Adder programs

HALF ADDER

module ha(s,ca,a,b);

input a,b;

output s,ca;

xor(s,a,b);

and(ca,a,b);

endmodule

//test-bench

module tstha();

reg a,b;

wire s,ca;

ha hh(s,ca,a,b);

initial

begin

a=0;b=0;

end

always

begin

#2 a=1;b=0;

#2 a=0;b=1;

#2 a=1;b=1;

#2 a=0;b=0;

end

initial $monitor($time , " a = %b , b = %b ,out carry = %b , outsum = %b " ,a,b,ca,s);

initial #24 $stop;

endmodule

FULL ADDER

module fa(sum,cout,a,b,cin);

input a,b,cin; 

output sum,cout; 

wire s,c1,c2; 

ha ha1(s,c1,a,b), ha2(sum,c2,s,cin); 

or(cout,c2,c1);

endmodule

//test-bench

module tst_fa(); 

reg a,b,cin; 

fa ff(sum,cout,a,b,cin); 

initial

begin

a =0;b=0;cin=0; 

end

always

begin

#2 a=1;b=1;cin=0;#2 a=1;b=0;cin=1;

#2 a=1;b=1;cin=1;#2 a=1;b=0;cin=0;

#2 a=0;b=0;cin=0;#2 a=0;b=1;cin=0;

#2 a=0;b=0;cin=1;#2 a=0;b=1;cin=1;

#2 a=1;b=0;cin=0;#2 a=1;b=1;cin=0;

#2 a=0;b=1;cin=0;#2 a=1;b=1;cin=1;

end

initial $monitor($time ," a = %b, b = %b, cin = %b, 

outsum = %b, outcar = %b ", a,b,cin,sum,cout); 

initial #30 $stop ; 

endmodule