anchor.diff:      Pid = spawn_link( fun() -> enter_loop( Driver, Parameters, From ) end ),
       wait( { Pid, Tag } ).
   
  --spec start_async( binary(), [ binary() ] ) -> { ok, { pid(), reference() } }.
  +-spec start_async( binary(), [ binary() ] ) -> { ok, msg_token() }.
   start_async( Driver, Parameters ) ->
       { _, Tag } = From = from(),
       Pid = spawn_link( fun() -> enter_loop( Driver, Parameters, From ) end ),
       { ok, { Pid, Tag } }.
   
  --spec start_link_async( binary(), [ binary() ] ) -> { ok, { pid(), reference() } }.
  +-spec start_link_async( binary(), [ binary() ] ) -> { ok, msg_token() }.
   start_link_async( Driver, Parameters ) ->
       { _, Tag } = From = from(),
       Pid = spawn_link( fun() -> enter_loop( Driver, Parameters, From ) end ),
  
positive.code:     Pid ! { stop, From },
      wait( To ).
  
  -spec stop_async( pid() ) -> { ok, { pid(), reference() } } | { error, timeout }.
  stop_async( Pid ) ->
      { From, To } = from_to( self(), Pid ),
      Pid ! { stop, From },
  
negative.code: from( ) ->
      { self(), make_ref() }.
  
  -spec wait( msg_token() ) ->
      any() | { error, timeout }.
  wait( Id ) ->
      receive
  