Before you can simulate something - anything - you have to build a model of it.

Building the model is not at all a trivial thing, so you need to think carefully whether it's actually going to be easier to just build a real, hardware, prototype - rather than find a simulator, learn how to use it, build your model, run it, debug it, etc.

As already noted, a chip with built-in debug (such as SiLabs) is great for this kind of thing.


Of course, you don't have to (I might say shouldn't) just build a prototype of the entire system all at once - rather, do one subsystem at a time...