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29 lines
1.1 KiB
Markdown
29 lines
1.1 KiB
Markdown
# Contributor notes
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## Commands
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```sh
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make # build bin/mos6502
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make test # core checks
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make debug # strict warning build and checks
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make sanitize # ASan/UBSan build and checks
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make snake # assemble and run the SDL game (requires SDL2 + cc65)
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```
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## Architecture
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- `CPU6502` contains CPU-visible and interrupt-line state.
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- `Bus6502` owns RAM and Easy6502 MMIO; CPU code only uses bus accessors.
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- `cpu_step` executes one instruction or interrupt and returns status/opcode/cycles.
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- `src/opcode.c` has a 256-entry descriptor table for all 151 official encodings.
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- `src/frontend.c` is an optional SDL2 frontend with a dependency-free stub.
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- `tests/run_tests.c` is the in-tree test harness; `tests/run_suite.c` runs external ROMs.
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The target is the NMOS 6502. Preserve decimal-mode flag behavior, zero-page
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wrapping, the indirect-JMP page-wrap bug, stack push order, and page-cross cycle
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rules. Do not silently accept undocumented opcodes.
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The virtual machine exposes game state at `$00FB`, high/game score at `$00FC/$00FD`, random input
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at `$00FE`, keyboard input at `$00FF`, and a 32x32 framebuffer at
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`$0200-$05FF`.
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