feat(apu): add timer/sequencer/LFSR fields for channel output tracking

src/native_core/apu/api.rs

@@ -34,6 +34,12 @@ impl Apu {
             frame_reset_delay: 0,
             pending_frame_mode_5step: false,
             pending_frame_irq_inhibit: false,
+            pulse_timer_counter: [0; 2],
+            pulse_duty_step: [0; 2],
+            triangle_timer_counter: 0,
+            triangle_step: 0,
+            noise_timer_counter: 0,
+            noise_lfsr: 1, // LFSR initialized to 1 per NES hardware
         }
     }
 
@@ -227,6 +233,13 @@ impl Apu {
         out.push(self.frame_reset_delay);
         out.push(u8::from(self.pending_frame_mode_5step));
         out.push(u8::from(self.pending_frame_irq_inhibit));
+        out.extend_from_slice(&self.pulse_timer_counter[0].to_le_bytes());
+        out.extend_from_slice(&self.pulse_timer_counter[1].to_le_bytes());
+        out.extend_from_slice(&self.pulse_duty_step);
+        out.extend_from_slice(&self.triangle_timer_counter.to_le_bytes());
+        out.push(self.triangle_step);
+        out.extend_from_slice(&self.noise_timer_counter.to_le_bytes());
+        out.extend_from_slice(&self.noise_lfsr.to_le_bytes());
     }
 
     pub fn load_state_tail(&mut self, state: ApuStateTail) {
@@ -260,5 +273,11 @@ impl Apu {
         self.frame_reset_delay = state.frame_reset_delay;
         self.pending_frame_mode_5step = state.pending_frame_mode_5step;
         self.pending_frame_irq_inhibit = state.pending_frame_irq_inhibit;
+        self.pulse_timer_counter = state.pulse_timer_counter;
+        self.pulse_duty_step = [state.pulse_duty_step[0] & 0x07, state.pulse_duty_step[1] & 0x07];
+        self.triangle_timer_counter = state.triangle_timer_counter;
+        self.triangle_step = state.triangle_step & 0x1F;
+        self.noise_timer_counter = state.noise_timer_counter;
+        self.noise_lfsr = if state.noise_lfsr == 0 { 1 } else { state.noise_lfsr };
     }
 }

src/native_core/apu/types.rs

@@ -48,6 +48,15 @@ pub struct Apu {
     pub(crate) frame_reset_delay: u8,
     pub(crate) pending_frame_mode_5step: bool,
     pub(crate) pending_frame_irq_inhibit: bool,
+    // Pulse channel timers & duty sequencers
+    pub(crate) pulse_timer_counter: [u16; 2],
+    pub(crate) pulse_duty_step: [u8; 2],
+    // Triangle channel timer & sequencer
+    pub(crate) triangle_timer_counter: u16,
+    pub(crate) triangle_step: u8,
+    // Noise channel timer & LFSR
+    pub(crate) noise_timer_counter: u16,
+    pub(crate) noise_lfsr: u16,
 }
 
 pub struct ApuStateTail {
@@ -81,6 +90,12 @@ pub struct ApuStateTail {
     pub frame_reset_delay: u8,
     pub pending_frame_mode_5step: bool,
     pub pending_frame_irq_inhibit: bool,
+    pub pulse_timer_counter: [u16; 2],
+    pub pulse_duty_step: [u8; 2],
+    pub triangle_timer_counter: u16,
+    pub triangle_step: u8,
+    pub noise_timer_counter: u16,
+    pub noise_lfsr: u16,
 }
 
 impl Default for Apu {

src/native_core/bus/state.rs

@@ -112,6 +112,31 @@ impl NativeBus {
         let frame_reset_delay = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
         let pending_frame_mode_5step = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
         let pending_frame_irq_inhibit = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
+        let pulse_timer_counter = [
+            u16::from_le_bytes([
+                sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+                sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+            ]),
+            u16::from_le_bytes([
+                sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+                sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+            ]),
+        ];
+        let mut pulse_duty_step = [0u8; 2];
+        pulse_duty_step.copy_from_slice(sio::take_exact(data, &mut cursor, 2, BUS_STATE_CTX)?);
+        let triangle_timer_counter = u16::from_le_bytes([
+            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+        ]);
+        let triangle_step = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
+        let noise_timer_counter = u16::from_le_bytes([
+            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+        ]);
+        let noise_lfsr = u16::from_le_bytes([
+            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
+        ]);
         self.apu.load_state_tail(ApuStateTail {
             frame_cycle,
             frame_mode_5step,
@@ -143,6 +168,12 @@ impl NativeBus {
             frame_reset_delay,
             pending_frame_mode_5step,
             pending_frame_irq_inhibit,
+            pulse_timer_counter,
+            pulse_duty_step,
+            triangle_timer_counter,
+            triangle_step,
+            noise_timer_counter,
+            noise_lfsr,
         });
         let mapper_len = sio::take_u32(data, &mut cursor, BUS_STATE_CTX)? as usize;
         let mapper_state = sio::take_exact(data, &mut cursor, mapper_len, BUS_STATE_CTX)?;

src/runtime/constants.rs

@@ -1,6 +1,6 @@
 pub const FRAME_WIDTH: usize = 256;
 pub const FRAME_HEIGHT: usize = 240;
 pub const FRAME_RGBA_BYTES: usize = FRAME_WIDTH * FRAME_HEIGHT * 4;
-pub const SAVE_STATE_VERSION: u32 = 1;
+pub const SAVE_STATE_VERSION: u32 = 2;
 
 pub(crate) const SAVE_STATE_MAGIC: &[u8; 8] = b"NESRT001";