From ac95670cfcbb4f708f19668cce648617c1a8a06b Mon Sep 17 00:00:00 2001
From: Adrian Conlon <Adrian.conlon@gmail.com>
Date: Fri, 12 Jan 2018 20:13:35 +0000
Subject: [PATCH] Add support for 6502 pin 38 (SO: set overflow)

Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
---
 M6502/inc/mos6502.h   | 4 ++++
 M6502/src/mos6502.cpp | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/M6502/inc/mos6502.h b/M6502/inc/mos6502.h
index ffc959d..8ac47a6 100644
--- a/M6502/inc/mos6502.h
+++ b/M6502/inc/mos6502.h
@@ -53,6 +53,8 @@ namespace EightBit {
 		uint8_t& S() { return s; }
 		uint8_t& P() { return p; }
 
+		PinLevel& SO() { return m_soLine;  }	// In
+
 	protected:
 		virtual void reset() final;
 
@@ -664,5 +666,7 @@ namespace EightBit {
 
 		std::array<int, 0x100> m_timings;
 		std::array<opcode_decoded_t, 0x100> m_decodedOpcodes;
+
+		PinLevel m_soLine = Low;
 	};
 }
\ No newline at end of file
diff --git a/M6502/src/mos6502.cpp b/M6502/src/mos6502.cpp
index 4406e93..3a9b923 100644
--- a/M6502/src/mos6502.cpp
+++ b/M6502/src/mos6502.cpp
@@ -32,6 +32,8 @@ EightBit::MOS6502::MOS6502(Bus& bus)
 	A() = 0;
 	P() = RF;
 	S() = Mask8;
+
+	raise(SO());
 }
 
 int EightBit::MOS6502::step() {
@@ -39,6 +41,10 @@ int EightBit::MOS6502::step() {
 	auto returned = 0;
 	if (LIKELY(powered())) {
 		ExecutingInstruction.fire(*this);
+		if (UNLIKELY(lowered(SO()))) {
+			P() |= VF;
+			raise(SO());
+		}
 		if (UNLIKELY(lowered(NMI()))) {
 			raise(NMI());
 			interrupt(NMIvector);