Lecture 07 - Memoy Test 02 - Testing and Testable Design...

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1 1 Testing and Testable Design Testing and Testable Design `x{Üwtw aÉâÜtÇ| Dept. of EE Univ. of Texas at Dallas 2 Memory Testing Session 07 Session 07
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2 3 Key Issues Motivation for testing memories Modeling memory chips Reduced functional fault models Traditional tests March tests Pseudorandom memory tests 4 Classical Tests
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3 5 Purpose 1. Cover traditional tests Zero-One (MSCAN) Checkerboard GALPAT and Walking 1/0 2. Cover tests for stuck-at, transition and coupling faults MATS and MATS+ March C- March A and March B 3. Comparison of march tests Functional RAM Chip Testing 6 When a test detects faults of a particular type, it detects: all subtypes of that type; e.g., if it detects TFs it has to detect all < /0> and < /1> TFs all positions of each subtype (addr. a-cell < or > v-cell) A complete test detects all faults it is designed for It may, additionally, and unintentionally, detect also other faults But not all subtypes and not all positions of each of these faults Example : MATS+ : { M0: c (w0); M1: (r0,w1); M2: (r1,w0)} Detects all AFs Detects all SAFs Detects all < /0> TFs Does not detect all < /1> TFs MATS+ does not detect TFs Fault coverage of MATS+ AFs, SAFs < /0> TFs Fault Coverage of Tests < /1 > TFs
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4 7 Traditional tests are older tests Usually developed without explicitly using fault models Usually they also have a relatively long test time Some have special properties in terms of: detecting dynamic faults locating (rather than only detecting ) faults Many traditional tests exist: 1. Zero-One (Usually referred to as Scan Test or MSCAN ) 2. Checkerboard 3. GALPAT and Walking 1/0 4. Sliding Diagonal 5. Butterfly 6. Many, many others Traditional Tests 8 Minimal test, consisting of writing & reading 0s and 1s Step 1: write 0 in all cells Step 2: read all cells Step 3: write 1 in all cells Step 4: read all cells March notation for Scan test : { c (w0); c (r0); c (w1); c (r1)} Test length: 4 n operations; which is O( ) Zero-One Test (Scan Test, (M)SCAN)
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5 9 Fast X addressing Rows Row 000000 stripe 111111 000000 111111 Checker 010101 board 101010 010101 101010 Columns MSCAN: { M0: c (w0); M1: c (r0); M2: c (w1); M3: c (r1)} Fault detection capability: AFs not detected Condition AF not satisfied : 1. (r x ,…,w *) 2. (r *,…,w ). So, not all AFs are detected. If address decoder maps all addresses to a single cell , then it can only be guaranteed that one cell is fault free Not all TFs are detected. E.g. Not all < /1> TFs are detected because not all transitions are generated. Not all CFs are detected because not all transitions are generated. < ; > CFids are not detected because in M3, the expected value is the same as the value induced by CFs.
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This note was uploaded on 08/23/2009 for the course EE 6303 taught by Professor Mehrdadnourani during the Fall '08 term at University of Texas at Dallas, Richardson.

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Lecture 07 - Memoy Test 02 - Testing and Testable Design...

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