EE 231 Fall 2010 1 EE 231 Lab 2 Introduction to Verilog HDL and Quartus In the previous lab you designed simple circuits using discrete chips. In this lab you will do the same but by programming the CPLD. At the end of the lab you should be able to understand the process of programming a PLD, and the advantages of such an approach over using discrete components. 1. Prelab 1. Read the material provided in the supplementary section 3. 2. Using the schematics of the board, if the CPLD sends a logic 1 to one of the LEDs, would it turn on or off? 2. Lab 1. Write a gate-level Verilog program to implement the half adder circuit shown in Figure 1. Figure 1. Half Adder Circuit 2. Assign your two inputs to two of the push buttons and your two outputs to two of the LEDs. Before you continue, ask the TA to check your assignment. 3. Simulate your designed circuit, and perform both functional and timing simulations. Print your waveforms. Are the two waveforms the same? Discuss. 4. Write a Verilog program to implement the same half adder circuit using dataflowEE 231 Fall 2010 2 modeling and resimulate your circuit. Note: you don’t have to respecify your waveforms as you have already saved them in a file. 5. Program your CPLD to implement your circuit and verify that it works. Ask the TA to initial your labbook once you have it working. 6. Use vectors to describe your inputs and outputs. Send signals to all of the LEDs to have them off when you send them a logic 0 and turn on when you send them a logic 1, and similarly, the input to be logic 1 into your circuit when you press the button and zero otherwise. 3. Supplementary Material 3.1 Introduction to Verilog 1. In order to write a Verilog HDL description of any circuit you will need to write a module which is the fundamental descriptive unit in Verilog. A module is a set of text describing you circuit and is enclosed by the keywords module and endmodule. 2. As the program describes a physical circuit you will need to specify the inputs, the outputs, the behavior of the circuit and how the gates are wired. To accomplish this, you need the keywords input, output, and wire to define the inputs, outputs and the wiring between the gates, respectively. 3. There are multiple ways to model a circuit: • Gate-level modeling • Dataflow modeling • Behavioral modeling • Or a combination of the above. 4. A simple program modeling a circuit (see Figure 2) at the gate-level, is described below. 5. As seen above the outputs come first in the port list followed by the inputs. 6. Single line comments begin with // 7. Multi-line comments are enclosed by /* … */ 8. Verilog is case sensitive. 9. A simple program modeling a circuit using dataflow is provided below.EE 231 Fall 2010 3 Figure 2. A Simple Circuit Program 1 Simple program in Verilog modeling a circuit at the gate level module simple_circuit(output D, E, input A, B, C); wire w1; and G1(w1,A,C); not G2(E,C); or G3(D,w1,E); endmodule // no semi-colon Program 2 Simple program in Verilog modeling a circuit using dataflow using vectors module simple_circuit(output [1:0] Y, input [0:2] X); assign Y[1] = (X[0] & X[1]) | ~X[2]; assign Y[0] = ~X[2]; endmodule 10. You can use identifies describing multiple bits known as vectors. 11. Given an identifier [7:0] X you can assign values by assign [7:0] X = 8’b00001111; where the 8’b specifies that we are defining an 8-bit binary number and 00101011 is that 8-bit binary number. You can also assign parts of the number asEE 231 Fall 2010 4 assign [2:0] X = 3’b101; which assigns only the last three bits of X. 3.2 Using Quartus To implement the circuits that you will design on the CPLD there are a few key steps. 1. Write your program using Verilog HDL. 2. Compile your code. 3. Correct any syntax errors. 4. Simulate your circuit to make sure you are getting the behavior you expect. 5. Download your program onto the CPLD. 6. Test the operation of the circuit. Quartus helps you implement all of the above easily. The following sections describe how to do those basic steps. 3.2.1 Start a New Project 1. Select File > New Project Wizard. 2. Set the directory name. Make sure that you create a new project for each project and do not just copy the directory over. 3. Set the name of the project. It will be simple if you name it by the lab name, e.g., Lab1. 4. Click Yes to create a directory if it does not exist. 5. You can add existing files if you already have them, otherwise select Next. 6. Next you need to specify the device that you are using. Set the Device Family to MAXII and select EPM2210F324C3. 7. Press Next. 8. Press Finish. 3.2.2 Writing the CodeEE 231 Fall 2010 5 1. Select File > New. 2. Choose Verilog HDL File. 3. Click Ok. 4. Select File > Save As. For one file project name, the name of the file should be the same as the project. In addition, the module name should be the same as the file name. 5. Choose Save as type, and select Verilog HDL File. 6. Put a check-mark in the box Add file to current project. Unless the file is part of the project you won’t be able to proceed. IF you don’t add the file now you can always latter add it by selecting Project > Add/Remove Files in Project. 7. Click Save. 8. Now you are ready to type in your program. 3.2.3 Compiling 1. Select Processing > Start Compilation, or click on the play icon on the toolbar. 2. You can click on Processing > Compilation Report to see the results of the compilation. 3. If there are no errors, then you program is correct from the syntax point of view. This does not mean that your program will do what you want because you may have some logic errors. 3.2.4 Pin Assignment You need to specify which outputs. Some pins have already been wired to the LEDs and the push buttons. A list of those pins is provided in Table 1. 1. Select Assignments > Assignment Editor. 2. Under Category select Pin. 3. Double click on <<new>>, a drop-down menu will appear, select the input or output you want. 4. In the column labeled Location select the pin you want. Table 1 shows the locations of hardwire for your evaluation board. For example, if you wanted toEE 231 Fall 2010 6 connect the output ”E” to the first red LED, you would select Location Pin U4