From b5fee5b5d915c98252b9c452c78cf7827eb5e30d Mon Sep 17 00:00:00 2001
From: Adrian Conlon <Adrian.conlon@gmail.com>
Date: Thu, 18 Jan 2018 21:17:45 +0000
Subject: [PATCH] Make explicit the notion of page based loads in M6502.

Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
---
 M6502/inc/mos6502.h   | 12 ++++++------
 M6502/src/mos6502.cpp | 28 +++++++++++++++++++---------
 2 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/M6502/inc/mos6502.h b/M6502/inc/mos6502.h
index 21f9a5a..937ee81 100644
--- a/M6502/inc/mos6502.h
+++ b/M6502/inc/mos6502.h
@@ -65,7 +65,9 @@ namespace EightBit {
 			adjustNegative(datum);
 		}
 
-		void getWord(uint8_t page, uint8_t offset, register16_t& output);
+		void getWordPaged(uint8_t page, uint8_t offset, register16_t& output);
+		uint8_t getBytePaged(uint8_t page, uint8_t offset);
+		void setBytePaged(uint8_t page, uint8_t offset, uint8_t value);
 
 		virtual void push(uint8_t value) final;
 		virtual uint8_t pop() final;
@@ -83,12 +85,12 @@ namespace EightBit {
 
 		void Address_ZeroPageIndirect() {
 			Address_ZeroPage();
-			getWord(0, MEMPTR().low, MEMPTR());
+			getWordPaged(0, MEMPTR().low, MEMPTR());
 		}
 
 		void Address_Indirect() {
 			Address_Absolute();
-			getWord(MEMPTR().high, MEMPTR().low, MEMPTR());
+			getWordPaged(MEMPTR().high, MEMPTR().low, MEMPTR());
 		}
 
 		void Address_ZeroPageX() {
@@ -117,7 +119,7 @@ namespace EightBit {
 
 		void Address_IndexedIndirectX() {
 			Address_ZeroPageX();
-			getWord(0, MEMPTR().low, MEMPTR());
+			getWordPaged(0, MEMPTR().low, MEMPTR());
 		}
 
 		bool Address_IndirectIndexedY() {
@@ -310,8 +312,6 @@ namespace EightBit {
 		void JMP_ind();
 		void BRK();
 
-		const uint16_t PageOne = 0x100;
-
 		// All interrupt vectors are on the 0xFF page
 		const uint8_t IRQvector = 0xfe;
 		const uint8_t RSTvector = 0xfc;
diff --git a/M6502/src/mos6502.cpp b/M6502/src/mos6502.cpp
index 57984e2..f412089 100644
--- a/M6502/src/mos6502.cpp
+++ b/M6502/src/mos6502.cpp
@@ -47,23 +47,33 @@ int EightBit::MOS6502::step() {
 
 void EightBit::MOS6502::reset() {
 	Processor::reset();
-	getWord(0xff, RSTvector, PC());
+	getWordPaged(0xff, RSTvector, PC());
 }
 
-void EightBit::MOS6502::getWord(uint8_t page, uint8_t offset, register16_t& output) {
-	BUS().ADDRESS().low = offset;
-	BUS().ADDRESS().high = page;
-	output.low = getByte();
+void EightBit::MOS6502::getWordPaged(uint8_t page, uint8_t offset, register16_t& output) {
+	output.low = getBytePaged(page, offset);
 	BUS().ADDRESS().low++;
 	output.high = getByte();
 }
 
+uint8_t EightBit::MOS6502::getBytePaged(uint8_t page, uint8_t offset) {
+	BUS().ADDRESS().low = offset;
+	BUS().ADDRESS().high = page;
+	return getByte();
+}
+
+void EightBit::MOS6502::setBytePaged(uint8_t page, uint8_t offset, uint8_t value) {
+	BUS().ADDRESS().low = offset;
+	BUS().ADDRESS().high = page;
+	setByte(value);
+}
+
 void EightBit::MOS6502::interrupt(uint8_t vector) {
 	raise(HALT());
 	pushWord(PC());
 	push(P());
 	setFlag(P(), IF);
-	getWord(0xff, vector, PC());
+	getWordPaged(0xff, vector, PC());
 }
 
 int EightBit::MOS6502::execute(uint8_t cell) {
@@ -352,11 +362,11 @@ int EightBit::MOS6502::execute(uint8_t cell) {
 ////
 
 void EightBit::MOS6502::push(uint8_t value) {
-	setByte(PageOne + S()--, value);
+	setBytePaged(1, S()--, value);
 }
 
 uint8_t EightBit::MOS6502::pop() {
-	return getByte(PageOne + ++S());
+	return getBytePaged(1, ++S());
 }
 
 ////
@@ -535,5 +545,5 @@ void EightBit::MOS6502::BRK() {
 	pushWord(PC());
 	PHP();
 	setFlag(P(), IF);
-	getWord(0xff, IRQvector, PC());
+	getWordPaged(0xff, IRQvector, PC());
 }