module pwm4_basic(
input clk,
input rst,
input [3:0] duty,
output reg pwm_out
);
reg [3:0] clkframe;
always @(posedge clk) begin
if (rst) begin
pwm_out <= 4'b0;
clkframe <= 4'b0;
end
else begin
if (clkframe < duty) begin
pwm_out <= 1'b1;
clkframe = clkframe + 1;
end
else begin
if (clkframe < 4'b1111)
clkframe = clkframe + 1;
else
clkframe <= 4'b0;
pwm_out <= 1'b0;
end
end
end
endmodule