Objective: LogicWorks is an interactive circuit design tool that allows you to r

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Objective:
LogicWorks is an interactive circuit design tool that allows you to run quick and efficient
simulations on screen. It’s the fastest solution to help you learn digital logic. The purpose
of this lab is to let you get familiar with the LogicWorks software. Note that this lab
assignment is an individual assignment, which means each student needs to complete it
independently.
Problem statement:
1. Create a 4-to-1 multiplexer using ONLY tri-state buffers and inverters in LogicWorks.
Multiplexing is a generic term used to describe the operation of sending one or more digital
signals over a common transmission line at different times and as such, the device we use
to do just that is called a Multiplexer (hereafter, MUX). A 4-to-1 MUX consists of four
data input lines as D0 to D3, two select lines as S0 and S1 and a single output line Y. It is a
combinational logic circuit designed to switch one of four input lines through to a single
common output line by the application of two select signals (i.e., S0 and S1). In other
words, the select lines S0 and S1 together select one of the four input lines to connect it to
the output line. Please read textbook page 140 section 3-7 Multiplexers before
implementing this lab assignment. You can test out your circuit by using binary switches
and a Hex keyboard (use Ctrl-F to show signal values).
a. This MUX should have two select lines S0 and S1, four input lines D0 ~ D3, and one
output line Y.
b. The output should match the following table:
S1 S0 || Y
0 0 || D0
0 1 || D1
1 0 || D2
1 1 || D3
In other words, when S0 and S1 are both zero the MUX will select input D0 for use as the
output.
2. Use the created circuit from step 1 to create a part in LogicWorks. This can be
accomplished by using a LogicWorks part called “port in”.2
a. You will need a “port in” for each of the six inputs. Label each “port in” using the
text tool (Ctrl – E). Make sure you click the “port in” part and name them with their
appropriate name such as S0, S1, D0, D1 … and so on. Note that the text labels should
become purple.
b. There will be one output line which will require the use of a “port out” part in
LogicWorks. Name it as Y. Use the same method above to label the port out part.
c. Save your LogicWorks file and leave it as an open circuit.
3. With the circuit from step 2 create a part and save it into a library file.
a. Open a new device symbol. (File->New->Device Symbol)
b. Select the Options menu, and then “Subcircuit and Parts Type”. This opens another
window. Select “Create a sub-circuit symbol and select an open circuit to attach to it”.
Click the subcircuit that you have created in Step 2.
c. Auto-create a device symbol if desired. (Under the Options menu)
d. Layout the part graphic as desired. If you want, you can create almost any shape in
LogicWorks since it is only a logical representation and not an actual part. Ensure pins are
in the correct location.
e. Save the part to a new library (File->Save). The name of the library file should be the
first initial of your first name and your last name. For example, student Andrew Jordan’s
library file would be AJordan.clf.
4. Submit your library file from within the Canvas.
Additional Notes: You can add more parts to this library for later use. One useful device
produces a constant 1 signal. It can be created by using an inverted ground. Remember to
always test your circuit for the correct output. Please read the following FAQ section so
that your questions might be answered before you visit your grader. A rubric of this
assignment is provided as the last section of this document.
Frequently-asked questions (FAQ) from students:
1. How to I save my circuit?
Answer: Once your circuit is complete, go to File>New> select device symbol. Then go to
Options>Subcircuit and Part Type> Create a symbol and select an open circuit to attach.
Then go to Option>Auto create symbol and select Generate. To save the symbol to your
library, go to File>Save as and select your library (.clf) file.3
2. I saved my circuit in my library but I can’t open my library file?
Answer: You cannot directly open library files, instead create a circuit (.cct) test file and go
to File>Libraries>Open lib and select your library. You should see your part appear in the
window on the right.
3. I copied the solution from the lecture slide, but it doesn’t match up with the truth table?
Answer: In LogicWorks, the tri-state buffer has a NOT gate on the enable port, so you have
to inverse the signal going into that port for each gate.
4. How do I provide an input/output to the circuit?
Answer: Use the port in/port out parts to allow the circuit to receive input and give an
output.
5. The binary probe shows an X/C/Z instead of a 0/1?
Answer: An X/C/Z means that there is an error and somewhere in the circuit there is most
likely a wire that isn’t connected or 2 wires shouldn’t be connected.
Rubric
If your design and logic for the circuit is correct, however, your circuit is not working at
all, you will receive 20 of the 100 points.
If your design and logic for the circuit is correct, however, your circuit isn’t connected
fully or has a single error, you will receive a penalty of 5 points.
If your design and logic is flawed with small errors such as misplacing S0, S1 or the
variables, you will receive a penalty of 10 points.
If you turn in a circuit that uses AND gates and OR gates, you will receive 0% credit as
this lab assignment explicitly asks you to use tri-state buffers and invertors only.
If you turned in a circuit that does not function at all and is incorrect with design and logic
for the lab, you will receive 0% credit.

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