$01/1:   6510 On-chip 8-bit Input/Output Register

   +----------+---------------------------------------------------+
   | Bits 7-6 |   Undefined                                       |
   | Bit  5   |   Cassette Motor Control                          |
   |          |   0 = ON, 1 = OFF                                 |
   | Bit  4   |   Cassette Switch Sense: 1 = Switch Closed        |
   | Bit  3   |   Cassette Data Output Line                       |
   | Bit  2   |   /CHAREN Signal (0=Swith Char. ROM In)           |
   | Bit  1   |   /HIRAM Signal (0=Switch Kernal ROM Out)         |
   | Bit  0   |   /LORAM Signal (0=Switch BASIC ROM Out)          |
   +----------+---------------------------------------------------+

   Default Value is $37/55.

  Flash_8 only:

   +--------+-----------------------------------------------------+
   | Bit  7 |   1 = 1 Mhz, 0 = 8 Mhz (if DIP1 closed)             |
   | Bit  6 |   (?)                                               |
   +--------+-----------------------------------------------------+

   Default Value is $37/55.