# VLSI Questions and Answers – Built-in Self Test

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This set of VLSI Multiple Choice Questions & Answers (MCQs) focuses on “Built-in Self Test”.

1. Built-in self test aims to
a) reduce test pattern generation cost
b) reduce volume of test data
c) reduce test time
d) all of the mentioned

Explanation: Built-in self test objectives are to reduce test pattern generation cost, to reduce volume of test data and to reduce test time.

2. In data compression technique, comparison is done on
a) test response
b) entire test data
c) data inputs
d) output sequences

Explanation: In data compression technique, comparison is made on compacted test response instead on entire test data.

3. Signature analysis performs
b) multiplication
c) polynomial division
d) amplifies

Explanation: Signature analysis performs polynomial division that is division of data out of the device under test.

4. The signature analysis method can be represented mathematically as
a) R(x) = P(x) * C(x)
b) R(x) = P(x) / C(x)
c) R(x) = C(x) / P(x)
d) R(x) = C(x) * P(x)

Explanation: The signature analysis method is represented mathematically as R(x) = P(x) / C(x) where R(x) is the signature, C(x) is characteristic polynomial.

5. Transition counting does the count of transition only in one specific direction at a time.
a) true
b) false

Explanation: Transition counting does the count of transition in specified direction (0 t0 1 or 1 to 0).

6. BILBO uses only the signature analysis.
a) true
b) false

Explanation: Built-in logic block observer method uses signature analysis in conjunction with a scan path.

7. In which mode, storage elements are used independently?
a) normal mode
b) test 1 mode
c) test 2 mode
d) final mode

Explanation: In normal mode, storage elements are used independently and in this mode signal B1=B2=1.

8. Storage elements are connected as a serial shift register when
a) B1=B2=1
b) B1=B2=0
c) B1=0, B2=1
d) B1=1, B2=0

Explanation: When B1=B2=0 storage elements are configured as scan path, they are connected as serial shift register.

9. The circuit is configured as LFSR, when
a) B1=B2=1
b) B1=B2=0
c) B1=0, B2=1
d) B1=1, B2=0

Explanation: When B1=1 and B2=0 the circuit is configured as LFSR mode and can be used as either polynomial divider or random test pattern generator.

10. The BILBO is reset, when
a) B1=B2=1
b) B1=B2=0
c) B1=0, B2=1
d) B1=1, B2=0

Explanation: When B1=0 and B2=1 in the final mode, the BILBO is reset.

11. Self-checking technique consists of
a) supplying coded input data
b) receiving coded output data
c) supplying all possible input sequence
d) all of the mentioned

Explanation: Self-checking technique consists of supplying coded input data to the logic block under test and comparing the output.

12. The type of error in self-checking technique are
a) simple error
b) unidirectional error
c) multiple error
d) all of the mentioned

Explanation: The type of error in self-checking techniques are simple errors, unidirectional errors and multiple errors.

13. The parity check detection is done using
a) OR gate
b) AND gate
c) XOR gate
d) NOR gate

Explanation: The parity check detects simple errors using XOR gates and for each type of error, the approximate coding technique is used.

14. Which errors are detected using duplication codes?
a) single errors
b) unidirectional errors
c) bidirectional errors
d) multiple errors 