$D011/53265/VIC+17:  Control Register 1

   +----------+---------------------------------------------------+
   | Bit  7   |    Raster Position Bit 8 from $D012               |
   | Bit  6   |    Extended Color Text Mode: 1 = Enable           |
   | Bit  5   |    Bitmap Mode: 1 = Enable                        |
   | Bit  4   |    Blank Screen to Border Color: 0 = Blank        |
   | Bit  3   |    Select 24/25 Row Text Display: 1 = 25 Rows     |
   | Bits 2-0 |    Smooth Scroll to Y Dot-Position (0-7)          |
   +----------+---------------------------------------------------+

   Default Value: $9B/155 (%10011011).

Kernal-Reference:

 LDA $D011   : $F88D $FC95
 STA $D011   : $F892 $FC9A