From b1a2222b559bd1973ffc8d5ea02f14abf3e12bca Mon Sep 17 00:00:00 2001
From: AnonymusRaccoon <tr.tristan-roux@outlook.fr>
Date: Wed, 12 Feb 2020 16:51:13 +0100
Subject: [PATCH] Adding the RTI

---
 sources/CPU/CPU.cpp                     |  2 ++
 sources/CPU/CPU.hpp                     |  3 +++
 sources/CPU/Instructions/Interrupts.cpp | 12 ++++++++++++
 3 files changed, 17 insertions(+)

diff --git a/sources/CPU/CPU.cpp b/sources/CPU/CPU.cpp
index f1c3e4f..aeeefa0 100644
--- a/sources/CPU/CPU.cpp
+++ b/sources/CPU/CPU.cpp
@@ -203,6 +203,8 @@ namespace ComSquare::CPU
 		switch (opcode) {
 		case Instructions::BRK:      return 7 + this->BRK();
 
+		case Instructions::RTI:	     return 6 + this->RTI();
+
 		case Instructions::ADC_IM:   return 2 + this->ADC(this->_getImmediateAddr());
 		case Instructions::ADC_ABS:  return 4 + this->ADC(this->_getAbsoluteAddr());
 		case Instructions::ADC_ABSl: return 5 + this->ADC(this->_getAbsoluteLongAddr());
diff --git a/sources/CPU/CPU.hpp b/sources/CPU/CPU.hpp
index c864ee8..960dbae 100644
--- a/sources/CPU/CPU.hpp
+++ b/sources/CPU/CPU.hpp
@@ -187,6 +187,7 @@ namespace ComSquare::CPU
 	enum Instructions
 	{
 		BRK = 0x00,
+		RTI = 0x40,
 
 		ADC_DPXi = 0x61,
 		ADC_SR = 0x63,
@@ -282,6 +283,8 @@ namespace ComSquare::CPU
 		unsigned RESB();
 		//! @brief Break instruction - Causes a software break. The PC is loaded from a vector table.
 		unsigned BRK();
+		//! @brief Return from Interrupt - Used to return from a interrupt handler.
+		unsigned RTI();
 		//! @brief Add with carry - Adds operand to the Accumulator; adds an additional 1 if carry is set.
 		//! @return The number of extra cycles that this operation took.
 		unsigned ADC(uint24_t valueAddr);
diff --git a/sources/CPU/Instructions/Interrupts.cpp b/sources/CPU/Instructions/Interrupts.cpp
index 8136db9..b175048 100644
--- a/sources/CPU/Instructions/Interrupts.cpp
+++ b/sources/CPU/Instructions/Interrupts.cpp
@@ -35,4 +35,16 @@ namespace ComSquare::CPU
 		this->_registers.p.d = false;
 		return !this->_isEmulationMode;
 	}
+
+	unsigned CPU::RTI()
+	{
+		this->_registers.p.flags = this->pop();
+		this->_registers.pc = this->pop16();
+
+		if (!this->_isEmulationMode) {
+			this->_registers.pbr = this->pop16();
+			return 1;
+		}
+		return 0;
+	}
 }
\ No newline at end of file