exam2.sol - ELEC 5970-001/6970-001 Special Topics in...

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ELEC 5970-001/6970-001 Special Topics in Electrical Engineering Low-Power Design of Electronic Circuits Fall 2005 Exam 2 Assigned 11/27/05, due 12/08/05 Attempt all three problems. Total points 30 Problem 1: A combinational one-bit adder cell with a carry input is fully tested by five vectors 000, 111, 001, 010 and 101. 10 points a. Give a procedure to re-sequence these vectors to minimize the peak power consumption during test. b. How will you further reduce the average power consumption of the re-sequenced test vectors. Solution: a. The following graph shows the Hamming distances (bit changes) between vectors. To have a shortest distance tour, we should enter and exit a node through unit distance edges. That means the node should have two unit-distance edges. We notice that 111 has only one unit-distance edge. So we can make it a start (or end) node. A shortest distance tour, 111, 101, 001, 000, 010, which has a total of 4 transitions, is shown on the graph. ELEC5970/6970 Exam 2 Solution Page 1 of 6 Fall 2005 000 111 001 010 101 3 2 2 3 1 2 1 1 2 1 Start
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b. If we repeat the vectors, the average number of transitions per vector will decrease, reducing the power consumption. This has the same effect as slowing down the clock. If two consecutive vectors have several transitions, several vectors can be inserted between them such that transitions are made gradually. In all of these methods the test time increases. The procedure of duplicating vectors or clock slowing are applicable to sequential circuits as well. Problem 2:
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This note was uploaded on 09/17/2011 for the course ELEC 6970 taught by Professor Staff during the Spring '08 term at Auburn University.

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exam2.sol - ELEC 5970-001/6970-001 Special Topics in...

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