Verilog仿真错误。 Modelsim Altera 10.1b

Question

This is my gate level code for A 4 bit full adder.

//Define stimulus
 module stimulus;

//setup variables
  reg[3:0] A,B;
  reg C_IN;
  wire [3:0] SUM;
  wire C_OUT;

//Instantiate 4 bi full adder
  fulladd4 FA1_4(SUM,C_OUT,A,B,C_IN);

//Setup for monitoring the values
  initial
 begin
 $monitor($time," A= %b,B= %b,C_IN= %b, --- C_OUT= %b, SUM= %b  \n",A,B,C_IN,C_OUT,SUM);
end

//Stimulate Inputs
initial
begin
 A = 4'd0; B = 4'd0; C_IN = 1'b0;
 #5 A = 4'd1; B = 4'd2;
 #5 A = 4'd3; B = 4'd4;
end
endmodule





//Define full 1 bit adder
 module fulladd(sum, c_out,a,b,c_in);

//I/O Ports Declaration
 output sum,c_out;
 input a,b,c_in;


 //Internal nets
 wire s1, c1, s2;

//Instantating the gates
 xor (s1,a,b);
 and (c1,a,b);
 xor (sum,s1,c_in);
 and (s2,s1,c_in);
 xor (c_out,s2,c1);

 endmodule

 //Define a 4 bit full adder
 module fulladd4(sum,c_out,a,b,c_in);

//I/O Ports declaration
 output [3:0] sum;
 output c_out;
 input [3:0] a,b;
 input c_in;

  //internal nets
   wire c1,c2,c3;

 //Instantiate 4 full 1 bit adders
  fulladd fa0(sum[0],c1,a[0],b[0],c_in);
  fulladd fa1(sum[1],c2,a[1],b[1],c1);
  fulladd fa2(sum[2],c3,,a[2],b[2],c2);
 fulladd fa3(sum[3],c_out,a[3],b[3],c3);

 endmodule

It show a fatal error while simulating.

** Fatal: (vsim-3365) C:/altera/12.1/modelsim_ase/Full_Bit_Adder.v(67): Too many port connections. Expected 5, found 6.

Time: 0 ps Iteration: 0 Instance: /fulladd4/fa2 File: C:/altera/12.1/modelsim_ase/Full_Bit_Adder.v

This is the error that it shows

Can someone please explain me my mistake

Answer 1

In the 67th line there are two commas after c3. If you remove one of them, it should be working.

Answer 2

fulladd fa2(sum[2],c3,,a[2],b[2],c2);

you have used 2 commas consecutively. This is resulting in error because simulation tool takes it as 6 ports but we require only 5.