CSE 370 Laboratory
Logic Circuits - III
Assigned: Monday, January
Due: End of Lab Section
this laboratory assignment you will continue to learn how to use the Aldec
Active-HDL tool. This time the focus will be on how to create Verilog modules.
You will also see how Verilog modules can be used as test fixtures to help you
verify your circuit's behavior. By the end of this lab you should feel
comfortable creating a Verilog module directly and setting up a test fixture.
**Save all the files that you create in this lab. We will use them later.**
- Read Part 1 of Tutorial
#2 to familiarize yourself with test fixtures and how to use them to
test a circuit in Active-HDL. You will need to know this for the next
- Complete Tutorial
#3 which describes how to write simple Verilog modules and use them in
schematics. As part of the tutorial, you will write and test the Verilog
module for a full-adder; a full adder is an adder that handles both
carry-in and carry-out conditions in addition to the sums and two inputs.
You should create a test schematic by using the provided test fixture: FA_tf.v (right click and "save as" if the
download doesnít start automatically). Test fixtures will be covered in
more detail later so donít worry too much about why it works. However the
basic premise is the test fixture generates a signal and checks to see if
the returned signal is the expected output. An example of how to hook up
your test fixture is below.
To test to see if your full adder works you do not have to manually create
signals and simulate it in Active-HDL. Since you now have a test fixture,
the test fixture should generate the signals so all you need to do is run
the simulation. The test fixture should pass in a series of values to your
full adder, if all goes well the console at the bottom will inform you
that your full adder passed. If there are errors it will let you know as
**Warning: Do not put complete
faith in test fixtures, you should always practice common sense and make
sure that the values that come out make sense. If you see a value like: X,
that probably is not right.
**Important: In Tutorial #2 the four-bit
full adder is made with the pink lib370 gates.†
However, since we will eventually be putting this four-bit adder on
standard industry hardware, when designing your schematic in part 3, you MUST
use the built-in symbols included with Active HDL, these are yellow. If you have any pink gates,
when you get to the lab where you need to put this design onto the FPGA (Field
Programmable Gate Array), it will not work.
- Complete Part 2 of Tutorial #2 , which describes
how to use buses and bus inputs and output terminals. A bus is simply a
large group of wires, which means they can handle more than 1 signal, for
example: an 8-bit bus can have 8 different signals across it. In Part 2
you will create a four-bit full adder by using one-bit full adders you
created in Task 2. You can test your four bit full adder by using this
test fixture: addsub4_tf.v.
- Create a Block Diagram in Active-HDL to detect a
Fibonacci number between 1 and 15. These numbers would be: 1, 2, 3, 5, 8,
13. Test it with the provided test fixture here: fibonacci_tf.v.
Once again, since you will have to wire up this circuit on your breadboard,
you will need to construct it with logic available on the chips in your
kit, (such as NANDs and NORs and NOTs). You can refer to the chip map to recall what logic gates are available to
you. If you would like your TA to check your Boolean logic before moving
onto to the last step of building your circuit on the actual board, feel
free to call over a TA.
Donít cares can be useful when simplifying a circuit. As long as you are
feeling up to it, you may treat 0 as a donít care, though you should let
your TA know if you have done so when the TA comes to check off your
Fibonacci circuit. And finally, whether or not your output is Active-High
or Active-Low is up to you.
- Using the logic you created in Active-HDL, follow it and
build your Fibonacci Detector on the circuit board. You will need 4
switches and 1 LED. We suggest that you use SW0 through SW3, where SW3 is
the most significant and SW0 is the least. If you have any trouble with
this last part and your logic is correct, you should check your wiring
with the logic probe. You can use the logic probe to trace through each
step of the circuit and check for unexpected outputs or inputs.
needs to "Check You Off" for each of the tasks listed below.
- Demonstrate your working 4-bit full adder design from
Do not wire up this circuit
with your chips on your board.
- Demonstrate your working Fibonacci circuit from
Do wire up your Fibonacci
circuit with your chips on your board.