$1C03/7171/VIA2+3:   Data Direction Register A

   +----------+---------------------------------------------------+
   | Bit  x   |   1 = Pin PAx set to Output, 0 = Input            |
   +----------+---------------------------------------------------+

ROM-Reference:

 STA $1C03  : $F596 $F5D6 $FDAF $FE0A $FE1A