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Rearrange the RESET handler for cycle accuracy. Use more of the general interrupt handler, but with "dummy" stack write access.

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Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2019-01-08 23:09:52 +00:00
parent 25321e78e7
commit 047babbe7c
2 changed files with 21 additions and 8 deletions
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3
M6502/inc/mos6502.h
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@ -76,6 +76,9 @@ namespace EightBit {
virtual void push(uint8_t value) final;
virtual uint8_t pop() final;
// Dummy stack push, used during RESET
void dummyPush(uint8_t value);
// Addressing modes
register16_t Address_Absolute();

26
M6502/src/mos6502.cpp
View File

@ -72,17 +72,21 @@ void EightBit::MOS6502::handleIRQ() {
}
void EightBit::MOS6502::interrupt() {
uint8_t vector = RSTvector;
if (!m_handlingRESET) {
const bool nmi = m_handlingNMI;
const bool irq = m_handlingIRQ;
const bool hardware = nmi || irq;
const bool software = !hardware;
const bool reset = m_handlingRESET;
const bool nmi = m_handlingNMI;
const bool irq = m_handlingIRQ;
const bool hardware = nmi || irq || reset;
const bool software = !hardware;
if (reset) {
dummyPush(PC().high);
dummyPush(PC().low);
dummyPush(P());
} else {
pushWord(PC());
push(P() | (software ? BF : 0));
setFlag(P(), IF); // Disable IRQ
vector = nmi ? NMIvector : IRQvector;
}
setFlag(P(), IF); // Disable IRQ
const uint8_t vector = reset ? RSTvector : (nmi ? NMIvector : IRQvector);
jump(getWordPaged(0xff, vector));
m_handlingRESET = m_handlingNMI = m_handlingIRQ = false;
}
@ -392,6 +396,12 @@ uint8_t EightBit::MOS6502::pop() {
return getBytePaged(1, ++S());
}
void EightBit::MOS6502::dummyPush(const uint8_t value) {
addCycle();
BUS().DATA() = value;
BUS().ADDRESS() = register16_t(S()--, 1);
}
////
EightBit::register16_t EightBit::MOS6502::Address_Absolute() {