Implement Bitplane Selection #27
Description
The XO Chip instructions reference bitplanes when drawing to the screen. In the default implementation of the Chip8 specification, we assume there is only a single plane. The bitplane variable is a single byte value that encodes which bitplane should be active. There are only four choices:
0- means neither bitplanes are selected.1- means that the first bitplane is selected - this is the default value and is set when the emulator starts for Chip8 compability.2- means that the second bitplane is selected.3- means that both the first and second bitplane is selected.
For this issue, the bitplane selector should be created and should be instantiated as 1 when the emulator starts up. The bitplane selection instruction Fn01 should be implemented that will store the value of n to the bitplane selector variable. The drawing, scrolling, and clearing instructions will be updated to work on separate bitplanes in a different issue.