tildearrow Sound Unit

a fantasy sound chip, used in the specs2 fantasy computer designed by tildearrow.

it has the following capabilities:

8 channels of either waveform or sample
stereo sound
8 waveforms (pulse, saw, sine, triangle, noise, periodic noise, XOR sine and XOR triangle)
128 widths for the pulse wave
per-channel resonant filter
ring modulation
volume, frequency and cutoff sweep units (per-channel)
phase reset timer (per-channel)

effects

10xx: set waveform
- 0: pulse wave
- 1: sawtooth
- 2: sine wave
- 3: triangle wave
- 4: noise
- 5: periodic noise
- 6: XOR sine
- 7: XOR triangle
12xx: set pulse width (0 to 7F)
13xx: set resonance of filter (0 to FF)
- despite what the internal effects list says (0 to F), you can use a resonance value from 0 to FF (255)
14xx: set filter mode and ringmod
- bit 0: ring mod
- bit 1: low pass
- bit 2: high pass
- bit 3: band pass
15xx: set frequency sweep period low byte
16xx: set frequency sweep period high byte
17xx: set volume sweep period low byte
18xx: set volume sweep period high byte
19xx: set cutoff sweep period low byte
1Axx: set cutoff sweep period high byte
1Bxx: set frequency sweep boundary
1Cxx: set volume sweep boundary
1Dxx: set cutoff sweep boundary
1Exx: set phase reset period low byte
1Fxx: set phase reset period high byte
20xx: toggle frequency sweep
- bit 0-6: speed
- bit 7: up direction
21xx: toggle volume sweep
- bit 0-4: speed
- bit 5: up direction
- bit 6: loop
- bit 7: alternate
22xx: toggle cutoff sweep
- bit 0-6: speed
- bit 7: up direction
4xxx: set cutoff (0 to FFF)