mirror of
https://github.com/MoleskiCoder/EightBit.git
synced 2024-06-22 18:29:27 +00:00
147 lines
7.5 KiB
C++
147 lines
7.5 KiB
C++
#include "pch.h"
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#include "../inc/MC6850.h"
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#include <cassert>
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EightBit::mc6850::mc6850() {
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Ticked.connect([this](EightBit::EventArgs&) {
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step();
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});
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RaisedPOWER.connect([this](EventArgs) {
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m_startup = ColdStart;
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});
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}
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DEFINE_PIN_LEVEL_CHANGERS(RXDATA, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(TXDATA, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(RTS, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(CTS, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(DCD, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(RXCLK, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(TXCLK, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(CS0, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(CS1, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(CS2, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(RS, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(RW, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(E, mc6850);
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DEFINE_PIN_LEVEL_CHANGERS(IRQ, mc6850);
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void EightBit::mc6850::reset() {
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if (m_startup == ColdStart) {
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raise(IRQ());
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raise(RTS());
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}
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m_statusRDRF = false;
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m_statusTDRE = true;
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m_statusOVRN = false;
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lower(DCD());
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m_startup = WarmStart;
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m_statusRead = false;
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}
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void EightBit::mc6850::step() {
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resetCycles();
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if (!activated())
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return;
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Accessing.fire();
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const bool writing = lowered(RW());
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//const bool reading = !writing;
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const bool registers = lowered(RS());
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//const bool transferring = !registers;
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if (registers) {
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if (writing) {
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m_counterDivide = (CounterDivideSelect)(DATA() & (CR0 | CR1));
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if (m_counterDivide == MasterReset) {
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reset();
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} else {
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m_wordSelect = (WordSelect)((DATA() & (CR2 | CR3 | CR4)) >> 2);
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m_transmitControl = (TransmitterControl)((DATA() & (CR5 | CR6)) >> 5);
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m_receiveControl = (ReceiveControl)((DATA() & CR7) >> 7);
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match(RTS(), transmitReadyHigh());
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}
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} else {
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DATA() = status();
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}
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} else {
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raise(IRQ());
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if (writing)
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startTransmit();
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else
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completeReceive();
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}
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// Catch the transition to lost carrier
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if (lowered(m_oldDCD) && raised(DCD())) {
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raise(IRQ());
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m_statusRead = false;
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}
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m_oldDCD = DCD();
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Accessed.fire();
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}
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uint8_t EightBit::mc6850::status() {
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uint8_t status = 0;
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status = setBit(status, STATUS_RDRF, m_statusRDRF);
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status = setBit(status, STATUS_TDRE, m_statusTDRE);
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status = setBit(status, STATUS_DCD, raised(DCD()));
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status = setBit(status, STATUS_CTS, raised(CTS()));
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status = clearBit(status, STATUS_FE);
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status = setBit(status, STATUS_OVRN, m_statusOVRN);
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status = clearBit(status, STATUS_PE);
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status = setBit(status, STATUS_IRQ, lowered(IRQ()));
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return status;
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}
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std::string EightBit::mc6850::dumpStatus() {
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const auto value = status();
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std::string returned;
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returned += "(";
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returned += (value & STATUS_IRQ) ? "IRQ " : "- ";
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returned += (value & STATUS_PE) ? "PE " : "- ";
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returned += (value & STATUS_OVRN) ? "OVRN " : "- ";
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returned += (value & STATUS_FE) ? "FE " : "- ";
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returned += (value & STATUS_CTS) ? "CTS " : "- ";
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returned += (value & STATUS_DCD) ? "DCD " : "- ";
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returned += (value & STATUS_TDRE) ? "TDRE " : "- ";
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returned += (value & STATUS_RDRF) ? "RDRF " : "- ";
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returned += ") ";
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return returned;
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}
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void EightBit::mc6850::markTransmitComplete() {
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m_statusTDRE = lowered(CTS());
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if (m_statusTDRE && transmitInterruptEnabled())
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lower(IRQ());
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Transmitted.fire();
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}
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void EightBit::mc6850::markReceiveStarting() {
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m_statusOVRN = m_statusRDRF; // If the RDR was already full, this means we're losing data
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m_statusRDRF = true;
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if (receiveInterruptEnabled())
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lower(IRQ());
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Receiving.fire();
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}
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void EightBit::mc6850::startTransmit() {
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TDR() = DATA();
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m_statusTDRE = false;
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Transmitting.fire();
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}
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void EightBit::mc6850::completeReceive() {
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DATA() = RDR();
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m_statusOVRN = m_statusRDRF = false; // Any existing data overrun is now moot.
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Received.fire();
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}
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