1module top(input clk, input btn, output [7:0] led); 2 localparam ctr_width = 24; 3 localparam ctr_max = 2**ctr_width - 1; 4 reg [ctr_width-1:0] ctr = 0; 5 reg [9:0] pwm_ctr = 0; 6 reg dir = 0; 7 8 always@(posedge clk) begin 9 ctr <= dir ? ctr - 1'b1 - btn: ctr + 1'b1 + btn; 10 if (ctr[ctr_width-1 : ctr_width-3] == 0 && dir == 1) 11 dir <= 1'b0; 12 else if (ctr[ctr_width-1 : ctr_width-3] == 7 && dir == 0) 13 dir <= 1'b1; 14 pwm_ctr <= pwm_ctr + 1'b1; 15 end 16 17 reg [9:0] brightness [0:7]; 18 localparam bright_max = 2**10 - 1; 19 reg [7:0] led_reg; 20 21 genvar i; 22 generate 23 for (i = 0; i < 8; i=i+1) begin 24 always @ (posedge clk) begin 25 if (ctr[ctr_width-1 : ctr_width-3] == i) 26 brightness[i] <= bright_max; 27 else if (ctr[ctr_width-1 : ctr_width-3] == (i - 1)) 28 brightness[i] <= ctr[ctr_width-4:ctr_width-13]; 29 else if (ctr[ctr_width-1 : ctr_width-3] == (i + 1)) 30 brightness[i] <= bright_max - ctr[ctr_width-4:ctr_width-13]; 31 else 32 brightness[i] <= 0; 33 led_reg[i] <= pwm_ctr < brightness[i]; 34 end 35 end 36 endgenerate 37 38 assign led = led_reg; 39endmodule 40