Changes
/* Reading of write-only I/O registers */
There is no hardware that is driving these registers so the data is what is last on the z80 data bus.
NOTE: That because 7fxx is mapped to gate-array and both read/write can access it it is possible to read the colour register and display a raster on the screen. In this case the raster will use colours based on the last byte of the instruction.
===Reading of unmapped ASIC register RAM===
