# 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. - this may be used to attenuate the triangle and noise channels. - will not work if a sample is playing. - **`12xx`**: set duty cycle or noise mode of channel. - may be 0-3 for the pulse channels and 0-1 for the noise channel. - **`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; 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. # DPCM frequency table val | 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 # length counter table val | 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 reference: [NESdev](https://www.nesdev.org/wiki/APU_Length_Counter)