h/v counters

snes-core/src/cpu/vectors.rs

@@ -46,7 +46,7 @@ impl CPU {
     }
 
     fn push_emulation_interrupt(&mut self, bus: &mut Bus) {
-        if ! self.registers.emulation_mode {
+        if !self.registers.emulation_mode {
             self.phk(bus);
         }
         self.do_push(bus, &[

snes-core/src/ppu/ppu.rs

@@ -2,6 +2,8 @@ use super::registers::PPURegisters;
 
 pub struct PPU {
     framebuffer: Vec<u8>,
+    h_count: u16,
+    v_count: u16,
     pub registers: PPURegisters,
 }
 
@@ -9,21 +11,58 @@ impl PPU {
     pub fn new() -> Self {
         Self {
             framebuffer: vec![],
+            h_count: 0,
+            v_count: 0,
             registers: PPURegisters::new(),
         }
     }
 
     pub fn tick(&mut self, cpu_cycles: usize) {
-        for _ in 0..cpu_cycles {
-            self.do_cycle();
+        for _ in 0..(cpu_cycles * 2) {
+            self.dot_cycle();
         }
     }
 
-    pub fn do_cycle(&mut self) {
+    pub fn dot_cycle(&mut self) {
+        self.increment_hv_count();
+    }
 
+    fn increment_hv_count(&mut self) {
+        self.h_count += 1;
+        if self.h_count > 339 {
+            self.h_count = 0;
+            self.v_count += 1;
+            if self.v_count > 261 {
+                self.v_count = 0;
+            }
+        }
     }
 
     pub fn framebuffer(&self) -> &Vec<u8> {
         &self.framebuffer
     }
+}
+
+
+#[cfg(test)]
+mod ppu_general_test {
+    use super::*;
+
+    #[test]
+    fn test_increment_hv_count() {
+        let mut ppu = PPU::new();
+        ppu.increment_hv_count();
+        assert_eq!(ppu.h_count, 1);
+
+        ppu.h_count = 339;
+        ppu.increment_hv_count();
+        assert_eq!(ppu.h_count, 0);
+        assert_eq!(ppu.v_count, 1);
+
+        ppu.h_count = 339;
+        ppu.v_count = 261;
+        ppu.increment_hv_count();
+        assert_eq!(ppu.h_count, 0);
+        assert_eq!(ppu.v_count, 0);
+    }
 }

snes-core/src/ppu/registers.rs

@@ -60,6 +60,8 @@ pub const WOBJLOG: u16      = 0x212B;  // Window 2 Mask Logic (W)
 pub const TMW: u16          = 0x212E;  // Window Area Main Screen Disable (W)
 pub const TSW: u16          = 0x212F;  // Window Area Sub Screen Disable (W)
 
+// PPU Interrupts
+pub const RDNMI: u16        = 0x4210;  // V-Blank NMI Flag
 
 pub const MAX_BG_WIDTH: usize  = 16 * 64;
 pub const MAX_BG_HEIGHT: usize = 16 * 64;