Course Profile Computer Engineering (ICE4M), Grade 12, University/College Preparation, Combined
Unit 3: Digital Logic and Electronic Circuits
Time: 25 hours
Activity
3.1 | Activity 3.2 | Activity 3.3
Unit Description
Students are
challenged to integrate and assemble a digital “gaming wheel” circuit that
incorporates a clock circuit and two-state devices, which are commonly called
“flip-flops.” Flip-flops make up the building blocks for basic memory units
used in sequential logic operations. They are used extensively as the basis for
digital memory storage and transfer, such as in registers. Initial activities
are skill builders through hands-on activities; students arrange simple logic
to create R-S, D, and J-K flip-flops and develop truth tables to understand their
function. Students identify and hardwire circuits to create D, R-S, and J-K
flip-flops and develop truth tables. Students research and design a clock
circuit that is used to understand the shifting of data in response to timed
clock pulses.
Unit Synopsis Chart
|
Activity |
Time |
Learning Expectations |
Assessment Categories |
Tasks |
|
3.1 |
8 hours |
SPV.02, SP1.02,
SP1.05, SP1.06, SP1.07 CGE2b, 2c, 3c |
Application |
Understand the
role and concept of flip-flops by hardwiring an R-S flip-flop using basic
logic gates. |
|
3.2 |
7 hours |
TF1.05, SP1.03 CGE2b, 2c, 3c |
Thinking/Inquiry Application |
Use D and J-K
flip-flops to investigate how clocks are used in triggering flip-flops. |
|
3.3 |
10 hours |
TF1.05, SP1.03 CGE2b, 2c, 3c |
Thinking/Inquiry Application |
Integrate a clock
circuit, flip-flops, and shift registers in a game spinner circuit. |
Activity
3.1: Non-clocked Flip-Flops
Time: 8 hours
Description
This activity
focuses on hardwiring a non-clocked R-S flip-flop and understanding the role of
flip-flops and data flow in computer memory circuits. Students use basic logic
gates to construct an R-S flip-flop. They describe the structure of flip-flops
and construct truth tables to identify outcomes based on inputs to the flip-flop.
They also use Boolean expressions to describe logic circuits.
Strand(s) & Learning Expectations
Ontario Catholic
School Graduate Expectations
CGE2b - read,
understand, and use written materials effectively;
CGE2c - present
information and ideas clearly and honestly and with sensitivity to others;
CGE3c - think
reflectively and creatively to evaluate situations and solve problems.
Strand(s): Skills and Processes
Overall
Expectations
SPV.02 - use Boolean
equations to represent computer logic circuits.
Specific
Expectations
SP1.02 - build flip-flops using simple logic gates from schematics;
SP1.05 - simplify
Boolean equations accurately;
SP1.06 - draw
circuits that represent Boolean equations;
SP1.07 - develop
truth tables to represent Boolean equations.
IC1.06 - use
appropriate strategies to avoid potential health and safety problems associated
with computer use, such as musculo-skeletal disorders and eye strain.
Prior Knowledge & Skills
·
Familiarity with
basic electronic components, symbols, and characteristics;
·
Understanding of
logic gates;
·
Familiarity with
use of truth tables;
·
Ability to
manipulate Boolean expressions.
Planning Notes
·
For students who
have not taken the Grade 11 Computer Engineering course and are not familiar
with basic electronic components, review Grade 11, University/College
Preparation, Unit 3.
·
The glossary is
referred to in various activities. Students develop and add to this section of
their notebooks on an ongoing basis.
·
Have ready access
to resource materials for researching integrated circuits and flip-flops.
·
Review safety
with electricity and the proper handling and storage of batteries.
·
Prepare
pre-sorted kits with appropriate components: breadboard, integrated circuits,
5-volt regulator, battery, battery clip, and wire.
·
Ensure
parts/components storage area is well organized and assist in the management
and distribution of parts/components.
·
Ensure a supply
of spare components and supplies are available.
·
Ensure students
do not wear acrylic or wool sweaters before handling computer components.
·
Ensure students
discharge themselves before handling components or computers.
·
Hardwire each
circuit ahead of time so students can refer to teacher sample for reference.
