27 lines
1.3 KiB
Markdown
27 lines
1.3 KiB
Markdown
# OKI MSM5232
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a rather primitive (but powerful) sound generator chip used in some arcade boards and even synthesizers (like Korg Poly-800).
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it has 8 channels in 2 groups (of 4 channels each). each group can be configured with an envelope and the ability to produce 2', 4', 8' and/or 16' square/noise overtones on 8 outputs (four (2', 4', 8' and 16') per group).
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however, this chip cannot entirely produce sound alone. it has to be paired with either an external envelope generator or capacitors to assist the internal envelope generator.
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it also has no fine tune whatsoever. the frequency resolution is exactly a semitone.
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Furnace implements this chip in a way that allows the following features:
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- internal (capacitors) or external (volume macro) envelope modes per group
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- the ability to change the volume of each output (this can be used to generate saw waves if you set each part/overtone's volume to exactly half of the previous one)
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- global fine tune
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- global vibrato (some arcade boards played with the clock input to simulate vibrato)
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# effects
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- `10xy`: set group control.
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- `x` sets sustain mode.
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- `y` is a 4-bit mask which toggles overtones.
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- `11xx`: set noise mode.
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- `12xx`: set group attack (0 to 5).
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- only in internal (capacitor-based) envelope mode.
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- `13xx`: set group decay (0 to 11).
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- only in internal (capacitor-based) envelope mode.
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