2021ERS220C01 Question Paper PDF

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Department of Electrical, Electronic and Computer Engineering

Class Test 1 : Fill-in and e-Grading Study units 1 - 6 Copyright reserved

Digital Systems ERS220 8 September 2021

ASSESSMENT ID : 2021ERS220C01 Student details Surname:

Name:

Contact Telephone number:

Student number: Test venue:

Confirm via the tick-box on the AMS that you submit to the integrity statement issued by the UP Department of Enrolment and Student Administration. Ensure that you have read and understood the important information for this assessment, and the instructions and rules for electronic submission (available on the server). Examination information Maximum marks:

25

Full marks:

Total number of pages (including this page):

4

Duration of paper (excluding AMS grace periods):

Open / closed book:

25 20 minutes

Open (restricted): official textbook; and formal Class Notes and Lecture Slides, which will be supplied electronically on the AMS. Calculations can be performed in unused portions of your Submission spreadsheet, but default calculator applications installed on the EECE Lab computers, or pocket calculators are also allowed. The circuit simulation packages on the EECE Lab computers (LT-Spice and Orcad) are allowed when you are expected to perform simulations. No device with an enabled communication port (of whatsoever kind) is allowed. No memory devices of any kind are allowed. For on-line assessments, students will be expected to use the same sources. IMPORTANT ASSESSMENT INFORMATION

1. The test & examination regulations of the University of Pretoria apply. The departmental rules relevant to electronically graded

assessments apply for both an-campus and online assessments (including grace periods for filling in the electronic sheet, preparing files in the correct format for images and videos, and uploading files to the AMS). 2. Answer all the questions and provide your answers as instructed. 3. Show all calculations where applicable. Always give equations in symbolic form before numerical values are substituted. No marks will

be given for correct answers without symbolic equations and/or calculations to support them. Clearly specify definitions if notation different from the prescribed class notes or textbook is used. 4. Use clearly justified and educated engineering approximations and state assumptions, where/as appropriate. 5. For on-campus assessments, questions on the fill-in paper must be answered in indelible ink (except red and black). Answers in pencil

or red/black ink will not be marked. Answers on the green scanning sheets or on photographed/scanned images may be completed in pencil or ink, provided everything is legible. Rough work paper is turned in, but it is not marked. For online assessments, use the templates provided on lined or unlined paper for your handwritten answer(s), scan or photograph and video your work according to instructions, along with your physical student card, signature and date (on each page), and upload the file(s) to the AMS. If you wish, your photograph need not be visible. Photo’s must preferably be in the jpg, png, bmp, or heic image format, but pdf will also be accepted. The accepted video formats are m4v and mp4, and video files may be zipped before upload. Multiple files may be uploaded for a single question using the same file base name, and appending _1, _2, etc. The maximum size of any single file is 128 MB, and your total AMS quota per assessment is 256 MB.

Internal examiner: Prof T-H Joubert

External examiner: -

Marks Q1

Q2 /6

Q3 /4

Q4 /10

Q5 /3

Total: /2

/25

Section A: Introduction to digital systems 1.

[20] (6)

Complete the number system conversion table below. Number system

Base

Decimal

3

Number Consider the decimal number in your personalised Excel Submission Sheet.

10

Binary

1.1a

1.1b

Octal

1.1c

1.1d

Hexadecimal

1.1e

1.1f

1.2 will be marked from your image file named Q1 (preferably jpg, but png and bmp are also acceptable). The consequence of failure to comply with the instructions here is a marks penalty. Images must preferably be jpg, but heic, png and bmp are also good, and even a pdf will be accepted. Multiple files may be uploaded using the base name Q1 and appending _1, _2, etc. Please use the template below on lined or unlined paper for your answer, scan or photograph your physical work along with your physical student card, signature, and date (on each page), and upload the file to the AMS. If you wish, your photograph need not be visible. 1.2 Show your calculations:

3

1.2a Binary: 1.2b Octal:

Date

1.2c Hexadecimal:

2.

Place your student card here when you scan or photograph your work.

Your signature

(4)

Consider the Boolean expression for F found in your Excel Submission Sheet.

