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https://github.com/quattromusic/6502-simulator
A simple to use 6502 simulator, featuring a code viewer, keyboard input and a display!
https://github.com/quattromusic/6502-simulator
6502 assembly emulator simulator
Last synced: 8 days ago
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A simple to use 6502 simulator, featuring a code viewer, keyboard input and a display!
- Host: GitHub
- URL: https://github.com/quattromusic/6502-simulator
- Owner: QuattroMusic
- Created: 2024-09-05T16:53:01.000Z (2 months ago)
- Default Branch: main
- Last Pushed: 2024-10-23T20:40:40.000Z (13 days ago)
- Last Synced: 2024-10-24T06:24:20.935Z (13 days ago)
- Topics: 6502, assembly, emulator, simulator
- Language: Assembly
- Homepage:
- Size: 3.85 MB
- Stars: 4
- Watchers: 1
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# 6502-Simulator
A simple to use 6502 simulator, featuring a code viewer, keyboard input and a display!
![[image]](_data/6502.png)
![[video]](_data/hello_6502.gif)
## Technical specifications
- 32kB RAM and ROM
- 120x80 display
- Date and time in RAM
- Keyboard input
- Frequency selector in the range of 1Hz to 1GHz
### Address Space
```
┌───────────────┐
│ │ 0x0000
│ Zero Page │
│ │ 0x00FF
├───────────────┤
│ │ 0x0100
│ Stack │
│ │ 0x01FF
├───────────────┤
│ │ 0x0200
│ RAM │
│ │ 0x7FFF
├───────────────┤
│ │ 0x8000
│ ROM │
│ │ 0xFFF9
├───────────────┤
│ NMI Vector │ 0xFFFA
│ (unused) │ 0xFFFB
├───────────────┤
│ RES Vector │ 0xFFFC & 0xFFFD
├───────────────┤
│ IRQ Vector │ 0xFFFE
│ (unused) │ 0xFFFF
└───────────────┘
```
The Zero Page is considered as RAM, it's just an optimized way for the memory operations (less cycles).
The RAM is then subdivided as below:
```
┌───────────────┐
│ │ 0x0200
│ Display │
│ │ 0x277F
├───────────────┤
│ Keyboard │ 0x2780
│ Input │
├───────────────┤
│ Year │ 0x2781 & 0x2782
├───────────────┤
│ Month │ 0x2783
├───────────────┤
│ Day │ 0x2784
├───────────────┤
│ Hours │ 0x2785
├───────────────┤
│ Minutes │ 0x2786
├───────────────┤
│ Seconds │ 0x2787
├───────────────┤
│ Milliseconds │ 0x2788 & 0x2789
├───────────────┤
│ │ 0x278A
│ RAM │
│ │ 0x7FFF
└───────────────┘
```
The Year and the Milliseconds section is stored as little-endian (see programmers model)
Note: you can use the display space as RAM storage without any problem, but not the input and date space.
The keyboard input only works when the display is open
### Programmers Model
At the beginning of the exectution, the 6502 will read the data at the address `0xFFFC` and `0xFFFD` (RES Vector).
The resulted address will give the entry point of your program (see examples or the minimal code).
Multiple byte data is stored in little-endian, so, the address `0x1234` will be stored the RAM as `0x34` and `0x12`
The 6502 features 3 general purpose 8b registers, called `A` (accumulator), `X` and `Y`.
Then there's the 16b `PC` (Program Counter) used to point at the instruction in the ROM,
an 8b register `S`, which points to the next free slot in the stack (0xFF at startup, downwards)
and the 8b `P` reg, which includes the flags used for comparisons and branching.
```
MSB LSB
┌───┬───┬───┬───┬───┬───┬───┬───┐
P = │ N │ V │ - │ B │ D │ I │ Z │ C │
└───┴───┴───┴───┴───┴───┴───┴───┘
```
- `N`: Negative result
- `V`: Overflow
- `B`: BRK instruction
- `D`: Decimal mode
- `I`: IRQ disable (unused)
- `Z`: zero result
- `C`: Carry = !Borrow
For a complete list of the implemented intrinsics, you may look at this [cheatsheet](https://www.atarimania.com/documents/6502%20(65xx)%20Microprocessor%20Instant%20Reference%20Card.pdf)
## Installation
1. Download the simulator from this repository
2. Download the [Vasm compiler](http://www.compilers.de/vasm.html) (`vasm6502_oldstyle.exe`) and add it to the same folder of the executable, or setup environment variables
3. Enjoy!
## How to use
1. Open the simulator
2. Create a file on your pc
3. Drag and drop the file on the simulator
4. Open your favourite IDE and edit the file
5. Enjoy!
Note: every time you save the file, the program automatically reload it
### Minimal Code
```
.org $8000
init:
; your code here!
.org $FFFC
.word init
.word $0000
```
## Roadmap
### Version 1.0
- [x] display
- [x] keyboard input
- [x] date in memory
- [x] fix / improve 6502 engine
### Version 2.0
- [x] render and gui revamp
- [ ] calculator / conversion panel
- [ ] options panel + save configurations to file
- [ ] browser panel
### Version 3.0
- [ ] panel for the 6502 instruction set
- [ ] use an internal 6502 compiler
### Version 4.0
- [ ] error handling
- [ ] code editor instead of code viewer
# License
I don't like the way the license system works, so instead of searching for a license that satisfies me, I'm making my own version.
#### What this software allows you to do
You can keep the source code on your devices; you may compile it and use it for private or public use.
#### What this software doesn't allow you to do
Even if you've modified it, I don't want you to use this product for commercial use or to distribute under your name;
I put a lot of effort on this project, for learning purposes, and to make it possible for everyone to use a 6502 simulator to learn assembly in the easiest possible way.
#### In short
Use it wherever you want, but please do not use this project for commercial purposes; it's an educational tool that I want accessible to everyone.
## Contact me
Questions? Bugs? Ideas? Feel free to contact me on Discord `@quattromusic`!
Join [my server](https://discord.gg/wXECkMJb6V) for the latest news.