Verilog Coding
Contents
1. Perform the following steps to implement the three bit wide 5 to 1 multiplexer 1 Create a new Quartus II project for your circuit 2 Create a Verilog module for the three bit wide 5 to 1 multiplexer Connect its select inputs to switches SW1 7 15 and use the remaining 15 switches SW 14 to provide the five 3 bit inputs U to Y Connect the SW switches to the red lights LEDR and connect the output M to the green lights LEDG 2_ 0 3 Include in your project the required pin assignments for the DE2 board Compile the project 4 Download the compiled circuit into the FPGA chip Test the functionality of the three bit wide 5 to 1 multiplexer by toggling the switches and observing the LEDs Ensure that each of the inputs U to Y can be properly selected as the output M Part IV Figure 6 shows a 7 segment decoder module that has the three bit input c2c1co This decoder produces seven outputs that are used to display a character on a 7 segment display Table 1 lists the characters that should be displayed for each valuation of c2c1co To keep the design simple only four characters are included in the table plus the blank character which is selected for codes 100 111 The seven segments in the display are identified by the indices 0 to 6 shown in the figure Each segment is illuminated by driving it to the logic value 0 You are to write a Verilog module that implements logic functions that represent circuits needed to activate2. code not shown endmodule Figure 8 Verilog code for the circuit in Figure 7 SWi7 SWig SWi5 Character pattern 000 H E L L O 001 E L L O H 010 L L O HE O11 L O HEL 100 O H E L L Table 2 Rotating the word HELLO on five displays Perform the following steps 1 2 Create a new Quartus II project for your circuit Include your Verilog module in the Quartus II project Connect the switches SW 17 15 to the select inputs of each of the five instances of the three bit wide 5 to 1 multiplexers Also connect SW 14 to each instance of the multiplexers as required to produce the patterns of characters shown in Table 2 Connect the outputs of the five multiplexers to the 7 segment displays HEX4 HEX3 HEX2 HEX and HEXO Include the required pin assignments for the DE2 board for all switches LEDs and 7 segment displays Compile the project Download the compiled circuit into the FPGA chip Test the functionality of the circuit by setting the proper character codes on the switches SW 14 o and then toggling SW 7_15 to observe the rotation of the characters Part VI Extend your design from Part V so that is uses all eight 7 segment displays on the DE2 board Your circuit should be able to display words with five or fewer characters on the eight displays and rotate the displayed word when the switches SW17_15 are toggled If the displayed word is HELLO then your circuit should produce the patterns shown in Tabl
3. each of the seven segments Use only simple Verilog assign statements in your code to specify each logic function using a Boolean expression C3 i 7 segment decoder 0 Figure 6 A 7 segment decoder C2C1Co Character 000 001 010 O11 100 101 110 111 orm a Table 1 Character codes Perform the following steps 1 Create a new Quartus II project for your circuit 2 Create a Verilog module for the 7 segment decoder Connect the c2ccg inputs to switches SW2_9 and connect the outputs of the decoder to the HEXO display on the DE2 board The segments in this display are called HEX09 HEX0 HEXO corresponding to Figure 6 You should declare the 7 bit port output 0 6 HEXO in your Verilog code so that the names of these outputs match the corresponding names in the DE2 User Manual and the DE2 pin_assignments csv file 3 After making the required DE2 board pin assignments compile the project 4 Download the compiled circuit into the FPGA chip Test the functionality of the circuit by toggling the SW2_0 switches and observing the 7 segment display Part V Consider the circuit shown in Figure 7 It uses a three bit wide 5 to 1 multiplexer to enable the selection of five characters that are displayed on a 7 segment display Using the 7 segment decoder from Part IV this circuit can display any of the characters H E L O and blank The character codes are set according to Table by using the s
4. the DE2 System CD and in the University Program section of Altera s web site The procedure for making pin assignments is described in the tutorial Quartus IT Introduction using Verilog Design which is also available from Altera It is important to realize that the pin assignments in the DE2 pin assignments csv file are useful only if the pin names given in the file are exactly the same as the port names used in your Verilog module The file uses the names SW 0 SW 17 and LEDR 0 LEDR 17 for the switches and lights which is the reason we used these names in Figure 1 Simple module that connects the SW switches to the LEDR lights module part SW LEDR input 17 0 SW toggle switches output 17 0 LEDR red LEDs assign LEDR SW endmodule Figure Verilog code that uses the DE2 board switches and lights Perform the following steps to implement a circuit corresponding to the code in Figure on the DE2 board 1 Create a new Quartus II project for your circuit Select Cyclone IT EP2C35F672C6 as the target chip which is the FPGA chip on the Altera DE2 board 2 Create a Verilog module for the code in Figure 1 and include it in your project 3 Include in your project the required pin assignments for the DE2 board as discussed above Compile the project 4 Download the compiled circuit into the FPGA chip Test the functionality of the circuit by toggling the switches and observing the LEDs Part II Fig
