Overview for the used adresses in i/o-area. Hardware-developer: This is no dictate for you. But for compatibility you should use free adresses. Mail me the adress from your hardware. I will add it to this list. solder@gmx.net

$fd00-$feff       plus/4-i/o-area
  $fd00-$fd0f     ACIA-chip (6551/8551)
    $fd00-$fd03   effective range for ACIA
    $fd03-$fd0f   mirrors of $fd00-$fd03
  $fd10-$fd1f     Userport 6529B-chip (original)
    $fd10         effective adress for 6529B (original)
    $fd10-$fd1f   mirrors of $fd10 (original)
  $fd10-$fd1f     Userport-area (plus/4 with expansion)
    $fd10         6529B-chip from userport
    $fd11-$fd12   Centronics-printerport
    $fd13-$fd14   Low-/high-switching for OS96
    $fd15         Register for CSORY-RAM-expansion
    $fd16         Register for Hannes-RAM-expansion
    $fd17         Register for EPROM-/sRAM-expansion
    $fd18-$fd1f   free (best for internal expansion)
  $fd20-$fd2f     used by different hardware, decoded by PLA (pin 18)
  $fd30-$fd3f     6529B for keyboard
    $fd30         effective adress for this 6529B
    $fd31-$fd3f   mirrors of $fd30
  $fd40-$fd5f     SID-card, area for SID-chip
    $fd40-$fd5d   SID-chip
    $fd5e         DAC on digiblaster add-on
    $fd5f         ADC on digiblaster add-on
  $fd60-$fd7f     Area for expansion-userport
    $fd60-$fd63   ACIA on card 1
    $fd64-$fd67   ACIA on card 2
    $fd68-$fd6b   ACIA on card 3
    $fd6c-$fd6f   ACIA on card 4
    $fd70-$fd73   6529B-emulation on card 1
      $fd70       effective adress for 6529B-emulation
      $fd71-$fd73 mirrors of $fd70
    $fd74-$fd77   6529B-emulation on card 2
      $fd74       effective adress for 6529B-emulation
      $fd75-$fd77 mirrors of $fd74
    $fd78-$fd7b   6529B-emulation on card 3
      $fd78       effective adress for 6529B-emulation
      $fd79-$fd7b mirrors of $fd78
    $fd7c-$fd7f   6529B-emulation on card 4
      $fd7c       effective adress for 6529B-emulation
      $fd7d-$fd7f mirrors of $fd7c
  $fd80-$fd8f     Joyport on SID-card
     $fd80        effective adress for joyport
     $fd81-$fd8f  mirrors of $fd80
  $fd90-$fdcf     free
  $fdd0-$fddf     Area for ROM-banking
  $fde0-$fde1     MIDI-interface
  $fde2-$fdef     free
  $fdf0-$fdfd     free
  $fdfe           Register on EPROM-card
  $fdff           Register on sRAM-card
  $fe00-$fe7f     free (best usage for a RAM-drive...)
  $fe80-$fe9f     SID-card, mirror from $fd40... for hungarian-compatibility
    $fe80-$fe9d   SID-chip
    $fe9e         DAC on digiblaster add-on
    $fe9f         ADC on digiblaster add-on
  $fea0-$febf     free (?)
  $fec0-$fecf     Floppy 1551, device 9
  $fed0-$feef     free (?)
  $fef0-$feff     Floppy 1551, device 8

note: please don't use mirror-adresses in your programs. Perhaps a mirror-
adress is decoded better later (like $fd10-$fd1f). Your programs will not
work then.