[转]产生任意Duty的PWM波形验证

用MedicalRadiate 3M主板上的FPGA产生500Hz可调PWM;3M板FPGA_CLK由STM32提供的72MHz frequence.

2.pwm.v

 1 `timescale 1ns / 1ps
 2 module pwm(
 3 input clk_72m,
 4 input rst_n,
 5 output reg clk_50k,        
 6 output reg pwm_wave        //generator 500Hz pwm
 7     );
 8 reg rst_n1,rst_n2;
 9 
10 
11 parameter       PERIOD = 1440,
12                     PULSEWIDTH = 720,
13                     SIZE =11;    //1440=10110100000,共11位
14 reg[SIZE-1:0] counter_div; 
15 
16 
17 parameter        DUTY = 40;    //40%
18 
19 reg [6:0] pwm_counter;
20 
21 //reg X;
22 //reg duty;
23 //////////////////////////////////////////////////////////////////////////////////    
24 //异步复位，同步释放
25 always@(posedge clk_72m or negedge rst_n)
26     if(!rst_n)
27         rst_n1<=1'b0;
28     else
29         rst_n1<=1'b1;
30         
31 always@(posedge clk_72m or negedge rst_n)
32     if(!rst_n)
33         rst_n2<=1'b0;
34     else
35         rst_n2<=rst_n1;
36 //////////////////////////////////////////////////////////////////////////////////
37 //generator 50KHz clock;
38 always@(posedge clk_72m or negedge rst_n2)
39     if(!rst_n2)
40         counter_div<=0;    
41     else if(counter_div<PERIOD-1)
42       counter_div<=counter_div+1'b1;
43     else
44       counter_div<=1'b0;
45        
46 always@(posedge clk_72m or negedge rst_n2)
47     if(!rst_n2)     
48         clk_50k<=1'b0;
49     else if(counter_div<PULSEWIDTH)
50         clk_50k<=1'b1;
51     else
52         clk_50k<=1'b0;
53 //Modelsim verify ok!
54 //////////////////////////////////////////////////////////////////////////////////
55 
56 always@(posedge clk_50k or negedge rst_n2)
57     begin
58         if(!rst_n2)
59             pwm_counter<=1'b0;
60         else if(pwm_counter==99)
61             pwm_counter<=1'b0;
62         else
63             pwm_counter<=pwm_counter+1'b1;
64     end
65     
66 always@(posedge clk_50k or negedge rst_n2)
67     begin
68         if(!rst_n2)
69             pwm_wave <= 1'b0;
70         else if(pwm_counter==0)
71             pwm_wave <= 1'b1;
72         else if(pwm_counter<DUTY)
73             pwm_wave <= 1'b1;
74         else 
75             pwm_wave <= 1'b0;
76     end
77 //Modelsim verify ok!    
78 endmodule

2.pwm_tb.v

 1 `timescale 1ns / 1ps
 2 
 3 module pwm_tb;
 4 
 5     // Inputs
 6     reg clk_72m;
 7     reg rst_n;
 8 
 9     // Outputs
10     wire pwm_wave;
11 
12     // Instantiate the Unit Under Test (UUT)
13     pwm pwm_tb (
14         .clk_72m(clk_72m), 
15         .rst_n(rst_n), 
16         .clk_50k(clk_50k),
17         .pwm_wave(pwm_wave)
18     );
19 
20     parameter PERIOD = 14;
21     initial begin
22         // Initialize Inputs
23         clk_72m = 0;
24         forever 
25             #(PERIOD/2)    clk_72m=~clk_72m;
26     end
27 
28     initial begin
29         rst_n = 0;
30             #100 rst_n=1;
31       end
32 
33         
34 endmodule

4.pwm_ucf.ucf

 1 NET "clk_72m"                LOC = "L22";    
 2 NET "rst_n"                    LOC = "G21";    
 3 NET "clk_50k"                LOC = "C22";        
 4 NET "pwm_wave"         LOC = "C21";
 5 #Created by Constraints Editor (xc3s400-fg456-4) - 2013/05/16
 6 NET "clk_72m" TNM_NET = clk_72m;
 7 TIMESPEC TS_clk_72m = PERIOD "clk_72m" 14 ns HIGH 50%;
 8 
 9 
10  NET "clk_72m" CLOCK_DEDICATED_ROUTE = FALSE; 
11 
12 //由于FPGA_CLK没有接专用GCLK上面所以加上述说明语句