• TheZipCreator (63/63) Oct 16 2022 I've recently been messing around with the MOS 6502 processor

TheZipCreator <thezipcreator protonmail.com> writes:

I've recently been messing around with the MOS 6502 processor 
which was used in many retro systems of the 1980s, however, 
what's annoyed me is that there isn't really an easy way just to 
mess around with code and see what happens. The closest thing is 
the [Virtual 6502](https://www.masswerk.at/6502/) which is 
decent, but it's online which means you have to deal with 
uploading files and such, and it also doesn't really have enough 
configuration options for my taste. Considering I like D and that 
I couldn't find a DUB package that already emulated the 6502, I 
decided to make my own emulator, which is currently called 
Emu6502 (very original name, I know). It supports most features 
of the 6502, with the exception of a few small things (which are 
listed under the TODO section of the readme). Here's an example 
program:

```d
module example;

import std.stdio;
import emu6502;

void main() {
   ubyte[0x10000] memory;
   ubyte[] code = [

                       // loop:
     0xBD, 0x0E, 0x80, //   lda data,x
     0x8D, 0x00, 0xE0, //   sta $E000

     0xE8,             //   inx
     0xD0, 0xF5,       //   bne loop
     0x00,             //   brk
                       // data: .asciiz 'Hello, World!\n'
     0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x2C, 0x20, 0x57, 0x6F, 0x72, 
0x6C, 0x64, 0x21, 0x0A, 0x00
   ];
   // put code into memory
   foreach(i, b; code)
     memory[0x8000+i] = b;
   // set reset vector
   memory[0xFFFC] = 0x00;
   memory[0xFFFD] = 0x80;
   // create emulator
   auto emu = new Emu6502(
     (ushort address) {
       return memory[address];
     },
     (ushort address, ubyte value) {
       if(address == 0xE000)
         write(cast(char)value);
       else
         memory[address] = value;
     },
     (ubyte n) {}
   );
   emu.reset();
   emu.throwExceptionOnBreak = true;
   // run until brk triggered
   try {
     while(true)
       emu.step();
   } catch(BreakException) {}
}
```

Links: [Github Repo](https://github.com/TheZipCreator/emu6502) 
[DUB Package](https://code.dlang.org/packages/emu6502)