f0 f1 e0e1e0e1 b Total faults = 12 Structural Equivalence collapsed faults = 8 Structural Dominance collapsed faults = 6 Functional dominance collapsed faults = 4 Two tests, {01,10}, cover all faults

16 August 29, 2003Agrawal: VDAT'0316 8-bit Ripple Carry Adder (RCA)

17 August 29, 2003Agrawal: VDAT'0317 XOR Cell a b c d e f g h i j k m c 0 c 1 d0d1d0d1 Functional Dom. examples: d 0 j 0, k 1 g 0

18 August 29, 2003Agrawal: VDAT'0318 Collapsed Dominance Matrix of XOR Cell a0a1b0b1c0c1d0d1m0m1a0a1b0b1c0c1d0d1m0m1 a0111a0111 a1111a1111 b0111b0111 b1111b1111 c01c01 c11c11 d01d01 d11d11 m0111m0111 m1111m1111 24x24 matrix is reduced to a 10x10 matrix. Inputs Output Collapsed faults

19 August 29, 2003Agrawal: VDAT'0319 Fault Collapsing Using Functional Dominance Circuit name All faults Number of collapsed faults Structural equivalence Functional dominance xor cell2416 (0.67)4 (0.17) Full-adder6038 (0.63)14 (0.23) 8-bit adder466290 (0.62)112 (0.24) C499exp*27101574 (0.58)586 (0.22) * C499exp implements C1355 with XOR cells.

20 August 29, 2003Agrawal: VDAT'0320 Conclusion Functional dominances can be found for small cells and then applied via hierarchical collapsing to large circuits. With functional dominances, the number of faults for ATPG reduces to about 25%; usually gives smaller test set. Caution: fault coverage may not be correct when the collapsed fault set contains redundant faults; coverage may be evaluated for equivalence collapsed set. References: Prasad et al., ITC’02, pp. 391- 397; Agrawal et al., ITC’03.


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