Mini-Lab: Digital Logic
In this mini-lab you will
experiment with digital logic design using the Logicly simulator.
Start the Logicly simulator by going to https://logic.ly/demo/. If this
does not work in your browser, you may download Logicly from https://logic.ly/.
- Add two Toggle Switches and
an AND gate to your circuit board. Wire the two switches to the
AND gate. Add a light bulb
to your circuit board and wire the output of your AND gate to the
light bulb. Once you have
this simple circuit set up, experiment
with flipping the switches to change the inputs to your AND gate. Make sure that the gate
does what you expect it to do. Repeat the experiment with the OR
gate and the NOT gate. There is nothing to turn in for this
- Here is the truth table for the exclusive or function (xor):
A B | Out
0 0 | 0
0 1 | 1
1 0 | 1
1 1 | 0
Write a Boolean expression that corresponds to this truth table, and
implement your expression using AND, OR, and NOT gates in
Test your circuit to make sure that it generates the appropriate
output for all possible inputs. For this exercise you will hand in
your Boolean expression as well as a print-out or drawing of your
Saving your work: If you have downloaded Logicly to
your own machine, you can go to File->Save As to save your
file. If you are running Logicly through the browser, you cannot save
the circuit board as a file, but you can take a screenshot to capture
your circuit diagrams.
- Screenshot on a mac: Press Shift + Command + 4,
then move the crosshairs to where you want to start the screenshot,
and then drag them to select the area you want to capture. It will
save the screenshot in a .png on your desktop.
- Screenshot on a pc:
- Follow these instructions to Use
- Open a Word document. Go to the Insert menu, choose to
insert a screenshot, and either choose a shot that it available,
or choose to select an area of the screen to insert in your
- Follow one of these
suggestions to take a screenshot.
- The exclusive or function can be generalized to any number of
inputs. No matter how many inputs there are, the output is true if and
only if exactly one of the inputs is true. Create a truth table for a
three input exclusive or function. Write a Boolean expression that
corresponds to that truth table, and implement your expression in
gates using Logicly.
Hint: Your Boolean
expression will probably include AND clauses that include three
terms. For example: A'B'C.
For this exercise you will hand in your truth table, your Boolean
expression, and a print-out or drawing of your circuit.
- (IF YOU HAVE TIME) During class we worked through the design
of a binary adder. The first step was to build a half adder, a
circuit that could add two bits together as long as there was no
carry-in from a previous add. For this exercise you will build a half
subtractor, a circuit that can subtract two bits as long as there is
no borrow from a previous pair of bits. Build and test a circuit that
implements the following truth tables:
Subtraction of 2 bits: X Y Result X Y Borrow
---------------------- -------|------ -------|------
0 0 | 0 0 0 | 0 (F)
X 0 0 1 1 -------|------ -------|------
-Y -0 -1 -0 -1 0 1 | 1 0 1 | 1 (T)
-- -- -- -- -------|------ -------|------
Result: 0 1 1 0 1 0 | 1 1 0 | 0 (F)
Borrow? F T F F -------|------ -------|------
1 1 | 0 1 1 | 0 (F)
Submit your results
- Submit your solutions to the exercises above.
You may print them out or submit your file(s) on Moodle.