5. Laboratory Exercise 1 Switches Lights and Multiplexers The purpose of this exercise is to learn how to connect simple input and output devices to an FPGA chip and implement a circuit that uses these devices We will use the switches SW17_9 on the DE2 board as inputs to the circuit We will use light emitting diodes LEDs and 7 segment displays as output devices Part I The DE2 board provides 18 toggle switches called SW 17_0 that can be used as inputs to a circuit and 18 red lights called LEDR 7_0 that can be used to display output values Figure 1 shows a simple Verilog module that uses these switches and shows their states on the LEDs Since there are 18 switches and lights it is convenient to represent them as vectors in the Verilog code as shown We have used a single assignment statement for all 18 LEDR outputs which is equivalent to the individual assignments assign LEDR 17 SW 17 assign LEDR 16 SW 16 assign LEDR 0 SW 0 The DE2 board has hardwired connections between its FPGA chip and the switches and lights To use SW 17_9 and LEDR 7 0 it is necessary to include in your Quartus II project the correct pin assignments which are given in the DE2 User Manual For example the manual specifies that SW is connected to the FPGA pin N25 and LEDRo is connected to pin AE23 A good way to make the required pin assignments is to import into the Quartus II software the file called DE2_pin assignments csv which is provided on
6. ct the required pin assignments for the DE2 board As discussed in Part I these assignments ensure that the input ports of your Verilog code will use the pins on the Cyclone II FPGA that are connected to the SW switches and the output ports of your Verilog code will use the FPGA pins connected to the LEDR and LEDG lights 4 Compile the project 5 Download the compiled circuit into the FPGA chip Test the functionality of the eight bit wide 2 to 1 multiplexer by toggling the switches and observing the LEDs Part III In Figure 2 we showed a 2 to 1 multiplexer that selects between the two inputs x and y For this part consider a circuit in which the output m has to be selected from five inputs u v w x and y Part a of Figure 4 shows how we can build the required 5 to 1 multiplexer by using four 2 to 1 multiplexers The circuit uses a 3 bit select input 28 S9 and implements the truth table shown in Figure 4b A circuit symbol for this multiplexer is given in part c of the figure Recall from Figure 3 that an eight bit wide 2 to 1 multiplexer can be built by using eight instances of a 2 to 1 multiplexer Figure 5 applies this concept to define a three bit wide 5 to 1 multiplexer It contains three instances of the circuit in Figure 4a So S Sq m 000 u 001 v 010 w 0 11l x 100 y 101 y 110 y P11 y b Truth table c Symbol Figure 4 A 5 to 1 multiplexer Figure 5 A three bit wide 5 to 1 multiplexer
7. e 3 SWi7 SWig SWis5 Character pattern 000 H E L L O 001 H E L L O 010 H E L L O 011 H E L L O 100 E L L O H 101 L L O H E 110 L O H E L 111 O H E L L Table 3 Rotating the word HELLO on eight displays Perform the following steps 1 Create a new Quartus II project for your circuit and select as the target chip the Cyclone II EP2C35F672C6 2 Include your Verilog module in the Quartus II project Connect the switches SW 17 15 to the select inputs of each instance of the multiplexers in your circuit Also connect SW 14 to each instance of the multiplexers as required to produce the patterns of characters shown in Table 3 Hint for some inputs of the multiplexers you will want to select the blank character Connect the outputs of your multiplexers to the 7 segment displays HEX7 HEXO 3 Include the required pin assignments for the DE2 board for all switches LEDs and 7 segment displays Compile the project 4 Download the compiled circuit into the FPGA chip Test the functionality of the circuit by setting the proper character codes on the switches SW 14 o and then toggling SW 7_15 to observe the rotation of the characters Copyright 2006 Altera Corporation
8. ure 2a shows a sum of products circuit that implements a 2 to 1 multiplexer with a select input s If s 0 the multiplexer s output m is equal to the input x and if s 1 the output is equal to y Part b of the figure gives a truth table for this multiplexer and part c shows its circuit symbol X D S y a Circuit S m 0 i x 0 z 1 y y 1 b Truth table c Symbol Figure 2 A 2 to 1 multiplexer The multiplexer can be described by the following Verilog statement assign m s amp x s amp y You are to write a Verilog module that includes eight assignment statements like the one shown above to describe the circuit given in Figure 3a This circuit has two eight bit inputs X and Y and produces the eight bit output M If s 0 then M X while if s 1 then M Y We refer to this circuit as an eight bit wide 2 to 1 multiplexer It has the circuit symbol shown in Figure 3b in which X Y and M are depicted as eight bit wires Perform the steps shown below x 0 mo Yo 1 a Circuit b Symbol Figure 3 An eight bit wide 2 to 1 multiplexer 1 Create a new Quartus II project for your circuit 2 Include your Verilog file for the eight bit wide 2 to 1 multiplexer in your project Use switch SW 17 on the DE2 board as the s input switches SW7_9 as the X input and SW 15 8 as the Y input Connect the SW switches to the red lights LEDR and connect the output M to the green lights LEDG 7 0 3 Include in your proje
9. witches SW 4_0 and a specific character is selected for display by setting the switches SW 7_15 An outline of the Verilog code that represents this circuit is provided in Figure 8 Note that we have used the circuits from Parts III and IV as subcircuits in this code You are to extend the code in Figure 8 so that it uses five 7 segment displays rather than just one You will need to use five instances of each of the subcircuits The purpose of your circuit is to display any word on the five displays that is composed of the characters in Table 1 and be able to rotate this word in a circular fashion across the displays when the switches SW 17_15 are toggled As an example if the displayed word is HELLO then your circuit should produce the output patterns illustrated in Table 2 7 segment decoder Figure 7 A circuit that can select and display one of five characters module part5 SW HEX0 input 17 0 SW toggle switches output 0 6 HEX0 7 seg displays wire 2 0 M mux_3bit_S5tol MO SW 17 15 SW 14 12 SW 11 9 SW 8 6 SW 5 3 SW 2 0 M char_7seg HO M HEX0 endmodule implements a 3 bit wide 5 to 1 multiplexer module mux _3bit_Stol S U V W X Y M input 2 0 S U V W X Y output 2 0 M code not shown endmodule implements a 7 segment decoder for H E L O and blank module char_7seg C Display input 2 0 C input code output 0 6 Display output 7 seg code
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