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Swap fixed/unfixed page usage

This commit is contained in:
Adrian Conlon 2024-03-18 21:04:50 +00:00
parent 8b6c4a205e
commit c397b4c41b
2 changed files with 24 additions and 16 deletions
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33
M6502/inc/mos6502.h
View File

@ -105,7 +105,7 @@ namespace EightBit {
// Addressing modes
constexpr void noteUnfixedPage() noexcept { m_unfixed_page = BUS().ADDRESS().high; }
constexpr void noteFixedPage(uint8_t page) noexcept { m_fixed_page = page; }
constexpr void Address_Immediate() noexcept { BUS().ADDRESS() = PC()++; }
void Address_Absolute() noexcept { BUS().ADDRESS() = fetchWord(); }
@ -115,11 +115,23 @@ namespace EightBit {
void Address_ZeroPageWithIndex(uint8_t index) noexcept { AM_ZeroPage(); BUS().ADDRESS().low += index; }
void Address_ZeroPageX() noexcept { Address_ZeroPageWithIndex(X()); }
void Address_ZeroPageY() noexcept { Address_ZeroPageWithIndex(Y()); }
void Address_AbsoluteWithIndex(uint8_t index) noexcept { Address_Absolute(); noteUnfixedPage(); BUS().ADDRESS() += index; }
void Address_AbsoluteX() noexcept { Address_AbsoluteWithIndex(X()); }
void Address_AbsoluteY() noexcept { Address_AbsoluteWithIndex(Y()); }
void Address_IndexedIndirectX() noexcept { Address_ZeroPageX(); BUS().ADDRESS() = getWordPaged(); }
void Address_IndirectIndexedY() noexcept { Address_ZeroPageIndirect(); noteUnfixedPage(); BUS().ADDRESS() += Y(); }
void Address_AbsoluteWithIndex(uint8_t index) noexcept {
Address_Absolute();
const auto address = BUS().ADDRESS() + index;
noteFixedPage(address.high);
BUS().ADDRESS().low = address.low;
}
void Address_IndirectIndexedY() noexcept {
Address_ZeroPageIndirect();
const auto address = BUS().ADDRESS() + Y();
noteFixedPage(address.high);
BUS().ADDRESS().low = address.low;
}
// Addressing modes, with read
@ -184,19 +196,13 @@ namespace EightBit {
}
void maybe_fixup() noexcept {
const auto fixed_page = BUS().ADDRESS().high;
BUS().ADDRESS().high = m_unfixed_page;
if (m_unfixed_page != fixed_page) {
memoryRead();
BUS().ADDRESS().high = fixed_page;
}
if (BUS().ADDRESS().high != m_fixed_page)
fixup();
}
void fixup() noexcept {
const auto fixed_page = BUS().ADDRESS().high;
BUS().ADDRESS().high = m_unfixed_page;
memoryRead();
BUS().ADDRESS().high = fixed_page;
BUS().ADDRESS().high = m_fixed_page;
}
void maybe_fixupR() noexcept { maybe_fixup(); memoryRead(); }
@ -288,6 +294,7 @@ namespace EightBit {
bool m_handlingNMI = false;
bool m_handlingINT = false;
uint8_t m_unfixed_page = 0;
//uint8_t m_unfixed_page = 0;
uint8_t m_fixed_page = 0;
};
}

7
M6502/src/mos6502.cpp
View File

@ -427,9 +427,10 @@ void EightBit::MOS6502::branch(const int condition) noexcept {
const auto relative = int8_t(fetchByte());
if (condition) {
swallow();
m_unfixed_page = PC().high;
jump(PC() + relative);
BUS().ADDRESS() = PC();
const auto address = PC() + relative;
noteFixedPage(address.high);
jump(address);
BUS().ADDRESS().low = address.low;
maybe_fixup();
}
}