CLXCON

         This register controls which bitplanes are included (enabled) in
         collision detection, and their required state if included. It also
         controls the individual inclusion of odd numbered sprites in the
         collision detection, by logically ORing them with their correspond-
         ing even numbered sprite. Writing to this register resets the bits
         in CLXCON2.


         +------+----------+-----------------------------------------------+
         | BIT# | FUNCTION | DESCRIPTION                                   |
         +------+----------+-----------------------------------------------+
         | 15   | ENSP7    | Enable Sprite 7 (ORed with Sprite 6)          |
         | 14   | ENSP5    | Enable Sprite 5 (ORed with Sprite 4)          |
         | 13   | ENSP3    | Enable Sprite 3 (ORed with Sprite2)           |
         | 12   | ENSP1    | Enable Sprite 1 (ORed with Sprite 0)          |
         | 11   | ENSP6    | Enable bit plane 6 (match reqd. for collision |
         | 10   | ENSP5    | Enable bit plane 5 (match reqd. for collision |
         | 09   | ENSP4    | Enable bit plane 4 (match reqd. for collision |
         | 08   | ENSP3    | Enable bit plane 3 (match reqd. for collision |
         | 07   | ENSP2    | Enable bit plane 2 (match reqd. for collision |
         | 06   | ENSP1    | Enable bit plane 1 (match reqd. for collision |
         | 05   | ENSP6    | Match value for bit plane 6 collision         |
         | 04   | ENSP5    | Match value for bit plane 5 collision         |
         | 03   | ENSP4    | Match value for bit plane 4 collision         |
         | 02   | ENSP3    | Match value for bit plane 3 collision         |
         | 01   | ENSP2    | Match value for bit plane 2 collision         |
         | 00   | ENSP1    | Match value for bit plane 1 collision         |
         +------+----------+-----------------------------------------------+


   Note: Disable bit planes cannot prevent collisions. Therefore if all
         bitplanes are disabled, collision will be continuous, regardless
         of the match values.