NATIONAL OPEN UNIVERSITY OF NIGERIA

UNIVERSITY VILLAGE, PLOT 91, CASDASTRAL ZONE, NNAMDI AZIKIWE EXPRESS WAY, JABI, ABUJA.
FACULTY OF SCIENCES
JANUARY 2021 EXAMINATION

CIT 344 – Introduction to Computer Design

Credit: 3 units

TIME ALLOWED: 2½ Hours

INSTRUCTION: Answer Question 1 and any other FOUR (4) Questions

QUESTION ONE (22 marks)

(a) i. Carry out the binary division of 1011 by 11 (1 mark)

ii. Convert decimal number 10 to its binary equivalent (1 mark)

iii. Convert the binary number 101012 to its decimal equivalent (1 mark)

iv. Explain Sum-of-Weights method of number conversion (1 mark)

v. Convert 22 in base 8 into its decimal equivalent. (1 mark)

vi. Calculate the octal subtraction of (232)8 from (417)8 (1 mark)

(b) Distinguish between Combinational and Sequential Logic (4 marks)

(c) i. Construct the Truth-Table for NAND based S-R Latch (2 marks)

ii. Draw the logic gates for NOR Based S-R Latch (2 marks)

(d) What is a Register? (1 mark)

(e) What is a Finite State Machine? (1 mark)

(f) Explain different types of Random Access Memory (RAM) (2 marks)

(g) What is pipelining? (1 mark)

(h) Mention any THREE Microprocessor Components (3 marks)

QUESTION TWO (12 marks)

(a) Distinguish between Half Adder and Full Adder. (4 marks)

(b) Given a 1-bit Half Adder:

i. Draw the Truth Table (1 mark)

ii. Draw Karnaugh Map for Sum (1 mark)

iii. Simplify the Sum-of-Product (SOP) for the output Sum (1 mark)

iv. Draw Karnaugh Map for Carry (1 mark)

v. Simplify the Sum-of-Product (SOP) for the output Carry (1 mark)

vi. Draw Logic Circuit (3 marks)

QUESTION THREE (12 marks)

(a). Using the truth table for 7 Segment LED Decoder given below with 4 inputs A, B, C, D and 7 outputs a, b, c, d, e, f, g to answer the following questions. Truth Table

i. Write out the Boolean function for the expression of a (2 marks)

ii. Draw the K-Map for a (4 marks)

iii. Simplify the expression obtained from a through the K-map (2 marks)

(b) Evaluate this expression (PQ)  (PQ) using Truth Table (2½ marks)

(c) What is a Demultiplexer? (1½ marks)

QUESTION FOUR

(a). Construct the truth –Table for Sequence of States of a 4-Bit Johnson Counter (5 marks)

(b) Mention and explain two applications of Shift Registers (3 marks)

(c) Distinguish between encoder and decoder (4 marks)

QUESTION FIVE (12 marks)

(a) Given the expression for the SOP where output Z = Ì… Ì… Ì…

i. Draw the Karnaugh Maps (4 marks)

ii. Simplify the expression (1 marks)

iii. Draw the logic gates (4 marks)

(b) Explain the term Bus (1 mark)

(c) Explain the term Polling (2 marks)

QUESTION SIX (12 marks)

(a). Construct the Truth-table for a 3-to-8 decoder with enable (5 marks)

(b) List and explain the various applications of Decoders (3 marks)

(c) Draw the block diagram for Sequential Circuit (2 marks)

(d) Explain Synchronous and Asynchronous sequential circuits (2 marks)