+------------------------------------------------------------------------
  |
  |      RAM EXPANSION UNIT (REU) 1700/1764/1750
  |
  +------------------------------------------------------------------------
  |
  |   $DF00/57088/REU+0        Status Register (read only)
  |   $DF01/57089/REU+1        Command Register
  |   $DF02/57090/REU+2        C64 Base Address - Low-Byte
  |   $DF03/57091/REU+3        C64 Base Address - High-Byte
  |   $DF04/57092/REU+4        REU Base Address - Low-Byte
  |   $DF05/57093/REU+5        REU Base Address - High-Byte
  |   $DF06/57094/REU+6        REU Base Address - Bank-Number
  |   $DF07/57095/REU+7        Transfer Length - Low-Byte
  |   $DF08/57096/REU+8        Transfer-Length - High-Byte
  |   $DF09/57097/REU+9        Interrupt Mask Register
  |   $DF0A/57098/REU+10       Address Control Register
  |
  +------------------------------------------------------------------------