SUBDESIGN  add16
(
   a[15..0],b[15..0],ci  :INPUT;
   c[15..0],co[16..0]    :OUTPUT;
)
BEGIN
co[0]=ci;
FOR i IN  0 TO 15 GENERATE
c[i]=a[i] $ b[i] $ co[i];
co[i+1]=(a[i] & b[i])#((a[i] $ b[i])& co[i]);
END GENERATE;
END;