Make sure you can detect infinite loops in your emulator.
Load it at 0x0000 in memory, jump to 0x0400 and start executing. I suggest to start with the 6502_functional_test.bin. (Ignore the bcd_verify.bin.) The nice thing about them is that they're not NES specific, so you don't need e.g.nes ROM loading for this. There are the CPU test roms I used in the beginning. I very strongly suggest that you grab yourself some test ROMs, set up automatic tests and start implementing the opcodes. First do the CPU and forget that you're trying to emulate an NES. The first thing I would recommend is not to try and do everything at once. However, yes, the wiki can be pretty cryptic, so you might need a little. How do I know? I wrote one myself, and I deliberately did it without looking at other emulators' sources. The NES Dev Wiki has almost everything you need to write a fully functional, mostly cycle accurate emulator. But all of the NES docs are pretty technical and I struggle to close the gap there is between these two systems with very little success. and these have been explained in CHIP-8 tutorial in a very layman terms. I suppose I could go on GitHub (and I have done it once, actually) to look up how things are done but not only it feels like cheating, but also I don't think I will learn anything by copying others.ĭo you know any resources that cover the topic in-depth and try to be as beginner-friendly as possible? I understand basics like CPU, clock rate, registers, memory, opcodes, etc.
I Googled a lot and searched this subreddit too, but it turns out that NES despite being a very popular system doesn't have any comprehensive or begginer-friendly emulation guide. Even the simplest stuff in emulation can be broken by little errors and when it comes here to NES I have huge problems with grasping major concepts yet implement any of the opcodes so that they could work. While I can make some sense out of these and maybe tinker myself around, there's no way that once I finish my emulator it will be able to run or do anything. I only used it for hardware reference and memory map.Īnd that would be about it. NES Dev Wiki - information here is actually pretty scarce, doesn't even have opcodes listed.The instructions are not explained what they do (took me a while to realize ADC is acumulator + memory address + carry flag byte) and says which flags are influenced by the opcode but it doesn't say why or how and at the end of the day I can't implement them well. My biggest problem is, it's super cryptic for somebody who is new to this. That's the only source I actually found out what different addressing modes do. Easy 6502 by skilldrick - the one I learned the most from, actually.So far I managed to find these resources the best: Just don't get me as a lazy person - previous emulator was my first experience with this kind of stuff and I'm constantly learning the low-level things I need to know for this kind of stuff. I was very surprised that despite how popular of a system (and still relatively simple) NES is, there is not a single guide that covers everything in detail. Making CHIP-8 was not only easy because of how simple system it is, but also explicit and comprehensive reference. I really tried but I have encountered some issues. So after finishing a CHIP-8 emulator (which basically is a Hello World!) I decided to make a NES emulator.
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