Husky MP2500 Manual page 321

31.4.1.6 Lightpen registers
The clear lightpen latch and reset lightpen latch registers are not
implemented.
31.4.1.7 Character set
The MP2500 BIOS provides the full IBM character set in both text and
graphics modes. The IBM PC BIOS only provides the full set in text modes;
in graphics modes, characters 00H..7FH only are defined.
An application can replace the character definitions for ASCII 80..FFH used
in graphics modes by changing the contents of vector 1FH (ie
0007CH..0007FH) to point to its own definitions.
Chapter 31: Hardware 299