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Unformatted text preview: 10/27/2011 1 ECE 553: TESTING AND TESTABLE DESIGN OF DIGITAL SYSTES Functional testing 10/27/2011 2 Overview • Motivation and introduction • Structure independent approach • Structure dependant approach • Organization/architecture dependant approach – Microprocessor testing – Memory testing • Summary 10/27/2011 3 Motivation and Introduction • Ref: Abramovici, et. Al – Reference book Section 18.2 of the text (for understanding the problem) • Motivation – Structural information can facilitate testing – we show this for combinational and sequential circuits – Organization/Architecture information can make testing of microprocessors and memories practical – Develop fault models when we are to use this kind of information 10/27/2011 4 Structure independent approach • Combinational circuit testing – Exhaustive testing of circuits that do not have very large number of inputs – Note: if a fault can cause the circuit to behave like a circuit with states (i.e. causes increase in the number of states – combinational circuit becomes sequential in nature) then exhaustive testing may not fully test the circuit. Example of such a fault is stuck-open fault in a CMOS implementation 10/27/2011 5 Structure independent approach • Combinational circuit testing (contd.) – A non-exhaustive functional test must be carefully designed otherwise it may not achieve the desired objective. Consider a 2-to-1 mux. A non-exhaustive functional test is given below: A B S D S A B D 1 x 0 0 0 0 0 0 x x x 1 1 1 1 1 10/27/2011 6 Structure independent approach • Combinational circuit testing (contd.) – A fully specified test can potentially be (the one that repeats values in the test) as follows: – This test can not test stuck-at fault on the control line S A B S D S A B D 1 1 0 0 0 0 0 0 0 1 0 1 1 1 1 1...
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This note was uploaded on 03/13/2012 for the course ECE 553 taught by Professor Ece553 during the Winter '08 term at University of Wisconsin.
- Winter '08