Merge pull request #2 from nick-less/master

IRQ handling

include/Cpu65816.hpp

@@ -45,6 +45,10 @@ class Cpu65816 {
         void setRESPin(bool);
         void setRDYPin(bool);
 
+        void setIRQPin(bool value) { mPins.IRQ = value;}
+        void setNMIPin(bool value) { mPins.NMI = value;}
+        void setABORTPin(bool value) { mPins.ABORT = value;}
+
         // Temporary
         bool executeNextInstruction();
         void setXL(uint8_t x);
@@ -78,10 +82,18 @@ class Cpu65816 {
         uint16_t mD = 0;
 
         struct {
-            // Reset to true means low power mode (do nothing)
+            // Reset to true means low power mode (do nothing) (should jump indirect via 0x00FFFC)
             bool RES = true;
             // Ready to false means CPU is waiting for an NMI/IRQ/ABORT/RESET
             bool RDY = false;
+
+            // nmi true execute nmi vector (0x00FFEA)
+            bool NMI = false;
+            // irq true exucute irq vector (0x00FFEE)
+            bool IRQ = false;
+            // abort true execute abort vector (0x00FFE8)
+            bool ABORT = false;
+
         } mPins;
 
         Stack mStack;

src/Cpu65816.cpp

@@ -98,11 +98,33 @@ bool Cpu65816::executeNextInstruction() {
     if (mPins.RES) {
         return false;
     }
+    if ((mPins.IRQ) && (!mCpuStatus.interruptDisableFlag())) {
+        /*
+        The program bank register (PB, the A16-A23 part of the address bus) is pushed onto the hardware stack (65C816/65C802 only when operating in native mode).
+        The most significant byte (MSB) of the program counter (PC) is pushed onto the stack.
+        The least significant byte (LSB) of the program counter is pushed onto the stack.
+        The status register (SR) is pushed onto the stack.
+        The interrupt disable flag is set in the status register.
+        PB is loaded with $00 (65C816/65C802 only when operating in native mode).
+        PC is loaded from the relevant vector (see tables).
+        */
+        if (!mCpuStatus.emulationFlag())  {
+            mStack.push8Bit(mProgramAddress.getBank());
+            mStack.push16Bit(mProgramAddress.getOffset());
+            mStack.push8Bit(mCpuStatus.getRegisterValue());
+            mCpuStatus.setInterruptDisableFlag();
+            mProgramAddress = Address(0x00,mSystemBus.readTwoBytes(Address(0x00,0xFFEE)));
+        } else {
+            mStack.push16Bit(mProgramAddress.getOffset());
+            mStack.push8Bit(mCpuStatus.getRegisterValue());
+            mCpuStatus.setInterruptDisableFlag();
+            mProgramAddress = Address(0x00,mSystemBus.readTwoBytes(Address(0x00,0xFFFE)));
+        }
+    }
 
     // Fetch the instruction
     const uint8_t instruction = mSystemBus.readByte(mProgramAddress);
     OpCode opCode = OP_CODE_TABLE[instruction];
-
     // Execute it
     return opCode.execute(*this);
 }

src/opcodes/OpCode_Interrupt.cpp

@@ -89,6 +89,7 @@ void Cpu65816::executeInterrupt(OpCode &opCode) {
                 mProgramAddress = newProgramAddress;
                 addToCycles(7);
             }
+            break;
         }
         default: {
             LOG_UNEXPECTED_OPCODE(opCode);