·
Use a variety of
visual aids to enhance presentations, e.g., PowerPoint,
overhead, computer graphics.
Teaching/Learning Strategies
1. The teacher reviews safety considerations
with students about working with electronic components, specifically
emphasizing the dangers of short-circuiting a battery and damage by static
electricity.
2. Students complete Appendix 3.1.5 – Electronic
Safety Quiz. Reinforce the importance of safety by having a summary of safety
rules posted in the classroom.
3. Students develop dexterity by hardwiring two
simple circuits on the breadboard. It may be useful to have the backing of a
breadboard stripped off to show how it is constructed and how the holes are
connected together (see Appendix 3.1.1 – Breadboards).
4. The teacher reviews and demonstrates the
proper use of circuit building tools, e.g., Integrated Circuit (IC) insertion
tool, IC removal tool. Using the proper tools assists in minimizing damage to
fragile components.
5. Students research how to identify pins on an
IC and draw diagrams, in their glossaries, of the internal structure of the
basic logic gate ICs – AND (7408), NAND (7400), OR (7432), NOR (7402), NOT
(7404) (Appendix 3.1.2 – Block and Pinout Diagrams).
6. The teacher reviews Boolean algebra and has
students apply knowledge to simplify Boolean expressions for combination logic
circuits (Appendix 3.1.3 – Combinational Logic Circuits from Boolean
Expressions).
7. Students pair up to research the function and
possible applications for flip-flops.
8. The teacher leads a class discussion on the
function and application of flip-flops, e.g., building blocks of memory
circuits used in RAM and CPU registers, by having groups contribute their
findings to the class.
9. Students hardwire an R-S flip-flop using both
NAND gates and OR gates. Students use their prior knowledge from Grade 11 to
complete a truth table. Students research the prohibited states of a flip-flop
(Appendix 3.1.4 – R-S Flip-Flop Circuits).
Assessment & Evaluation of
Student Achievement
·
To reinforce the
importance of safety when working with electronic components, tools, and electricity,
students complete a safety quiz (see Appendix 3.1.5 – Electronic Safety Quiz).
·
The completion of
hardwired circuits is assessed using a rubric
·
At the end of
this activity, students write a quiz to test their knowledge of Boolean
expressions and flip-flops (Appendix 3.1.7 – Activity 1 Quiz).
Accommodations
·
Consult
individual student IEPs for specific direction or accommodation for individuals
·
Monitor
individual progress in dexterity and allow extra time to complete circuits.
·
Establish a
‘buddy system’ for example to assist in identifying components for students who
are colour blind and where fine motor skills are required.
·
Have large
lighted magnifiers for students who are visually impaired.
Resources
Print
Smyth,
Graham and Christine Stephenson. Computer
Engineering: An Activities-Based Approach. Toronto: Holt Software, 2000.
ISBN 0-921598-36-X
Tokheim, Roger. Digital Electronics, 4th ed. McGraw Hill Book Company,
1994. ISBN 002-801853-2
Websites
Electronics
Basics – http://www.epanorama.net/basics.html
Marshall Brain’s How
Stuff Works – http://www.howstuffworks.com/
Appendix 3.1.1 – Breadboards
Breadboards are a
convenient way to experiment and connect circuits so that parts are not damaged
or made unusable by soldering. The breadboard is built with conductive channels
underneath in vertical and horizontal columns. Two rows at both the top and
bottom of the breadboard, conveniently labelled + and &, supply power for the whole length of the breadboard when power, such
as a battery, is connected to it. While
each hole in one row is connected together, each of these rows is separate from
each other.
The same logic is
applied to the columns. Each of the five holes in the column is connected to
each other, but all columns are separate from each other.
Students wire the
two circuits, one series and one parallel, and demonstrate their capability to
understand the breadboard and wiring of circuits.
Photographic Views
Appendix 3.1.2
Block and Pinout Diagrams
The following is a
reference for the teacher.
Appendix 3.1.3
Combinational Logic Circuits from
Boolean Expressions
Circuits that are
defined by a Boolean equation can be implemented directly from that expression.
