BPLCON2

 +------+----------+--------------------------------------------------------+
 | BIT# | BPLCON2  | DESCRIPTION                                            |
 +------+----------+--------------------------------------------------------+
 | 15   | X        | don`t care- but drive to 0 for upward compatibility!   |
 | 14   | ZDBPSEL2 | 3 bit field which selects which bitplane is to be used |
 |      |          | for ZD when ZDBBPEN is set- 000 selects BB1 and 111    |
 |      |          | selects BP8.                                           |
 | 13   | ZDBPSEL1 |                                                        |
 | 12   | ZDBPSEL0 |                                                        |
 | 11   | ZDBPEN   | Causes ZD pin to mirror bitplane selected by ZDBPSELx  |
 |      |          | bits. This does not disable the ZD mode defined by     |
 |      |          | ZDCTEN, but rather is "ored" with it.                  |
 | 10   | ZDCTEN   | Causes ZD pin to mirror bit #15 of the active entry in |
 |      |          | high color table. When ZDCTEN is reset ZD reverts to   |
 |      |          | mirroring color (0).                                   |
 | 09   | KILLEHB  | Disables extra half brite mode.                        |
 | 08   | RDRAM=0  | Causes color table address to read the color table     |
 |      |          | instead of writing to it.                              |
 | 07   | SOGEN=0  | When set causes SOG output pin to go high              |
 | 06   | PF2PRI   | Gives playfield 2 priority over playfield 1.           |
 | 05   | PF2P2    | Playfield 2 priority code (with resp. to sprites).     |
 | 04   | PF2P1    |                                                        |
 | 03   | PF2P0    |                                                        |
 | 02   | PF1P2    | Playfield 1 priority code (with resp. to sprites).     |
 | 01   | PF1P1    |                                                        |
 | 00   | PF1P0    |                                                        |
 +------+----------+--------------------------------------------------------+