Digital Electronics Question Paper of 3rd Semester ECE16 Download Previous Years Question Paper 1

Digital Electronics

(EC-205, DEC-2005)

Note: Section A is compulsory. Attempt any four questions from Section  and any two questions from  Section C.

Section-A

a) What is Excess-3 and Gray code?

b) Why ASCll-code is a 7-bit code?

c) Add (7F)16 & (BA)16.

d) Differentiate between half and full subtractors.

e) Compare a decoder with a demultiplexer.

f) What is meant by a state diagram?

g) What is meant by ‘accuracy’ of and A/D/converter

h) Difference between PLA and ROM?

i) Explain the problem of ‘current hogging’ in DCTL.

j) Explain the operation of CMOS(NOR gate).

Section-B

2. Represent the following decimal numbers in twos complement format:

 i) +3           ii) +25         iii) –5          iv) –11        v) –9

3. Write the full name in :a) ASCll code b) EBCDIC code c) Excess –3 code

4. Minimize the following function and realize using minimum no of gates:

 f1 = -Σm(0,3,5,6,9,10,12,15)

5. Design a BCD to Excess-3 code converter using minimum no of NAND gates

6. Design a four bit subtract or using four bit adder and minimum no of EX-OR gates.

Section-C

7. Obtain the output wave forms of a 5-stage ring-counter. Draw its state diagram

8. Explain the following codes and give example using four bits.

 a) CSB b)COB c)CTC d) CCD

9. Explain & compare the following with its block diagram.

a) Linear selection addressing

b) Coincidence selection addressing