61 lines
		
	
	
		
			2 KiB
		
	
	
	
		
			Markdown
		
	
	
	
	
	
			
		
		
	
	
			61 lines
		
	
	
		
			2 KiB
		
	
	
	
		
			Markdown
		
	
	
	
	
	
# tildearrow Sound Unit
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a fantasy sound chip, used in the specs2 fantasy computer designed by tildearrow.
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it has the following capabilities:
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- 8 channels of either waveform or sample
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- stereo sound
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- 8 waveforms (pulse, saw, sine, triangle, noise, periodic noise, XOR sine and XOR triangle)
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- 128 widths for the pulse wave
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- per-channel resonant filter
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- ring modulation
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- volume, frequency and cutoff sweep units (per-channel)
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- phase reset timer (per-channel)
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# effects
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- `10xx`: **set waveform.**
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  - `0`: pulse wave
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  - `1`: sawtooth
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  - `2`: sine wave
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  - `3`: triangle wave
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  - `4`: noise
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  - `5`: periodic noise
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  - `6`: XOR sine
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  - `7`: XOR triangle
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- `12xx`: **set pulse width.** range is `0` to `7F`.
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- `13xx`: **set resonance of filter.** range is `0` to `FF`.
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  - despite what the internal effects list says (`0` to `F`), you can use a resonance value from `0` to `FF` (255).
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- `14xx`: **set filter mode and ringmod.**
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  - bit 0: ring mod
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  - bit 1: low pass
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  - bit 2: high pass
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  - bit 3: band pass
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- `15xx`: **set frequency sweep period low byte.**
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- `16xx`: **set frequency sweep period high byte.**
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- `17xx`: **set volume sweep period low byte.**
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- `18xx`: **set volume sweep period high byte.**
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- `19xx`: **set cutoff sweep period low byte.**
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- `1Axx`: **set cutoff sweep period high byte.**
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- `1Bxx`: **set frequency sweep boundary.**
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- `1Cxx`: **set volume sweep boundary.**
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- `1Dxx`: **set cutoff sweep boundary.**
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- `1Exx`: **set phase reset period low byte.**
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- `1Fxx`: **set phase reset period high byte.**
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- `20xx`: **toggle frequency sweep.**
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  - bit 0-6: speed
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  - bit 7: up direction
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- `21xx`: **toggle volume sweep.**
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  - bit 0-4: speed
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  - bit 5: up direction
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  - bit 6: loop
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  - bit 7: alternate
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- `22xx`: **toggle cutoff sweep.**
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  - bit 0-6: speed
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  - bit 7: up direction
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- `4xxx`: **set cutoff.** range is `0` to `FFF`.
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# info
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this chip uses the [Sound Unit](../4-instrument/soundunit.md) and [Generic Sample](../4-instrument/amiga.md) instrument editors.
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