pad.refresh(pad_minrow, pad_mincol, screen_minrow, screen_mincol, screen_maxrow, screen_maxcol)
  
	Instance Public methods
	Refreshes the pad.  pad_minrow and pad_mincol+ define the
upper-left corner of the rectangle to be displayed. 
screen_minrow, screen_mincol,
screen_maxrow, screen_maxcol define the edges of
the rectangle to be displayed on the screen.