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--调节两个LED灯亮度
1 module led_pwm ( 2 clk, 3 rst, 4 //cnt1_pwm, 5 out1, 6 out2, 7 out3, 8 out4 9 ); 10 11 input clk, rst; 12 //input [19:0] count_pwm; 13 output reg out1, out2; 14 output out3, out4; 15 16 reg [19:0] cnt; 17 reg [19:0] cnt1_pwm = 21'd2, cnt2_pwm = 21'd52_4288; 18 reg [25:0] cnt_s; 19 20 always @ (posedge clk, negedge rst) 21 if (!rst) 22 begin 23 cnt_s <= 0; 24 cnt1_pwm <= 21'd1; 25 cnt2_pwm <= 21'd52_4288; 26 end 27 else if (cnt_s == 26'd1000_0000) //计0.2秒 28 begin 29 cnt_s <= 0; 30 cnt1_pwm <= {cnt1_pwm[18:0], cnt1_pwm[19]}; //调节脉宽 31 cnt2_pwm <= {cnt2_pwm[0], cnt2_pwm[19:1]}; 32 33 //cnt1_pwm <= (cnt1_pwm >> 2)|(cnt1_pwm << 19);//right 34 //cnt2_pwm <= (cnt2_pwm << 2)|(cnt2_pwm >> 19);//left 35 end 36 else 37 cnt_s <= cnt_s + 1; 38 39 // 40 always @ (posedge clk, negedge rst) 41 if (!rst) 42 cnt <= 21'h0; 43 else if (cnt == 21'd55_0000) //一个周期 44 cnt <= 21'b0; 45 else 46 cnt <= cnt + 1'b1; 47 48 49 // pwm生成 50 always @ (posedge clk, negedge rst) 51 if (!rst) 52 out1 <= 1'b0; 53 else if (cnt <= cnt1_pwm) 54 out1 <= 1'b0; 55 else 56 out1 <= 1'b1; 57 58 always @ (posedge clk, negedge rst) 59 if (!rst) 60 out2 <= 1'b0; 61 else if (cnt <= cnt2_pwm) 62 out2 <= 1'b0; 63 else 64 out2 <= 1'b1; 65 66 assign out3 = 1'b0; 67 assign out4 = 1'b0; 68 69 endmodule