mirror of
https://github.com/MoleskiCoder/EightBit.git
synced 2024-11-19 02:08:25 +00:00
106 lines
2.1 KiB
C++
106 lines
2.1 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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}
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void EightBit::M6532::tick() {
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if (selected()) {
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// Process interrupts
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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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if (m_allowPA7Interrupts && (PA() & 0x80))
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IF() &= 0x40;
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if (m_allowTimerInterrupts && (m_timerInterval == 0))
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IF() &= 0x80;
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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() & (0x80 & 0x40);
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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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}
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}
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}
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}
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}
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void EightBit::M6532::initialise() {
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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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