I have a small question about mouse handling in mode $101  (640X480X256)

Somehow I can't move the mouse to the lower part of the screen  - the
largest Y-coordinate the mosue returns are 199...

What is the problem here ?

Area(0,0,640*8,480*8);
Sense(640,480);

procedure Area(x1,y1,x2,y2 : Integer); assembler;
asm
  mov ax,7;xor ch,ch;xor dh,dh;mov cx,x1;mov dx,x2;int 33h
  mov ax,8;xor ch,ch;xor dh,dh;mov cx,y1;mov dx,y2;int 33h
end;

procedure Sense(x,y:Integer); assembler; asm
  mov ax,1ah; mov bx,x; mov cx,y; xor dx,dx; int 33h end;

hope this helps.....