Agnus/
                  Read/   Denise/
Register Address  Write   Paula         Function
-------- -------  -----   -------       --------
VSSTOP     1CA      W      A( e ) vertical line position for vsync stop
VSSTRT     1E0      W      A( e ) vertical sync start   (varvsy)
VTOTAL     1C8      W      A( e ) highest numbered vertical line
                                      (VARBEAMEN=1)