Impl vblank irq

1 files changed, 31 insertions, 0 deletions

diff --git a/vdp.cpp b/vdp.cpp
index 74b9f65..e497bdf 100644
--- a/vdp.cpp
+++ b/vdp.cpp
@@ -2,6 +2,7 @@
  */
 
 #include "vdp.hpp"
+#include "musashi-m68k/m68k.h"
 
 #include <cstring>
 #include <cstdio>
@@ -75,6 +76,36 @@ void VDP::Write(const uint32_t offset, const enum bitness bitness, const uint32_
     }
 }
 
+#define MODESET2_DISP_MASK (1)
+#define MODESET2_DISP_SHIFT (6)
+#define MODESET2_DISP_EXTRACT(reg) \
+    (((reg) & (MODESET2_DISP_MASK << MODESET2_DISP_SHIFT)) >> MODESET2_DISP_SHIFT)
+
+#define MODESET2_IE0_MASK (1)
+#define MODESET2_IE0_SHIFT (5)
+#define MODESET2_IE0_EXTRACT(reg) \
+    (((reg) & (MODESET2_IE0_MASK << MODESET2_IE0_SHIFT)) >> MODESET2_IE0_SHIFT)
+
+bool VDP::Scanline()
+{
+    const uint16_t mode_set_2 = _reg[static_cast<size_t>(RegID::kModeSet2)];
+    if (!MODESET2_DISP_EXTRACT(mode_set_2)) {
+        return true;
+    }
+    _lines_counter++;
+    const uint16_t lines_per_screen = _status.pal_mode ? kLinesPerScreenPAL : kLinesPerScreenNTSC;
+    if (_lines_counter >= lines_per_screen) {
+        _lines_counter = 0;
+        if (MODESET2_IE0_EXTRACT(mode_set_2)) {
+            m68k_set_irq(6);
+            _status.vblank = true;
+            return true;
+        }
+    }
+    _status.vblank = false;
+    return false;
+}
+
 void VDP::Reset()
 {
     _status = {};