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furnace/doc/7-systems/nes.md
Electric Keet f36370b26e Docs updates. 
Moving info around in instrument pages to add descriptions of SSG-EG and CSM! Also, a bunch of other little stuff.
2024-09-06 01:57:01 -05:00

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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 Family Computer (Famicom), especially in Japan.
the console is powered by the Ricoh 2A03, a CPU with sound generator built-in. it has five channels: 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)
- short noise may sound very different depending on its initial LFSR state. more info can be found at [NESdev](https://forums.nesdev.org/viewtopic.php?t=11535).
- `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) and available pitches are limited. see "DPCM samples" below.
- `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.
## info
this chip uses the [NES](../4-instrument/nes.md) instrument editor.
## chip config
the following options are available in the Chip Manager window:
- **Clock rate**: sets the rate at which the chip will run.
- **DPCM channel mode**: allows you to set which mode to use for the DPCM channel.
- DPCM: the default mode, playing 1-bit DPCM samples as supported by the hardware.
- PCM: this mode provides crisper 7-bit samples by writing to the delta counter directly. uses a lot of CPU time in console.
## DPCM samples
due to hardware limitations, a loop in a DPCM sample must start on a multiple of 512 samples (512, 1024, 1536...) and have a length that is a multiple of 128 plus 8 samples (136, 264, 392...)
NES DPCM only has 16 preset sample rates, shown in a table below. for help adapting samples to work with this, see the [limited samples guide](../9-guides/limited-samples.md).
## 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
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 | tracker | NTSC freq | NTSC pitch | PAL freq | PAL pitch
-----:|:-------:|----------:|:----------:|----------:|:----------:
`00` | `C-3` | 4181.7Hz | C-8 - 2¢ | 4177.4Hz | C-8 - 4¢
`01` | `D-3` | 4709.9Hz | D-8 + 4¢ | 4696.6Hz | D-8 - 1¢
`02` | `E-3` | 5264.0Hz | E-8 - 3¢ | 5261.4Hz | E-8 - 4¢
`03` | `F-3` | 5593.0Hz | F-8 + 2¢ | 5579.2Hz | F-8 - 3¢
`04` | `G-3` | 6258.0Hz | G-8 - 4¢ | 6023.9Hz | G-8 - 70¢
`05` | `A-3` | 7046.4Hz | A-8 + 2¢ | 7044.9Hz | A-8 + 1¢
`06` | `B-3` | 7919.4Hz | B-8 + 4¢ | 7917.2Hz | B-8 + 3¢
`07` | `C-4` | 8363.4Hz | C-9 - 2¢ | 8397.0Hz | C-9 + 5¢
`08` | `D-4` | 9419.9Hz | D-9 + 4¢ | 9446.6Hz | D-9 + 9¢
`09` | `F-4` | 11186.1Hz | F-9 + 2¢ | 11233.8Hz | F-9 + 9¢
`0A` | `G-4` | 12604.0Hz | G-9 + 8¢ | 12595.5Hz | G-9 + 7¢
`0B` | `A-4` | 13982.6Hz | A-9 - 12¢ | 14089.9Hz | A-9 + 1¢
`0C` | `C-5` | 16884.6Hz | C-10 + 15¢ | 16965.4Hz | C-10 + 23¢
`0D` | `E-5` | 21306.8Hz | E-10 + 17¢ | 21315.5Hz | E-10 + 18¢
`0E` | `G-5` | 24858.0Hz | G-10 - 16¢ | 25191.0Hz | G-10 + 7¢
`0F` | `C-6` | 33143.9Hz | C-11 - 18¢ | 33252.1Hz | C-11 - 12¢
reference: [NESdev](https://www.nesdev.org/wiki/APU_DMC#Pitch_table)
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