How to solve xilinx error ''Simulator:793 - Unable to elaborate instantiated module Half_Adder''?

Question

I am making 2-bit multiplier using half adders in verilog in Xilinx ISE 14.7, but I am getting the error. The modules codes are shown below:

module Half_Adder (S, C, A, B);

output S;
output C;
input A;
input B;

xor x1(S,A,B);
and a1(C,A,B);

endmodule

Verilog module of 2-bit multiplier:

module multiplier_2bit (A,B,C);

input [1:0] A;
input [1:0] B;    
output [3:0] C;

wire   w1;
wire [1:0] w2;
wire [2:0] S;

and g0(C[0], A[0],B[0]);
and g1(w1,A[0],B[1]);
and g2(w2[0],A[1],B[0]);    

assign C[1] = S[0];

Half_Adder (S,C,w1,w2);

and g3(w1,A[0],B[1]);
and g4(w2[0],A[1],B[0]);
and g5(w2[1],A[1],B[1]);

assign C[2] = S[1];

Half_Adder (S,C,w1,w2);    

endmodule

Please tell me where I am making mistakes.

Answer 1

You forgot to name the two instances of Half_Adder. It has to be like:

Half_Adder my_ha_0 (...) ;

Also you are mapping multi-bit values to 1-bit values while port mapping:

Half_Adder (S,C,w1,w2);

w2 and S are two-bit and three-bit wires, while your Half_Adder expects one-bit inputs/outputs.