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74 lines
2.7 KiB
Markdown
74 lines
2.7 KiB
Markdown
# emul
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This folder contains a couple of tools running under the [libz80][libz80]
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emulator.
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## Not real hardware
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In the few emulated apps described below, we don't try to emulate real hardware
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because the goal here is to facilitate userspace development.
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These apps run on imaginary hardware and use many cheats to simplify I/Os.
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For real hardware emulation (which helps developing drivers), see the `hw`
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folder.
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## Build
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First, make sure that the `libz80` git submodule is checked out. If not, run
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`git submodule init && git submodule update`.
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After that, you can run `make` and it builds all applications.
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## forth
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Collapse OS' Forth interpreter, which is in the process of replacing the
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zasm-based project.
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The Forth interpreter is entirely self-hosting, that is, it assembles its
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binary with itself.
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There are 3 build stages.
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**Stage 0**: At this stage, all we have are our bootstrap binaries, `boot.bin`
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and `z80c.bin`. We concatenate them into `forth0.bin` ans then wrap the
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emulator around it which is named `stage1` (because it builds the stage 1) to
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have a barebone forth interpreter.
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**Stage 1**: The `stage1` binary allows us to augment `forth0.bin` with
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the compiled dictionary of a full Forth interpreter. We feed it with
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`$(FORTHSRCS)` and then dump the resulting compiled dict.
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From there, we can create `forth1.bin`, which is wrapped by both the `forth`
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and `stage2` executables. `forth` is the interpreter you'll use.
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**Stage 2**: `stage2` is used to resolve the chicken-and-egg problem and use
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the power of a full Forth intepreter, including an assembler, to assemble
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`z80c.bin`. This is a manual step executed through `make updatebootstrap`.
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Normally, running this step should yield the exact same `boot.bin` and
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`z80c.bin` as before, unless of course you've changed the source.
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## runbin
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This is a very simple tool that reads binary z80 code from stdin, loads it in
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memory starting at address 0 and then run the code until it halts. The exit
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code of the program is the value of `A` when the program halts.
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This is used for unit tests.
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## Problems?
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If the libz80-wrapped zasm executable works badly (hangs, spew garbage, etc.),
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it's probably because you've broken your bootstrap binaries. They're easy to
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mistakenly break. To verify if you've done that, look at your git status. If
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`boot.bin` or `z80c.bin` are modified, try resetting them and then run
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`make clean all`. Things should go better afterwards.
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If that doesn't work, there's also the nuclear option of `git reset --hard`
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and `git clean -fxd`.
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If that still doesn't work, it might be because the current commit you're on
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is broken, but that is rather rare: the repo on Github is plugged on Travis
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and it checks that everything is smooth.
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