Is it feasible to emulate this in Simavr?

[Nejat Dilek]

I have designed a cartridge to be used on C64.

https://github.com/nejat76/IRQHack64 

It uses an arduino pro mini on board and drives an 27c512 eprom's A8-A15 address pins. Firmware uses tight loops with microsecond timing sensitive delays to achieve it's stuff while driving the eprom. 

The question is : Is it feasible to emulate this hardware with simavr and pair it with an open source c64 emulator? Can I get a cycle exact performance out of it? 

Cartridge has an sd card interface over spi but I'll not emulate it with simavr, rather I'll just use an abstraction over the sd card/fat interface accessing the files directly for development purposes,

Best regards,

Nejat

ps: This is my first message and this is a fantastic project by the way!

[Giles Atkinson]

Nejat,

Interesting retro project!  May I suggest that you put a PNG of the schematic in your README? Not everyone has Eagle installed.  I am intrigued that the EPROM is not driven directly by the C64, and would like to see more.

That Arduino looks to be based on the 328, which is well-supported by simavr.  In my experience, the interfaces for integrating to external simulations are very good.  Cycle-accurate timing may be more trouble: simavr uses the same instruction timing for all variants and I think there has been not much attention to transitions like waking from sleep.   The code should be easy to modify to be more accurate and PRs are welcomed, though accepted slowly.

Giles

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