mirror of
https://github.com/MoleskiCoder/EightBit.git
synced 2024-06-11 10:29:31 +00:00
131 lines
2.6 KiB
C++
131 lines
2.6 KiB
C++
#include "stdafx.h"
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#include "M6532.h"
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#include <cassert>
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EightBit::M6532::M6532() noexcept {
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Ticked.connect([this](EightBit::EventArgs&) {
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step();
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});
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}
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DEFINE_PIN_LEVEL_CHANGERS(RES, M6532);
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DEFINE_PIN_LEVEL_CHANGERS(RW, M6532);
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DEFINE_PIN_LEVEL_CHANGERS(IRQ, M6532);
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DEFINE_PIN_LEVEL_CHANGERS(RS, M6532);
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DEFINE_PIN_LEVEL_CHANGERS(CS1, M6532);
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DEFINE_PIN_LEVEL_CHANGERS(CS2, M6532);
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void EightBit::M6532::step() {
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resetCycles();
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if (!activated())
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return;
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Accessing.fire(EventArgs::empty());
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if (lowered(RES())) {
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reset();
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raise(RES());
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return;
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}
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if (--m_currentIncrement == 0) {
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m_currentIncrement = m_timerIncrement;
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--m_timerInterval;
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}
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const bool interruptPA7 = m_allowPA7Interrupts && (PA() & Bit7);
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if (interruptPA7)
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setFlag(IF(), Bit6);
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const bool interruptTimer = m_allowTimerInterrupts && (m_timerInterval == 0);
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if (interruptTimer)
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setFlag(IF(), Bit7);
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interruptPA7 || interruptTimer ? lower(IRQ()) : raise(IRQ());
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const auto read = raised(RW());
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const auto write = lowered(RW());
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assert(read == !write);
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const auto ram = lowered(RS());
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if (ram) {
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auto& cell = RAM().reference(address() & 0x7f);
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read ? DATA() = cell : cell = DATA();
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} else {
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const auto a0 = address() & 0b00001;
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const auto a1 = address() & 0b00010;
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const auto a2 = address() & 0b00100;
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const auto a3 = address() & 0b01000;
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const auto a4 = address() & 0b10000;
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const auto portControls = a2 == 0;
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const auto otherControls = a2 == 1;
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if (portControls) {
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switch (a0 | a1) {
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case 0b00:
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// R/W output reg A
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break;
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case 0b01:
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read ? DATA() = DDRA() : DDRA() = DATA();
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break;
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case 0b10:
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// R/W output reg B
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break;
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case 0b11:
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read ? DATA() = DDRB() : DDRB() = DATA();
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break;
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}
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} else {
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if (read && !a4 && a2) {
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m_allowPA7Interrupts = !a1;
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m_edgeDetection = a0 ? Positive : Negative;
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}
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if (read && a2 && a0) {
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DATA() = IF();
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clearFlag(IF(), Bit6);
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}
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m_allowTimerInterrupts = !!a3;
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if (write && a4) {
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m_timerInterval = DATA();
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switch (a1 | a0) {
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case 0b00:
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m_timerIncrement = One;
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break;
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case 0b01:
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m_timerIncrement = Eight;
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break;
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case 0b10:
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m_timerIncrement = SixtyFour;
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break;
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case 0b11:
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m_timerIncrement = OneThousandAndTwentyFour;
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break;
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}
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m_currentIncrement = m_timerIncrement;
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clearFlag(IF(), Bit7);
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}
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}
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}
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Accessed.fire(EventArgs::empty());
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}
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void EightBit::M6532::reset() {
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PA() = m_dra = m_ddra = 0; // Zero port A registers
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PB() = m_drb = m_ddrb = 0; // Zero port B registers
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m_allowTimerInterrupts = m_allowPA7Interrupts = false; // Interrupts are disabled
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}
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