Fixed STAT interrupt not triggering

velllu · Sep 29, 2024 · 37b3f6c · 37b3f6c
1 parent d97ee4c
commit 37b3f6c
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Showing 2 changed files with 31 additions and 26 deletions.
diff --git a/src/gpu/blanks.rs b/src/gpu/blanks.rs
@@ -2,7 +2,7 @@ use crate::{
     common::Bit,
     consts::{
         cpu::IF,
-        gpu::{LY, LYC, STAT},
+        gpu::{LYC, STAT},
     },
     GameBoy,
 };
@@ -11,24 +11,32 @@ use super::GpuState;
 
 impl GameBoy {
     pub(super) fn hblank(&mut self) {
+        if self.gpu.ticks == 0 {
+            self.gpu.x = 0;
+            self.gpu.y += 1;
+            self.gpu.fifo.clear();
+
+            self.layers
+                .iter_mut()
+                .for_each(|layer| layer.at_hblank(&self.bus, &self.gpu));
+        }
+
         // Setting interrupts
         if self.gpu.ticks == 0 {
-            let interrupt_flag = self.bus.read(IF);
+            let mut interrupt_flag = self.bus.read(IF);
             let stat = self.bus.read(STAT);
 
             // Stat interrupt. Stat.3 indicates HBlank
             if stat.get_bit(3) {
-                self.bus.write(IF, interrupt_flag | 0b00000010);
+                interrupt_flag |= 0b00000010;
             }
-        }
 
-        if self.gpu.ticks == 0 {
-            self.gpu.x = 0;
-            self.gpu.fifo.clear();
+            // Stat interrupt. We need to check for LYC == LY
+            if stat.get_bit(6) && self.gpu.y == self.bus.read(LYC) {
+                interrupt_flag |= 0b00000010;
+            }
 
-            self.layers
-                .iter_mut()
-                .for_each(|layer| layer.at_hblank(&self.bus, &self.gpu));
+            self.bus.write(IF, interrupt_flag);
         }
 
         self.switch_when_ticks(
@@ -47,6 +55,17 @@ impl GameBoy {
         /// Amount of ticks needed to render a vblank line
         const VBLANK_LINE_TICKS: u16 = 456;
 
+        if self.gpu.ticks == 0 {
+            self.layers
+                .iter_mut()
+                .for_each(|layer| layer.at_vblank(&self.bus, &self.gpu));
+        }
+
+        // After every line
+        if self.gpu.ticks % VBLANK_LINE_TICKS == 0 {
+            self.gpu.y += 1;
+        }
+
         // Setting interrupts
         if self.gpu.ticks == 0 {
             let mut interrupt_flag = self.bus.read(IF);
@@ -60,25 +79,14 @@ impl GameBoy {
                 interrupt_flag |= 0b00000010;
             }
 
-            // Stat interrupt. We also need to check for LYC == LY
-            if stat.get_bit(6) && self.bus.read(LY) == self.bus.read(LYC) {
+            // Stat interrupt. We need to check for LYC == LY
+            if stat.get_bit(6) && self.gpu.y == self.bus.read(LYC) {
                 interrupt_flag |= 0b00000010;
             }
 
             self.bus.write(IF, interrupt_flag);
         }
 
-        if self.gpu.ticks == 0 {
-            self.layers
-                .iter_mut()
-                .for_each(|layer| layer.at_vblank(&self.bus, &self.gpu));
-        }
-
-        // After every line
-        if self.gpu.ticks % VBLANK_LINE_TICKS == 0 {
-            self.gpu.y += 1;
-        }
-
         // There are 10 lines of vblank
         self.switch_when_ticks(VBLANK_LINE_TICKS * 10, GpuState::OamSearch);
     }

diff --git a/src/gpu/pixel_transfer/mod.rs b/src/gpu/pixel_transfer/mod.rs
@@ -85,8 +85,6 @@ impl GameBoy {
             self.gpu.state = GpuState::HBlank;
             self.gpu.ticks = 0;
             self.gpu.number_of_slices_pushed = 0;
-            self.gpu.x = 0;
-            self.gpu.y += 1;
 
             return;
         }
@@ -102,7 +100,6 @@ impl GameBoy {
                 .for_each(|layer| layer.get_tile_step_1(&self.gpu, &self.bus)),
 
             false => {
-                // TODO: Figure out why this is needed, it's driving me crazy
                 // This is where the X pointer would be if we always pushed 8 pixels at a
                 // time (which happens when SCX is not a multiple of 8)
                 self.gpu.virtual_x = (self.gpu.number_of_slices_pushed - 1) * 8;