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furnace/doc/7-systems/nes.md
Electric Keet a9d4bf1fdc Accurate number! 
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2023-06-30 20:41:16 -07:00

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# NES
the console from Nintendo that plays Super Mario Bros. and helped revive the agonizing video game market in the US during mid-80s.
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.
# effects
- `11xx`: **write to delta modulation counter.** range is `00` to `7F`.
- this may be used to attenuate the triangle and noise channels; at `7F`, they will be at about 57% volume.
- will not work if a sample is playing.
- `12xx`: **set duty cycle or noise mode of channel.**
- may be `0` to `3` for the pulse channels:
- `0`: 12.5%
- `1`: 25%
- `2`: 50%
- `3`: 75%
- may be `0` or `1` for the noise channel:
- `0`: long (15-bit LFSR, 32767-step)
- `1`: short (9-bit LFSR, 93-step)
- `13xy`: **setup sweep up.**
- `x` is the time.
- `y` is the shift.
- set to `0` to disable it.
- `14xy`: **setup sweep down.**
- `x` is the time.
- `y` is the shift.
- set to `0` to disable it.
- `15xx`: **set envelope mode.**
- `0`: envelope + length counter. volume represents envelope duration.
- `1`: length counter. volume represents output volume.
- `2`: looping envelope. volume represents envelope duration.
- `3`: constant volume. default value. volume represents output volume.
- Pulse and noise channels only.
- you may need to apply a phase reset (using the macro) to make the envelope effective.
- `16xx`: **set length counter.**
- see table below for possible values.
- this will trigger phase reset.
- `17xx`: **set frame counter mode.**
- `0`: 4-step.
- NTSC: 120Hz sweeps and lengths; 240Hz envelope.
- PAL: 100Hz sweeps and lengths; 200Hz envelope.
- Dendy: 118.9Hz sweeps and lengths; 237.8Hz envelope.
- `1`: 5-step.
- NTSC: 96Hz sweeps and lengths; 192Hz envelope.
- PAL: 80Hz sweeps and lengths; 160Hz envelope.
- Dendy: 95.1Hz sweeps and lengths; 190.2Hz envelope.
- `18xx`: **set PCM channel mode.**
- `00`: PCM (software).
- `01`: DPCM (hardware).
- when in DPCM mode, samples will sound muffled (due to its nature), availables pitches are limited, and loop point is ignored.
- `19xx`: **set triangle linear counter.**
- `00` to `7F` set the counter.
- `80` and higher halt it.
- `20xx`: **set DPCM frequency.**
- only works in DPCM mode.
- see table below for possible values.
# tables
## short noise frequencies (NTSC)
note | arpeggio | fundamental | MIDI note | pitch
:---- | -------: | ----------: | --------: | :----------
`C-0` | @0 | 4.7 Hz | -9.47 | `d_1` + 53¢
`C#0` | @1 | 9.5 Hz | 2.53 | `D-0` + 53¢
