fix timers

src/processor/gpu.rs

@@ -64,11 +64,10 @@ impl GPU {
 }
 
 impl CPU {
-    pub fn advance_gpu_clock(&mut self, steps: u8) {
+    pub fn advance_gpu_clock(&mut self, steps: usize) {
         let lcdc = self.get_lcdc();
         if lcdc.enable {
-            let real_steps = (steps as usize) * 4;
-            self.gpu.mode_clock += real_steps;
+            self.gpu.mode_clock += steps;
             match self.gpu.mode {
                 DrawMode::HBlank => {
                     // mode 0: hblank

src/processor/mod.rs

@@ -1,15 +1,15 @@
-use self::{gpu::GPU, memory::Memory};
+use self::{gpu::GPU, memory::Memory, timer::Timers};
 use crate::{
     util::{clear_bit, get_bit},
     verbose_println,
 };
 use minifb::Window;
-use std::{mem::transmute, time::Duration};
 
 pub mod gpu;
 mod instructions;
 pub mod memory;
 mod opcodes;
+mod timer;
 
 #[derive(PartialEq)]
 pub(crate) enum Flags {
@@ -32,12 +32,13 @@ pub struct CPU {
     window: Window,
     gpu: GPU,
     halted: bool,
+    timers: Timers,
 }
 
 // Hz
-const CLOCK_SPEED: f64 = 4.194304 * 1000000.;
+const CLOCK_SPEED: usize = 4194304;
 const SPEEDUP: f64 = 1.;
-const FF04_SPEED: f64 = 16384.;
+// const FF04_SPEED: f64 = 16384.;
 
 impl CPU {
     pub fn new(
@@ -57,6 +58,7 @@ impl CPU {
             window,
             gpu: GPU::new(enable_tile_window),
             halted: false,
+            timers: Timers::init(),
         }
     }
 
@@ -91,32 +93,6 @@ impl CPU {
         self.increment_timers(cycles);
     }
 
-    fn increment_timers(&mut self, cycles: u8) {
-        let secs = (cycles * 4) as f64 / CLOCK_SPEED;
-        self.advance_gpu_clock(cycles);
-
-        self.memory.set(
-            0xFF04,
-            self.memory
-                .get(0xFF04)
-                .wrapping_add((FF04_SPEED * secs) as u8),
-        );
-        let (timer_enabled, timer_rate) = self.timer_scale();
-        if timer_enabled {
-            let (val, wrap) = self
-                .memory
-                .get(0xFF05)
-                .overflowing_add((secs * timer_rate as f64) as u8);
-            if wrap {
-                self.memory.set(0xFF05, self.memory.get(0xFF06));
-                self.memory.set(0xFF0F, set(self.memory.get(0xFF0F), 2));
-            } else {
-                self.memory.set(0xFF05, val);
-            }
-        }
-        spin_sleep::sleep(Duration::from_secs_f64(secs / SPEEDUP));
-    }
-
     fn next_opcode(&mut self) -> u8 {
         let opcode = self.memory.get(self.reg.pc);
         self.reg.pc = self.reg.pc.wrapping_add(0x1);
@@ -171,18 +147,6 @@ impl CPU {
         self.reg.pc = addr;
         self.memory.ime = false;
     }
-
-    fn timer_scale(&self) -> (bool, usize) {
-        let timer_control = self.memory.get(0xFF07);
-        let timer_enable = get_bit(timer_control, 2);
-        let timer_rate = match (get_bit(timer_control, 1), get_bit(timer_control, 0)) {
-            (true, true) => 256,
-            (true, false) => 64,
-            (false, true) => 16,
-            (false, false) => 1024,
-        };
-        (timer_enable, timer_rate)
-    }
 }
 
 #[derive(Clone, Copy)]

src/processor/timer.rs

@@ -0,0 +1,63 @@
+use std::time::Duration;
+
+use crate::{
+    processor::{CLOCK_SPEED, CPU, SPEEDUP},
+    util::{get_bit, set_bit},
+};
+
+pub(super) struct Timers {
+    div_counter: usize,
+    tima_counter: usize,
+}
+
+impl Timers {
+    pub(super) fn init() -> Self {
+        Self {
+            div_counter: 0,
+            tima_counter: 0,
+        }
+    }
+}
+
+impl CPU {
+    pub(super) fn increment_timers(&mut self, machine_cycles: u8) {
+        let clock_cycles = (machine_cycles as usize) * 4;
+
+        self.advance_gpu_clock(clock_cycles);
+
+        self.timers.div_counter += clock_cycles;
+        let div_diff = (self.timers.div_counter / 256) as u8;
+        self.timers.div_counter = self.timers.div_counter % 256;
+        self.memory
+            .set(0xFF04, self.memory.get(0xFF04).wrapping_add(div_diff));
+
+        let (timer_enabled, timer_rate) = self.timer_scale();
+        if timer_enabled {
+            self.timers.tima_counter += clock_cycles;
+            let tima_diff = (self.timers.tima_counter / timer_rate) as u8;
+            self.timers.tima_counter = self.timers.tima_counter % timer_rate;
+            let (val, wrap) = self.memory.get(0xFF05).overflowing_add(tima_diff);
+            if wrap {
+                self.memory.set(0xFF05, self.memory.get(0xFF06));
+                self.memory.set(0xFF0F, set_bit(self.memory.get(0xFF0F), 2));
+            } else {
+                self.memory.set(0xFF05, val);
+            }
+        }
+
+        let secs = clock_cycles as f64 / CLOCK_SPEED as f64;
+        spin_sleep::sleep(Duration::from_secs_f64(secs / SPEEDUP));
+    }
+
+    fn timer_scale(&self) -> (bool, usize) {
+        let timer_control = self.memory.get(0xFF07);
+        let timer_enable = get_bit(timer_control, 2);
+        let timer_rate = match (get_bit(timer_control, 1), get_bit(timer_control, 0)) {
+            (true, true) => 256,
+            (true, false) => 64,
+            (false, true) => 16,
+            (false, false) => 1024,
+        };
+        (timer_enable, timer_rate)
+    }
+}