三分频电路Verilog设计

三分频用两个在不同的时钟沿的序列发生器来构成一个3分频信号：

`timescale 1ns/10ps
module div_3(clkin,clkout1,clkout2,clkout3);
input clkin;
output clkout1,clkout2,clkout3;
reg [1:0] step1,step0;
always @(posedge clkin)
begin
  case(step0)
    2'b00: step0 <= 2'b01;
    2'b01: step0 <= 2'b10;
    2'b10: step0 <= 2'b00;
    default: step0 <= 2'b00;
  endcase
end
always@(negedge clkin)
begin
  case(step1)
  2'b00: step1 <= 2'b01;
  2'b01: step1 <= 2'b10;
  2'b10: step1 <= 2'b00;
  default: step1 <= 2'b00;
endcase
end
assign clkout1 = step0;
assign clkout2 = step1;
assign clkout3 = ~(step0|step1);
endmodule

测试程序如下：

module div_2_tb();
reg clkin;
wire clkout1,clkout2,clkout3;
div_3 wt (.clkin(clkin),  .clkout1(clkout1),.clkout2(clkout2),.clkout3(clkout3));

initial 
begin
  clkin = 0;
end

always
  begin
    #10 clkin = ~clkin;
  end
  
endmodule