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Unformatted text preview: ECE 553: Testing and Testable Design of Digital Systems Department of Electrical and Computer Engineering University of WisconsinMadison ECE 553 : Testing and Testable Design of Digital Systems Fall 20112012 Final Examination SOLUTION CLOSED BOOK Kewal K. Saluja Date: December 17, 2011 Place: Room 2540 Engineering Hall Time: 2:45  4:45 PM Duration: 120 minutes PROBLEM TOPIC POINTS SCORE 1 Test Economics 15 2 Fault Simulation 10 3 Test Generation 6 4 Test Compaction 8 5 Memory Test 14 6 Pseudoexhaustive test 10 7 DFT: Full and Partial scan 16 8 BIST 12 9 Boundary Scan 9 TOTAL 100 Last Name: SOLUTION First Name: Show your work carefully for both full and partial credit. You will be given credit only for what appears on your exam. Use extra sheets if you need more space to write 1 Fall 2011 (Lec: Saluja, TA: Millican) ECE 553: Testing and Testable Design of Digital Systems 1. ( 15 points ) Test Economics A board manufacturer uses 25 ICs of the same kind. The IC vendor provided the following specifications of its product: Area of the IC, A = 0.75 sq cm. Fault density, f = 1.45 faults/sq cm Clustering factor, = 0.11 Fault coverage, T = 90% Cost of the IC = $ 4.00 Now answer the following, and while answering you must show your work. (a) ( 3 points ) Determine the Defect Level of the product sold by the IC vendor. Using the equation for Defect level DL = 1 parenleftbigg + TAf + Af parenrightbigg and substituting T = 0.90, A = 0.75, f = 1.45 and = 0.11 we get DL ( T ) = 0.0104179, i.e. 10418 ppm (b) ( 5 points ) Determine the average cost of producing a good board. You can ignore the cost of printed circuit, the board hardware, and the test equipment. Probability of a board being good is (1 DL ) 25 . Which is 0.769. Hence the average cost of a good board will be 25 4 . 769 . which is $ 129.93. (c) ( 7 points ) The board manufacturer is willing to pay $0.50 more for each IC, provided the IC vendor will raise the fault coverage to 95%. Is this a good deal for the board manufacturer? You must provide a quantitative reasoning and you must show your work. We can determine the defect level (DL) for T = 0.95. Which is 5100 ppm. Again the probability of a board being good will be 0.880032. This will result into average cost of a board to be 25 4 . 5 . 88 . Which is $127.84. Hence, this is a better deal for the board manufacturer. 2 Fall 2011 (Lec: Saluja, TA: Millican) ECE 553: Testing and Testable Design of Digital Systems 2. ( 10 points ) Parallel Fault Simulation The circuit of Fig 1 is to be simulated using parallel fault simulation method for the following input pattern: A B C = 1 0 1 A B C 1 3 2 4 5 7 8 9 6 Figure 1: Combinational Circuit for Parallel Fault Simulation Assuming that the word size of a computer is 5 bits and the bits are numbered from 0 to 4 starting from the right most bit as shown in the Fig 2....
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