24 lines
2.0 KiB
Markdown
24 lines
2.0 KiB
Markdown
# george-emu
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a ramshackle emulator for george 😌
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plenty of inspiration & guidance taken from [emulator_6502](https://docs.rs/emulator_6502/latest/emulator_6502/) (don't use `george-emu` in a serious project! `emulator_6502` is the crate you're looking for)
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## structure
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see [the george wiki](https://git.augustkline.com/august/george/wiki) for how george works, why she exists, who she is, etc.
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the george emulator contains 3 main structs: `Cpu`, `Mem`, and `MemMappedDevice`. `Cpu` represents a 65c02 processor, with functions for interacting with memory and executing instructions. `Mem` is a collection of `MemMappedDevice`'s, which each hold the data for some address space. `Mem` can add `MemMappedDevice`'s, and read from and write to them. A `MemMappedDevice` can have multiple banks at the same address space, and can translate 'global' addresses to 'local' ones (e.g. 0xFFFF in the system's [memory map](https://git.augustkline.com/august/george-hardware/src/branch/main/memory.md) corresponds to 0x1FFF in the ROM).
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## font generation
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george uses a modified version of [cozette](https://github.com/slavfox/Cozette) for her main font. the modified version has 8 pixel wide characters for use with the character generator rom, and has a limit of 256 (0xFF) characters. the toolchain to generate a rom binary is still pretty clunky, and someday i might get around to streamlining it, but for now to make any changes:
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- open `./src/Cozette.sfd` in fontforge
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- make your edits
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- to reorder glyphs, edit `./src/georgeencoding.txt` and load it with "Encoding -> Load Encoding -> (select georgeencoding.txt, name it whatever) -> Reencode -> (name of encoding)"
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- ensure that there are exactly 256 characters in the font
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- generate a bdf font with "File -> Generate Fonts... -> (name of the font, select bdf in the options panel)"
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- open the generated bdf file in a text editor and change the line `FONTBOUNDINGBOX 11 13 0 -3` to `FONTBOUNDINGBOX 8 13 0 -3`
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- now open the font in [bdf view](https://emurenmrz.github.io/bdf_view/), and export a single-row png
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