GATE-ECE-2017

Question

 

answer is D but I'm getting A. pls tell where am I going wrong?

Comments

Check my approach  aditi19 . I'm getting the same.

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answer key is wrong then? :P

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Sorry I have taken the NOR gate earlier.

It should be option D itself :).

Answer 1

answer is D

if x=1 then  $0\rightarrow 1\rightarrow 3\rightarrow 0\rightarrow 1\rightarrow 3\rightarrow 0\rightarrow 1\rightarrow 3............$

if x=0 then  $0\rightarrow 1\rightarrow 3\rightarrow1\rightarrow 3\rightarrow 1\rightarrow 3\rightarrow $

one thing we should note is that

after a few clock cycle 

 means at x=0     after few clock cycle  it will move from 1 to 3 ,3 to 1,1 to 3 .........................

Answer 2

$$D_a = Q_a{\oplus }Q_b\\ D_b = (Q_a.x)'$$

 

$$Q_a$$	$$Q_b$$	$$Q_a^+$$	$$Q_b^+$$	$$D_a$$	$$D_b$$
0	0	0	1	0	1
0	1	1	1	1	1
1	0	1	x'	1	x'
1	1	0	x'	0	x'

CASE 1: When X = 1,

Only three states are possible for this case.

 

CASE 2: When X = 0,

Only two states are possible. for this case.

Therefore, OPTION D is Correct.