`D-0` | @2 | 18.9 Hz | 14.55 | `D-1` + 55¢
`D#0` | @3 | 25.3 Hz | 19.53 | `G-1` + 53¢
`E-0` | @4 | 37.9 Hz | 26.55 | `D-2` + 55¢
`F-0` | @5 | 50.6 Hz | 31.57 | `G-2` + 57¢
`F#0` | @6 | 75.8 Hz | 38.55 | `D-3` + 55¢
`G-0` | @7 | 95.3 Hz | 42.51 | `F#3` + 51¢
`G#0` | @8 | 120.3 Hz | 46.55 | `A#3` + 55¢
`A-0` | @9 | 150.4 Hz | 50.41 | `D-4` + 41¢
`A#0` | @10 | 200.5 Hz | 55.39 | `G-4` + 39¢
`B-0` | @11 | 300.7 Hz | 62.41 | `D-5` + 41¢
`C-1` | @12 | 601.4 Hz | 74.41 | `D-6` + 41¢
`C#1` | @13 | 1202.8 Hz | 86.41 | `D-7` + 41¢
`D-1` | @14 | 2405.6 Hz | 98.41 | `D-8` + 41¢
`D#1` | @15 | 4811.2 Hz | 110.41 | `D-9` + 41¢
reference: [NESdev](https://www.nesdev.org/wiki/APU_Noise)
## length counter table
<!-- organized by input value... of little use -->
<!--
value | raw | NTSC | PAL | Dendy | NTSC 5-step | PAL 5-step | Dendy 5-step
-----:|----:|------:|------:|------:|------------:|-----------:|-------------:
`00` | 10 | 83ms | 100ms | 84ms | 104ms | 125ms | 105ms
`01` | 254 | 2.1s | 2.5s | 2.1s | 2.6s | 3.2s | 2.7s
`02` | 20 | 166ms | 200ms | 168ms | 208ms | 250ms | 210ms
`03` | 2 | 17ms | 20ms | 17ms | 21ms | 25ms | 21ms
`04` | 40 | 333ms | 400ms | 336ms | 417ms | 500ms | 421ms
`05` | 4 | 33ms | 40ms | 34ms | 42ms | 50ms | 42ms
`06` | 80 | 667ms | 800ms | 673ms | 833ms | 1.0s | 841ms
`07` | 6 | 50ms | 60ms | 50ms | 63ms | 75ms | 63ms
`08` | 160 | 1.3s | 1.6s | 1.3s | 1.7s | 2.0s | 1.7s
`09` | 8 | 67ms | 80ms | 67ms | 83ms | 100ms | 84ms
`0A` | 60 | 500ms | 600ms | 505ms | 625ms | 750ms | 631ms
`0B` | 10 | 83ms | 100ms | 84ms | 104ms | 125ms | 105ms
`0C` | 14 | 117ms | 140ms | 118ms | 146ms | 175ms | 147ms
`0D` | 12 | 100ms | 120ms | 101ms | 125ms | 150ms | 126ms
`0E` | 26 | 217ms | 260ms | 219ms | 271ms | 325ms | 273ms
`0F` | 14 | 117ms | 140ms | 118ms | 145ms | 175ms | 147ms
`10` | 12 | 100ms | 120ms | 101ms | 125ms | 150ms | 126ms
`11` | 16 | 133ms | 160ms | 135ms | 167ms | 200ms | 168ms
`12` | 24 | 200ms | 240ms | 202ms | 250ms | 300ms | 252ms
`13` | 18 | 150ms | 180ms | 151ms | 188ms | 225ms | 189ms
`14` | 48 | 400ms | 480ms | 404ms | 500ms | 600ms | 505ms
`15` | 20 | 167ms | 200ms | 168ms | 208ms | 250ms | 210ms
`16` | 96 | 800ms | 960ms | 807ms | 1.0s | 1.2s | 1.0s
`17` | 22 | 183ms | 220ms | 185ms | 229ms | 275ms | 231ms
`18` | 192 | 1.6s | 1.9s | 1.6s | 2.0s | 2.4s | 2.0s
`19` | 24 | 200ms | 240ms | 202ms | 250ms | 300ms | 252ms
`1A` | 72 | 600ms | 720ms | 606ms | 750ms | 900ms | 757ms
`1B` | 26 | 217ms | 260ms | 219ms | 271ms | 325ms | 273ms
`1C` | 16 | 133ms | 160ms | 135ms | 167ms | 200ms | 168ms
`1D` | 28 | 233ms | 280ms | 235ms | 292ms | 350ms | 294ms
`1E` | 32 | 267ms | 320ms | 269ms | 333ms | 400ms | 336ms
`1F` | 30 | 250ms | 300ms | 252ms | 313ms | 375ms | 315ms
