You can read the source to existing projects (bsnes, SNES9X, gambatte etc.) The Gameboy would probably be the simplest hardware to work on.
> PS: I'm planning to use Java for this side-project.
Emulators typically use repetitive code, less than int-sized math, 2d arrays and pointer manipulation. Java is not good at dealing with any of those, so you might want to find a more fun language. Then again, one thing at a time.
Exactly, one thing at a time. Once I get a good grasp and managed to deliver a working emulator, then I can start thinking about improving/optimize or even port it to another language.
Right now I'm just trying to figure out the basic fundamental concept of "emulation" (what is it, what does it take, how can I write a simple one :)).
> PS: I'm planning to use Java for this side-project.
Emulators typically use repetitive code, less than int-sized math, 2d arrays and pointer manipulation. Java is not good at dealing with any of those, so you might want to find a more fun language. Then again, one thing at a time.