module pwm4_basic(
input clk,
input rst,
input [3:0] duty,
output reg pwm_out);
reg [3:0] cnt;
always@(posedge clk or posedge rst) begin
if(rst) begin
pwm_out <= 0;
cnt <= 4'd0;
end else begin
cnt <= cnt + 4'd1;
if(cnt < duty) begin
pwm_out <= 1;
end else begin
pwm_out <= 0;
end
end
end
endmodule