diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/apu.rs | 131 | ||||
| -rw-r--r-- | src/memory.rs | 3 |
2 files changed, 133 insertions, 1 deletions
@@ -34,6 +34,10 @@ const PULSE_TABLE: [u16; 31] = [ 0x41ec ]; +const NOISE_PERIOD_TABLE: [u16; 16] = [ + 4, 8, 16, 32, 64, 96, 128, 160, 202, 254, 380, 508, 762, 1016, 2034, 4068 +]; + const TND_TABLE: [u16; 203] = [ 0x0000, 0x01b7, 0x036a, 0x051a, 0x06c6, 0x086f, 0x0a15, 0x0bb7, 0x0d56, 0x0ef2, 0x108a, 0x121f, @@ -383,10 +387,125 @@ impl Triangle { } } + +pub struct Noise { + /* envelope */ + env_period: u8, + env_lvl: u8, + decay_lvl: u8, + env_start: bool, + env_loop: bool, + env_const: bool, + env_vol: u8, + /* length counter */ + len_lvl: u8, + /* timer */ + timer_period: u16, + timer_lvl: u16, + /* rng */ + shift_reg: u16, + loop_noise: bool, + /* channel */ + enabled: bool, +} + +impl Noise { + pub fn new() -> Self { + Noise {env_period: 0, env_lvl: 0, decay_lvl: 0, + env_start: false, env_loop: false, env_const: false, env_vol: 0, + len_lvl: 0, timer_period: 0, timer_lvl: 0, + shift_reg: 1, loop_noise: false, + enabled: false} + } + + pub fn write_reg1(&mut self, data: u8) { + self.env_loop = data & 0x20 == 0x20; + self.env_const = data & 0x10 == 0x10; + self.env_period = data & 0xf; + self.env_vol = data & 0xf; + } + + pub fn write_reg3(&mut self, data: u8) { + self.loop_noise = (data >> 7) == 1; + self.timer_period = NOISE_PERIOD_TABLE[data as usize & 0xf]; + } + + pub fn write_reg4(&mut self, data: u8) { + self.set_len(data >> 3); + self.env_start = true; + } + + pub fn output(&self) -> u8 { + let env = if self.env_const { self.env_vol } else { self.decay_lvl }; + let len = self.len_lvl > 0; + let shift = self.shift_reg & 1 == 0; + if self.enabled && shift && len { env } else { 0 } + } + + fn tick_env(&mut self) { + if !self.env_start { + if self.env_lvl == 0 { + self.env_lvl = self.env_period; + if self.decay_lvl == 0 { + if self.env_loop { + self.decay_lvl = 0xf; + } + } else { + self.decay_lvl -= 1; + } + } else { + self.env_lvl -= 1; + } + } else { + self.decay_lvl = 0xf; + self.env_start = false; + self.env_lvl = self.env_period; + } + } + + fn tick_length(&mut self) { + if self.len_lvl > 0 && !self.env_loop { + self.len_lvl -= 1 + } + } + + fn tick_timer(&mut self) { + if self.timer_lvl == 0 { + self.timer_lvl = self.timer_period; + /* shift register is clocked */ + let bit = if self.loop_noise {6} else {1}; + let feedback = (self.shift_reg & 1) ^ ((self.shift_reg >> bit) & 1); + self.shift_reg = (self.shift_reg >> 1) | (feedback << 14); + } else { + self.timer_lvl -= 1 + } + } + + #[inline(always)] + fn disable(&mut self) { + self.len_lvl = 0; + self.enabled = false; + } + + #[inline(always)] + fn enable(&mut self) { self.enabled = true } + + #[inline(always)] fn get_len(&self) -> u8 { self.len_lvl } + + #[inline(always)] + fn set_len(&mut self, d: u8) { + if self.enabled { + self.len_lvl = LEN_TABLE[d as usize] + } + } +} + + pub struct APU<'a> { pub pulse1: Pulse, pub pulse2: Pulse, pub triangle: Triangle, + pub noise: Noise, frame_lvl: u8, frame_mode: bool, /* true for 5-step mode */ frame_inh: bool, @@ -402,6 +521,7 @@ impl<'a> APU<'a> { APU { pulse1: Pulse::new(false), pulse2: Pulse::new(true), triangle: Triangle::new(), + noise: Noise::new(), frame_lvl: 0, frame_mode: false, frame_int: false, frame_inh: false, cpu_sampler: Sampler::new(mos6502::CPU_FREQ, CPU_SAMPLE_FREQ), audio_sampler: Sampler::new(mos6502::CPU_FREQ, AUDIO_SAMPLE_FREQ), @@ -427,7 +547,8 @@ impl<'a> APU<'a> { pub fn output(&self) -> u16 { let pulse_out = PULSE_TABLE[(self.pulse1.output() + self.pulse2.output()) as usize]; - let tnd_out = TND_TABLE[(self.triangle.output() * 3) as usize]; + let tnd_out = TND_TABLE[(self.triangle.output() * 3 + + self.noise.output() * 2) as usize]; pulse_out + tnd_out } @@ -435,6 +556,7 @@ impl<'a> APU<'a> { let res = if self.pulse1.get_len() > 0 { 1 } else { 0 } | (if self.pulse2.get_len() > 0 { 1 } else { 0 }) << 1 | (if self.triangle.get_len() > 0 { 1 } else { 0 }) << 2 | + (if self.noise.get_len() > 0 { 1 } else { 0 }) << 3 | (if self.frame_int { 1 } else { 0 }) << 6; if self.frame_lvl != 3 { self.frame_int = false; /* clear interrupt flag */ @@ -455,6 +577,10 @@ impl<'a> APU<'a> { 0 => self.triangle.disable(), _ => self.triangle.enable() } + match data & 0x8 { + 0 => self.noise.disable(), + _ => self.noise.enable() + } } pub fn write_frame_counter(&mut self, data: u8) { @@ -469,6 +595,7 @@ impl<'a> APU<'a> { if self.cycle_even { self.pulse1.tick_timer(); self.pulse2.tick_timer(); + self.noise.tick_timer(); } self.triangle.tick_timer(); } @@ -477,6 +604,7 @@ impl<'a> APU<'a> { self.pulse1.tick_env(); self.pulse2.tick_env(); self.triangle.tick_counter(); + self.noise.tick_env(); } fn tick_len_swp(&mut self) { @@ -485,6 +613,7 @@ impl<'a> APU<'a> { self.pulse2.tick_length(); self.pulse2.tick_sweep(); self.triangle.tick_length(); + self.noise.tick_length(); } fn tick_frame_counter(&mut self) -> bool { diff --git a/src/memory.rs b/src/memory.rs index db7b200..6eb796f 100644 --- a/src/memory.rs +++ b/src/memory.rs @@ -146,6 +146,9 @@ impl<'a> CPUMemory<'a> { 0x4008 => apu.triangle.write_reg1(data), 0x400a => apu.triangle.write_reg3(data), 0x400b => apu.triangle.write_reg4(data), + 0x400c => apu.noise.write_reg1(data), + 0x400e => apu.noise.write_reg3(data), + 0x400f => apu.noise.write_reg4(data), 0x4015 => apu.write_status(data), 0x4017 => apu.write_frame_counter(data), 0x4014 => ppu.write_oamdma(data, cpu), |