http://72.0.193.250/Documentation/macppc/adbkeycodes/
http://m0115.web.fc2.com/m0115.jpg
[Inside Macintosh volume V, pages 191-192]
+ http://www.opensource.apple.com/source/IOHIDFamily/IOHIDFamily-421.18.3/IOHIDFamily/Cosmo_USB2ADB.c
ADB Signaling
http://kbdbabel.sourceforge.net/doc/kbd_signaling_pcxt_ps2_adb.pdf
ADB Overview & History