Better irq timing

drhelius · Sep 11, 2024 · 8e49f07 · 8e49f07
1 parent 39050eb
commit 8e49f07
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Showing 3 changed files with 24 additions and 6 deletions.
diff --git a/src/huc6280.cpp b/src/huc6280.cpp
@@ -80,6 +80,7 @@ void HuC6280::Reset()
     m_clock = 0;
     m_clock_cycles = 0;
     m_last_instruction_cycles = 0;
+    m_checking_irqs = false;
     m_irq1_asserted = false;
     m_irq2_asserted = false;
     m_nmi_requested = false;
@@ -102,7 +103,7 @@ void HuC6280::Reset()
     ClearDisassemblerCallStack();
 }
 
-unsigned int HuC6280::Tick()
+unsigned int HuC6280::TickOPCode()
 {
     m_memory_breakpoint_hit = false;
     m_skip_flag_transfer_clear = false;
@@ -126,6 +127,14 @@ unsigned int HuC6280::Tick()
 
     m_last_instruction_cycles = m_cycles;
 
+    m_checking_irqs = true;
+
+    return m_cycles;
+}
+
+unsigned int HuC6280::TickIRQ()
+{
+    m_cycles = 0;
     bool irq_pending = false;
     u16 irq_pending_low = 0;
     u16 irq_pending_high = 0;
@@ -194,6 +203,8 @@ unsigned int HuC6280::Tick()
         SetFlag(FLAG_INTERRUPT);
     }
 
+    m_checking_irqs = false;
+
     return m_cycles;
 }
 

diff --git a/src/huc6280.h b/src/huc6280.h
@@ -97,7 +97,8 @@ class HuC6280
     void Init(Memory* memory, HuC6270* huc6270);
     void Reset();
     bool Clock();
-    unsigned int Tick();
+    unsigned int TickOPCode();
+    unsigned int TickIRQ();
     void AssertIRQ1(bool asserted);
     void AssertIRQ2(bool asserted);
     void RequestNMI();
@@ -134,8 +135,9 @@ class HuC6280
     u8 m_zn_flags_lut[256];
     unsigned int m_cycles;
     unsigned int m_clock;
-    unsigned int m_clock_cycles;
+    int m_clock_cycles;
     unsigned int m_last_instruction_cycles;
+    bool m_checking_irqs;
     bool m_irq1_asserted;
     bool m_irq2_asserted;
     bool m_nmi_requested;

diff --git a/src/huc6280_inline.h b/src/huc6280_inline.h
@@ -31,8 +31,14 @@ inline bool HuC6280::Clock()
 
     if (m_clock % k_huc6280_speed_divisor[m_speed] == 0)
     {
-        if (m_clock_cycles == 0)
-            m_clock_cycles = Tick();
+        if (m_clock_cycles <= 0)
+        {
+            if (m_checking_irqs)
+                m_clock_cycles += TickIRQ();
+            else
+                m_clock_cycles += TickOPCode();
+        }
+
         m_clock_cycles--;
         instruction_completed = (m_clock_cycles == 0);
     }
@@ -44,7 +50,6 @@ inline bool HuC6280::Clock()
 
 inline void HuC6280::AssertIRQ1(bool asserted)
 {
-    // Debug("IRQ1 asserted: %s", asserted ? "true" : "false");
     m_irq1_asserted = asserted;
     if (m_irq1_asserted)
         SetBit(m_interrupt_request_register, 1);