NanoBoard Atari Centipede WIP ============================= The Nanoboard implementation of Centipede is currently suspended. It is currently a a point where the demo will run and you can start a game - sometimes (see below). The main point of this exercise was to get the 6502 core running on the Nanoboard, and also get the pokey (sound core) running. Both these aims have been achieved. Due to technical issues, this game shall remain WIP until the PACE project (proper) commences. Technical Notes =============== Both the 6502 and the pokey (sound) cores run correctly as far as I can tell. The game will play the attract mode and you can coin up and start a game, with the following notes: The game timing in Centipede is run off the Vblank signal and an IRQ derived from the video timing, roughly 1/32 of a vertical trace period (see MAME for more details). Furthermore, the game code does some checking of these times and will hang if the timings do not meet expectations. I have derived a vblank from the (70Hz) vsync which is produced by the current design on the Nanoboard. I also derived a periodic IRQ signal completely asynchronous to the vsync/vblank. This is enough to run Centipede (which expects a 60Hz vsync) about 20% of the time; this means that a few 'resets' may be required before the game will start properly. The trackball (analogue) inputs also require an interface, whether that be via interfacing a real trackball or a simulation as per MAME via the keyboard. The pokey sounds right except for the 'shot' noise which I suspect is filtered on the real PCB (I haven't looked yet). When Centipede is re-visited, these issues shall be resolved properly. Credits ======= Both the 6502 and the pokey sound core were taken from Mike's Asteroids project. Contact =======