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Nov. 21, 2006ATS'06 1 Spectral RTL Test Generation for Gate-Level Stuck-at Faults Nitin Yogi and Vishwani D. Agrawal Auburn University, Department of ECE,

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Presentation on theme: "Nov. 21, 2006ATS'06 1 Spectral RTL Test Generation for Gate-Level Stuck-at Faults Nitin Yogi and Vishwani D. Agrawal Auburn University, Department of ECE,"— Presentation transcript:

1 Nov. 21, 2006ATS'06 1 Spectral RTL Test Generation for Gate-Level Stuck-at Faults Nitin Yogi and Vishwani D. Agrawal Auburn University, Department of ECE, Auburn, AL 36849, USA

2 ATS'062 Nov. 21, 2006 Outline Need for High Level Testing Problem and Approach Spectral analysis and test generation RTL testing approach Experimental Results Conclusion

3 ATS'063 Nov. 21, 2006 Need for High Level Testing Motivations for high level testing:  Reduced test generation complexity Reduced time and cost for test development  Early resolution of testability issues  Difficulty of gate-level test generation for black box cores with known functionality

4 ATS'064 Nov. 21, 2006 Problem and Approach The problem is …  Develop an effective RTL ATPG method And our approach is:  Implementation-independent characterization: RTL test generation Spectral analysis of RTL vectors  Test generated to cover faults in gate-level implementation: Generation of spectral vectors Fault simulation and vector compaction

5 ATS'065 Nov. 21, 2006 Faults Modeled for an RTL Module Combinational Logic FF Inputs Outputs RTL stuck-at fault sites A circuit is an interconnect of several RTL modules.

6 ATS'066 Nov. 21, 2006 Spectral Characterization of a Digital Bit-Stream 1 1 1 1 1 -1 1 -1 1 1 -1 -1 1 -1 -1 1 1 1 1 1 -1 -1 -1 -1 1 -1 1 -1 -1 1 -1 1 1 1 -1 -1 -1 -1 1 1 1 -1 -1 1 -1 1 1 -1 H 8 = w0w0 w1w1 w2w2 w3w3 w4w4 w5w5 w6w6 w7w7 Walsh functions (order 8) Walsh functions: a complete orthogonal set of basis functions that can represent any arbitrary bit-stream. Walsh functions form the rows of a Hadamard matrix. Example of Hadamard matrix of order 8 time

7 ATS'067 Nov. 21, 2006 Walsh Coefficients of a Bit-Stream A bit-stream is correlated with each row of Hadamard matrix. Highly correlated basis functions => retained as essential components Others => noise. Bit stream to analyze Correlating with Walsh functions by multiplying with Hadamard matrix. Essential component (others noise) Hadamard Matrix Bit stream Spectral coeffs.

8 ATS'068 Nov. 21, 2006 Bit-Stream Generation New spectrums are generated retaining essential components and adding random noise. New spectrums are converted into bit-streams by multiplying with Hadamard matrix. Any number of bit-streams can be generated; All contain the same essential components but differ in noise Perturbation multiplying with Hadamard matrix Original spectrumEssential component retained New bit-stream Bits changed New spectrum

9 ATS'069 Nov. 21, 2006 RTL Testing Approach (Circuit Characterization) RTL test generation:  Test vectors generated for RTL faults (PIs, POs and inputs - outputs of RTL modules and flip-flops.) Spectral analysis:  Test sequences for each input bit-stream are analyzed using Hadamard matrix.  Amount of perturbation is determined by a gradually increasing noise level.

10 ATS'0610 Nov. 21, 2006 Power Spectrum: “Interrupt” Signal Spectral Coefficients Normalized Power Essential components Noise components Random level (1/128) PARWAN Processor Circuit

11 ATS'0611 Nov. 21, 2006 Power Spectrum: “Ready” Signal Random level (1/128) Examples of Essential components Examples of Noise components Normalized Power Spectral Coefficients PARWAN Processor Circuit

12 ATS'0612 Nov. 21, 2006 Power Spectrum: “DataIn[5]” Signal Random level (1/128) Normalized Power Spectral Coefficients Examples of Essential components Examples of Noise components PARWAN Processor Circuit

