# Digital Logic - Unit Wise Questions

2. Subtract: 1010.110 – 101.101 using both 2's and 1's complement. [5]

1.

i) Which one of the following is hexadecimal equivalent of (5073.052)8?

a) A3C.150 b) B2B.140 c) A3B.150 d) B3A.150

11.Subtract: 675.6 – 456.4 using both 10's and 9's complement.[5]

12.What is university logic gate? Realize NAND and NOR as an universal logic gates. [1+2+2]

1.

ii) Which one of the following is 9's complement of (3578.501)10?

a) 4926.947 b) 3926.947 c) 4926.937 d) None of the Above

3. Simplify (Using k-map) the given Boolean function in both SOP and POS using the don’t

care condition d:

4. Define decoder. Draw logic diagram and truth table of 3 to 8-line decoder. [1 + 4]

1.

iii) Which one of the following is the equivalent reflected code of 1101?

a) 1001 b) 1011 c) 1000 d) 1010

13. Simplify (using K- map) the given Boolean function F in both SOP and POS using don't care conditions D: B'CD' + A'BC'D

F = B'C'D' + BCD' + ABCD' [2+3]

1.

iv) When output will go high in NOR Gate?

a) if all inputs are high b) if any input is high c) if any input is low d) if all inputs are low

14.Define encoder: Draw logic diagram and truth table of octal - to - binary encoder. [1 + 4]

5. Define ROM. Implement the following combinational logic function using ROM: [2 + 3]

15.What is D flip-flop? Explain clocked RS flip-flop with its logic diagram and truth table.[1+4]

6. What are the drawbacks of clocked RS flip flop? Explain the operation of JK Flip flop along with its circuit diagram and characteristic table. [2+3]

1.

v) According to Boolean algebra: What is the value of

a) X̄ b)1 c)0 d) X

16.Design MOD - 5 counter with state and timing diagram.[2+1+2]

1.

vi) The logic circuits whose outputs at any instant of time depends only on the present input but also on the past outputs are called

a) Combinational circuits b) Sequential circuits c) Latches d) Flip-flops

7. What is T flip-flop? Explain clocked JK flip-flop with its logic diagram and truth table. [1 + 4]

17. Design a 4 - bit serial into parallel- out shift register with timing diagram. [3+2]

8. Design MOD - 7 counter with state and timing diagram. [2 + 1 + 2]

1.

vii) If Q = 1, the output is said to be

a) Reset b) Set c) Previous state d) current state

1.

viii) Which one of the following are also called ripple counters?

a) SSI counters b) Synchronous counters c) Asynchronous counters d) VLSI counters

1.

ix) How many flip-flops are required to construct MOD-30 counter?

a) 5 b) 6 c) 4 d) 8

1.

x) How much storage capacity does each stage in a shift register represent?

a) One bit b) Two bits c) Four bits d) Eight bits

18. Write difference between PLA and PAL. Design a PLA circuit with given functions.

F1 (A, B, C) = Σ (2, 3, 5)

F2 (A, B, C) = Σ (0, 4, 5, 7). Design PLA program table also.[3+7]

9. Define PLA. Design a PLA circuit with given functions.

F1 (A, B, C) = Σ (3, 5, 6, 7)

F2 (A, B, C) = Σ (0, 2, 4, 7). Design PLA program table also. [3 + 7]

10. Distinguish between sequential and combinational logic with example? Discuss the design procedure of combinational logic. [4+6]

19.Define D flip-flop. Design a Master-slave flip-flop by using JK flip-flop along with its circuit diagram and truth table. [2+8]

11. A sequential circuit with two D flip-flops, A and B, two inputs x and y, and one output z, is specified by the following next state and output equations [4+3+3]

A(t+1) = x'y + x A

B(t +1) = x'B + x A

z = B

a) Draw the logic diagram.

b) Derive the state table.

c) Derive the state diagram.

20.Write down the difference between asynchronous and synchronous counter. Design a 4-bit binary ripple counter along with its circuit, state and timing diagram. [3+7]

3. Simplify given Boolean function in both SOP and POS using K-Map where d represents don't care condition.

F(A,B,C,D)=

5. Define Priority encoder. Design 4:2 priority encoder with its block diagram, truth table, circuit diagram and mathematical expression.

6. Why NAND and NOR gates are called universal gates? Realize NAND gate as universal gate.

7. What is race around condition? Explain how JK master flip flop is used to eliminate race around condition.

8. Differentiate between synchronous and ripple counter. Design mod 7 ripple counter with its state diagram, sequence table,logic diagram and timing diagram.

9. Define PLA with its block diagram.Realize BCD to gray code converter using PAL.

10. What is register? Explain types of registers depending on input output with its block diagram and logic diagram.

11. What is state diagram? A sequential circuit with two D flip-flops A and B, one input x and one output z by the following next state and output equations:

A(t+1)= A'+B, B(t+1)=B'x, z= A+B'

i) Draw the logic diagram of the circuit

ii) Draw the state table

iii) Draw the state diagram of the circuit

2. Subtract 11101.111-10100.101 using 1's and 2's complement.

4. Define combinational circuit. Write a combinational circuit design procedure. Design a half adder with its truth table, logic diagram and Boolean expression.