The MOS 6502 CPU spawned the microcomputer age in the mid 1970s, and was the common runtime for one of MSFT's earliest products, MSBASIC. While the original first MS product targeted the Altair 8080, it was the abundance of 6502-based computers (Apple I & II, PET, CBM, etc.) that made MSBASIC truly popular and considerably helped the MSFT brand in its early days.
Running MSBASIC on a rust-based CPU emulator on a VM in the Azure cloud is a geeky, but also educational showcase how the whole computer industry has evolved over the past 50 years.
This project is also my first foray into programming with rust; the code in this repo is the journey to get hopefully close to idiomatic rust programming. My notes on and sources for the journey to rust.
A 6502 emulator written in Rust Usage: r6502.exe [OPTIONS] [COMMAND] Arguments: [COMMAND] [default: run] [possible values: run, debug] Options: -b, --binary <BINARY> Path to binary file to load and run -f <FORMAT> File format of the binary file to load Possible values: - bin: Plain binary with no header, little endian byte order - prg: Like a bin file, but with a 16 byte header that indicates the load address -l, --load-address <LOAD_ADDRESS> Load address (u16) for binary to be loaded to (inferred for .prg); if no start_addr it is also used as start address -s, --start-address <START_ADDRESS> Start address (u16) for binary to be started with; can be hex address in 0x1234 format -r, --read-only loaded binary is read-only in memory (simulate ROM) -h, --help Print help (see a summary with '-h') -V, --version Print version With an empty program, the reset vector 0xFFFE points to a BRK instruction, halting the "program" after one instruction.
cargo run --bin r6502 -- No binary file specified, running empty program with single BRK instruction PC: FFFE: A: 00 X: 00 Y: 00 S: 00000000 SP: 01FC Instructions: 1; Cycles: 7; Clock speed: 1.045 MHz Program finished after 6 μs: done.Debugging with step and disassembly listing is also possible.
cargo run --bin r6502 -- debug -b ./cli/tests/assets/euclid_gcd.prg -s 0x0200 Loaded 476 bytes at address 0040; read-only mem=false PC: 0200: A: 00 X: 00 Y: 00 S: 00000000 SP: 01FF (dbg)> di 0200 LDA $40 0202 SEC 0203 SBC $41 0205 BEQ $12 (0219) 0207 BMI $05 (020E) 0209 STA $40 020B JMP $0202 020E LDX $40 0210 LDY $41 0212 STX $41 (dbg)> (dbg)> s PC: 0202: A: 78 X: 00 Y: 00 S: 00000000 SP: 01FF (dbg)> PC: 0203: A: 78 X: 00 Y: 00 S: 00000001 SP: 01FF (dbg)> h Usage: step (s) - step one instruction disassemble (di) - disassemble instructions from current PC continue (c) - continue execution <empty line> - repeat last command quit (q) - quit debugger (dbg)>Please use the issues tracker in the home repo: https://github.com/davidjenni/6502-emu/issues
This project will welcome contributions in the near future. At this stage, we're not ready for contributions, but do welcome your suggestions via this repository's issue tracker.
Information on how to setup a local dev environment is also detailed in this document.
See details in CONTRIBUTING
See details in CODE_OF_CONDUCT