For example, to construct a circuit whose output is y = AC + BC' + A'C, we look
at how the separate terms are related in the overall expression. This Boolean
expression contains three terms (AC, BC', A'C) “ORed” together, as determined
by the “+”" sign. A three-input OR gate is required with inputs that are
equal to AC, BC', and A'BC, respectively. If a three-input OR gate is
unavailable, two OR gates can be combined:
Each OR gate input
is an AND product term, which means that an AND gate with appropriate inputs
can generate each term. Note the use of inverters to produce the A' and C'
terms in the expression.
|
Boolean Theorem |
Logic Circuit |
|
X * 0=0 |
|
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X * 1 = 1 |
|
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X * X = X |
|
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X * X’ = 0 |
|
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X + 0 = X |
|
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X + 1 = 1 |
|
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X + X = X |
|
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X + X = 1 |
|
Appendix 3.1.3 (Continued)
Multivariable
Theorems
|
1. |
X + Y = Y + X |
|
6. |
(W + X)(Y + Z) =
WY + XY + WZ + XZ |
|
2. |
X * Y = Y * X |
|
7. |
X + XY = X |
|
3. |
X + (Y + Z) = (X +
Y) + Z = X + Y + Z |
|
8. |
X + X’Y = X + Y |
|
4. |
X(YZ) = (XY)Z =
XYZ |
|
9. |
(X + Y)’ = X’ * Y’ |
|
5. |
X(Y + Z) = XY + XZ |
|
10. |
(X * Y)’ = X’ + Y’ |
Example
of simplifying a Boolean expression with associated logic circuit
Y = [(A'+C) * (B+D')]'
= (A'+C)' + (B+D')'
= (A*C') + (B'+D)
= AC' + B'D
Consult textbook
resources for more samples of creating logic circuits from Boolean expressions
and for deriving the Boolean expression from a logic circuit.
Appendix 3.1.4
R-S Flip-Flop Circuits
Students consult
their glossary for pinout diagrams of the researched gates. Students hardwire
the circuit and fill in the truth table. The teacher provides feedback during
hardwiring to ensure a working circuit.
Truth Table
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State |
S |
R |
Q |
Q' |
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Truth Table
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State |
S |
R |
Q |
Q' |
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Appendix 3.1.5
Electronic Safety Quiz
Name:
Date:
Answer the following
questions.
1. What type of clothing should be avoided when
working with electronic parts?
2. What tool should be used when placing an (IC)
onto the breadboard? Why?
3. What tool should be used when removing an IC
from the breadboard?
4. Describe how electronic devices should be
handled to avoid damage.
5. What might you do before touching an
electronic device to avoid static damage?
6. Why might you put a piece of masking tape
over the terminals of a 9-volt battery?
7. What might happen if a battery short
circuits?
8. Why is checking polarity important when power
is about to be connected to your circuit?
Teacher Answer
Sheet
1. Avoid acrylic or wool sweaters
2. Use the IC insertion tool because it
precisely places the IC into the holes on the breadboard, otherwise, you might
severely damage the legs.
3. Use a IC extraction tool because the IC is
tight in the board and removing it using fingers or screwdrivers can cause
damage to the legs.
4. Use an antistatic pad to place devices on;
hold the parts by the casing and not the leads; gently place or remove
components.
5. Use an antistatic wrist strap or discharge
yourself by touching a grounded metal object, such as a computer casing, table
leg, or doorknob.
6. A piece of masking tape over the terminals of
a 9-volt battery will keep any wires, tools, or other metal objects from
shorting the terminals when stored.
7. If a battery short circuits, it becomes very
hot and may explode.
8. Checking polarity is important because
certain electronic components are susceptible to damage when power is applied
in the wrong direction.
Appendix 3.1.6
Rubric to
Assess Hardwired Circuits
|
Category/ Criteria |
Level 1 |
Level 2 |
Level 3 |
Level 4 |
|
Thinking/
Inquiry Truth Table |
- demonstrates
limited understanding of the relationship between inputs and outputs |
- demonstrates
some understanding of the relationship between inputs and outputs |
- demonstrates
considerable understanding of the relationship between inputs and outputs |
- thoroughly
understands the relationship between inputs and outputs |
|
Application Hardwiring |
- uses proper
circuit-building techniques with limited effectiveness |
- uses proper
circuit-building techniques with some effectiveness |
- uses proper
circuit-building techniques with considerable effectiveness |
- uses proper
circuit-building techniques with a high degree of effectiveness |
Note: A student whose achievement is below Level 1 (50%) has not met the
expectations for this assignment or activity.
