84 lines
4.4 KiB
Markdown
84 lines
4.4 KiB
Markdown
# NES
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the console from Nintendo that plays Super Mario Bros. and helped revive the agonizing video game market in the US during mid-80s.
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also known as Famicom. it is a five-channel sound generator: first two channels play pulse wave with three different duty cycles, third is a fixed-volume triangle channel, fourth is a noise channel (can work in both pseudo-random and periodic modes) and fifth is a (D)PCM sample channel.
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# effects
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- `11xx`: write to delta modulation counter.
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- this may be used to attenuate the triangle and noise channels.
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- will not work if a sample is playing.
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- `12xx`: set duty cycle or noise mode of channel.
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- may be 0-3 for the pulse channels and 0-1 for the noise channel.
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- `13xy`: setup sweep up.
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- `x` is the time.
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- `y` is the shift.
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- set to 0 to disable it.
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- `14xy`: setup sweep down.
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- `x` is the time.
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- `y` is the shift.
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- set to 0 to disable it.
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- `15xx`: set envelope mode.
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- `0`: envelope + length counter (volume represents envelope duration).
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- `1`: length counter (volume represents output volume).
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- `2`: looping envelope (volume represents envelope duration).
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- `3`: constant volume (default; volume represents output volume).
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- pulse and noise channels only.
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- you may need to apply a phase reset (using the macro) to make the envelope effective.
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- `16xx`: set length counter.
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- see table below for possible values.
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- this will trigger phase reset.
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- `17xx`: set frame counter mode.
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- `0`: 4-step.
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- NTSC: 120Hz sweeps and lengths; 240Hz envelope.
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- PAL: 100Hz sweeps and lengths; 200Hz envelope.
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- Dendy: 118.9Hz sweeps and lengths; 237.8Hz envelope.
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- `1`: 5-step.
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- NTSC: 96Hz sweeps and lengths; 192Hz envelope.
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- PAL: 80Hz sweeps and lengths; 160Hz envelope.
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- Dendy: 95.1Hz sweeps and lengths; 190.2Hz envelope.
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- `18xx`: set PCM channel mode.
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- `00`: PCM (software).
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- `01`: DPCM (hardware).
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- when in DPCM mode, samples will sound muffled (due to its nature), availables pitches are limited and loop point is ignored.
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# length counter table
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val | raw | NTSC | PAL | Dendy | NTSC 5-step | PAL 5-step | Dendy 5-step
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----|-----|-------|-------|-------|-------------|------------|--------------
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00 | 10 | 83ms | 100ms | 84ms | 104ms | 125ms | 105ms
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01 | 254 | 2.1s | 2.5s | 2.1s | 2.6s | 3.2s | 2.7s
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02 | 20 | 166ms | 200ms | 168ms | 208ms | 250ms | 210ms
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03 | 2 | 17ms | 20ms | 17ms | 21ms | 25ms | 21ms
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04 | 40 | 333ms | 400ms | 336ms | 417ms | 500ms | 421ms
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05 | 4 | 33ms | 40ms | 34ms | 42ms | 50ms | 42ms
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06 | 80 | 667ms | 800ms | 673ms | 833ms | 1.0s | 841ms
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07 | 6 | 50ms | 60ms | 50ms | 63ms | 75ms | 63ms
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08 | 160 | 1.3s | 1.6s | 1.3s | 1.7s | 2.0s | 1.7s
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09 | 8 | 67ms | 80ms | 67ms | 83ms | 100ms | 84ms
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0A | 60 | 500ms | 600ms | 505ms | 625ms | 750ms | 631ms
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0B | 10 | 83ms | 100ms | 84ms | 104ms | 125ms | 105ms
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0C | 14 | 117ms | 140ms | 118ms | 146ms | 175ms | 147ms
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0D | 12 | 100ms | 120ms | 101ms | 125ms | 150ms | 126ms
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0E | 26 | 217ms | 260ms | 219ms | 271ms | 325ms | 273ms
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0F | 14 | 117ms | 140ms | 118ms | 145ms | 175ms | 147ms
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10 | 12 | 100ms | 120ms | 101ms | 125ms | 150ms | 126ms
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11 | 16 | 133ms | 160ms | 135ms | 167ms | 200ms | 168ms
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12 | 24 | 200ms | 240ms | 202ms | 250ms | 300ms | 252ms
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13 | 18 | 150ms | 180ms | 151ms | 188ms | 225ms | 189ms
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14 | 48 | 400ms | 480ms | 404ms | 500ms | 600ms | 505ms
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15 | 20 | 167ms | 200ms | 168ms | 208ms | 250ms | 210ms
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16 | 96 | 800ms | 960ms | 807ms | 1.0s | 1.2s | 1.0s
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17 | 22 | 183ms | 220ms | 185ms | 229ms | 275ms | 231ms
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18 | 192 | 1.6s | 1.9s | 1.6s | 2.0s | 2.4s | 2.0s
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19 | 24 | 200ms | 240ms | 202ms | 250ms | 300ms | 252ms
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1A | 72 | 600ms | 720ms | 606ms | 750ms | 900ms | 757ms
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1B | 26 | 217ms | 260ms | 219ms | 271ms | 325ms | 273ms
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1C | 16 | 133ms | 160ms | 135ms | 167ms | 200ms | 168ms
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1D | 28 | 233ms | 280ms | 235ms | 292ms | 350ms | 294ms
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1E | 32 | 267ms | 320ms | 269ms | 333ms | 400ms | 336ms
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1F | 30 | 250ms | 300ms | 252ms | 313ms | 375ms | 315ms
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reference: [NESdev](https://www.nesdev.org/wiki/APU_Length_Counter)
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