Keyboard (INT 09h)

        Every timer someone hits a key on the keyboard, an INT 09h
        is generated. The INT 09h handler reads the keyboard scancode
        from port 060 and translates it into ascii. Both the scancode
        and ascii code is placed in the keyboard buffer. Use INT 16h
        to read the scan- and ascii-code. The interrupt handler
        must do this:

          1.  Read the character from port 060.
          2.  Set bit 7 on port 061.
          3.  Reset bit 7 on port 061.
          4.  Convert scancode to ascii and place both in buffer.
          5.  Send EOI (20h) to port 20h