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Introduction To Digital Electronics Question Paper

Introduction To Digital Electronics

Course:Bachelor Of Science Information Technology

Institution: Kenyatta University question papers

Exam Year:2008

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2007/2008
INSTITUTE OF OPEN LEARNING
SUPPLEMENTARY/SPECIAL EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE
INFORMATION TECHNOLOGY
SIT 112: INTRODUCTION TO DIGITAL ELECTRONICS
DATE: Friday 10th October 2008_______________ TIME: 1.00pm – 3.00pm
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INSTRUCTIONS: Answer question ONE and any other TWO questions

Q1. (a) (i) Calculate the bytes needed to represent the decimal value 846569
in BCD.
(ii) Explain the advantages of digital techniques over analoque.
(iii) A typical CD-ROM can store 650 megabytes of digital data. Since
mega = 220, calculate the bits of data that the CD-ROM can hold.

(b) (i) Determine the waveform at the output of a NOR gate for the input
waveforms in Fig Q1(b).
Fig Q 1(b)
(ii) Implement the logic circuit that has the expression
x = AB. (C + D) using NOR and NAND gates.

(c) Design a logic circuit that has three inputs A, B, and C and whose output
will be HIGH only when a majority of the inputs are HIGH.

(d) Discuss the advantages and disadvantages of synchronous counter over
asynchronous counter.

(e) (i) Describe the function of a sample and hold circuit.
(ii) Each segment of a typical 7-segment LED display is rated to
operate at 10mA at 2.7V for normal brightness. Calculate the
value of the current-limiting resistor needed to operate to produce
approximately 10mA per segment.

Q2.(a) Simplify z = A C ( A BDC )+ ABCD + ABC

(b) Design a Gray-to-Binary converter.

Q3. (a) Use a K map to simplify y = C(A B D + D)+ ABC + D

(b) Prove that the XNOR output expression is the exact inverse of XOR
output expression using Boolean algebra.

Q4. (a) Describe how the BCD adder circuit detects the need for a correction and
executes it.

(b) Design a MOD-10 counter that will count from 0000 (zero) through 1001
(decimal 9).

Q5. (a) Design a 2-decade BCD D/A converter.

(b) Consider a memory of size 16 words. Find the binary address of each
location.

Introduction To Digital Electronics Question Paper

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