Question

module DIGITADD(
    input [3:0] A,
    input [3:0] B,
    input CIN,
    output COUT,
    output [3:0] SUM
    );

  reg [4:0] s2;
assign SUM = s2[3:0];
assign COUT = s2[4];

//BCD ADDER PART 
always @ ( * )
begin
    s2 = A + B + CIN;
    if (s2 > 9)
    begin
        s2 = s2 + 6;
    end
end
endmodule

TEST BENCH

module DIGITADD_tb(
  reg [3:0] A,
  reg [3:0] B,
  reg CIN,
  wire COUT,
  wire [3:0] SUM);

  DIGITADD uut(
    .A(A),
    .B(B),
    .CIN(CIN),
    .COUT(COUT),
    .SUM(SUM));

  initial begin
    $dumpfile("dump.vcd");
    $dumpvars(1,DIGITADD_tb);
    #10;
     #10 A=4'b0000;B=4'b0011;CIN=1'b0;
    #10 A=4'b0111;B=4'b1000;CIN=1'b1;
    $finish;
  end
endmodule

Answer 1

您已在端口列表的样式中在测试平台中添加了局部变量：

module DIGITADD_tb(
  reg [3:0] A,
  reg [3:0] B,
  reg CIN,
  wire COUT,
  wire [3:0] SUM);

应该是：

module DIGITADD_tb(); //<-- no ports 
  reg [3:0] A; //<-- semicolon
  reg [3:0] B;
  reg   CIN;
  wire COUT;
  wire [3:0] SUM;

测试平台出错，因为'DIGITADD'的输入端口'A'必须是网络

1 个答案: