Tilemap X Scroll MSB Register

Next Register Number	$2F
Readable	Yes
Writable	Yes
Short Description	Sets the pixel offset (two high bits) used for drawing Tilemap graphics on the screen.

Bits 7-2 Reserved, must be 0

Bits 1-0 Tilemap X-offset, top two bits of it (0 after a reset)

Meaningful Range is 0-319 in 40 char mode, 0-639 in 80 char mode.

The low eight bits of the offset value are stored in NextReg:$30.