-->
<!-- organized by resulting times... more useful! -->
value | raw | NTSC | PAL | Dendy | NTSC 5-step | PAL 5-step | Dendy 5-step
-----:|----:|------:|------:|------:|------------:|-----------:|-------------:
`03` | 2 | 17ms | 20ms | 17ms | 21ms | 25ms | 21ms
`05` | 4 | 33ms | 40ms | 34ms | 42ms | 50ms | 42ms
`07` | 6 | 50ms | 60ms | 50ms | 63ms | 75ms | 63ms
`09` | 8 | 67ms | 80ms | 67ms | 83ms | 100ms | 84ms
`00` | 10 | 83ms | 100ms | 84ms | 104ms | 125ms | 105ms
`0B` | 10 | 83ms | 100ms | 84ms | 104ms | 125ms | 105ms
`0D` | 12 | 100ms | 120ms | 101ms | 125ms | 150ms | 126ms
`10` | 12 | 100ms | 120ms | 101ms | 125ms | 150ms | 126ms
`0C` | 14 | 117ms | 140ms | 118ms | 146ms | 175ms | 147ms
`0F` | 14 | 117ms | 140ms | 118ms | 145ms | 175ms | 147ms
`1C` | 16 | 133ms | 160ms | 135ms | 167ms | 200ms | 168ms
`11` | 16 | 133ms | 160ms | 135ms | 167ms | 200ms | 168ms
`13` | 18 | 150ms | 180ms | 151ms | 188ms | 225ms | 189ms
`02` | 20 | 166ms | 200ms | 168ms | 208ms | 250ms | 210ms
`15` | 20 | 167ms | 200ms | 168ms | 208ms | 250ms | 210ms
`17` | 22 | 183ms | 220ms | 185ms | 229ms | 275ms | 231ms
`12` | 24 | 200ms | 240ms | 202ms | 250ms | 300ms | 252ms
`19` | 24 | 200ms | 240ms | 202ms | 250ms | 300ms | 252ms
`0E` | 26 | 217ms | 260ms | 219ms | 271ms | 325ms | 273ms
`1B` | 26 | 217ms | 260ms | 219ms | 271ms | 325ms | 273ms
`1D` | 28 | 233ms | 280ms | 235ms | 292ms | 350ms | 294ms
`1F` | 30 | 250ms | 300ms | 252ms | 313ms | 375ms | 315ms
`1E` | 32 | 267ms | 320ms | 269ms | 333ms | 400ms | 336ms
`04` | 40 | 333ms | 400ms | 336ms | 417ms | 500ms | 421ms
`14` | 48 | 400ms | 480ms | 404ms | 500ms | 600ms | 505ms
`0A` | 60 | 500ms | 600ms | 505ms | 625ms | 750ms | 631ms
`1A` | 72 | 600ms | 720ms | 606ms | 750ms | 900ms | 757ms
`06` | 80 | 667ms | 800ms | 673ms | 833ms | 1.0s | 841ms
`16` | 96 | 800ms | 960ms | 807ms | 1.0s | 1.2s | 1.0s
`08` | 160 | 1.3s | 1.6s | 1.3s | 1.7s | 2.0s | 1.7s
`18` | 192 | 1.6s | 1.9s | 1.6s | 2.0s | 2.4s | 2.0s
`01` | 254 | 2.1s | 2.5s | 2.1s | 2.6s | 3.2s | 2.7s
reference: [NESdev](https://www.nesdev.org/wiki/APU_Length_Counter)
## DPCM frequency table
value | NTSC | PAL
------|----------:|----------:
`00` | 4181.7Hz | 4177.4Hz
`01` | 4709.9Hz | 4696.6Hz
`02` | 5264.0Hz | 5261.4Hz
`03` | 5593.0Hz | 5579.2Hz
`04` | 6257.9Hz | 6023.9Hz
`05` | 7046.3Hz | 7044.9Hz
`06` | 7919.3Hz | 7917.2Hz
`07` | 8363.4Hz | 8397.0Hz
`08` | 9419.9Hz | 9446.6Hz
`09` | 11186.1Hz | 11233.8Hz
`0A` | 12604.0Hz | 12595.5Hz
`0B` | 13982.6Hz | 14089.9Hz
`0C` | 16884.6Hz | 16965.4Hz
`0D` | 21306.8Hz | 21315.5Hz
`0E` | 24858.0Hz | 25191.0Hz
`0F` | 33143.9Hz | 33252.1Hz
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