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(ELEC151)[2010](s)midterm~2064^_10283.pdf
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- 1 C The Hong Kong University of Science and Technology Department of Electrical and Computer Engineering ELEC 151 Midterm Exam 19 March 2010 (4:30pm-5:45pm) Name: Student Number 1. This is a closed book examination. 2. Answer all questions in this examination paper in the space provided. 3. Show all your calculations and steps clearly. No works will be given for unjustified answers. Question Number Total Marks Score 1 2 3 4 Total - 2 C Question 1: (a). Convert the unsigned binary number 1110102 to (i)decimal number, (ii)BCD code and (iii)hexadecimal number. (b). Given a 16-bit word N, N=1110 0101 0100 1001, find the decimal value of N represented if it is (i) an unsigned binary number (ii) a number in twos complement code (iii) a number in sign-and-magnitude code (c) Suppose a memory with a 8-bit word is used to store the unsigned binary integer and another 4-bit word for the binary fraction. What will be on the memory if the number in decimal equals to 3.66?

- 3 C Question 2: (a). Use DeMorgans theorem to convert F = A.(B+C) .(A+D) to NOR-NOR form. (b). A circuit is given below, (i). Determine the simplified Boolean functions of outputs X and Y. (ii). Fill in the K-maps of outputs X and Y below. Output X Output Y (iii). Implement the simplified Boolean function of X by 2-input NAND gates only and draw the circuit schematic. AB CD AB CD - 4 C Question 3: Design a combination logic circuit with 4 inputs (A,B,C,D) and one output F, where F=1 when an even number of inputs = 1 and when A=B=C=D=0. (a). Fill in truth table provided below. (b). Express F in sum of minterms representation. (c). Express F in product of maxterms representation. (d). Fill in the K-map below and obtain the simplified expression of F. (e). Implement F by XOR and/or XNOR gates only. Truth table for part (a). K-map for output F in part (d). A B C D F AB CD

Question 4:
A combinational circuit is specified by the following three Boolean functions: F1(A,B,C)=m(0,3,6) F2(A,B,C)=M(0,4,6,7) F3(A,B,C)=(A+B)+ABC
Implement the circuit with one decoder and NAND gates.
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- 5 C