Anna University

Digital Logic Circuits (DLC)

Important Questions

Digital Logic Circuits (DLC)

Important Questions

Common To

EE46igital Logic Circuits

EC1261A Digital Logic Circuits

080280029igital Logic Circuits

131405igital Logic Circuits

10133EE406Aigital Logic Circuits

Unit I

1. Obtain the minimum SOP using Quine McCluskey’s method and verify using K – Map.

F = m0 + m2 + m4 + m8 + m9 + m10 + m11+ m12 + m13

2. Determine the prime implicants of the following function using tabulation method and verify using K –Map. F = (A,B,C,D) = ∑ (3,4,5,7,9,13,14,15)

3. Design a Binary to BCD code converter and BCD to Excess -3 code converter.

4. Reduce the given expressions using Boolean algebra:

(1) x’y’z’ + x’y’z + x’yz + xy’z + xyz

(2) p’q’r + p’qr’ + p’qr + pqr’ + pq’r’

5. Design a decimal adder to add two decimal digits.

Unit II

1. Design a asynchronous decade counter using JK flipflop.

2. Design a 8 X1 Mux using 2 X1 multiplexers.

3. Design a synchronous counter using JK flipflop in the sequence 7,4,3,1,5,0,7….

4. Draw and explain the block diagram of Mealy circuit

5. Design a MOD -5 synchronous counter using JK flip-flops .Draw a timing diagram.

6. Design a 2 bit Magnitude Comparator.

Unit III

1. Describe the steps involved in design of asynchronous sequential circuit in detail with an example.

2. Explain the working of a 3 – input TTL totem-pole NAND gate.

3. Explain the concept and implementation of ECL logic family.

4. Explain In detail about FPGA.

5. A combinational circuit is defined by the functions .

F1 (A,B,C ) =∑ (3,5,6,7)

F2 (A,B,C ) =∑ (0,2,4,7).Implement the circuit with PLA

Unit IV

1. Design an asynchronous sequential circuit that has two inputs X2 and X1 and one output Z. When

X1 = 0, that output Z is 0. The first change in X2 that occurs while X1 is 1 will cause output Z to be 1. The output Z will remain 1 until X1 returns to 0.

2. An asynchronous sequential circuit has two internal states and one output. The excitation and

output functions describing the circuit are

Y1 = x1x2 + x1 y’2 + x’2y1

Y2 = x2 + x1 y’1y2 + x’1y1

Z = x2 + y1

a) Draw the logic diagram of the circuit.

b) Derive the transition table and output map.

c) Obtain a flow table for the circuit.

3. The Circuit has two inputs T (toggle) and C (clock) and one output Q. The output state is complemented if T=1 and clock C changes from 1 to 0 otherwise, under any other input condition, the output Q remains unchanged. Derive the primitive flow table and implication table and the logic diagram.

4. Draw the State diagram and obtain the primitive flow table for a circuit with two inputs X1 and X2 and two outputs Z1 and Z2 that satisfies the following conditions.

1) When X1 X2 =00, output Z1 Z2 =00.

2) When X1 = 1 and X2 change from 0 to 1, the output Z1 Z2 =01.

3) When X2 = 1 and X1 change from 0 to 1, output Z1 Z2 =10.

4) Otherwise output does not change.

5. Implement the following Boolean functions with a PLA.

F1 (A, B, C) = ∑ (0, 1, 2, 4)

F2 (A, B, C) = ∑ (0, 5, 6, 7)

F3 (A, B, C) = ∑ (0, 3, 5, 7)

Unit V

1. Write VHDL program for 4x1 multiplexer.

2. Explain in detail the design procedure for register transfer language.

3. Write an HDL behavioral description of JK flip-flop using if-else statement based on the value of present state.

4. Write VHDL program for 4-bit ripple counter.

5. Explain the design procedure of RTL using VHDL

For the student , by the student , to the student !!