pdm

module pdm #(parameter BITS=8) (
    input clk,
    input [BITS-1:0] level,
    output out
);
    reg [BITS-1:0] c;
    reg [BITS-1:0] swap;
    integer k;
    always@*
        for(k=0;k<BITS;k=k+1)
            swap[k]=c[BITS-1-k];

    always@(posedge clk)
        c<=c+1;
    assign out=swap<level;
endmodule