BPLCON1

 +------+---------+---------------------------------------------------------+
 | BIT# | BPLCON1 | DESCRIPTION                                             |
 +------+---------+---------------------------------------------------------+
 | 15   | PF2H7=0 | (PF2Hx =) Playfield 2 horizontal scroll code, x=0-7     |
 | 14   | PF2H6=0 |                                                         |
 | 13   | PF2H1=0 |                                                         |
 | 12   | PF2H0=0 |                                                         |
 | 11   | PF1H7=0 | (PF1Hx =) Playfield 1 horizontal scroll code, x=0-7     |
 | 10   | PF1H6=0 | where PFyH0=LSB=35ns SHRES pixel (bits have been        |
 | 09   | PF1H1=0 | renamed, old PFyH0 now PFyH2, ect). Now that the scroll |
 | 08   | PF1H0=0 | range has been quadrupled to allow for wider (32 or     |
 |      |         | 64 bits) bitplanes.                                     |
 | 07   | PF2H5   |                                                         |
 | 06   | PF2H4   |                                                         |
 | 05   | PF2H3   |                                                         |
 | 04   | PF2H2   |                                                         |
 | 03   | PF1H5   |                                                         |
 | 02   | PF1H4   |                                                         |
 | 01   | PF1H3   |                                                         |
 | 00   | PF1H2   |                                                         |
 +------+---------+---------------------------------------------------------+