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axel Build Status

The 6800 ("sixty-eight hundred") is an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips.

The 6800 has a 16-bit address bus that can directly access 64 kB of memory and an 8-bit bi-directional data bus. It has 72 instructions with seven addressing modes for a total of 197 opcodes. The original MC6800 could have a clock frequency of up to 1 MHz. Later versions had a maximum clock frequency of 2 MHz.

Assembler Design

  • Fast, LL(1) of the 6800 assembly language
  • Strongly typed, with mypy --strict
  • Multipass assembler:
    • Symbol table and IR pass
    • Opcode byte translation pass
  • Verbose errors and adept parser error recovery
  • Fully tested with robust test suite. (> 90% coverage)

Not Yet Implemented

I am considering designing a DSL compiler in haskell or C to do the instruction -> opcode translation state machine.

  • Interrupt flag and instructions (wont do)
  • DATA and rom directives
    • Needs Parser extension
  • 65 of the 72 ISA opcode mnemonic translations

Pull requests are welcome!

Development

Install dependencies with poetry.

Run poetry install.

During development, run make start to start and run assembler on the healthkit program in etc/.

Tests

Run make test

License

GPL-v3.0, or by request, Apache License 2.0.