Camden Dixie O'Brien
2a3949e09f
This enables waiting on them with memory.atomic.wait32 (there is no wait8) which is needed to avoid spinning when waiting for a key.
74 lines
2.3 KiB
Markdown
74 lines
2.3 KiB
Markdown
# Wipforth
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Wipforth is a simple Forth implementation that runs in the WebAssembly
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virtual machine. It does I/O via memory-mapped peripherals, which are
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emulated in JavaScript.
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- For the Forth kernel, see [wipforth.wat](./wipforth.wat)
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- For the JavaScript emulator, see [emu.js](./emu.js)
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- For the Forth prelude, which is loaded at start-up, see
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[prelude.f](./prelude.f)
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- For a description of the peripherals, see the
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[Peripherals](#peripherals) section below.
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## Building and Running Locally
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You'll need:
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- [WABT](https://github.com/WebAssembly/wabt)
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- [Guile](https://www.gnu.org/software/guile/) (or bring your own HTTP
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server -- see note below)
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To run, first compile the WebAssembly module:
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```
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wat2wasm --enable-threads wipforth.wat
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```
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Then run the development server:
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```
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guile server.scm
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```
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You should then be able to open <http://localhost:8080> in a browser
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and use the system from there.
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**NOTE**: The server is very simple and just serves the files with the
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cross-origin isolation headers required for `SharedMemoryBuffer` use.
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You could use any HTTP server that sets these headers.
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## Peripherals
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### Terminal
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| Name | Address | Size / B | Access |
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|--------|---------|----------|--------------|
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| TXBUF | 00h | 32 | write |
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| RXBUF | 20h | 32 | read |
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| TXHEAD | 40h | 4 | atomic read |
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| TXTAIL | 44h | 4 | atomic write |
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| RXHEAD | 48h | 4 | atomic write |
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| RXTAIL | 4Ch | 4 | atomic read |
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For both sending (`TX`) and receiving (`RX`), there are three
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registers: `xBUF`, `xHEAD` and `xTAIL`:
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- `xBUF` registers are 32-byte FIFO ring buffers used for data
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- The `xHEAD` and `xTAIL` registers specify the start and end of data
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in the ring buffer, `xHEAD` being the offset of the first byte of
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data, and `xTAIL` being the offset of the first byte *after* the data.
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In order to be distinguishable from the empty state, the ring buffers
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must never be completely full -- there must always be *at least one*
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unoccupied byte between the tail and the head.
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### System status
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| Name | Address | Size / B | Access |
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|----------|---------|----------|--------------|
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| SYSREADY | 50h | 1 | atomic write |
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The `SYSREADY` register is used to indicate when the system has booted
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up and is ready for user input.
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