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GATE | GATE-CS-2016 (Set 1) | Question 18

We want to design a synchronous counter that counts the sequence 0-1-0-2-0-3 and then repeats. The minimum number of J-K flip-flops required to implement this counter is   Note : This question was asked as Numerical Answer Type.

(A)



1

(B)



2

(C)

4

(D)

5


Answer: (C)
Explanation:

Total 4. 2 J-K flip- flops for synchronous counter + 2 J-K flip-flop to make 2 bit counter. Actually, when we are repeating again then after 3 we don\’t know that our Synchronous counter will go to which zero. To make it work right, we need to move it to 1st zero after 3 2nd zero after 1 3rd zero after 2 i.e. 0 -> 1 -> 0 -> 2 -> 0 -> 3 (from here it again go to 1st zero). In order to decide which zero to move on we use counter from 1 to 3, I have attached truth table of normal 2 bit synchronous counter using JK flip flop. // This Explanation has been contributed by Mohit Gupta 

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