夏宇聞verilog第十章答案_練習五

源碼：

module sel8_1(
			a0,
			a1,
			a2,
			a3,
			a4,
			a5,
			a6,
			a7,
			b,
			sel
			);
input [3:0] a0,a1,a2,a3,a4,a5,a6,a7;
input [2:0] sel;
output [3:0] b;
reg [3:0] b;
// reg [3:0] c;
// c = 4'b1100;
//在always裏面的每一個信號都必須是reg
//reg信號也是不能在alway外的
always@(a0 or a1 or a2 or a3 or a4 or a5 or a6 or a7 or sel)
begin

case(sel)
3'b000: b = a0;
3'b001: b = a1;
3'b010: b = a2;
3'b011: b = a3;

3'b100: b = a4;
3'b101: b = a5;
3'b110: b = a6;
3'b111: b = a7;

default:  b = 4'bx;
endcase	

end 

endmodule

測試代碼：

`timescale 1ns/1ns
module sel8_1tb;
reg [3:0] a0,a1,a2,a3,a4,a5,a6,a7;
reg [2:0] sel;
wire [3:0] b;

initial
begin
	sel	= 3'b0;
	repeat(16)
	begin
		#5
		sel = sel + 3'b1;
		a0	 = {$random}%16;
		a1	 = {$random}%16;
		a2	 = {$random}%16;
		a3	 = {$random}%16;
		a4	 = {$random}%16;
		a5	 = {$random}%16;
		a6	 = {$random}%16;
		a7	 = {$random}%16;
		
	end
end
	
sel8_1 mysel8_1(
			.a0(a0),
			.a1(a1),
			.a2(a2),
			.a3(a3),
			.a4(a4),
			.a5(a5),
			.a6(a6),
			.a7(a7),
			.b(b),
			.sel(sel)
			);//這種連接的工作，可以寫一個插件，如果有機會的話
endmodule

現象;