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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 1 Examinations 2009/
Module Title: Digital Systems 1
Module Code: ELTR
School: Electrical and Electronic Engineering
Programme Title: Bachelor of Engineering in Electronic Engineering
Programme Code: EELXE_7_Y EELES_8_Y KCOME_6_Y
External Examiner(s): Dr A Donnellan Dr P O’Sullivan
Internal Examiner(s): Mr J O’Sullivan
Instructions: Attempt any three questions. All questions carry equal marks. Ensure that you include the Return Sheet with your answer book.
Duration: Two hours
Sitting: Winter 2009
Requirements for this examination: N/A
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
You are expected to present your material in a neat and clear fashion. Start each question on a new page. Remember that you have plenty of time for this exam – two hours for three questions.
Q1. (a) For each of the logic gates, AND, NOR, and Ex-OR, write down the following: i) a logic symbol ii) a truth table iii) a Boolean expression [6 marks]
(b) Use a truth table to show that A + BC = A ( B + C )is true. [5 marks]
(c) Use a K-map to minimise the following expression: Z = ABCD + BCD + ABCD + ABCD + ACD + ABC D [7 marks]
(d) Using a truth table, identify the basic gate represented by the following symbol
[2 marks]
Q2. (a) The binary number system is a base-2 counting system. In your own words
explain what is meant by this statement and hence explain how counting is accomplished using the binary system. [2 marks]
(b) Construct a table showing the decimal, binary and hexadecimal equivalents of all possible 4-bit binary numbers. [4 marks]
(c) Use the table in (b) to carry out the following conversions: (i) E37A 16 to binary (ii) 11110010101 2 to hex [2 marks]
(d) Perform the following conversions showing all working (i) 27 10 to binary (ii) 11010 2 to decimal [4 marks]
(e) Explain what is meant by the two’s complement binary number system and state why this system is so widely used in computers. [2 marks]
(f) Using 8-bit two’s complement numbers throughout, perform the following arithmetic operations, and in each case convert your result to decimal to verify that your answer is correct. (i) 2310 + 35 10 (ii) 2310 – 35 10
(Note: 23 10 = 10111 2 35 10 = 100011 2 ) [6 marks]
CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 1 Examinations 2009/
Module Title: Digital Systems 1
RETURN SHEET
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Figure 1
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Name: Return this sheet with your answer book.
