diff --git a/src/apu.rs b/src/apu.rs index 5b39157..65eb2ee 100644 --- a/src/apu.rs +++ b/src/apu.rs @@ -5,7 +5,7 @@ use types::ch1::{Sweep, SweepDirection}; use types::ch3::Volume as Ch3Volume; use types::ch4::{CounterWidth, Frequency as Ch4Frequency, PolynomialCounter}; use types::common::{EnvelopeDirection, FrequencyHigh, SoundDuty, VolumeEnvelope}; -use types::{ChannelControl, FrameSequencerState, SoundOutput}; +use types::{ChannelControl, SoundOutput}; pub mod gen; mod types; @@ -26,8 +26,7 @@ pub struct Apu { ch4: Channel4, // Frame Sequencer - frame_seq_state: FrameSequencerState, - div_prev: Option, + div_prev: Option, prod: Option>, sample_counter: u64, @@ -95,41 +94,30 @@ impl BusIo for Apu { impl Apu { pub(crate) fn tick(&mut self, div: u16) { - use FrameSequencerState::*; self.sample_counter += SAMPLE_INCREMENT; - // the 5th bit of the high byte - let bit_5 = (div >> 13 & 0x01) as u8; - - if let Some(0x01) = self.div_prev { - if bit_5 == 0x00 { - // Falling Edge, step the Frame Sequencer - self.frame_seq_state.step(); - - match self.frame_seq_state { - Step0Length => self.handle_length(), - Step2LengthAndSweep => { - self.handle_length(); - self.handle_sweep(); - } - Step4Length => self.handle_length(), - Step6LengthAndSweep => { - self.handle_length(); - self.handle_sweep(); - } - Step7VolumeEnvelope => self.handle_volume(), - Step1Nothing | Step3Nothing | Step5Nothing => {} - }; - } + // Length Control (256Hz) + if self.falling_edge(13, div) { + self.handle_length(); } + // Sweep (128Hz) + if self.falling_edge(14, div) { + self.handle_sweep(); + } + + // Volume Envelope (64Hz) + if self.falling_edge(15, div) { + self.handle_volume(); + } + + self.div_prev = Some(div); + self.ch1.clock(); self.ch2.clock(); self.ch3.clock(); self.ch4.clock(); - self.div_prev = Some(bit_5); - if self.sample_counter >= SM83_CLOCK_SPEED { self.sample_counter %= SM83_CLOCK_SPEED; @@ -176,7 +164,8 @@ impl Apu { if self.ctrl.enabled { // Frame Sequencer reset to Step 0 - self.frame_seq_state = Default::default(); + // TODO: With the current implementation of the frame sequencer, + // what does this even mean? // Square Duty units are reset to first step self.ch1.duty_pos = 0; @@ -338,6 +327,13 @@ impl Apu { &mut self.ch4.current_volume, ); } + + fn falling_edge(&self, bit: u8, div: u16) -> bool { + match self.div_prev { + Some(p) => (p >> bit & 0x01) == 0x01 && (div >> bit & 0x01) == 0x00, + None => false, + } + } } #[derive(Debug, Default)] diff --git a/src/apu/types.rs b/src/apu/types.rs index f8a69b9..4bbc289 100644 --- a/src/apu/types.rs +++ b/src/apu/types.rs @@ -427,41 +427,6 @@ pub(crate) mod common { } } -#[derive(Debug, Clone, Copy)] -pub(crate) enum FrameSequencerState { - Step0Length, - Step1Nothing, - Step2LengthAndSweep, - Step3Nothing, - Step4Length, - Step5Nothing, - Step6LengthAndSweep, - Step7VolumeEnvelope, -} - -impl FrameSequencerState { - pub(crate) fn step(&mut self) { - use FrameSequencerState::*; - - *self = match *self { - Step0Length => Step1Nothing, - Step1Nothing => Step2LengthAndSweep, - Step2LengthAndSweep => Step3Nothing, - Step3Nothing => Step4Length, - Step4Length => Step5Nothing, - Step5Nothing => Step6LengthAndSweep, - Step6LengthAndSweep => Step7VolumeEnvelope, - Step7VolumeEnvelope => Step0Length, - }; - } -} - -impl Default for FrameSequencerState { - fn default() -> Self { - Self::Step0Length - } -} - bitfield! { pub struct SoundOutput(u8); impl Debug;