Appendix
3.1.7 – Activity 1 Quiz
Name:
_____________________________
1. Express the output of the following circuits
in Boolean terms.
a. 
b. 
c. 
2. Combine logic gates to produce an output
related to the following Boolean expressions:
a. f(A,B,C,D) = (`A·B Ĺ C ) +`CD
b. f(A,B,C) = [( A + C ) · B] + (`A · B ) + (B · `C)
3. What is an R-S flip-flop also called?
4. What does the R-S stand for and what effect
does it have on Q?
5. Draw the circuit diagram for an R-S flip-flop
using NAND gates.
6. Draw the block and pinout diagrams of a 7400
IC.
7. Discuss the connection between flip-flops and
memory devices.
Activity 3.2:
Clocked Flip-Flops
Time: 7 hours
Description
This activity
focuses on flip-flops in integrated circuit form and incorporating a clocked
circuit to alter the state of the flip-flop. Students are challenged to develop
a clocking circuit to be used in exploring the movements of stored data in
flip-flop circuits. They hardwire clocked R-S, D, and J-K flip-flops using
basic logic gates and construct truth tables to understand the relationship
between input and output states.
Strand(s) & Learning Expectations
Ontario Catholic
School Graduate Expectations
CGE2b - read,
understand, and use written materials effectively;
CGE2c - present
information and ideas clearly and honestly and with sensitivity to others;
CGE3c - think
reflectively and creatively to evaluate situations and solve problems;
Strand(s): Theory and Foundation, Skills and Processes
Specific
Expectations
TF1.05 - analyse the
role of flip-flops in the flow of data;
SP1.03 - incorporate
flip-flops in a clocked circuit to demonstrate information storage.
Prior Knowledge & Skills
·
Hardwiring skills
from Activity 3.1;
·
Knowledge of
integrated circuit identification from Activity 3.1;
·
Familiarity with
reading electronic circuit diagrams.
Planning Notes
·
Students
developed hardwiring skills in Activity 3.1. The ability to read electronic
circuit diagrams is important for students from this point onward. Close
monitoring during this activity may be needed to develop this skill.
·
Ensure
parts/components storage area is well organized and assist in the management
and distribution of the parts and components. Ensure spare components and
supplies are available.
·
Ensure students
do not wear acrylic or wool sweaters before handling components of computers.
Ensure students discharge themselves before handling components or computers.
·
Hardwire each
circuit ahead of time so students can refer to teacher sample for reference.
·
Use a variety of
visual aids to enhance presentations, e.g., PowerPoint,
overhead, computer graphics.
Teaching/Learning Strategies
·
The teacher leads
a discussion of the function of clocks in digital circuits and its role in the
timing and flow of data.
·
Students are
paired and presented with a challenge of designing a clock circuit that
generates a 1-kHz square wave for use in exploring clocked flip-flop circuits.
Students also research how a variety of frequencies might be achieved (Appendix
3.2.1 – Clock Circuit).
·
Students hardwire
clocked flip-flops using basic logic gates and complete truth tables as a
skill-building exercise (Appendix 3.2.2 – R-S, D, and J-K Flip-Flops Using
Basic Gates).
·
Students are
given a 7474 and a 7476 IC as mystery ICs. They connect the two circuits and
observe the differences in data flow between the two ICs to identify them as a
D or J-K flip-flop
(Appendix 3.2.3 – D and J-K Flip-Flops: IC Block and Pinout Diagrams).
·
Students research
and transfer information of the internal structure of the 7474 and 7476
integrated circuits into their glossary.
Assessment & Evaluation of
Student Achievement
·
A checklist is
provided for assessing the clocking circuit (Appendix 3.2.4 – Clock Circuit
Checklist).
·
Students’
flip-flop circuits are evaluated using a rubric
·
Check for
additions to glossary in this activity.
