Layer 2 X Scroll MSB Register

Number	TBRegisterNumber::$71
Readable	TBRegisterReadable::Yes
Writable	TBRegisterWritable::Yes
Short Description	ShortDesc::Sets the pixel offset used for drawing Layer 2 graphics on the screen.

   bits 7:1 = Reserved, must be 0
   bit 0 = MSB of scroll amount

This is most significant bit for high resolution 320x256x8 and 640x256x4 Layer 2 modes (valid range of scroll values is then 0..319, in 640x256x4 mode the layer is scrolling by two pixels horizontally)

The low 8 bits are defined by {{#ask: TBRegisterNumber::$16 }} ($16)

(introduced by core 3.0.6 (+-1))