HSSTOP

         BIT#  15  14  13  12  11  10  09  08  07  06  05  04  03  02  01  00
                x   x   x   x   x   x   x   x  h8  h7  h6  h5  h4  h3  h2  h1


         Sets # of colour clocks for sync stop.
         See BEAMCON0 for details of when these 2 are active.