Major work

src/apu.rs

@@ -46,13 +46,20 @@ struct DeltaChannel {
     enabled: bool,
 }
 
+struct FrameCounter {
+    count: usize,
+    mode_5_step: bool,
+    interrupt_enabled: bool,
+    irq: bool,
+}
+
 pub struct APU {
     pulse_1: PulseChannel,
     pulse_2: PulseChannel,
     triangle: TriangleChannel,
     noise: NoiseChannel,
     dmc: DeltaChannel,
-    frame_counter: u8,
+    frame_counter: FrameCounter,
 }
 
 impl std::fmt::Debug for APU {
@@ -74,7 +81,12 @@ impl APU {
             triangle: TriangleChannel { enabled: false },
             noise: NoiseChannel { enabled: false },
             dmc: DeltaChannel { enabled: false },
-            frame_counter: 0,
+            frame_counter: FrameCounter {
+                mode_5_step: false,
+                interrupt_enabled: true,
+                count: 0,
+                irq: false,
+            },
         }
     }
     pub fn read_reg(&mut self, offset: u16) -> u8 {
@@ -98,11 +110,28 @@ impl APU {
             0x11 => {
                 // TODO: load dmc counter with (val & 7F)
             }
-            _ => panic!("No register at {:X}", offset),
+            _ => (),
+            // _ => panic!("No register at {:X}", offset),
         }
     }
 
-    pub fn run_one_clock_cycle(&mut self) -> bool {
+    pub fn run_one_clock_cycle(&mut self, ppu_cycle: usize) -> bool {
+        if ppu_cycle % 6 == 1 {
+            // APU Frame Counter clock cycle
+            if !self.frame_counter.mode_5_step
+                && self.frame_counter.interrupt_enabled
+                && self.frame_counter.count == 14914
+            {
+                self.frame_counter.irq = true;
+            } else if !self.frame_counter.mode_5_step
+                && self.frame_counter.interrupt_enabled
+                && self.frame_counter.count == 14915
+            {
+                self.frame_counter.irq = true;
+                self.frame_counter.count = 0;
+            }
+            self.frame_counter.count += 1;
+        }
         false
     }
     pub fn peek_nmi(&self) -> bool {
@@ -112,10 +141,11 @@ impl APU {
         false
     }
     pub fn peek_irq(&self) -> bool {
-        false
+        self.frame_counter.irq
     }
     pub fn irq_waiting(&mut self) -> bool {
-        // TODO: implement logic
-        false
+        let res = self.frame_counter.irq;
+        self.frame_counter.irq = false;
+        res
     }
 }