Changes
/* Effort done */
* LowerROM has .eZZ file extension
* UpperROM has .e00 ot eFF file extension (hexa)
In r005.4, I added another UpperROM set : .f00 to .fFF. If you press "space" during a reset_key ("page up" key), upperROM files used are *.f00 to *.fFF instead of *.e00 to *.eFF. *.eZZ is still used in both case.
=== DONE: Another disk selector ===
In some emulators, keyboard is mapped directly behind PIO.
In original schematic, PIO is the only one component having a low state reset (0), I think that imply a 0 value as state init of internal components variable. Data bus of Z80 seems having a pull-up state (read 1 when nothing is plugged), for example a unplugged ROM does respond xFF in data-bus.
=== TODO : Scanline ===