2.1 will be marked from your image file named Q2 (preferably jpg, but png and bmp are also acceptable). The consequence of failure to comply with the instructions here is a marks penalty. Images must preferably be jpg, but heic, png and bmp are also good, and even a pdf will be accepted. Multiple files may be uploaded using the base name Q2 and appending _1, _2, etc. Please use the template below on lined or unlined paper for your answer, scan or photograph your physical work along with your physical student card, signature, and date (on each page), and upload the file to the AMS. If you wish, your photograph need not be visible. 2.1. a. Without any minimisation of the expression, show a gate-level implementation of F using only 2-input gates. Also include any literal inverters in the schematic diagram. b. Indicate the critical path on your logic circuit diagram. Include the literal inverters. c. Estimate the number of transistors in your circuit, including the literal inverters. (Tip: read points 3 and 4 under the “IMPORTANT ASSESSMENT INFORMATION” on p.1. )

4 2 1 1

2.1a Logic gate circuit: Your signature 2.1b Critical path: 2.1c Size estimate:

3.

Date

Place your student card here when you scan or photograph your work.

(10)

Consider the following Boolean expression for G:

G = X’Y + Y’Z 3.1. Rewrite the equation for G in the form required for a single CMOS block implementation (apart from literal inverters, no cascading is allowed)

G= ERS220 Class Test 1 © Trudi Joubert, Dept. EEC Eng, University of Pretoria, 2021

2

2

3.2. The following parameters hold for the CMOS gate: VDD = 5 V; VSS = 0 V; VIH = VOH = 4 V; VIL = VOL = 1V

3

a. An input voltage of 1.5 V is presented to the gate, and this signal must cause a change in the gate’s output logic value. Describe the consequences for the circuit operation. b.What simulation tool would you use to confirm that the consequences you expect are indeed the case? Justify your answer.

2 1

3.3. Show a look-up table (LUT) implementation of G.

3 Tools

3.4. Write the short notation Product-of-Maxterms form for the expression G.

2

G=

Section B: Combinational logic design 4.

Afdeling B: Kombinasie-logika ontwerp

[5]

Optimise K for the number of gates by using a Karnaugh map. Derive K in the Sum-ofProducts form.

3

Circles of 4.1 will be marked from from your image file named Q4 (preferably jpg, but png and bmp are also acceptable). The consequence of failure to comply with the instructions here is a marks penalty. Images must preferably be jpg, but heic, png and bmp are also good, and even a pdf will be accepted. Multiple files may be uploaded using the base name Q4 and appending _1, _2, etc. Please use the template below on lined or unlined paper for your answer, scan or photograph your physical work along with your physical student card, signature, and date (on each page), and upload the file to the AMS. If you wish, your photograph need not be visible. ERS220 Class Test 1 © Trudi Joubert, Dept. EEC Eng, University of Pretoria, 2021

3

4.1

2

4.2 K =

1

Disease-bearing mosquitoes are attracted by several human odour compounds, with lactic acid1 being an important one. It is hypothesised that a lure possessing attractant odours may protect people from being bitten. A proposal is made that a sock infused with sweat during intense exercise will contain adequate lactic acid concentration to be an effective odorous attractant for mosquitoes. Care must be taken with the aldehyde2 compounds that commonly cause foot malodour, because they mask the lure odours. A researcher designs an experiment to confirm mosquito behaviour with the sweaty sock decoy (SSD). A digital system must be able to validate the SSD state by indicating the predicted success of the SSD. The researcher is also interested to learn whether the malodorous aldehydes still have an effect when the SSD has dried. The digital system must have the following signals: • The output D indicates a high likelihood of a successful SSD decoy function. • The output S indicates that the SSD is still smelly after drying. • A moisture sensor indicates with M when high levels of foot perspiration have been conducive to odour absorption into the sock. • An aldehyde sensor indicates with A when the aldehyde concentration exceeds a masking threshold. • A lactic acid sensor indicates with L when the intensity of exercise was adequate to generate lactic acid levels that are above an effective lure threshold. Lactic acid can only be sensed in a moist environment. Construct a truth table for the SSD sensing system, presenting D and S to indicate successful 5.1. decoy function and dry smelliness, respectively. 5.

M 0 0 0 0 1 1 1 1

A 0 0 1 1 0 0 1 1

L 0 1 0 1 0 1 0 1

D

**********************

1 2

S

NB:

Assume positive logic throughout.

END

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https://www.sciencedirect.com/science/article/pii/S0960982219302155 https://malariajournal.biomedcentral.com/articles/10.1186/1475-2875-9-239

ERS220 Class Test 1 © Trudi Joubert, Dept. EEC Eng, University of Pretoria, 2021

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