Description
3 Overview
While the ultimate goal of this lab is to load a simple design onto the Basys board (after you have written
and compiled your code), it is always a good idea to simulate your design first to detect any problems
right away. Once you are convinced your design works, you will load it onto the board.
4 Preparation
Inside My Documents, create a directly called ECE2700. Then, create a directory called Lab1 inside your
ECE2700 directory. The program we will be using is called Xilinx ISE. To run the program, double click
on the Xilinx ISE Design Suite 13.2 icon located on the Desktop, as shown below.
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5 Writing Verilog Code and Simulating Your Design
Click on File → New Project. Type in myandgate in the Name field. Select the Lab1 folder for the
Location field. Make sure that the Top-level source type is set to HDL, as shown in the following
screenshot.
Click Next. You are now asked to specify some settings for the project. You should specify Spartan3E
for Family, XC3S250E for Device, TQ144 for Package if you have the original Basys board and CP132 if
you have the Basys 2 board, and -4 for Speed. Please carefully examine the chip on your board
to make sure that you have specified the correct device. You may have the XC3S100E
device instead of the XC3S250E device. Click Next.
You should see something like the following screen. Click Finish.
You are now ready to write your first Verilog code. Since we will first simulate our design before
implementing it on the Basys board, select the Simulation radio button, as shown below. Make sure the
top box is selected to Behavioral.
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To add a new file to the project, click on Project → New Source. A popup window will open. Select
Verilog Module and specify myandgate.v as the filename.
Click on the Next button, and again for the Define Module (you don’t have to specify anything here).
A summary window will show up. Click Finish.
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Under the Hierarchy window, you should now see your myandgate file, as shown below.
Click on it and type in the following code.
module myandgate(a, b, F);
input a, b;
output F;
and and1(F, a, b);
endmodule
Note that the above piece of code simply uses the built-in AND gate and define a new AND gate in
which the input ports appear before the output port.
You will now create a testbench to verify your design. Repeat the above steps for adding a new file.
Use myandgatetest.v as the filename. Fill in the testbench code with all 4 test cases (see page 16 of
Verilog for Digital Design). Save your work. Remember that X s and Y s in the testbench correspond
to a and b in your code.
Now we will check for syntax error and simulate your AND gate design. Click on myandgatetest in
the Hierarchy window. In the Processes window below, expand the ISim Simulator. Double click on
Behavioral Check Syntax.
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Check the Console to see whether your design contains any syntax error. Fix them if needed then
double click on the Simulate Behavioral Model in the Processes window. This should bring up a waveform
window. Here, you cannot see the results clearly because of the timescale. Click on the following magnifier
icon to see the results.
You should see the results for the AND gate similar to the one shown below. Make sure your design
is correct
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6 Implementation on the Basys Board
Now that you have verified that your design is correct, you are ready to load your design onto the board.
Close the waveform window. In the main window, right click on the myandgate Verilog file. Select Source
Properties. Under View Association, select All.
Right click on the myandgatetest Verilog file and select Source Properties. Under View Association,
select Simulation.
Above the Hierarchy window, select the Implementation radio button.
We are almost there. Now we need to tell the program which pins on the board we would like to use.
On your Basys board, locate switches sw0 and sw1. Also locate the LED LD0. We will map the inputs
a and b to the switches and the output F to the LED. The idea is that the LED will light up if both
inputs are 1 (thus implementing the AND gate). To assign pins, click on Project → New Source. Select
Implementation Constraints File and name it myandgate. Click Next then Finish.
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Open the UCF file you’ve just created. Look inside the file MainBasys.ucf (or MainBasys2.ucf if you
are using the Basys 2 board), which can be found on the course website. Locate the lines that contain
SW0, SW1, and LD0. Once you find them, copy the 3 lines over to the UCF file in the main window.
Change the NET name in each line to exactly correspond to your input and output names. Caution:
Do not refer to the little flyer with pin assignment that comes with your kit. Some of the
pin numbers are incorrect!
Save your changes. Click on myandgate in the Hierarchy window. In the Processes window, double-click
on Synthesize – XST. You should see a message indicating that the process was completed successfully.
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Now you will generate the bit file for the FPGA. To do this, right click on the Generate Programming
File option in the Processes window. Select Process Properties then Startup Options. For the FPGA
Start-Up Clock, select JTAG Clock. This step ensures that you use the clock on the FPGA. Click OK.
Double click on the Generate Programming File option. This may take a while. Once the process is
finished, you should see the following message.
You are finally ready to load your program onto the FPGA. It’s time to connect the board to your
computer. A red light should illuminate to indicate that a power connection has been established. Make
sure SW8 is down to indicate that you will power the board via the USB port. Very Important! Make
sure the jumper is set to JTAG, not PROM. See the location of this below.
Double click on the Configure Target Device, as shown below.
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You will see the following warning the first time you do this. Click OK.
This will bring up a new window. Double click on Boundary Scan inside the left menu bar.
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Now, in the main window, right click and select Initialize Chain. You should see the following window
shortly after.
A pop-up window will appear. Click Yes.
Now select the bit file you have just generated. It should be inside your myandgate directory.
You will see the following pop-up window. Click No.
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Yet another pop-up window will appear. Click on Bypass.
You should now see a summary window. Click OK.
Back to the iMPACT window, the bit file you selected should now be associated with the FPGA. Right
click and select Program to load the bit file onto the FPGA.
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The process should be a success, as shown before.
You have just loaded your design onto the FPGA board. Play with SW0 and SW1. What happens if
you flip them up at the same time? That’s right, you’re looking at your newly built AND gate!
If you make any modification to the Verilog code, be sure to regenerate the bit file. Afterwards, you
will need to reload it onto the FPGA. To do this, restart the Manage Configuration Project option as
shown below. Then, proceed as before.
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There are many steps for loading your design onto the FPGA board. However, you will become more
familiarized with them as the semester progresses. In summary, you need to do the following.
1. Write your Verilog code.
2. Simulate your design to make sure it is correct.
3. Create and generate a UCF file to specify pin assignments.
4. Generate the bit file.
5. Use iMPACT to upload your bit file to the FPGA.
7 Fun Stuff
Xilinx ISE has various features and though we will not have time to learn them all, I encourage you to
experiment. For example, if you double click on View RTL Scheme (expand the Synthesize – XST option
to see it) and click on Start with a schematic of the top-level block, you will see a circuit diagram for
your AND gate.
Double clicking on it will show how the design is implemented.
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You can also right click on the View Technology Schematic option. Double click on the design will
yield the following.
Double clicking inside the LUT (lookup table) box will cause a new window to pop up. You can see
the schematic, equation, truth table, and even k-map of your design.
Have fun!
8 TA Checkoff
• (4 points) Complete pre-lab work prior to start of the lab.
• (16 points) Correct simulation of the AND gate.
• (20 points) Correct implementation of the AND gate on the Basys board.
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