移位寄存器+多路选择器

我的代码：

module top_module ( input clk, input [7:0] d, input [1:0] sel, output [7:0] q 
);wire [7:0] w1;wire [7:0] w2;wire [7:0] w3;my_dff8 my_dff8_1(.clk(clk),.d(d),.q(w1));my_dff8 my_dff8_2(.clk(clk),.d(w1),.q(w2));my_dff8 my_dff8_3(.clk(clk),.d(w2),.q(w3));always@(d or w1 or w2 or w3 or sel)beginif(sel == 2'b00 )q <= d;else if(sel == 2'b01 )q <= w1;else if(sel == 2'b10 )q <= w2;elseq <= w3;endendmodule

 答案：

module top_module (input clk,input [7:0] d,input [1:0] sel,output reg [7:0] q
);wire [7:0] o1, o2, o3;		// output of each my_dff8// Instantiate three my_dff8smy_dff8 d1 ( clk, d, o1 );my_dff8 d2 ( clk, o1, o2 );my_dff8 d3 ( clk, o2, o3 );// This is one way to make a 4-to-1 multiplexeralways @(*)		// Combinational always blockcase(sel)2'h0: q = d;2'h1: q = o1;2'h2: q = o2;2'h3: q = o3;endcaseendmodule