cpu/cpu - Handle halt mode

cpu/cpu.cpp

@@ -56,7 +56,10 @@ void Cpu::step()
 {
   if(!handleInterrupts()) // if no isr has been called, decode an instruction
     {
-      executeInstruction();
+      if (halted)
+        processed_mcycles += 4;
+      else
+        executeInstruction();
     }
 }
 
@@ -77,6 +80,8 @@ void Cpu::reset()
   state.IME = IME_OFF;
   state.IE = 0;
   state.IF = 0;
+
+  halted = false;
 }
 
 u8 Cpu::readPC8()
@@ -225,6 +230,10 @@ bool Cpu::handleInterrupts()
   // servicable interrupts (assuming IME is on)
   u8 si = state.IE & state.IF & INT_MASK;
 
+  // Once there's an interrupt we exit halt mode
+  if (si)
+    halted = false;
+
   if (state.IME == IME_SCHEDULED)
     state.IME = IME_ON;
   else if (state.IME == IME_ON && si != 0)

cpu/cpu.h

@@ -91,6 +91,8 @@ struct Cpu_state {
   u8 IE;
   u8 IF;
 
+  bool halted;
+
   void setAF(u16 v);
   u16 getAF();