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Add support for emulated SYNC and RDY lines. Untested, but feel close.

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Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2019-01-08 23:55:27 +00:00
parent 047babbe7c
commit 01175cf9eb
2 changed files with 12 additions and 13 deletions
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10
M6502/inc/mos6502.h
View File

@ -43,7 +43,9 @@ namespace EightBit {
const auto& P() const { return p; }
auto& NMI() { return m_nmiLine; } // In
auto& SO() { return m_soLine; } // In
auto& SO() { return m_soLine; } // In
auto& SYNC() { return m_syncLine; } // Out
auto& RDY() { return m_rdyLine; } // In
protected:
virtual void handleRESET() final;
@ -185,8 +187,10 @@ namespace EightBit {
uint8_t s = 0; // stack pointer
uint8_t p = 0; // processor status
PinLevel m_nmiLine = PinLevel::Low;
PinLevel m_soLine = PinLevel::Low;
PinLevel m_nmiLine = PinLevel::Low; // Active low
PinLevel m_soLine = PinLevel::Low; // Active low
PinLevel m_syncLine = PinLevel::Low; // Active high
PinLevel m_rdyLine = PinLevel::Low; // Active high
register16_t m_intermediate;

15
M6502/src/mos6502.cpp
View File

@ -21,13 +21,12 @@ void EightBit::MOS6502::powerOn() {
int EightBit::MOS6502::step() {
resetCycles();
ExecutingInstruction.fire(*this);
if (LIKELY(powered())) {
if (LIKELY(powered() && raised(RDY()))) {
if (UNLIKELY(lowered(SO())))
handleSO();
lower(SYNC()); // Instruction fetch beginning
opcode() = fetchByte();
if (UNLIKELY(lowered(HALT())))
handleHALT();
else if (UNLIKELY(lowered(RESET())))
if (UNLIKELY(lowered(RESET())))
handleRESET();
else if (UNLIKELY(lowered(NMI())))
handleNMI();
@ -46,10 +45,6 @@ void EightBit::MOS6502::handleSO() {
P() |= VF;
}
void EightBit::MOS6502::handleHALT() {
opcode() = 0xea; // NOP
}
void EightBit::MOS6502::handleRESET() {
raise(RESET());
m_handlingRESET = true;
@ -58,14 +53,12 @@ void EightBit::MOS6502::handleRESET() {
void EightBit::MOS6502::handleNMI() {
raise(HALT());
raise(NMI());
m_handlingNMI = true;
opcode() = 0x00; // BRK
}
void EightBit::MOS6502::handleIRQ() {
raise(HALT());
raise(INT());
m_handlingIRQ = true;
opcode() = 0x00; // BRK
@ -107,6 +100,8 @@ uint8_t EightBit::MOS6502::busRead() {
int EightBit::MOS6502::execute() {
raise(SYNC()); // Instruction fetch has now completed
switch (opcode()) {
case 0x00: fetchByte(); interrupt(); break; // BRK (implied)