13 ATS'0613 Nov. 21, 2006 Power Spectrum: A Random Signal Normalized Power Average level (1/128) Spectral Coefficients

14 ATS'0614 Nov. 21, 2006 Selecting Minimal Vector Sequences Using ILP Fault simulation of new sequences  A set of perturbation vector sequences {V 1, V 2,.., V M } are generated.  Vector sequences are fault simulated and faults detected by each is obtained. Compaction problem  Find minimum set of vector sequences which cover all the detected faults.  Minimize Count {V 1, …,V M } to obtain compressed seq. {V 1,…,V C } where {V 1, …,V C } {V 1, …, V M } Fault Coverage {V 1, …,V C } = Fault Coverage {V 1, …,V M }  Compaction problem is formulated as an Integer Linear Program (ILP) [1]. [1] P. Drineas and Y. Makris, “Independent Test Sequence Compaction through Integer Programming," Proc. ICCD’03, pp. 380-386.

15 ATS'0615 Nov. 21, 2006 Results: Circuit Characteristics RTL Spectral ATPG technique applied to the following benchmarks:  4 ITC’99 high level RTL circuits  4 ISCAS’89 circuits.  PARWAN processor (Z. Navabi, VHDL: Analysis and Modeling of Digital Systems, McGraw-Hill, 1993.) Characteristics of benchmark circuits: ATPG for RTL faults and fault simulation performed using commercial sequential ATPG tool Mentor Graphics FlexTest. Results obtained on Sun Ultra 5 machines with 256MB RAM. CircuitbenchmarkPIsPOsFFs b01ITC’99225 b09ITC’991128 b11ITC’997631 b14ITC’993454239 s1488ISCAS’898196 s5378ISCAS’893649179 s9234ISCAS’893739211 s35932ISCAS’89363201728 PARWANprocessor112353

16 ATS'0616 Nov. 21, 2006 Results for b11-A** No. of RTL faults Number of Vectors RTL test cov. (%) CPU* seconds No. of spec. components Gate level test cov. (%) 24022476.1653025674.09 * Sun Ultra 5, 256MB RAM** Area-optimized synthesis in Mentor’s Leonardo No. of gate-level faults RTL ATPG Spectral Test Sets FlexTest Gate-level ATPG Gate level cov. (%) Number of vectors CPU* seconds Gate level cov. (%) Number of vectors CPU* seconds 238088.8476873784.624681866 RTL characterization: RTL-ATPG results:

17 ATS'0617 Nov. 21, 2006 b11-A Circuit

18 ATS'0618 Nov. 21, 2006 PARWAN processor

19 ATS'0619 Nov. 21, 2006 Results Circuit name No. of gate- level faults RTL-ATPG spectral testsFlexTest Gate-level ATPGRandom inputs Cov. (%) No. of vectors CPU (secs) Cov. (%) No. of vectors CPU (secs) No. of vectors Cov (%) b01-A22899.571281999.7775164097.78 b01-D29098.771281999.7791164095.80 b09-A88284.6864073084.56436384384011.71 b09-D104884.2176881578.8255557576806.09 b11-A238088.8476873784.624681866384045.29 b11-D307089.25102498786.163653076384041.42 b142589485.096656543668.7850065741280074.61 s1488418495.6551210398.42470131160067.47 s53781558476.492432208876.798354439384067.10 s5378*1594473.59139971873.3133222567288062.77 s92342897617.366472120.1469671824116015.44 s9234*2940049.47832273448.74123654119217633.06 s3593210320495.70256180195.99744319232050.70 PARWAN538089.111344100687.117183626640076.63 * Reset input added.

20 ATS'0620 Nov. 21, 2006 Conclusion Spectral RTL ATPG technique applied to ITC’99 and ISCAS’89 benchmarks, and a processor circuit. Vectors generated for RTL faults were spectrally analyzed and new vectors generated through perturbation. In most cases, Spectral RTL ATPG gave similar or better test coverage in shorter CPU time as compared to sequential ATPG Test generation using Spectral RTL ATPG brings with it the benefits of high level testing Techniques that will enhance Spectral ATPG are:  Efficient RTL ATPG  Accurate determination and use of noise components  Better compaction algorithms

21 ATS'0621 Nov. 21, 2006 Questions ? Thank You !


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