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### emu8910
This repository contains a Typescript implementation of General Instrument's [AY-3-8910](https://en.wikipedia.org/wiki/General_Instrument_AY-3-8910) PSG (programmable sound generator).
It implements most of the PSG's original registers. A datasheet can be found [here](http://map.grauw.nl/resources/sound/generalinstrument_ay-3-8910.pdf).
Sound output is achieved in the browser through an AudioContext() hook. <br>
This emulator also adds interrupt support (with variable frequency) for updating the PSG's registers.
FIR filter data generated using:
[https://www.arc.id.au/FilterDesign.html](https://www.arc.id.au/FilterDesign.html)
Compile with `tsc emu8910.ts`.
To use simply create a PSG49 object as follows:
```
var emu8910 = new PSG49(YM_CLOCK_ZX, 50);
```
Which sets the default clock speed and interrupt frequency.
To play a FYM module:
```
song = new FYMReader(<BUFFER>);
emu8910.interrupt.routine = <ISR_FUNC>
emu8910.clock.frequency = song.getClockRate()
emu8910.interrupt.frequency = song.getFrameRate()
```
This sets the ISR (Interrupt Service Routine) function, clock and interrupt frequency for a specific song.
To stop playback:
```
emu8910.driver.device.suspend()
emu8910.interrupt.frequency = 0
```
To resume:
```
emu8910.driver.device.resume()
emu8910.interrupt.frequency = song.getFrameRate()
```
Note: You can access the emulator's internal register file with `emu8910.register`.
These registers need to be updated at the frequency of the ISR.
Files:
* src/emu8910.ts - Core emulator implementation
* fym.js - FYM (Fast YM) format parser
* update.js - Register parser
* index.html - HTML boilerplate
To run demo start web server: `python -m http.server 8000` and navigate to `index.html`.
Then click anywhere on the page to start audio output.
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