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CPU Dummy Reads - Fixes Cobra Triangle and Ironsword

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This commit is contained in:
Souryo 2014-06-28 15:48:30 -04:00
parent 5caf188286
commit 8187539fcb
1 changed files with 38 additions and 26 deletions
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64
Core/CPU.h
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@ -97,14 +97,16 @@ private:
}
}
bool IsPageCrossed(uint16_t valA, int8_t valB)
bool CheckPageCrossed(uint16_t valA, int8_t valB)
{
return ((valA + valB) & 0xFF00) != (valA & 0xFF00);
_pageCrossed = ((valA + valB) & 0xFF00) != (valA & 0xFF00);
return _pageCrossed;
}
bool IsPageCrossed(uint16_t valA, uint8_t valB)
bool CheckPageCrossed(uint16_t valA, uint8_t valB)
{
return ((valA + valB) & 0xFF00) != (valA & 0xFF00);
_pageCrossed = ((valA + valB) & 0xFF00) != (valA & 0xFF00);
return _pageCrossed;
}
void MemoryWrite(uint16_t addr, uint8_t value)
@ -174,20 +176,26 @@ private:
uint8_t GetAbs() { return MemoryRead(GetAbsAddr()); }
uint16_t GetAbsAddr() { return ReadWord(); }
uint8_t GetAbsX() { return MemoryRead(GetAbsXAddr()); }
uint16_t GetAbsXAddr() {
uint8_t GetAbsX() { return MemoryRead(GetAbsXAddr(false)); }
uint16_t GetAbsXAddr(bool dummyRead = true) {
uint16_t baseAddr = ReadWord();
if(IsPageCrossed(baseAddr, X())) {
SetPageCrossed();
bool pageCrossed = CheckPageCrossed(baseAddr, X());
if(pageCrossed || dummyRead) {
//Dummy read done by the processor (only when page is crossed for READ instructions)
MemoryRead(baseAddr + X() - (pageCrossed ? 0x100 : 0));
}
return baseAddr + X();
}
uint8_t GetAbsY() { return MemoryRead(GetAbsYAddr()); }
uint16_t GetAbsYAddr() {
uint8_t GetAbsY() { return MemoryRead(GetAbsYAddr(false)); }
uint16_t GetAbsYAddr(bool dummyRead = true) {
uint16_t baseAddr = ReadWord();
if(IsPageCrossed(baseAddr, Y())) {
SetPageCrossed();
bool pageCrossed = CheckPageCrossed(baseAddr, Y());
if(pageCrossed || dummyRead) {
//Dummy read done by the processor (only when page is crossed for READ instructions)
MemoryRead(baseAddr + Y() - (pageCrossed ? 0x100 : 0));
}
return baseAddr + Y();
@ -206,27 +214,37 @@ private:
uint8_t GetIndX() { return MemoryRead(GetIndXAddr()); }
uint16_t GetIndXAddr() {
uint8_t zero = ReadByte() + X();
uint8_t zero = ReadByte();
//Dummy read
MemoryRead(zero);
zero += X();
uint16_t addr;
if(zero == 0xFF) {
addr = MemoryRead(0xFF) | MemoryReadWord(0x00) << 8;
addr = MemoryRead(0xFF) | MemoryRead(0x00) << 8;
} else {
addr = MemoryReadWord(zero);
}
return addr;
}
uint8_t GetIndY() { return MemoryRead(GetIndYAddr()); }
uint16_t GetIndYAddr() {
uint8_t GetIndY() { return MemoryRead(GetIndYAddr(false)); }
uint16_t GetIndYAddr(bool dummyRead = true) {
uint8_t zero = ReadByte();
uint16_t addr;
if(zero == 0xFF) {
addr = MemoryRead(0xFF) | MemoryReadWord(0x00) << 8;
addr = MemoryRead(0xFF) | MemoryRead(0x00) << 8;
} else {
addr = MemoryReadWord(zero);
}
if(IsPageCrossed(addr, Y())) {
SetPageCrossed();
bool pageCrossed = CheckPageCrossed(addr, Y());
if(pageCrossed || dummyRead) {
//Dummy read done by the processor (only when page is crossed for READ instructions)
MemoryRead(addr + Y() - (pageCrossed ? 0x100 : 0));
}
return addr + Y();
}
@ -360,9 +378,7 @@ private:
void BranchRelative(bool branch) {
int8_t offset = GetImmediate();
if(branch) {
if(IsPageCrossed(PC(), offset)) {
SetPageCrossed();
}
CheckPageCrossed(PC(), offset);
IncCycleCount(1);
SetPC(PC() + offset);
@ -382,10 +398,6 @@ private:
}
}
void SetPageCrossed() {
_pageCrossed = true;
}
bool IsPageCrossed() {
bool pageCrossed = _pageCrossed;
_pageCrossed = false;