Resources
Print
Smyth,
Graham and Christine Stephenson. Computer
Engineering: An Activities-Based Approach. Toronto: Holt Software, 2000.
ISBN 0-921598-36-X
Tokheim, Roger. Digital Electronics, 4th ed. McGraw Hill Book Company,
1994. ISBN 002-801853-2
Websites
University
of Sidney Australia – http://www.eelab.usyd.edu.au/digital_tutorial/part2/flip-flop01.html
Marshall Brain’s How
Stuff Works – http://www.howstuffworks.com/
Appendix 3.2.1
Clock Circuit
The following
circuit is a reference circuit that generates a 1-kHz square wave using a
555-timer circuit. Clocked circuits can be developed using logic gates,
however, the versatility and proven history of the 555 timer make it the most
reasonable choice for building a clocking mechanism.
A block diagram
showing pins and labels is provided as reference.
Appendix 3.2.2
R-S, D, and J-K Flip-Flop Using Basic
Gates
Students consult
their glossary for pinout diagrams of the gates. Students hardwire the circuit
and fill in the truth table. The teacher provides formative assessment during
hardwiring to ensure a working circuit.
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State |
S |
R |
clock |
Q |
Q' |
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State |
D |
clock |
Q |
Q' |
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State |
J |
K |
clock |
Q |
Q' |
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Appendix
3.2.3
D and J-K Flip-Flop: IC Block and
Pinout Diagrams
The following is a
reference diagram for the teacher.
Appendix 3.2.4
Clock
Circuit Checklist
Assess the clock
circuit using the following checklist
|
Expectation |
Yes |
|
There is a neatly
drawn diagram of the clock circuit. |
|
|
Formula showing
calculations of frequency is evident. |
|
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Circuit is neatly
wired. |
|
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Circuit is
functional. |
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Students are able
to identify components as to their function. |
|
Activity 3.3: Clocked Data Transfer
Time: 10 hours
Description
This activity
focuses on students integrating a clock, flip-flop, and a shift register into a
gaming wheel circuit. This circuit serves as the basis for understanding the
role of each section. Students learn how flip-flops are incorporated into shift
registers and how shift registers are used to move data. Students hardwire and
analyse the flow of data and explain the function of each section and how they
interact with each other.
Strand(s) & Learning Expectations
Ontario Catholic
School Graduate Expectations
CGE2b - reads,
understands, and uses written materials effectively;
CGE2c - presents
information and ideas clearly and honestly and with sensitivity to others;
CGE3c - thinks
reflectively and creatively to evaluate situations and solve problems.
Strand(s): Theory and Foundation, Skills and Processes
Specific Expectations
TF1.05 - analyse the
role of flip-flops in the flow of data;
SP1.03 - incorporate
flip-flops in a clocked circuit to demonstrate information storage;
IC1.05 - communicate
the results of projects effectively both orally and in writing.
Prior Knowledge & Skills
·
Knowledge of
flip-flops from Activity 3.2;
·
Knowledge of
integrated circuit identification from Activity 3.1;
·
Familiarity with
reading electronic circuit diagrams from Activities 3.1 and 3.2.
Planning Notes
·
Ensure
parts/components storage area is well organized and assist in the management
and distribution of the parts and components. Ensure a supply of spare
components and supplies are available.
·
Ensure students
do not wear acrylic or wool sweaters before handling components of computers.
Ensure students discharge themselves before handling components or computers.
·
Hardwire each
circuit ahead of time so students can refer to teacher sample for reference.
·
Have a variety of
visual aids available to enhance student presentations, e.g., overhead projector,
LCD projector.
Teaching/Learning Strategies
1 Students are given two circuits using block
diagrams of the 74HC164 and the 74HC165. They research which block diagrams
correspond to the respective shift registers and obtain pinouts to hardwire the
circuits and develop truth tables for them (Appendix 3.3.1 – Shift Register
Circuits).
2 Students add integrated circuit pin diagrams
of the shift registers to their glossary (Appendix 3.3.2 – Shift Registers:
Block and Pinout Diagrams).
3. The teacher presents students with a
challenge. Using a clock, flip-flop, and shift register, arrange them in such a
manner that it simulates a gaming wheel circuit where LEDs light up
successively one at a time. Students are paired up to develop the circuit based
on previous skill building. A reference circuit is provided for the teacher
(Appendix 3.3.3 – Gaming Wheel Circuit).
