Since Quartus II projects have many, many files I went ahead and just put them all together in a zip file that you can download (to the right). The .pof file is all you really need to program the CPLD.
The Verilog Format
Verilog uses what are called modules. You can think of modules as similar to main() statements in C or Java. Here is a simple example with a few variable declarations:
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//Verilog_Project.v `timescale 1ns / 1ps //Used For Simulation module Verilog_Project(DIP_SWITCHES, LEDS); input [7:0] DIP_SWITCHES; //Declare 8 Inputs for Dips output [6:0] LEDS; //Declare 7 Outputs for LEDS reg [6:0] LEDS; //Declare 7 Registers for LEDS endmodule
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The above program creates a module with 8 inputs, 7 outputs and 7 registers for the outputs (notice how the variable names are also included with the 'module Verilog_Project' statement). This would be the same as a 20-pin IC that does nothing. Why does it do nothing? Easy, we haven't designed any logic circuitry for it yet.
Logic In Verilog
Now we'll explore how to create the actual logic circuitry, along with how some variables work in Verilog. Let's take a look at the complete program:
-------« Begin Code »-------
//Verilog_Project.v
`timescale 1ns / 1ps //Used For Simulation
module Verilog_Project(DIP_SWITCHES, LEDS);
input [7:0] DIP_SWITCHES; //Declare 8 Inputs for Dips
output [6:0] LEDS; //Declare 7 Outputs for LEDS
reg [6:0] LEDS; //Declare 7 Registers for LEDS
always
begin
case(DIP_SWITCHES) //abcdefg - 7 Segment Placement
8'b00000000 : LEDS = 7'b 1111110;
8'b00000001 : LEDS = 7'b 0110000;
8'b00000010 : LEDS = 7'b 1101101;
8'b00000100 : LEDS = 7'b 1111001;
8'b00001000 : LEDS = 7'b 0110011;
8'b00010000 : LEDS = 7'b 1011011;
8'b00100000 : LEDS = 7'b 1011111;
8'b01000000 : LEDS = 7'b 1110000;
8'b10000000 : LEDS = 7'b 1111111;
default : LEDS = 7'b 00000000;
endcase
end
endmodule
-------« End Code »-------
The new modification is an 'always' and a standard case (switch) statement. This means that the switch/case statement should 'always' be used. The way it works is, the 8-bit input from the Dip_Switches is stored in that input variable. Then the input is evaluated through the case/switch statement. If a match is found, then LEDS is given the corresponding value. If no match is found, the default case is used. Enough talk, let's program it!