Introduction to Computer Systems and Networks 1007 ICT

Software requirement:

You must use the Digitalworks logic simulator (Version 2.0) to create your circuits. Assignments submitted using other programs(including other versions of the Digitalworks logic simulator) will NOT be marked.

Submission Instructions:

You will be required to submit at least two files, a digital simulator circuit (created using the

Digital Works simulator Version 2.0) and a written report (in MS Word or a compatible format) as

described in the text below.

Individual Assignment:

This is an individual assignment. All work submitted must be your own work. As per the

warning given in the first lecture, you should be careful not to use the work of others as your

own nor have others use your work as their own.

Marking Scheme:

The assignment will be marked out of 100, with mark allocation according to the following table:

Aspect

Maximum Mark

Difficulty

70 (See Task Description)

Circuit (85)

Accuracy

10

Neatness

5

Completeness

5

Accuracy

5

Report (15)

Neatness, appropriate use of

5

language and layout.

TOTAL

100

Task Description:

You are to build (and test) ONE of the following digital logic circuits in the DigitalWorks logic

simulator (supplied on the Learning@Griffith website) and write a short report that describes the

circuit. The maximum mark that you are able to achieve on the assignment will be determined

by the difficulty of the circuit you decide to build.

Circuit Options

Circuit

Difficulty (Max mark)

Option1: 4 function 4 bit ALU

45

Option2: 8 function 4 bit ALU

70

Please note, however, it is better to have a fully functional and neatly drawn simple circuit than

a more complex one that is messily constructed and does not function properly.

Labelling

You must label each circuit and template that you construct with the Annotation tool (A) and

ensure that the Least Significant Bit (LSB) of each circuit or template is the right-most bit.

Each circuit and template must be labelled with:

1. Your name

2. Your student number

3. An appropriate label for each input

4. An appropriate label for each output

5. An appropriate label for the template that describes its function

Note: Be careful, Digitalworks does not update templates that have already been included in a

circuit. Subsequent changes to a template will not be reflected in the final circuit!

Testing

You will be provided with a test harness circuit. The test harness circuit will have interactive

inputs and LEDs for outputs. You must use this test harness circuit to interact with your ALU

and test that it works according to specification. To use the test harness circuit, open it up in

Digitalworks, embed your own circuit into the middle of the test harness, and wire the interactive

inputs and LEDs into your own circuit. You must submit a modified version of the test

harness with your circuit embedded into it.

Report Format

Your report must contain the following sections:

1. Your details: Name, student number, and email address

2. Circuit Name: The name of the circuit you have selected to build and draw.

3. Circuit Function: A brief (100-200 words) description of the function of your circuit.

4. Circuit diagram/s: A diagram of your circuit including all templates and their contents.

You must draw this diagram for yourself using the Digitalworks logic simulator. Copying

and pasting from the lecture notes or other sources is NOT permitted.

5. Truth tables: Showing all possible inputs and corresponding outputs for each component

individually. The column headings in your truth table should correspond to the labels on

your circuit diagram. You are not required to show the truth table for the complete 4 bit

ALU

CIRCUIT OPTION 1: 4 function 4-bit ALU (45 marks):

Your 4-bit ALU must implement the following functionality (It is imperative that the bit values for

S1 and S2 in this table correspond exactly to the functions in your circuit):

S1

S2

OUTPUT

0

0

Shift A Through (X = A)

0

1

Logical AND (X = A AND B)

1

0

Logical XOR (X = A XOR B)

1

1

Full adder (X = A + B)

In addition your circuit must include:

1. A multiplexor (comprised of a 2 to 4 Decoder and 4 input Selector)

Your circuit must use a separate template to represent each of the following components:

1. Full Adder

2. Logic Unit (Shift A Through, Full Adder, Logical AND, and Logical XOR)

3. 2 to 4 Decoder

4. 4 Input Selector

5. Multiplexor (Contains 2 to 4 Decoder and 4 Input Selector)

6. 1 Bit ALU (Contains Logic Unit and Multiplexor)

7. 4 Bit ALU (contains four 1 Bit ALUs)

Your 4 Bit ALU will consist of four 1 Bit ALUs wired together appropriately. You will be provided

with an interactive test harness circuit into which you can embed (and wire) your 4 Bit ALU

template for testing.

CIRCUIT OPTION 2: 8 function 4-bit ALU (70 marks):

Your 4-bit ALU must implement the following functionality (It is imperative that the bit values

for S1, S2, and S3 in this table correspond exactly to the functions in your circuit):

S1

S2

S3

OUTPUT

0

0

0

Shift A Through (X = A)

0

0

1

Shift input A Left (X = A Shifted right by 1 bit)

0

1

0

Shift Input A Right (X = A Shifted left by 1 bit)

0

1

1

Logical AND (X = A AND B)

1

0

0

Logical XOR (X = A XOR B)

1

0

1

Logical NOR (X = A NOR B)

1

1

0

Full adder (X = A + B)

1

1

1

Subtraction (using the Full Adder) (X = A - B)

In addition your circuit must include:

1. 3 multiplexors, 2 of these will be a combination of a 2 to 4 Decoder and a 4 input Selector,

the third multiplexor will consist of a 1 to 2 decoder and a 2 input selector.

Your circuit must use a separate template to represent each of the following components:

1. Full Adder

2. Logic Unit (Shift A Through, Full Adder, Logical AND, Logical NOR, Logical XOR, Shift A

Left, Shift A Right, Subtraction,)

3. 2 to 4 Decoder

4. 4 Input Selector

5. 1 to 2 Decoder

6. 2 Input Selector

7. Multiplexor (Contains 2 to 4 Input Decoder and 4 Input Selector)

8. Multiplexor (Contains 1 to 2 Input Decoder and 2 Input Selector)

9. 1 Bit ALU (Contains Logic Unit and Multiplexor)

10. 4 Bit ALU (contains four 1 Bit ALUs)

Your 4 Bit ALU will consist of four 1 Bit ALUs wired together appropriately. You will be provided

with an interactive test harness circuit into which you can embed (and wire) your 4 Bit ALU

template for testing.

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