“Digital Systems Testing and Design for Testability ”

Prof. Dr. V.N.Yarmolik

Lecture course: 32 hours lectures, 32 hours lab. works

4. Compact Testing

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4.Compact Testing

4.1. Transition Count Testing

Compact Testing – is a testing technique which is based on compact representation of test patterns that usually have a huge length, as well as compact form for the circuit under test output responses.

Test generation techniques:

Exhaustive tests generation based on so-called counter sequences, what allows to compress the test as a software algorithms or simple hardware counter.

Random tests, which have been generated as a random binary sequences with the real random nature or as pseudorandom sequences with high quality randomness properties.

Pseudorandom tests pattern generation according to the deterministic algorithms with the low overhead in time and hardware domains.There is a standard solution for so kind of generator which is called Linear Feedback Shift Register (LFSR)

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4.Compact Testing

4.1. Transition Count Testing

Compact forms for the circuit under test output response binary sequence y1y2y3,,…,yr

4. Signature Analyses

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4.Compact Testing

4.1. Transition Count Testing

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4.Compact Testing

4.2.Syndrome testing

Syndrome of an n-variable Boolean function is defined as

S R2n5;

Where R5 is estimated for r = 2n and equals the number of ones of the Boolean

4.Compact Testing

4.2.Syndrome testing

Properties of Syndrome S(F) for the general case

1.0 S(F) 1 where S(F)=0 if F=0 and S(F)=1 for F=1.

2.S(F)=1- S(F).

3.S(F+G)=S(F)+S(G)-S(FG), S(FG)=S(F)-S(FG),

4.Compact Testing

4.2.Syndrome testing

Statement 4.1. A two-level non-redundant combinational circuit described by a Boolean function F=G1xi+G2xi+G3, where i {1,2,3,…,n}; G1 0, G2 0, G3 1, and

dG1/xi = dG2/xi= dG3/xi= 0 is syndrome-testable with respect to xi iff the inequality

S(G1G3) S(G2G3 )

holds true.

Statement 4.2. If a two-level non-redundant combinational circuit described by a Boolean function F(x1 ,x2 ,x3 ,…,xn)=G1xi+G2xi+G3, where i {1,2,3,…,n}; G1 0,

G2 0, G3 1, and dG1/xi = dG2/xi= dG3/xi= 0 is syndrome untestable with respect to xi then the combinational circuit described by Boolean function F* (x1 ,x2 ,x3 ,…,xn ,c)= =cG1xi+G2xi+G3 is syndrome testable with respect to the variable xi

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