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Snes javascript emulator code how to#
Snes javascript emulator code Pc#
Snes javascript emulator code series#

Just don’t go crazy creating new objects and trigger GC, if you are using a language that has one.ĭo find a good library for your language that supports rendering 2D graphics, controllers, and audio. It’s a 8-bit processor, so emulation performance on today’s powerful machines is usually not an issue. People have written NES emulators using all kinds of languages - C/C++, JavaScript, Go, C#, etc. Language choice probably doesn’t matter that much. But most of those work are incremental and you can decide to stop at any time. If you want to support most of the games out there, prepare for a lot of work (implementing mappers and debugging). It took me about a week and half to add CPU, PPU, and a few mappers in order to get some of the major commercial games to work perfectly (Super Contra, Super Mario Bros, Shadow of the Ninja, etc). Different mappers have different capabilities.

Mappers - how mappers controls memory mapping.

iNES format - most games are in this format.

Snes javascript emulator code how to#

APU - APU registers, and how to generate square/triangle waves.

PPU - PPU registers, pattern table, name table, sprites, rendering pipeline, and scrolling.

CPU - instructions, addressing modes, registers and status flags, interrupts.

You need to have a good understanding of following topics: Before your startĪssuming you haven’t done NES programming on a real NES hardware before, there are a bundance of material that covers NES hardware behavior. Some game catridge come with more than 256KB of CHR ROM and swap/map portion of it on demand. Most importantly, they also come with special hardware, refered to as mappers, that dynamically maps ROM/RAM into CPU and PPU memory space, bypassing the limitation of 16-bit address space. They come with game data as ROMsm, sometimes their own battery-backed RAM, or some cases, their own audio processing unit.

Ĭatridge boards (and mappers) - there are many different kinds of game catridge boards.

Ĭontrollers - from classic NES controller to NES mouse.

One can still make good music with these - just not great sound effects.

ĪPU (Audio Processing Unit) supporting 2 pulse channel, 1 triangle channel, 1 noise channel, and 1 DMC (delta modulation) channel.

It supports pixel-level scrolling (which is a big deal back in that day). PPU (Picture Processing Unit) supporting rendering 256x240 screen composed of 8x8 tiles for background, up to 64 8x8 or 8x16 sprites for moving objects. Rest is either not wired up (and are mirrors of those 2KB), or mapped to special I/O registers, or catridge ROM/RAM space. In theory it can address 64K memory however it only has 2KB onboard RAM.

Snes javascript emulator code Pc#

It has 3 general purpose register A/X/Y, and 3 special register P (status) /SP (stack pointer) /PC (program counter, or instruction pointer), all of them being 8-bit except PC which is 16-bit. NES Hardware Capabilitiesīeing a 8-bit system in 80s, it has hilariously limited spec comparing to today’s standard:Ĩ-bit 6502 CPU running at 1.79 MHZ. More detailed technical writeup of emulating different components would come later as separate posts. This post is intended as a high-level overview of what it would take to write a NES emulator so that if you are interested to write your own you’d be prepared to know what is involved, or simply just to understand some of the interesting problems involved in writing one. Those 8-bit style games are also making a come back in indie games such as Shovel Knight and Stardew Valley. Many people growing up in the 80s probably have fond memory of playing 8-bit NES games - those games are surprisingly fun (and many of them challenging).

Snes javascript emulator code series#

I had a lot of fun building this emulator and is planning to write a series of post documenting my experience and maybe help anyone who also want to write one. I’ve recently wrote a NES Emulator NesChan. How to write your own NES emulator - overview