I hesitate to post this as it is a project that may never get off the ground, but
I have been looking at the C64 Reloaded MK2 for potential use to test a VIC-II circuit.
If I develop my own VIC-II circuit will the MK2 be able to determine the chip, or will it croak if things are not perfectly timed? The emulator does not output composite signals, sync, luma, etc. It outputs HDMI. What would be required to get working output? (There is possibly composite sync without colorburst available as the signals need to be generated by the emulator).
Potentially more sprites will be supported (16 or 24) as an option, by using past page mode (FPM) of the dynamic RAM and modifying the ras, cas signals. Ras and cas are not evenly distributed across the phi02 clock to give more time for burst access. The split is approximately 2/3 of a clock for FPM access and 1/3 of the clock for non FPM access. I think this should work for DRAMS 200ns and faster.
I think the C64 PAL chip does not care about the timing of RAS and CAS coming from the VIC-II.
Ras cycle:
BUS_SPRITE: rasr <= 32'b11100000000000000000011110000000;
Cas cycle:
BUS_SPRITE: casr <= 32'b11111000011000011000011111100000;
I was wondering if this would be compatible given that the board is using static RAM? I assume that the RAS and CAS are passed through latches to the SRAM and if CAS pulses high and low multiple times the SRAM will receive the proper addresses. I am also assuming RAS and CAS are not synchronized to the PHI02 clock.
I appreciate any comments