ppu can trigger NMIs

README.md

@@ -11,7 +11,7 @@ Usage:
 ```
 Make sure to compile with `--release` for 60 fps.
 
-![Screenshot](https://i.imgur.com/1TMHZrs.png)
+![Screenshot](https://i.imgur.com/4s4cDWHl.png)
 
 ### what works
 * CPU

src/main.rs

@@ -110,7 +110,7 @@ fn main() -> Result<(), Error> {
     }).collect();
     
     // Main loop
-    let mut run = true;
+    let mut run = false;
     while let Some(event) = events.next(&mut window) {
         if let Some(_) = event.render_args() {
             // Run enough clocks to render the next frame
@@ -121,8 +121,8 @@ fn main() -> Result<(), Error> {
                 let mut ppu = nes.ppu.borrow_mut();
                 let ppu_bus = nes.ppu_bus.borrow();
                 // main_texture.update(&mut texture_ctx, &ppu.canvas_main).unwrap();
-                pattern_table_textures[0].update(&mut texture_ctx, &ppu.get_pattern_table(&*ppu_bus, 0, 1)).unwrap();
-                pattern_table_textures[1].update(&mut texture_ctx, &ppu.get_pattern_table(&*ppu_bus, 1, 1)).unwrap();
+                pattern_table_textures[0].update(&mut texture_ctx, &ppu.get_pattern_table(&*ppu_bus, 0, 0)).unwrap();
+                pattern_table_textures[1].update(&mut texture_ctx, &ppu.get_pattern_table(&*ppu_bus, 1, 0)).unwrap();
                 palette_textures[0].update(&mut texture_ctx, &ppu.get_palette(&*ppu_bus, 0)).unwrap();
                 palette_textures[1].update(&mut texture_ctx, &ppu.get_palette(&*ppu_bus, 1)).unwrap();
                 palette_textures[2].update(&mut texture_ctx, &ppu.get_palette(&*ppu_bus, 2)).unwrap();
@@ -249,6 +249,13 @@ fn render_cpu(glyphs: &mut GlyphBrush<Resources, Factory>, cpu: &CPU, offset: [f
                 cpu.is_flag_set(Flags::CARRY) 
             ],
             offset);
+        glyphs.queue(Section {
+            text: &format!("({:#04x})", cpu.regs.flags.bits()),
+            scale: *FT_SCALE,
+            screen_position: (offset[0]+200.0, offset[1]+FT_SIZE_PX) ,
+            color: FT_COLOR_WHITE,
+            ..Section::default()
+        });
 
         let cpu_register_texts = [
             &format!("A: {0:#x} ({0})", cpu.regs.a),

src/nes.rs

@@ -74,7 +74,13 @@ impl NES {
         if self.clock_count % 3 == 0 {
             self.cpu.clock(&mut self.bus);
         }
-        self.ppu.borrow_mut().clock(&mut *self.ppu_bus.borrow_mut());
+        let mut ppu = self.ppu.borrow_mut();
+        ppu.clock(&mut *self.ppu_bus.borrow_mut());
+        if ppu.nmi {
+            ppu.nmi = false;
+            self.cpu.nmi(&mut self.bus);
+            debug!("NMI triggered by PPU.")
+        }
         if self.clock_count % 100000 == 0 {
             info!("clock {}", self.clock_count);
         }

src/nes/cpu.rs

@@ -123,6 +123,41 @@ impl CPU {
         self.curr_op = 0x00;
     }
 
+    fn interrupt<T: Memory>(&mut self, mem: &mut T, pc_addr: Addr) {
+        // push pc to stack
+        self.pushb_sp(mem, (self.regs.pc >> 8) as Byte);
+        self.pushb_sp(mem, self.regs.pc as Byte);
+
+        // push status reg with set interrupt flags to stack
+        self.set_flag(Flags::BREAK, false);
+        self.set_flag(Flags::UNUSED, true);
+        self.set_flag(Flags::IRQ, true);
+        self.pushb_sp(mem, self.regs.flags.bits());
+
+        // read new pc
+        let lo = mem.readb(pc_addr);
+        let hi = mem.readb(pc_addr + 1);
+        self.regs.pc = ((hi as Addr) << 8) | lo as Addr;
+    }
+
+    // Non maskable interrupt
+    pub fn nmi<T: Memory>(&mut self, mem: &mut T) {
+        let new_pc_addr = 0xFFFA;
+        self.interrupt(mem, new_pc_addr);
+        self.cycles_ahead = 8;
+    }
+
+    // Interrupt request: Same as nmi, but only takes place if interrupts are
+    // allowed
+    pub fn irq<T: Memory>(&mut self, mem: &mut T) {
+        if self.is_flag_set(Flags::IRQ) {
+            let new_pc_addr = 0xFFFE;
+            self.interrupt(mem, new_pc_addr);
+            self.cycles_ahead = 7;
+        }; 
+    }
+
+
     // True if the operation is not finished yet
     pub fn is_ahead(&self) -> bool {
         return self.cycles_ahead > 0;

src/nes/ppu.rs

@@ -98,10 +98,11 @@ pub struct PPU {
     pub regs: Registers,
     pub cycle: u16, 
     pub scanline: u16,
+    pub frame_ready: bool,
+    pub nmi: bool,
     pub canvas_main: Sprite,
     pub pattern_tables: [Sprite; 2],
     pub palettes: [Sprite; 8],
-    pub frame_ready: bool,
     addr_latch_set: bool,
     data_buffer: Byte,
 }
@@ -112,6 +113,8 @@ impl PPU {
             regs: Registers::new(),
             cycle: 0,
             scanline: 0,
+            frame_ready: false,
+            nmi: false,
             canvas_main: ImageBuffer::from_pixel(256, 240, PALETTE[&0x00]),
             pattern_tables: [
                 ImageBuffer::from_pixel(128, 128, PALETTE[&0x00]),
@@ -127,7 +130,6 @@ impl PPU {
                 ImageBuffer::from_pixel(4, 1, PALETTE[&0x00]),
                 ImageBuffer::from_pixel(4, 1, PALETTE[&0x00]),
             ], 
-            frame_ready: false,
             addr_latch_set: false,
             data_buffer: 0
         }
@@ -190,6 +192,9 @@ impl PPU {
         // set/clear vblank flag
         if self.scanline == 241 && self.cycle == 1 {
             self.set_status(Status::VERTICAL_BLANK, true);
+            if self.get_control(Control::ENABLE_NMI) {
+                self.nmi = true;
+            }
 
         } else if self.scanline == 261 && self.cycle == 1 {
             self.set_status(Status::VERTICAL_BLANK, false);
@@ -221,7 +226,7 @@ impl PPU {
                 // palette memory
                 let data = self.data_buffer;
                 self.data_buffer = mem.readb_ppu(addr);
-                
+
                 if addr > 0x3F00 {  // everything above 0x3F00 is palette
                    self.data_buffer 
                 } else {