úll

úll (Irish for 🍎 and written as ull when referring to the code) is a family of Rust crates currently aimed at emulating 8-bit machines, including the MOS 6502 and its offshoots. The primary focus at this stage of development is the 6502-based Apple II systems, but it would be a long-term goal to also include Z80-based systems as well, all with a cohesive API that shares common abstractions.

Getting started

ull

ull is a no_std base crate that hosts the shared primitives (Nibble, Byte, Word) plus the Bus trait and sample buses.

ull65

ull65 is a no_std 6502/65C02 CPU core with pluggable buses and instruction sets. More info can be found in the README.

Examples can be run using cargo run -p ull65 --example <name>.

• hello_world.rs copies "Hello, World!" into zero-page RAM, halts on BRK, then inspects memory.

  cargo run -p ull65 --example hello_world
  

• custom_instruction_set.rs starts from the MOS table, patches opcode $00, and stops once the custom handler advances the program counter.

  cargo run -p ull65 --example custom_instruction_set
  

• dma_loop.rs exercises Cpu::tick alongside a bus that keeps DMA bursts in sync with instruction timing.

  cargo run -p ull65 --example dma_loop
  

• apple1.rs wires the core up to a minimal Apple I bus so you can boot WOZMON and interact over the terminal to run BASIC.

  cargo run -p ull65 --example apple1
  

• nestest.rs runs the well-known NES CPU validation ROM using a Ricoh 2A03-style instruction set with a minimal NES bus.

  cargo run -p ull65 --example nestest