Download Logic symbol - Digital Systems - Exam and more Exams Digital Systems Design in PDF only on Docsity!
CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 1 Examinations 2010/
Module Title: Digital Systems 1
Module Code: ELTR
School: Electrical and Electronic Engineering
Programme Title: Bachelor of Engineering in Electronic Engineering
Programme Code: CR_EELXE_7_Y1 CR_EELES_8_Y
External Examiner(s): Dr A Donnellan
Mr I Kennedy
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 2010
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, OR, NAND, 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 the expression B AC B ( C A )is true. [5 marks]
(c) Use a K-map to minimise the following expression: Z ABCD BCD ABCD ABCD ACD ABCD [7 marks]
(d) Using a truth table, identify the basic gate represented by the following symbol
[2 marks]
Q2 (a) For the logic circuit, Figure 1 on the Return Sheet , write down the exact Boolean equation for the output Y. [3 marks]
(b) Complete the timing diagram on the Return Sheet , for this circuit. [5 marks]
(c) Re-draw the circuit in Figure 1 using NAND gates only. What is the advantage of carrying out the above exercise on this circuit? [6 marks]
(d) In a certain chemical processing plant, liquid chemicals are used in a manufacturing process. The chemicals are stored in three different tanks. A level sensor positioned near the bottom of each tank produces a LOW voltage when the level of chemical in the tank is close to empty.
Tests are being done on the rate of consumption of each chemical. A logic circuit with two separate outputs is required to monitor the level in each tank and indicate using HIGH voltages, when certain conditions occur.
One output will indicate when all three tanks are empty, the other output when any two tanks are empty.
(i) Draw a block diagram for the above logic circuit (ii) Derive a full truth table for the outputs of this circuit (iii) Using the truth table, write Boolean equations for the circuit [6 marks]
CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 1 Examinations 2010/
Module Title: Digital Systems 1
RETURN SHEET
A
B
C Y
Figure 1
C
A
B
Y
Name: Return this sheet with your answer book.
