module div15(clkin, clkout, rstn)
input clkin;
input rstn;
output clkout;
//自己补充
reg ...
wire ...
always @(posedge clkin or negedge rstn)
begin
if(!rstn)
clk_d2 <= 1'b0;
else
clk_d2 <= ~clk_d2;
end
assign clk_neg = ~clkin;
assign clkout = clk_neg ^ clk_d2;
endmodule
交替2分频和3分频即可
可以查一下关于小数分频的原理