# Sequential circuits

Question 1

Consider the following circuit involving three D-type flip-flops used in a certain type of counter configuration.

[caption width="800"] [/caption]

If at some instance prior to the occurrence of the clock edge, P, Q and R have a value 0, 1 and 0 respectively, what shall be the value of PQR after the clock edge?

• 000

• 001

• 010

• 011

Question 2

Consider the data given in previous question. If all the flip-flops were reset to 0 at power on, what is the total number of distinct outputs (states) represented by PQR generated by the counter?

• 3

• 4

• 5

• 6

Question 3

In the sequential circuit shown below,if the initial value of the output Q1Q0 is 00,what are the next four values of Q1Q0?

[caption width="800"] [/caption]
• 11, 10, 01, 00

• 10, 11, 01, 00

• 10, 00, 01, 11

• 11, 10, 00, 01

Question 4

The control signal functions of a 4-bit binary counter are given below (where X is “don’t care”) The counter is connected as follows:
The counter is connected as follows:
Assume that the counter and gate delays are negligible. If the counter starts at 0, then it cycles through the following sequence:

• 0, 3, 4

• 0, 3, 4, 5

• 0, 1, 2, 3, 4

• 0, 1, 2, 3, 4, 5

Question 5

You are given a free running clock with a duty cycle of 50% and a digital waveform f which changes only at the negative edge of the clock. Which one of the following circuits (using clocked D flip-flops) will delay the phase of f by 180°?

[caption width="800"] [/caption][caption width="800"] [/caption]
• A

• B

• C

• D

Question 6

Let k = 2n. A circuit is built by giving the output of an n-bit binary counter as input to an n-to-2n bit decoder. This circuit is equivalent to a

• k-bit binary up counter.

• k-bit binary down counter.

• k-bit ring counter.

• k-bit Johnson counter.

Question 7

[caption width="800"] [/caption]

The above sequential circuit is built using JK flip-flops is initialized with Q2Q1Q0 = 000. The state sequence for this circuit for the next 3 clock cycle is

• 001, 010, 011

• 111, 110, 101

• 100, 110, 111

• 100, 011, 001

Question 8

Consider the circuit in the diagram. The ⊕ operator represents Ex-OR. The D flipflops are initialized to zeroes (cleared).

The following data: 100110000 is supplied to the “data” terminal in nine clock cycles. After that the values of q2q1q0 are:

• 000

• 001

• 010

• 101

Question 9

Consider the following circuit involving a positive edge triggered D FF.

Consider the following timing diagram.
Let Ai represent the logic level on the line A in the i-th clock period.
Let A\' represent the complement of A. The correct output sequence on Y over the clock periods 1 through 5 is

• A0 Al A1\' A3 A4

• A0 Al A2\' A3 A4

• Al A2 A2\' A3 A4

• Al A2\' A3 A4 A5\'

Question 10

Consider the following circuit.

The flip-flops are positive edge triggered D FFs. Each state is designated as a two bit string Q0Q1. Let the initial state be 00. The state transition sequence is:

 A)
B)
C)
D)
• A

• B

• C

• D

There are 46 questions to complete.

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