Error with OBUF

[shar01]

Hi friends,

i am desining a simple adder for a project but ise keeps erroring as below:

ERROR:MapLib:979 - LUT3 symbol "Addup/Sum1" (output signal=Sum2_1_OBUF) has
input signal "Cin" which will be trimmed. See Section 5 of the Map Report
File for details about why the input signal will become undriven.

this is the simple programs for adder.

module FulAdder( Cout,Sum,A,B,Cin);
output Cout;
output Sum;
input A,B,Cin;

and an1 (Outan1,A,B);

xor x01 (Outxo1,A,B);

and an2 (Outan2,Cin,Outxo1);

or or1 (Outor1,Outan1,Outan2);

xor xo2 (Sum,Outxo1,Cin);

endmodule

********************

module Adder2(Cout,Sum2,A,B,Cin);
output Cout;
output [1:0] Sum2;

input [1:0] A;
input [1:0] B;
input Cin;

wire Outdow;

FulAdder Adddow (Outdow,Sum2[0],A[0],B[0],Cin);

FulAdder Addup (Cout,Sum2[1],A[1],B[1],Outdow);

endmodule

*****************************

eny body have any Idea what can i do ?

thanks to all.

[bassman59]

For starters, used named association for your module instances. 

And show the lower-level modules.

[vemulad · Accepted solution]

Hi,

In FULLADDER module, I dont see Cout is connected. See below. You have defined Cout as an output but didnot assign anything to it in the code. This is the reason the Cin input of Addup submodule is getting trimmed which results in MAP error. Please fix this in your code.

module FulAdder( Cout,Sum,A,B,Cin);
output Cout;
output Sum;
input A,B,Cin;
and an1 (Outan1,A,B);
xor x01 (Outxo1,A,B);
and an2 (Outan2,Cin,Outxo1);
or or1 (Outor1,Outan1,Outan2);
xor xo2 (Sum,Outxo1,Cin);

endmodule

Thanks,

Deepika.

[shar01]

Thanks alot frien. It solwed. that was an obviouse mistake of mine  :-).