From 872d2c2766536a372af5d1048bed7514078f9d31 Mon Sep 17 00:00:00 2001
From: Oxore <oxore@protonmail.com>
Date: Mon, 3 Oct 2022 00:31:53 +0300
Subject: Impl vblank irq

---
 emulator.cpp | 20 +++++++++++---------
 vdp.cpp      | 31 +++++++++++++++++++++++++++++++
 vdp.hpp      |  4 ++++
 3 files changed, 46 insertions(+), 9 deletions(-)

diff --git a/emulator.cpp b/emulator.cpp
index b5ad031..de9be02 100644
--- a/emulator.cpp
+++ b/emulator.cpp
@@ -328,8 +328,8 @@ int m68k_irq_ack(int level)
 {
     (void) level;
     // TODO
-    exit_error("IRQ ack");
-    return M68K_INT_ACK_SPURIOUS;
+    printf("IRQ ack\n");
+    return level;
 }
 
 static void make_hex(char* buff, unsigned int pc, unsigned int length)
@@ -480,17 +480,19 @@ int emulator(M68KDebuggingControl& m68k_debug)
                 break;
             }
             if (m68k_debug.IsRunning()) {
-                m68k_execute(10000);
+                do {
+                    m68k_execute(100000);
+                } while(!g_vdp.Scanline());
             }
             if (m68k_debug.HasBreakpoint()) {
                 m68k_debug.SetRunning(false);
                 m68k_debug.ResetPendingBreakpoint();
-                    const auto response =
-                        exchange_ctx.WrapDataToSend("S05");
-                    if (DEBUG_TRACE_GDB_REMOTE)
-                        printf("-> \"%s\"\n", response.c_str());
-                    if (send(conn_fd, &response[0], response.length(), 0) == -1)
-                        perror("Send failed (response)");
+                const auto response =
+                    exchange_ctx.WrapDataToSend("S05");
+                if (DEBUG_TRACE_GDB_REMOTE)
+                    printf("-> \"%s\"\n", response.c_str());
+                if (send(conn_fd, &response[0], response.length(), 0) == -1)
+                    perror("Send failed (response)");
             }
             // TODO turn off O_NONBLOCK and poll instead of sleep, only use
             // nonlock when freerunning
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 = {};
diff --git a/vdp.hpp b/vdp.hpp
index cd93938..9357377 100644
--- a/vdp.hpp
+++ b/vdp.hpp
@@ -13,6 +13,7 @@ class VDP {
         VDP(const uint32_t base_address_a = VDP_START): base_address(base_address_a) {}
         uint32_t Read(uint32_t offset, enum bitness);
         void Write(uint32_t offset, enum bitness, uint32_t value);
+        bool Scanline(); // Returns true if display disabled or vblank happened
         void Reset();
 
         const uint32_t base_address;
@@ -76,9 +77,12 @@ class VDP {
         static constexpr size_t kVRAMSize = 64*1024;
         static constexpr size_t kCRAMSize = 64*2;
         static constexpr size_t kVSRAMSize = 40*2;
+        static constexpr uint16_t kLinesPerScreenNTSC = 262;
+        static constexpr uint16_t kLinesPerScreenPAL = 312;
 
         StatusRegister _status{};
         bool _control_write_second_word{};
+        uint16_t _lines_counter{};
         uint8_t _address_mode{};
         uint16_t _address{};
         uint8_t _reg[kRegistersCount]{};
-- 
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