Electronics and Communication Engineering - Digital Electronics

21. 

The Boolean expression for the circuit of the given figure

A. A {F + (B + C) (D + E)}
B. A [F + (B + C) (DE)]
C. A + F + (B + C) (D + E)]
D. A [F + (BC) (DE)]

Answer: Option A

Explanation:

B and C in parallel give B + C. Similarly D and E in parallel give D + E. (B + C) in series with (D + E) give (B + C) (D + E). Since F is in parallel we get F + (B + C) (D + E). Finally A is in series. Therefore we get A[F + (B + C) (D + E)].


22. 

What will be BCD number when the output is 0.37 V?

A. 00110111
B. 10110111
C. 11001000
D. 01001000

Answer: Option A

Explanation:

BCD number is (00110111).


23. 

The first machine cycle of an instruction is always

A. a memory read cycle
B. a fetch cycle
C. a input/output read cycle
D. a memory write cycle

Answer: Option B

Explanation:

Fetch cycle is always first machine cycle.


24. 

A counter has N flip flops. The total number of states are

A. N
B. 2 N
C. 2N
D. 4 N

Answer: Option C

Explanation:

One flip-flop means 2 states and N flip-flops means 2N states.


25. 

Out of S, R, J, K, Preset, Clear inputs to flip flops, the synchronous inputs are

A. S, R, J, K only
B. S, R, Preset, Clear only
C. Preset, Clear only
D. S, R only

Answer: Option A

Explanation:

Preset and clear inputs are not applied in any fixed sequence.