component top 
    T_IO        : generic type = signed(10, 5)
    data_in     : in T_IO
    data_out    : out T_IO

type
  T_narrow: signed(6, 4, sat, round)

register
  storage: T_narrow = 0

begin
  storage = storage + convert(T_narrow, data_in)
  data_out = storage
end