4. Groups hardwire their circuits and then
present their design solution and working circuit to the class.
Assessment & Evaluation of
Student Achievement
·
Provide
diagnostic feedback of students’ progress as students are building their shift
register circuits.
·
The game spinner
circuits are assessed using a rubric.
·
Student
presentations are assessed using a rubric (Appendix 3.3.4 – Presentation
Rubric).
Resources
Smyth,
Graham and Christine Stephenson. Computer
Engineering: An Activities-Based Approach. Toronto: Holt Software, 2000.
ISBN 0-921598-36-X
Tokheim, Roger. Digital Electronics, 4th ed. McGraw Hill Book Company, 1994. ISBN 002-801853-2
Appendix 3.3.1
Shift Register Circuits
Internal block
diagrams for students
Appendix
3.3.2
Shift Registers: Block and Pinout
Diagrams
Students copy these
block and pinout diagrams for the D an J-K flip-flops into their glossaries.
Students use these diagrams for reference as they hardwire circuits.
Appendix 3.3.3
Gaming Wheel
Circuit (teacher reference)
When turning
on the power, the shift register must first be cleared to all zeros. When the
spin wheel switch is pressed, a single high must be loaded into position 0 on
the display, lighting LED 0. The 555-timer section acts as clock which starts
at a high frequency and gradually decreases in frequency until it stops. The
clock pulses are inputted into the shift register. Each clock pulse entering
the register will shift the high bit to the next position, lighting up LED 1,
then LED 2, etc. When the clock stops, a single LED should be lit on the wheel
in a random position.
The power-up
initializing circuitry consisting of R7 and C4 must first clear the shift
register and then set only the first output high. When power is first turned
on, the voltage at the top of the .01 uF capacitor, C4, starts low and
increases quickly to a high as it charges through resistor R7. The master reset
input to the 74HC164 register is held low just long enough for the all the
outputs of the register to be cleared to zero. At this point, all LEDs are off.
The circuit
that loads a single high to the register is the NAND gate configured as an RS
latch. The two resistors, R5 and R6, force the output of the NAND gate (ICa)
high when the power is first turned on. This high is applied to the data
inputs, Dsa and Dsb, of the shift register. On the very first low-to-high
transition of the clock, the high at the data inputs is transferred to output
Q0 of the register. This high is immediately fed back to the input of ICd and
resets the latch so that a low now appears at the data inputs, Dsa and Dsb.
Only one high was loaded into the register. Repeated clock pulses move the high
along until Q7 goes high. This high is fed back to the input of ICc
The 74HC164 8-bit
shift register is wired as a ring counter. The circuit has two characteristics
that make it a ring counter. One characteristic is feedback from the last Q0
bit and the last Q7 bit to a flip-flop. When the high reaches output Q7, after
clock pulse 8, a feedback line is run back to the flip-flop to transfer the
high back to output Q0. The second characteristic is the loading of a pattern
of 1s and 0s; these re-circulate as long as clock pulses reach the CP input of
the shift register.
Appendix 3.3.4
Presentation Rubric
|
Presentation |
Level 1 |
Level 2 |
Level 3 |
Level 4 |
|
Communication Organization Delivery |
- shows limited organization - demonstrates
limited command of presentation skills |
- shows moderate
organization - demonstrates a
moderate command of presentation skills |
- shows
considerable organization - demonstrates
considerable command of presentation skill |
- shows a high
degree of organization - demonstrates
extensive command of presentation skills |
|
Knowledge/
Understanding Content Knowledge |
- demonstrates
limited knowledge and ability to answer questions |
- demonstrates
some knowledge and answers rudimentary questions |
- demonstrates
considerable knowledge and is at ease with content |
- demonstrates
knowledge and includes explanations and elaboration |
|
Application Visuals |
- uses visuals
with limited effectiveness |
- uses visuals
with some effectiveness |
- uses visuals
with considerable effectiveness |
- uses visuals
effectively |
Note: A student whose achievement is below Level 1 (50%) has not met the
expectations for this assignment or activity.
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